System Design Description (SyDD) — ISO/IEC/IEEE 15289 — Description | IEEE 29148 §6.5
Generated 2026-03-27 — UHT Journal / universalhex.org
flowchart TB n0["system<br>Water Treatment Plant"] n1["component<br>Raw Water Intake"] n2["component<br>Coagulation and Flocculation"] n3["component<br>Sedimentation"] n4["component<br>Filtration"] n5["component<br>Disinfection"] n6["component<br>Chemical Storage and Dosing"] n7["component<br>Treated Water Storage and Pumping"] n8["component<br>Sludge Handling"] n9["component<br>SCADA and Instrumentation"] n10["component<br>Electrical Power and Emergency Gen"] n1 -->|Raw water| n2 n2 -->|Flocculated water| n3 n3 -->|Settled water| n4 n4 -->|Filtered water| n5 n5 -->|Disinfected water| n7 n6 -->|Coagulant and polymer| n2 n6 -->|Chlorine| n5 n3 -->|Settled sludge| n8 n4 -->|Backwash waste| n8 n9 -->|Supervisory control| n0 n10 -->|Power distribution| n0
Water Treatment Plant — Decomposition
| Ref | Requirement | V&V | Tags |
|---|---|---|---|
| SUB-REQS-001 | The Alum Bulk Storage and Metering System SHALL maintain a minimum of 30 days liquid alum supply at maximum dose rate (80 mg/L at 50 ML/d), requiring a minimum combined storage volume of 60,000 litres. | — | subsystem, chemical-dosing, alum, session-207 |
| SUB-REQS-002 | The Alum Bulk Storage and Metering System SHALL meter liquid alum within ±2% of the commanded dose rate over the operating range of 20 to 120 L/hr. | — | subsystem, chemical-dosing, alum, session-207 |
| SUB-REQS-003 | The Chlorine Gas Storage and Feed System SHALL operate under vacuum downstream of the cylinder regulator such that any leak in the feed line results in air ingress, not chlorine gas release. | — | subsystem, chemical-dosing, chlorine, safety, session-207 |
| SUB-REQS-004 | When chlorine gas concentration exceeds 1 ppm at any detection point, the Chemical Containment and Emergency Safety System SHALL automatically close all chlorine cylinder valves and activate the emergency scrubber within 5 seconds. | — | subsystem, chemical-dosing, chlorine, safety, session-207 |
| SUB-REQS-005 | While the chlorine room is occupied or chlorine cylinders are connected, the Chemical Containment and Emergency Safety System SHALL maintain forced exhaust ventilation at a minimum of 20 air changes per hour with the room at negative pressure relative to all adjacent spaces. | — | subsystem, chemical-dosing, chlorine, ventilation, session-207 |
| SUB-REQS-006 | The Caustic Soda Storage and Feed System SHALL adjust finished water pH to 7.0–7.5 within ±0.1 pH units of setpoint under steady-state flow conditions, achieving a Langelier Saturation Index between 0.0 and +0.5. | — | subsystem, chemical-dosing, caustic, session-207 |
| SUB-REQS-007 | The Fluorosilicic Acid Storage and Feed System SHALL maintain finished water fluoride concentration at 0.7 mg/L ±0.1 mg/L as verified by online fluoride analyser with 4-hour grab sample confirmation. | — | subsystem, chemical-dosing, fluoride, session-207 |
| SUB-REQS-008 | When geosmin or 2-methylisoborneol concentration in raw water exceeds 10 ng/L, the Powdered Activated Carbon Feed System SHALL be capable of delivering PAC at doses between 5 and 50 mg/L within 30 minutes of operator initiation. | — | subsystem, chemical-dosing, pac, session-207 |
| SUB-REQS-009 | The Chemical Containment and Emergency Safety System SHALL provide secondary containment for all liquid chemical storage areas rated for 110% of the largest single tank volume, with chemically resistant liners and sump pumps interlocked to prevent discharge to stormwater. | — | subsystem, chemical-dosing, containment, safety, session-207 |
| SUB-REQS-010 | The Chemical Dosing Control System SHALL implement flow-proportional dosing for alum, chlorine, caustic soda, and fluoride, adjusting dose rate within 10 seconds of a plant flow change exceeding 5% of current flow. | — | subsystem, chemical-dosing, control, session-207 |
| SUB-REQS-011 | When a duty metering pump fails or its discharge pressure drops below the minimum injection threshold, the Chemical Dosing Control System SHALL automatically switch to the standby pump within 30 seconds and annunciate the switchover to SCADA. | — | subsystem, chemical-dosing, control, redundancy, session-207 |
| SUB-REQS-012 | The Polymer Preparation and Feed System SHALL provide a minimum 45-minute polymer aging time through a three-stage tank system before the solution is available for dosing. | — | subsystem, chemical-dosing, polymer, session-207 |
| SUB-REQS-013 | The UV Disinfection Reactor SHALL deliver a validated UV dose of not less than 40 mJ/cm2 at all flow rates up to 200 L/s per reactor, at UV transmittance as low as 85%, with dose validation per USEPA UV Disinfection Guidance Manual. | — | subsystem, disinfection, uv, session-207 |
| SUB-REQS-014 | The Chlorine Contact Tank SHALL achieve a T10/T ratio of not less than 0.65 as validated by tracer study, with two parallel tanks each providing 15-minute detention time at peak flow of 580 L/s. | — | subsystem, disinfection, contact-tank, session-207 |
| SUB-REQS-015 | The CT Compliance Monitoring System SHALL calculate achieved CT at 15-minute intervals using outlet residual chlorine concentration and validated T10 time at current flow, and SHALL generate an alarm when achieved CT falls below 90% of required CT for the current water temperature and pH. | — | subsystem, disinfection, ct-compliance, session-207 |
| SUB-REQS-016 | The Disinfection Residual Analyser Network SHALL measure free chlorine residual with accuracy of ±0.02 mg/L at 1.0 mg/L across the range 0 to 5 mg/L, with automatic sample flow monitoring and alarm on loss of sample. | — | subsystem, disinfection, analyser, session-207 |
| SUB-REQS-017 | When any single UV reactor is offline for maintenance or lamp failure, the remaining duty reactors SHALL maintain the validated 40 mJ/cm2 dose at flows up to 75% of peak plant capacity (435 L/s total). | — | subsystem, disinfection, uv, redundancy, session-207 |
| SUB-REQS-018 | The UV Disinfection Reactor SHALL continuously monitor UV intensity at 254 nm with calibrated reference sensors, and SHALL automatically increase lamp power or reduce flow when measured intensity drops below the minimum required for dose compliance at current UVT and flow rate. | — | subsystem, disinfection, uv, monitoring, session-207 |
| SUB-REQS-019 | The Dual-Media Gravity Filter Cell SHALL reduce settled water turbidity from a maximum of 2 NTU to not more than 0.1 NTU in the individual filter effluent at filtration rates up to 6 m/hr, with media comprising 600 mm anthracite (effective size 1.0 mm, UC 1.4) over 300 mm silica sand (effective size 0.5 mm, UC 1.3). | — | subsystem, filtration, media, session-208 |
| SUB-REQS-020 | The Backwash Supply System SHALL deliver backwash water at a rising rate of 55 to 65 m/hr with flow regulation to within ±5% of setpoint, using duty/standby pumps each rated at 900 m3/hr at 15 m TDH, drawing from a dedicated 200 m3 backwash water storage tank. | — | subsystem, filtration, backwash, session-208 |
| SUB-REQS-021 | The Dual-Media Gravity Filter Cell SHALL reduce settled water turbidity from a maximum of 2 NTU to not more than 0.1 NTU in the individual filter effluent at filtration rates up to 6 m/hr, with media comprising 600 mm anthracite over 300 mm silica sand. | — | subsystem, filtration, media, session-208 |
| SUB-REQS-022 | The Air Scour Blower System SHALL deliver scour air at a superficial velocity of 45 to 55 m/hr uniformly across the filter floor area via the underdrain system, using duty/standby positive displacement blowers each rated at 1500 Nm3/hr at 0.5 bar gauge. | — | subsystem, filtration, air-scour, session-208 |
| SUB-REQS-023 | When a filter cell returns to service after backwash, the Filter-to-Waste System SHALL divert filtered water to the backwash waste holding tank until individual filter effluent turbidity is continuously below 0.15 NTU for a minimum of 15 minutes. | — | subsystem, filtration, filter-to-waste, session-208 |
| SUB-REQS-024 | The Filter Control and Instrumentation Panel SHALL continuously monitor differential pressure across the filter media bed over the range 0 to 3 m with accuracy of plus or minus 0.05 m, and SHALL initiate automatic backwash when headloss exceeds 2.5 m or filter run time exceeds 72 hours, whichever occurs first. | — | subsystem, filtration, control, headloss, session-208 |
| SUB-REQS-025 | The Filter Control and Instrumentation Panel SHALL monitor individual filter effluent turbidity via online laser nephelometer over the range 0 to 10 NTU with resolution of 0.001 NTU, and SHALL alarm at 0.3 NTU and automatically take the filter offline at 1.0 NTU. | — | subsystem, filtration, control, turbidity, session-208 |
| SUB-REQS-026 | The Filter Control and Instrumentation Panel SHALL execute an automated backwash sequence comprising: drain-down to media surface, air scour at 50 m/hr for 3 minutes, combined air-water wash for 4 minutes, high-rate water-only rinse at 60 m/hr for 8 minutes, and slow rinse at 20 m/hr for 5 minutes, with total sequence duration not exceeding 25 minutes. | — | subsystem, filtration, control, backwash-sequence, session-208 |
| SUB-REQS-027 | The Filtration Subsystem SHALL comprise a minimum of 8 filter cells arranged in two parallel trains of 4, such that with any one cell offline for backwash or maintenance the remaining 7 cells SHALL maintain the full plant production capacity of 50 ML/d at individual filter rates not exceeding 7 m/hr. | — | subsystem, filtration, redundancy, session-208 |
| SUB-REQS-028 | The Filter Underdrain and Support Gravel System SHALL distribute backwash water and air uniformly such that the variation in flow velocity across the filter floor area does not exceed plus or minus 10% of the mean, preventing media migration, gravel disruption, or dead zones during the combined air-water backwash phase. | — | subsystem, filtration, underdrain, session-208 |
| SUB-REQS-029 | The Backwash Supply System SHALL limit total backwash water consumption to not more than 4% of daily plant production, with the backwash storage tank refilled from the clear well at a rate sufficient to support sequential backwash of two filter cells within a 2-hour period. | — | subsystem, filtration, backwash, efficiency, session-208 |
| SUB-REQS-030 | While water level in the filter cell is below the top of the media bed, the Air Scour Blower System SHALL be interlocked to prevent air delivery, avoiding media displacement and underdrain damage from unsupported air scour. | — | subsystem, filtration, air-scour, safety, session-208 |
| SUB-REQS-031 | The Inclined Plate Settler Module SHALL achieve settled water turbidity of not more than 2 NTU at surface overflow rates up to 10 m/hr when receiving flocculated water with turbidity up to 50 NTU, using 60-degree inclined plates at 50 mm spacing providing a minimum effective settling area of 2500 m2 per basin. | — | subsystem, sedimentation, settler, session-208 |
| SUB-REQS-032 | The Sludge Scraper and Hopper System SHALL remove settled sludge from the basin floor at a scraper speed of 0.3 m/min without disturbing the sludge blanket or resuspending settled particles, with automatic desludging triggered when ultrasonic sludge blanket depth exceeds 0.5 m above the basin floor. | — | subsystem, sedimentation, sludge-scraper, session-208 |
| SUB-REQS-033 | The Sedimentation Basin Inlet Distribution System SHALL distribute flocculated water across the full basin cross-section with velocity variation not exceeding 10% of the mean, reducing inlet velocity from 0.3 m/s to below 0.05 m/s through the energy dissipation zone to prevent floc breakup. | — | subsystem, sedimentation, inlet, session-208 |
| SUB-REQS-034 | The Sedimentation Effluent Launder and Weir System SHALL collect settled water at a maximum weir overflow rate of 10 m3/hr per metre of weir length with V-notch weir crests adjustable to within plus or minus 10 mm to ensure uniform flow collection across the basin outlet. | — | subsystem, sedimentation, weir, session-208 |
| SUB-REQS-035 | The Sedimentation Subsystem SHALL comprise a minimum of 3 parallel basins such that with any one basin offline for cleaning or maintenance, the remaining basins SHALL maintain a minimum treatment capacity of 35 ML/d at surface overflow rates not exceeding 12 m/hr. | — | subsystem, sedimentation, redundancy, session-208 |
| SUB-REQS-036 | The Rapid Mix Chamber SHALL achieve a velocity gradient (G value) of 600 to 1000 s⁻¹ with a hydraulic detention time of 15 to 30 seconds at flows from 50% to 110% of design capacity. | — | subsystem, coag-floc, rapid-mix, session-209 |
| SUB-REQS-037 | The Rapid Mix Chamber SHALL provide a minimum of two coagulant injection points positioned within the high-shear zone such that coagulant is dispersed to 95% homogeneity within 5 seconds of injection. | — | subsystem, coag-floc, rapid-mix, session-209 |
| SUB-REQS-038 | The Flocculation Basin Train SHALL provide three-stage tapered-energy mixing with velocity gradients of 60–80 s⁻¹ (Stage 1), 30–50 s⁻¹ (Stage 2), and 10–20 s⁻¹ (Stage 3) and a total hydraulic retention time of not less than 20 minutes at design flow. | — | subsystem, coag-floc, flocculation, session-209 |
| SUB-REQS-039 | The Coagulation and Flocculation Subsystem SHALL comprise a minimum of 3 parallel flocculation trains such that with any one train offline for maintenance, the remaining trains SHALL treat not less than 100% of average daily demand. | — | subsystem, coag-floc, redundancy, session-209 |
| SUB-REQS-040 | The Flocculator Drive and Gearbox Assembly SHALL provide continuously variable paddle tip speed from 0.15 to 0.9 m/s via variable frequency drives with speed stability of ±1% of setpoint under varying load conditions. | — | subsystem, coag-floc, flocculator-drive, session-209 |
| SUB-REQS-041 | The Streaming Current Detector SHALL continuously measure the streaming current index of coagulated water within 30 seconds of the coagulant injection point and transmit a 4–20 mA signal proportional to SCI to the SCADA system at not less than 1 Hz update rate. | — | subsystem, coag-floc, scd, session-209 |
| SUB-REQS-042 | The Coagulation pH Control System SHALL maintain coagulation pH within the range 6.2 to 7.0 with a control accuracy of ±0.1 pH units under steady-state conditions and ±0.3 pH units during raw water alkalinity transients exceeding 20 mg/L CaCO3 change per hour. | — | subsystem, coag-floc, ph-control, session-209 |
| SUB-REQS-043 | When the streaming current index deviates beyond ±0.5 units from the operator-defined setpoint for more than 60 seconds, the Chemical Dosing Control System SHALL automatically adjust the coagulant dose rate by up to ±15% of the current dose within 30 seconds of the deviation being confirmed. | — | subsystem, coag-floc, dose-control, session-209 |
| SUB-REQS-044 | The Intake Screen and Trashrack Assembly SHALL provide coarse screening (75 mm bar spacing) followed by fine screening (6 mm aperture) and SHALL initiate automatic screen cleaning when differential head loss across the screen exceeds 150 mm. | — | subsystem, raw-water-intake, screen, session-209 |
| SUB-REQS-045 | The Raw Water Pumping Station SHALL deliver raw water at 580 to 870 L/s with 3 duty + 1 standby pumps, each VFD-controlled to modulate flow within ±5% of setpoint across the full operating range. | — | subsystem, raw-water-intake, pumping, session-209 |
| SUB-REQS-046 | The Flow Measurement and Control System SHALL measure raw water flow with accuracy of ±0.5% of reading using a full-bore electromagnetic flow meter and SHALL provide the master flow signal to SCADA for flow-proportional chemical dosing. | — | subsystem, raw-water-intake, flow, session-209 |
| SUB-REQS-047 | The Raw Water Quality Monitoring Station SHALL continuously measure turbidity, pH, temperature, conductivity, and dissolved oxygen with a sampling transport lag of not more than 60 seconds from the intake point. | — | subsystem, raw-water-intake, monitoring, session-209 |
| SUB-REQS-048 | When all duty pumps in the Raw Water Pumping Station are unavailable, the standby pump SHALL start automatically within 30 seconds of the last duty pump trip and SHALL maintain a minimum flow of 290 L/s. | — | subsystem, raw-water-intake, redundancy, session-209 |
| SUB-REQS-049 | The Master SCADA Server and Historian SHALL operate as a redundant hot-standby pair with automatic failover completing within 5 seconds and zero data loss for process values sampled at 1-second intervals. | — | subsystem, scada, scada-server, session-210 |
| SUB-REQS-050 | The Master SCADA Server and Historian SHALL store at least 12 months of online historical data at 1-second resolution for critical water quality parameters (turbidity, chlorine residual, pH, fluoride) and 10-second resolution for all other process variables. | — | subsystem, scada, scada-server, session-210 |
| SUB-REQS-051 | The Distributed PLC Network SHALL execute safety interlock logic within a scan time of 100 ms or less, and process control loops within a scan time of 500 ms or less, for all connected I/O points. | — | subsystem, scada, plc-network, session-210 |
| SUB-REQS-052 | The Distributed PLC Network SHALL maintain autonomous control of all assigned process areas when the SCADA server connection is lost, continuing the last valid control strategy for a minimum of 72 hours without operator intervention. | — | subsystem, scada, plc-network, session-210 |
| SUB-REQS-053 | The Process Instrumentation Field Network SHALL support a minimum of 200 field instruments connected via 4-20 mA HART, Modbus RTU (RS-485), or Profibus PA, with each instrument polled at its required sample rate without exceeding 95% bus utilisation on any segment. | — | subsystem, scada, field-instruments, session-210 |
| SUB-REQS-054 | The Industrial Network Infrastructure SHALL provide a redundant fibre-optic Ethernet backbone in ring topology with Rapid Spanning Tree or Media Redundancy Protocol failover completing within 50 ms. | — | subsystem, scada, network, session-210 |
| SUB-REQS-055 | The Industrial Network Infrastructure SHALL enforce IEC 62443-compliant network segmentation with VLAN isolation per process area, a DMZ firewall between OT and IT networks, and port-level access control on all managed switches. | — | subsystem, scada, network, cybersecurity, session-210 |
| SUB-REQS-056 | The Operator HMI Workstations SHALL provide role-based access control with at least three levels (operator, supervisor, engineer) and SHALL log all setpoint changes and manual overrides with timestamp, user identity, and previous value. | — | subsystem, scada, hmi, session-210 |
| SUB-REQS-057 | The Operator HMI Workstations SHALL annunciate all priority-1 alarms within 2 seconds of the alarm condition being detected by the PLC, via on-screen pop-up, audible horn, and flashing beacon in the control room. | — | subsystem, scada, hmi, session-210 |
| SUB-REQS-058 | The Remote Telemetry and Reporting Gateway SHALL transmit key compliance parameters (plant effluent turbidity, chlorine residual, pH, flow) to the state drinking water authority's compliance portal at intervals not exceeding 15 minutes. | — | subsystem, scada, telemetry, session-210 |
| SUB-REQS-059 | When the primary WAN link fails, the Remote Telemetry and Reporting Gateway SHALL activate the cellular backup link within 30 seconds and SHALL queue unsent data for up to 24 hours of link outage, transmitting the backlog upon link restoration. | — | subsystem, scada, telemetry, session-210 |
| SUB-REQS-060 | When utility power is lost, the Emergency Diesel Generator Set SHALL start and reach rated voltage and frequency within 10 seconds, and the automatic transfer switch SHALL transfer critical loads within 2 seconds of generator readiness. | — | subsystem, electrical-power, generator, session-210 |
| SUB-REQS-061 | The Emergency Diesel Generator Set SHALL provide a minimum of 72 hours of continuous operation at 75% rated load from on-site fuel storage, with the bulk fuel tank capacity of at least 10,000 litres and a day tank capacity of at least 500 litres with automatic refill. | — | subsystem, electrical-power, generator, session-210 |
| SUB-REQS-062 | The Main Utility Power Switchgear SHALL accept dual 11 kV utility feeds and provide automatic bus transfer between feeds within 100 ms upon detection of voltage sag below 90% or complete loss on the active feed. | — | subsystem, electrical-power, switchgear, session-210 |
| SUB-REQS-063 | The Uninterruptible Power Supply System SHALL provide 60 kVA of online double-conversion power to SCADA servers, PLC racks, and critical instrumentation with a minimum battery autonomy of 30 minutes at full rated load. | — | subsystem, electrical-power, ups, session-210 |
| SUB-REQS-064 | The Motor Control Centres SHALL provide variable frequency drives for all pump motors rated above 7.5 kW, with VFD efficiency not less than 97% at rated speed, and SHALL support Ethernet/IP communication for speed setpoint and status reporting to the local PLC. | — | subsystem, electrical-power, mcc, session-210 |
| SUB-REQS-065 | The Power Distribution and Protection Network SHALL maintain a site earthing grid resistance below 1 ohm and SHALL coordinate overcurrent protection devices to achieve fault discrimination such that only the device nearest the fault trips. | — | subsystem, electrical-power, protection, session-210 |
| SUB-REQS-066 | While operating on emergency diesel generation, the Electrical Power and Emergency Generation Subsystem SHALL maintain power to disinfection, SCADA, and treated water pumping subsystems at a minimum of 35 ML/d treatment capacity as required by SYS-REQS-005. | — | subsystem, electrical-power, degraded-mode, session-210 |
| SUB-REQS-067 | The Sludge Holding and Thickening Tank SHALL provide a combined storage volume of at least 400 m3, sufficient for 3 days of sludge production at peak plant throughput of 50 ML/d with raw water turbidity of 50 NTU and alum dose of 80 mg/L. | — | subsystem, sludge, holding-tank, session-210 |
| SUB-REQS-068 | The Mechanical Sludge Dewatering System SHALL dewater thickened alum sludge from 2-4% feed solids to a minimum cake solids content of 18% by weight, with polymer consumption not exceeding 5 kg of active polymer per dry tonne of sludge solids. | — | subsystem, sludge, dewatering, session-210 |
| SUB-REQS-069 | The Sludge Cake Storage and Disposal Hopper SHALL provide a minimum storage capacity of 60 m3, sufficient for 5 days of dewatered cake production, with a live-bottom discharge capable of loading a 10 m3 hook-lift bin within 15 minutes. | — | subsystem, sludge, cake-storage, session-210 |
| SUB-REQS-070 | The Supernatant and Filtrate Return System SHALL limit the total return flow to the plant headworks to no more than 10% of the concurrent raw water inflow, and SHALL equalise return flows in a 20 m3 sump with variable-speed pumps to prevent shock loading. | — | subsystem, sludge, return-system, session-210 |
| SUB-REQS-071 | The Mechanical Sludge Dewatering System SHALL be provided in a duty/standby configuration (two belt filter presses each rated at 25 m3/hr sludge feed) to ensure continuous dewatering capability during maintenance of one unit. | — | subsystem, sludge, dewatering, session-210 |
| SUB-REQS-072 | The Treated Water Clear Well SHALL provide a minimum combined effective storage volume of 10 ML across two cells, sufficient for 4.8 hours of peak demand at 50 ML/d plus a 1 ML fire reserve isolated by a weir at the cell outlet. | — | subsystem, treated-water, clear-well, session-210 |
| SUB-REQS-073 | The High-Lift Distribution Pump Station SHALL maintain discharge pressure between 350 kPa and 700 kPa across the full demand range from 200 L/s minimum night flow to 600 L/s peak day demand, with pump efficiency not less than 80% at best efficiency point. | — | subsystem, treated-water, distribution-pumps, session-210 |
| SUB-REQS-074 | The High-Lift Distribution Pump Station SHALL operate in a 3-duty 1-standby configuration with automatic lead-lag pump selection controlled by SCADA, and SHALL maintain the minimum discharge pressure of 350 kPa with any one pump out of service. | — | subsystem, treated-water, distribution-pumps, session-210 |
| SUB-REQS-075 | The Treated Water Quality Monitoring Station SHALL continuously measure treated water turbidity (range 0-1 NTU, resolution 0.001 NTU), free chlorine residual (range 0-5 mg/L, accuracy ±0.02 mg/L), pH (range 6-9), and fluoride (range 0-2 mg/L) with results available to SCADA within 60 seconds. | — | subsystem, treated-water, quality-monitoring, session-210 |
| SUB-REQS-076 | The Distribution Network Surge Protection System SHALL limit hydraulic transient pressures to no more than 150% of the maximum steady-state working pressure (700 kPa) during pump trip, rapid valve closure, or sudden demand change events. | — | subsystem, treated-water, surge-protection, session-210 |
| SUB-REQS-077 | When the SCADA server or network backbone fails, the Distributed PLC Network SHALL maintain autonomous local control of all process areas with PLC scan cycle time not exceeding 100 ms, retaining the last valid setpoints and alarm thresholds for a minimum of 72 hours without operator intervention, and SHALL resume SCADA data synchronisation within 30 seconds of network restoration. | — | subsystem, scada, degraded-mode, session-211 |
| SUB-REQS-078 | When the SCADA server or network backbone fails, the Distributed PLC Network SHALL maintain autonomous local control of all process areas with PLC scan cycle time not exceeding 100 ms, retaining the last valid setpoints and alarm thresholds for a minimum of 72 hours without operator intervention, and SHALL resume SCADA data synchronisation within 30 seconds of network restoration. | — | subsystem, scada, degraded-mode, session-211 |
| SUB-REQS-079 | SUB-REQS-021 is a duplicate of SUB-REQS-019 (dual-media gravity filter cell turbidity performance). SUB-REQS-019 is the authoritative version as it includes full media specification. | — | duplicate-of-SUB-REQS-019, session-213 |
| SUB-REQS-080 | SUB-REQS-077 and SUB-REQS-078 are textual duplicates of each other and functionally duplicate SUB-REQS-052 (Distributed PLC autonomous control). SUB-REQS-052 is the authoritative version for PLC scan time and autonomous operation requirements. | — | duplicate-of-SUB-REQS-052, session-213 |
| SUB-REQS-081 | When raw water turbidity exceeds 100 NTU as measured by the Raw Water Quality Monitoring Station, the Coagulation and Flocculation Subsystem SHALL increase coagulant dose to the pre-configured storm dose profile within 60 seconds of turbidity threshold exceedance, increase flocculator speed to the high-energy setpoints (Stage 1: 80 s-1, Stage 2: 50 s-1, Stage 3: 20 s-1), and the SCADA system SHALL alert operators to consider reducing plant throughput to maintain settled water turbidity below 5 NTU. Rationale: Storm events cause rapid raw water turbidity spikes that can overwhelm coagulation at normal doses, leading to settled water turbidity exceeding filter capacity and risking regulatory non-compliance. The 60-second response time ensures chemical dosing adjusts before high-turbidity slug passes through the rapid mix chamber. The staged G-value profile (80/50/20 s-1) follows standard tapered flocculation practice for high-turbidity conditions, promoting dense floc formation while preventing shear breakup. Alerting operators to reduce throughput is a defence-in-depth measure when turbidity approaches the design envelope limit. | Test | subsystem, coagulation, storm-response, session-213 |
| Ref | Requirement | V&V | Tags |
|---|---|---|---|
| IFC-DEFS-001 | The interface between the Alum Bulk Storage and Metering System and the Coagulation and Flocculation Subsystem SHALL deliver liquid alum through a 25mm PVC injection quill at the rapid-mix basin inlet, with a check valve and anti-siphon air gap to prevent process water backflow into the chemical storage area. | — | interface, chemical-dosing, alum, coagulation, session-207 |
| IFC-DEFS-002 | The interface between the Polymer Preparation and Feed System and the Coagulation and Flocculation Subsystem SHALL deliver diluted polymer solution through a diffuser nozzle at the first flocculation stage inlet, with injection velocity sufficient to achieve initial mixing within 5 seconds of contact. | — | interface, chemical-dosing, polymer, coagulation, session-207 |
| IFC-DEFS-003 | The interface between the Chlorine Gas Storage and Feed System and the Disinfection Subsystem SHALL deliver chlorine solution via a vacuum-operated ejector with motive water supply at 400–600 kPa, injecting into the chlorine contact tank inlet through a diffuser providing uniform distribution across the tank cross-section. | — | interface, chemical-dosing, chlorine, disinfection, session-207 |
| IFC-DEFS-004 | The interface between the Caustic Soda Storage and Feed System and the Treated Water Storage and Distribution Pumping Subsystem SHALL inject caustic soda solution at the clearwell outlet weir with static mixer achieving 95% mixing uniformity within 10 pipe diameters downstream. | — | interface, chemical-dosing, caustic, distribution, session-207 |
| IFC-DEFS-005 | The interface between the Chemical Dosing Control System and the SCADA and Instrumentation Subsystem SHALL exchange all chemical feed pump status, dose rates, tank levels, analyser readings, and alarm conditions via Modbus RTU at 9600 baud with 1-second polling interval, using dedicated RS-485 bus segments per chemical area. | — | interface, chemical-dosing, scada, control, session-207 |
| IFC-DEFS-006 | The interface between the Chemical Containment and Emergency Safety System and the SCADA and Instrumentation Subsystem SHALL provide hardwired discrete inputs for all gas detection alarms, scrubber status, and emergency shutdown states, independent of the Modbus communication path, with alarm response time not exceeding 500 milliseconds from detection to SCADA annunciation. | — | interface, chemical-dosing, safety, scada, session-207 |
| IFC-DEFS-007 | The interface between the Fluorosilicic Acid Storage and Feed System and the Treated Water Storage and Distribution Pumping Subsystem SHALL inject fluorosilicic acid downstream of the caustic soda injection point with a minimum 2-metre separation to prevent localised precipitation, using Hastelloy C-276 injection quill and PVDF tubing rated for 23% HFS acid. | — | interface, chemical-dosing, fluoride, distribution, session-207 |
| IFC-DEFS-008 | The interface between the Filtration Subsystem and the UV Disinfection Reactor SHALL deliver filtered water through a 600mm header with flow measurement (electromagnetic flowmeter, ±0.5% accuracy) and UVT measurement (online spectrophotometer at 254nm) upstream of the reactor inlet manifold. | — | interface, disinfection, filtration, session-207 |
| IFC-DEFS-009 | The interface between the UV Disinfection Reactor and the Chlorine Contact Tank SHALL convey UV-treated water through a 600mm pipeline with chlorine injection point located at least 3 pipe diameters upstream of the contact tank inlet diffuser wall to ensure initial mixing before baffled flow begins. | — | interface, disinfection, uv, contact-tank, session-207 |
| IFC-DEFS-010 | The interface between the Disinfection Residual Analyser Network and the SCADA and Instrumentation Subsystem SHALL transmit chlorine residual values from all 5 analyser locations via 4-20 mA signals with 1-second update rate, plus sample flow status as discrete inputs, to dedicated SCADA I/O modules in the disinfection area remote I/O cabinet. | — | interface, disinfection, scada, analyser, session-207 |
| IFC-DEFS-011 | The interface between the Sedimentation Subsystem and the Dual-Media Gravity Filter Cell SHALL convey settled water via a common filter influent channel at a maximum flow of 900 m3/hr, with settled water turbidity not exceeding 2 NTU under normal conditions and 5 NTU during storm events, distributed to individual filter cells via adjustable weir gates. | — | interface, filtration, sedimentation, session-208 |
| IFC-DEFS-012 | The interface between the Dual-Media Gravity Filter Cell and the Treated Water Storage and Distribution Pumping Subsystem SHALL convey filtered water via individual filter effluent pipes into a common filtered water header at a maximum combined flow of 900 m3/hr, with each filter effluent pipe fitted with a motorised butterfly valve for isolation and an electromagnetic flowmeter for flow measurement. | — | interface, filtration, treated-water, session-208 |
| IFC-DEFS-013 | The interface between the Backwash Supply System and the Dual-Media Gravity Filter Cell SHALL deliver backwash water via a common backwash header with individual motorised isolation valves per cell, at a flow rate of 800 to 1000 m3/hr per cell at a supply pressure of 12 to 18 m head, with Venturi-based flow measurement at plus or minus 2% accuracy. | — | interface, filtration, backwash, session-208 |
| IFC-DEFS-014 | The interface between the Air Scour Blower System and the Filter Underdrain and Support Gravel System SHALL deliver low-pressure air via a common air header with individual non-return and isolation valves per cell, at 1400 to 1600 Nm3/hr per cell at 0.4 to 0.6 bar gauge, with the air entering the underdrain plenum and distributing through underdrain orifices. | — | interface, filtration, air-scour, underdrain, session-208 |
| IFC-DEFS-015 | The interface between the Filter Control and Instrumentation Panel and the SCADA and Instrumentation Subsystem SHALL communicate via Modbus TCP over the plant Ethernet LAN, transmitting filter status, turbidity, headloss, flow rate, and valve positions at a minimum update rate of 1 second, and receiving operator commands for manual backwash initiation, setpoint changes, and filter mode selection. | — | interface, filtration, scada, control, session-208 |
| IFC-DEFS-016 | The interface between the Filter Control and Instrumentation Panel and the Backwash Supply System SHALL comprise 4-20 mA analog signals for backwash pump speed demand and discrete digital I/O for pump start/stop, valve open/close, and backwash sequence step status, with all control signals fail-safe to pump-stop on signal loss. | — | interface, filtration, control, backwash, session-208 |
| IFC-DEFS-017 | The interface between the Filter-to-Waste System and the Sludge Handling Subsystem SHALL convey filter-to-waste water by gravity via a 300 mm diameter pipe to the backwash waste holding tank at flows up to 150 m3/hr per filter cell, with a non-return valve to prevent backflow from the waste holding tank during high-level conditions. | — | interface, filtration, sludge, filter-to-waste, session-208 |
| IFC-DEFS-018 | The interface between the Filter Control and Instrumentation Panel and the Air Scour Blower System SHALL comprise discrete digital I/O for blower start/stop and run confirmation, with a hardwired interlock preventing blower start when filter water level is below the media surface level setpoint. | — | interface, filtration, control, air-scour, session-208 |
| IFC-DEFS-019 | The interface between the Coagulation and Flocculation Subsystem and the Sedimentation Basin Inlet Distribution System SHALL convey flocculated water via a common distribution channel at flows up to 900 m3/hr with a maximum channel velocity of 0.3 m/s, maintaining formed floc integrity through smooth transitions and no sharp bends within 5 m of the basin inlet. | — | interface, sedimentation, coagulation, session-208 |
| IFC-DEFS-020 | The interface between the Sedimentation Effluent Launder and Weir System and the Filtration Subsystem SHALL convey settled water via a common filter influent channel at flows up to 900 m3/hr with settled water turbidity not exceeding 2 NTU under normal operation and 5 NTU during storm surge conditions, with channel hydraulics providing equal head to all filter cells. | — | interface, sedimentation, filtration, session-208 |
| IFC-DEFS-021 | The interface between the Sludge Scraper and Hopper System and the Sludge Handling Subsystem SHALL convey settled sludge by gravity at 2 to 3 percent solids concentration via 200 mm diameter sludge withdrawal pipes with pneumatic mud valves, each hopper discharging up to 50 m3/hr during desludge cycles of 5 to 10 minutes duration. | — | interface, sedimentation, sludge, session-208 |
| IFC-DEFS-022 | The interface between Raw Water Intake Subsystem and Rapid Mix Chamber SHALL convey raw water via a gravity or pumped main at flows from 50% to 110% of design capacity with inlet turbidity measurement transmitted to SCADA within 5 seconds of sampling. | — | interface, coag-floc, raw-water, session-209 |
| IFC-DEFS-023 | The interface between Alum Bulk Storage and Metering System and Rapid Mix Chamber SHALL deliver liquid aluminium sulphate at 0–120 L/hr via a Hastelloy C-276 injection quill positioned in the high-shear zone, with flow measurement accuracy of ±2%. | — | interface, coag-floc, chemical, session-209 |
| IFC-DEFS-024 | The interface between Rapid Mix Chamber and Flocculation Basin Train SHALL convey coagulated water via a submerged orifice or short channel with a maximum head loss of 50 mm to avoid floc breakup during transfer. | — | interface, coag-floc, internal, session-209 |
| IFC-DEFS-025 | The interface between Flocculation Basin Train and Sedimentation Basin Inlet Distribution System SHALL transfer flocculated water at the full design flow range with a maximum approach velocity of 0.3 m/s to prevent floc shearing. | — | interface, coag-floc, sedimentation, session-209 |
| IFC-DEFS-026 | The interface between Streaming Current Detector and SCADA and Instrumentation Subsystem SHALL transmit streaming current index as a 4–20 mA analogue signal over a dedicated shielded pair, with data logging at 1-second intervals and alarm thresholds configurable by the operator. | — | interface, coag-floc, scada, session-209 |
| IFC-DEFS-027 | The interface between Coagulation pH Control System and Caustic Soda Storage and Feed System SHALL provide a 4–20 mA trim signal to adjust caustic soda dose rate with a response time of not more than 10 seconds from pH deviation detection to dose adjustment initiation. | — | interface, coag-floc, ph-chemical, session-209 |
| IFC-DEFS-028 | The interface between Intake Screen and Trashrack Assembly and Raw Water Pumping Station SHALL convey screened raw water via a gravity channel with a maximum velocity of 0.6 m/s to prevent resuspension of settled debris. | — | interface, raw-water-intake, session-209 |
| IFC-DEFS-029 | The interface between Raw Water Pumping Station and Flow Measurement and Control System SHALL convey pumped raw water via a DN750 rising main with the electromagnetic flow meter installed at a minimum of 5 pipe diameters downstream of any bend or valve. | — | interface, raw-water-intake, session-209 |
| IFC-DEFS-030 | The interface between Raw Water Quality Monitoring Station and SCADA and Instrumentation Subsystem SHALL transmit all measured parameters via 4–20 mA analogue signals or Modbus RTU over RS-485 with polling at not more than 5-second intervals. | — | interface, raw-water-intake, scada, session-209 |
| IFC-DEFS-031 | The interface between Process Instrumentation Field Network and Distributed PLC Network SHALL use 4-20 mA HART for analog instruments and Modbus RTU at 19200 baud on dedicated RS-485 bus segments, with a maximum of 31 devices per segment and end-to-end cable length not exceeding 1200 m. | — | interface, scada, field-to-plc, session-210 |
| IFC-DEFS-032 | The interface between Distributed PLC Network and Industrial Network Infrastructure SHALL use Ethernet/IP over redundant fibre-optic links at 100 Mbps minimum, with each PLC supporting dual Ethernet ports for network redundancy. | — | interface, scada, plc-to-network, session-210 |
| IFC-DEFS-033 | The interface between Industrial Network Infrastructure and Master SCADA Server and Historian SHALL use OPC-UA with a maximum data transfer latency of 500 ms from PLC scan completion to historian storage, supporting a minimum of 800 tags at 1-second polling. | — | interface, scada, network-to-server, session-210 |
| IFC-DEFS-034 | The interface between Master SCADA Server and Operator HMI Workstations SHALL deliver screen updates within 1 second of server data receipt, with alarm pop-ups displayed within 2 seconds of PLC alarm detection as required by SYS-REQS-008. | — | interface, scada, server-to-hmi, session-210 |
| IFC-DEFS-035 | The interface between Master SCADA Server and Remote Telemetry and Reporting Gateway SHALL export compliance parameters via a read-only OPC-UA endpoint across the DMZ firewall, with the gateway pulling data at 1-minute intervals and formatting reports per state regulatory template. | — | interface, scada, server-to-telemetry, session-210 |
| IFC-DEFS-036 | The interface between Distributed PLC Network and all process subsystem controllers SHALL exchange I/O data via hardwired signals (4-20 mA, 24 VDC digital) terminating at PLC I/O racks, with each process area PLC hosting sufficient local I/O capacity plus 20% spare for expansion. | — | interface, scada, plc-to-process, session-210 |
| IFC-DEFS-037 | The interface between Emergency Diesel Generator Set and Main Utility Power Switchgear SHALL use an automatic transfer switch rated for the full generator capacity (1.5 MVA) with open-transition transfer completing within 2 seconds and mechanical interlocking to prevent paralleling of generator and utility supplies. | — | interface, electrical-power, generator-to-switchgear, session-210 |
| IFC-DEFS-038 | The interface between Main Utility Power Switchgear and Motor Control Centres SHALL use XLPE/SWA cables rated for the full MCC bus capacity with protection coordination providing fault clearance within 200 ms at the MCC incoming breaker and discrimination with downstream motor starters. | — | interface, electrical-power, switchgear-to-mcc, session-210 |
| IFC-DEFS-039 | The interface between Main Utility Power Switchgear and Uninterruptible Power Supply System SHALL provide a dedicated 415 V feeder with automatic static bypass, and the UPS output SHALL feed a separate critical power distribution board serving SCADA, PLCs, and analysers. | — | interface, electrical-power, switchgear-to-ups, session-210 |
| IFC-DEFS-040 | The interface between Motor Control Centres and Distributed PLC Network SHALL provide hardwired 24 VDC digital I/O for motor run/stop/fault status and VFD speed feedback as a 4-20 mA analog signal, plus Ethernet/IP for extended diagnostics and speed setpoint. | — | interface, electrical-power, mcc-to-plc, session-210 |
| IFC-DEFS-041 | The interface between Sludge Scraper and Hopper System (Sedimentation) and Sludge Holding and Thickening Tank SHALL convey sludge by gravity through 200 mm diameter pipework with isolation valves, delivering sludge at 2-3% solids at a maximum flow rate of 50 m3/hr per basin. | — | interface, sludge, sed-to-holding, session-210 |
| IFC-DEFS-042 | The interface between Filter-to-Waste System (Filtration) and Sludge Holding and Thickening Tank SHALL convey spent backwash water at up to 200 m3 per backwash event through a dedicated 300 mm pipeline, with flow metering to track return water volumes. | — | interface, sludge, filter-to-holding, session-210 |
| IFC-DEFS-043 | The interface between Sludge Holding and Thickening Tank and Mechanical Sludge Dewatering System SHALL deliver thickened sludge at 2-4% solids via progressing cavity pump at a controlled feed rate of 10-25 m3/hr, with inline solids density measurement for dewatering optimisation. | — | interface, sludge, holding-to-dewatering, session-210 |
| IFC-DEFS-044 | The interface between Supernatant and Filtrate Return System and Raw Water Intake Subsystem headworks SHALL return supernatant and filtrate at a maximum combined flow rate not exceeding 10% of concurrent plant inflow, with turbidity monitoring triggering automatic shutoff if return turbidity exceeds 50 NTU. | — | interface, sludge, return-to-headworks, session-210 |
| IFC-DEFS-045 | The interface between Chlorine Contact Tank (Disinfection) and Treated Water Clear Well SHALL convey disinfected water by gravity through a 900 mm diameter pipeline, with the clear well inlet designed to distribute flow evenly across the full width of the receiving cell to minimise short-circuiting. | — | interface, treated-water, cct-to-clearwell, session-210 |
| IFC-DEFS-046 | The interface between Treated Water Clear Well and High-Lift Distribution Pump Station SHALL provide independent suction mains from each clear well cell to a common suction header, with isolation valves permitting single-cell maintenance without interrupting distribution pumping. | — | interface, treated-water, clearwell-to-pumps, session-210 |
| IFC-DEFS-047 | The interface between High-Lift Distribution Pump Station and the distribution network SHALL include a Woltman flow meter on the common discharge header (accuracy ±1% of reading at flows from 100-700 L/s), a pressure sustaining valve, and connection points for the surge protection vessel. | — | interface, treated-water, pumps-to-network, session-210 |
| IFC-DEFS-048 | The interface between Treated Water Quality Monitoring Station and SCADA and Instrumentation Subsystem SHALL transmit all analyser readings via 4-20 mA to the distribution area PLC, with instrument fault and calibration status as digital inputs, and SHALL support remote calibration initiation from SCADA. | — | interface, treated-water, monitoring-to-scada, session-210 |
| IFC-DEFS-049 | The interface between Powdered Activated Carbon Feed System and Rapid Mix Chamber SHALL inject PAC slurry at 5-50 mg/L through a dedicated injection quill positioned upstream of the coagulant injection point, with a minimum 2-second contact time before coagulant addition to maximise adsorption of taste-and-odour compounds before floc formation. Rationale: Powdered activated carbon must contact raw water before coagulant to adsorb taste-and-odour compounds (geosmin, MIB) while they are still dissolved. Once coagulant is added, PAC particles are encapsulated in floc and adsorption capacity drops. The 2-second minimum separation is derived from AWWA guidance for PAC application upstream of coagulation, which requires sufficient mixing time for initial adsorption before floc formation begins. | Test | interface, chemical-dosing, session-213 |
| Ref | Requirement | V&V | Tags |
|---|---|---|---|
| ARC-DECISIONS-001 | ARC: Chemical Storage and Dosing Subsystem — Centralised chemical building with distributed injection points. All bulk chemical storage is co-located in a single chemical building with secondary containment, shared ventilation, and unified safety monitoring, rather than distributing storage to each treatment process. Injection points are at the respective process locations (rapid-mix, flocculation inlet, contact tank, clearwell). This topology minimises the number of chlorine gas handling areas to one (reducing gas detection coverage requirements), consolidates spill containment infrastructure, and enables a single emergency scrubber to serve the chlorine room. The trade-off is longer chemical piping runs (up to 150m for PAC to raw water intake), which requires consideration of slurry settling velocity for PAC and polymer gel formation in deadleg sections. Vacuum chlorine feed was selected over direct-pressure feed to ensure inherent safety: any downstream leak draws air inward rather than releasing chlorine gas. | — | architecture, chemical-dosing, session-207 |
| ARC-DECISIONS-002 | ARC: Disinfection Subsystem — Dual-barrier UV+chlorine CT design. UV reactors are placed upstream of chlorine contact to provide primary Cryptosporidium barrier independent of chemical disinfection, while the chlorine contact tank provides the primary bacterial and viral inactivation barrier plus distribution system residual. This sequence was chosen over chlorine-first because UV efficacy is not affected by turbidity in the 0.05-0.3 NTU post-filtration range, while placing UV downstream of chlorine would require UV dose correction for chlorine demand. The 3+1 reactor configuration provides N+1 redundancy at 75% capacity, matching the plant's single-train-offline design basis. Medium-pressure lamps were selected over low-pressure high-output for their broader germicidal spectrum and smaller footprint despite higher energy cost (~0.04 kWh/m3 vs 0.02 kWh/m3). | — | architecture, disinfection, session-207 |
| ARC-DECISIONS-003 | ARC: Filtration Subsystem — Dual-media gravity filtration with combined air-water backwash was selected over mono-media or membrane filtration. Dual-media (anthracite/sand) provides depth filtration with longer filter runs and lower headloss development than mono-sand, reducing backwash frequency and water consumption. Gravity filters were chosen over pressure filters for the 50 ML/d capacity due to lower capital cost, easier media inspection, and simpler maintenance access. Combined air-water backwash with a separate air scour blower was chosen over surface wash or water-only backwash to achieve thorough media cleaning without the mechanical complexity of rotating surface wash arms. The 8-cell N+1 configuration with two parallel trains provides redundancy for backwash and maintenance while limiting individual cell filtration rate to 7 m/hr maximum, staying within the AWWA recommended range. Membrane filtration was rejected due to higher energy consumption (0.15 kWh/m3 for membranes vs 0.02 kWh/m3 for gravity media) and greater chemical cleaning requirements, inconsistent with the SYS-REQS-010 energy target. | — | architecture, filtration, session-208 |
| ARC-DECISIONS-004 | ARC: Sedimentation Subsystem — Inclined plate settlers were selected over conventional horizontal-flow basins or dissolved air flotation. Inclined plates achieve equivalent settling performance in one-third the footprint by reducing effective settling depth to 50 mm, critical for the constrained plant site. Three parallel basins with N+1 redundancy provide 35 ML/d with one basin offline, aligned with SYS-REQS-005. Chain-and-flight scrapers were chosen over travelling bridge scrapers due to lower headroom requirements and simpler mechanical drives. DAF was considered but rejected for this application because raw water turbidity is consistently below 50 NTU and algae loading is seasonal rather than chronic, making the energy cost of DAF air saturation systems unjustifiable against the SYS-REQS-010 energy efficiency target. | — | architecture, sedimentation, session-208 |
| ARC-DECISIONS-005 | ARC: Coagulation and Flocculation — Separate rapid-mix and multi-stage flocculation chosen over hydraulic inline static mixers. Three-stage tapered energy provides superior floc formation for the variable NOM and turbidity profile of the source water (5–200 NTU seasonal range). The streaming current detector provides closed-loop coagulant dose control to handle rapid raw water quality changes that a flow-proportional-only scheme cannot track. Dedicated coagulation pH loop avoids coupling with finished-water pH adjustment. Parallel trains (N+1) ensure maintenance without capacity reduction. | — | architecture, coag-floc, session-209 |
| ARC-DECISIONS-006 | ARC: Raw Water Intake — VFD-controlled vertical turbine pumps selected over fixed-speed centrifugals to enable continuous flow modulation matching plant demand without throttling losses. 3+1 pump arrangement chosen to meet SYS-REQS-005 (N-1 redundancy at average demand). Electromagnetic flow meters chosen over ultrasonic for superior accuracy (±0.5% vs ±1-2%) on this pipe size, critical because the master flow signal drives all downstream chemical dosing proportionality. Raw water quality monitoring placed at intake rather than headworks to maximise early warning time (3-5 min transport lag advantage). | — | architecture, raw-water-intake, session-209 |
| ARC-DECISIONS-007 | ARC: SCADA and Instrumentation — Distributed PLC architecture with centralised historian chosen over monolithic DCS. Each process area has an independent PLC executing local control logic, which ensures the plant continues operating in degraded mode when the SCADA server or network backbone fails. Hot-standby SCADA servers with OPC-UA aggregation provide the centralised view without being a single point of failure. IEC 62443 zone-and-conduit model chosen for cybersecurity because the plant must provide read-only telemetry to external agencies without exposing the OT network. Alternative considered: unified DCS platform — rejected because vendor lock-in limits future expansion and does not naturally support the DMZ architecture required for regulatory reporting. | — | architecture, scada, session-210 |
| ARC-DECISIONS-008 | ARC: Electrical Power and Emergency Generation — Single diesel generator with UPS bridge chosen over dual-generator N+1 redundancy. The 50 ML/d plant's critical load (~1.1 MW) fits within a single 1.5 MVA generator with adequate margin. The UPS bridges the 10-second transfer gap for SCADA and instrumentation. Dual utility feeds at 11 kV with automatic bus transfer provide the first tier of resilience before diesel starts. N+1 generation was considered but rejected: the plant is not classified as a critical national infrastructure site, and the additional capital and maintenance cost of a second generator is not justified when the utility supply has >99.95% historical availability. The load-shedding strategy (non-critical areas shed first) ensures 35 ML/d minimum capacity on generator alone. | — | architecture, electrical-power, session-210 |
| ARC-DECISIONS-009 | ARC: Sludge Handling — Belt filter press dewatering selected over centrifuge and drying beds. Belt presses achieve the 18% solids target with lower energy consumption and capital cost than centrifuges at this plant scale (approximately 1.5 dry tonnes/day average sludge production). Drying beds were rejected due to land area requirements and weather dependence in the plant's climate. Gravity thickening before dewatering reduces polymer consumption by concentrating feed solids from <1% to 2-4%. Supernatant return limited to 10% of inflow to avoid recycling Cryptosporidium oocysts and overwhelming coagulation. | — | architecture, sludge, session-210 |
| ARC-DECISIONS-010 | ARC: Treated Water Storage and Distribution Pumping — Two-cell clear well with VFD-controlled high-lift pumps selected over elevated tower storage. Below-ground clear well provides superior CT contact time, earthquake resilience, and aesthetic acceptability compared to an elevated tank. VFD pumps maintain constant pressure across the wide demand range (200-600 L/s) without pressure-reducing valves, saving 8-12% energy versus fixed-speed pumps with throttling. Hydropneumatic surge vessel selected for transient protection because the distribution main is 3.2 km to the first service reservoir — long enough for damaging water hammer if a pump trips at full speed without protection. Fire reserve weir ensures 1 ML is always available regardless of operational drawdown. | — | architecture, treated-water, session-210 |
flowchart TB n0["component<br>Alum Bulk Storage and Metering System"] n1["component<br>Polymer Preparation and Feed System"] n2["component<br>Chlorine Gas Storage and Feed System"] n3["component<br>Caustic Soda Storage and Feed System"] n4["component<br>Fluorosilicic Acid Storage and Feed System"] n5["component<br>Powdered Activated Carbon Feed System"] n6["component<br>Chemical Containment and Emergency Safety System"] n7["component<br>Chemical Dosing Control System"] n8["component<br>Alum Storage"] n9["component<br>Polymer Prep and Feed"] n10["component<br>Chlorine Gas Storage and Feed"] n11["component<br>Caustic Soda Storage and Feed"] n12["component<br>Fluorosilicic Acid Feed"] n13["component<br>PAC Feed System"] n14["component<br>Containment and Safety"] n15["component<br>Dosing Control System"] n15 -->|dose setpoint| n8 n15 -->|dose setpoint| n9 n15 -->|dose setpoint| n10 n15 -->|dose setpoint| n11 n15 -->|dose setpoint| n12 n15 -->|dose setpoint| n13 n14 -->|gas detection/shutdown| n10 n14 -->|safety interlock| n15
Chemical Storage and Dosing — Internal
flowchart TB n0["component<br>UV Disinfection Reactors"] n1["component<br>Chlorine Contact Tank"] n2["component<br>CT Compliance Monitor"] n3["component<br>Residual Analyser Network"] n0 -->|UV-treated water| n1 n3 -->|residual readings| n2 n2 -->|CT calculation| n1
Disinfection — Internal
flowchart TB n0["component<br>Dual-Media Gravity Filter Cell"] n1["component<br>Filter Underdrain and Support Gravel"] n2["component<br>Backwash Supply System"] n3["component<br>Air Scour Blower System"] n4["component<br>Filter Control and Instrumentation"] n5["component<br>Filter-to-Waste System"] n6["external<br>Sedimentation Subsystem"] n7["external<br>Treated Water Storage"] n8["external<br>SCADA System"] n9["external<br>Sludge Handling"] n6 -->|Settled water| n0 n0 -->|Filtered effluent| n7 n2 -->|Backwash water| n0 n3 -->|Scour air| n1 n4 -->|Valve commands| n0 n4 -->|Pump commands| n2 n4 -->|Blower start/stop| n3 n4 -->|FTW valve control| n5 n5 -->|Waste water| n9 n4 -->|Modbus TCP data| n8 n0 -->|Turbidity/headloss| n4
Filtration — Internal
flowchart TB n0["component<br>Inclined Plate Settler Module"] n1["component<br>Sludge Scraper and Hopper System"] n2["component<br>Basin Inlet Distribution"] n3["component<br>Effluent Launder and Weir"] n4["external<br>Coagulation/Flocculation"] n5["external<br>Filtration Subsystem"] n6["external<br>Sludge Handling"] n4 -->|Flocculated water| n2 n2 -->|Distributed flow| n0 n0 -->|Settled water| n3 n3 -->|To filter influent| n5 n1 -->|Sludge collection| n0 n1 -->|Withdrawn sludge| n6
Sedimentation — Internal
flowchart TB n0["component<br>Rapid Mix Chamber"] n1["component<br>Flocculation Basin Train"] n2["component<br>Flocculator Drive Assembly"] n3["component<br>Streaming Current Detector"] n4["component<br>Coagulation pH Control"] n0 -->|Coagulated water| n1 n2 -->|Mechanical drive| n1 n3 -->|SCI feedback| n0 n4 -->|pH trim signal| n0
Coagulation and Flocculation — Internal v2
flowchart TB n0["component<br>Intake Screen and Trashrack"] n1["component<br>Raw Water Pumping Station"] n2["component<br>Flow Measurement and Control"] n3["component<br>Raw Water Quality Monitor"] n0 -->|Screened water| n1 n1 -->|Raw water via rising main| n2 n3 -->|Quality data to SCADA| n2
Raw Water Intake — Internal
flowchart TB n0["component<br>Master SCADA Server and Historian"] n1["component<br>Distributed PLC Network"] n2["component<br>Process Instrumentation Field Network"] n3["component<br>Operator HMI Workstations"] n4["component<br>Industrial Network Infrastructure"] n5["component<br>Remote Telemetry and Reporting Gateway"] n2 -->|4-20mA HART and Modbus RTU| n1 n1 -->|Ethernet/IP fibre backbone| n4 n4 -->|OPC-UA process data| n0 n0 -->|HMI screens and alarms| n3 n3 -->|Operator commands| n4 n0 -->|Telemetry and reports| n5
SCADA and Instrumentation — Internal v2
flowchart TB n0["component<br>Main Utility Power Switchgear"] n1["component<br>Emergency Diesel Generator Set"] n2["component<br>Motor Control Centres"] n3["component<br>Uninterruptible Power Supply"] n4["component<br>Power Distribution and Protection"] n1 -->|1.5 MVA emergency power| n0 n0 -->|415V to MCCs| n2 n0 -->|415V to UPS| n3 n4 -->|Protection coordination| n0
Electrical Power and Emergency Generation — Internal
| Entity | Hex Code | Description |
|---|---|---|
| Air Scour Blower System | D6D51218 | Positive displacement rotary lobe blower system providing low-pressure air at 50 m/hr superficial velocity for filter media agitation during backwash. Two blowers (duty/standby) each rated at 1500 Nm3/hr at 0.5 bar gauge. Air distribution via the underdrain system orifices ensures uniform scour across the full filter floor area. Operates during the air-scour and combined air-water wash phases of the backwash sequence. Includes inlet filter, silencer, non-return valve, and discharge header with isolation valves per filter cell. Interlocked with backwash sequence controller to prevent air delivery when water level is below media surface. |
| Alum Bulk Storage and Metering System | D6A53018 | Aluminium sulphate (liquid alum, ~48% w/w Al2(SO4)3) coagulant storage and feed system for a 50 ML/d surface water treatment plant. Comprises two 30,000L FRP bulk storage tanks with level instrumentation, truck unloading pad with containment, and three progressive-cavity metering pumps (2 duty, 1 standby) rated 0–120 L/hr each. Dose is flow-proportional via SCADA with streaming-current analyser trim. Alum is injected at the rapid-mix basin inlet. Operating dose range 20–80 mg/L depending on raw water turbidity (5–500 NTU seasonal range). |
| Backwash Supply System | 55F73218 | Provides filtered water for backwashing filter cells at 60 m/hr rising rate. Comprises two 100% duty backwash pumps (one duty, one standby) rated at 900 m3/hr each at 15m TDH, backwash rate controller with Venturi flow measurement, backwash supply header with motorised isolation valves per filter cell, and a 200 m3 backwash water storage tank fed from the clear well. Backwash sequence is automated: drain-down, air scour, combined air-water wash, high-rate water-only rinse, slow rinse, filter-to-waste. Total backwash duration approximately 20 minutes per cell. |
| Caustic Soda Storage and Feed System | D6B73018 | Sodium hydroxide (50% w/w NaOH solution) storage and dosing system for post-disinfection pH correction. Two 10,000L polyethylene bulk tanks with secondary containment, truck unloading with dry-break couplings. Two diaphragm metering pumps (1 duty, 1 standby) rated 0–60 L/hr inject caustic into the post-chlorination clearwell outlet to raise finished water pH to 7.0–7.5 target range, controlling Langelier Saturation Index for distribution system corrosion control. Dose range 5–25 mg/L, paced by inline pH analyser feedback. |
| Chemical Containment and Emergency Safety System | 55F77859 | Integrated chemical spill containment, gas detection, and emergency response system for a water treatment plant chemical building housing chlorine gas, alum, caustic soda, fluorosilicic acid, and PAC. Includes: secondary containment berms and sumps for all liquid chemical storage areas rated for 110% largest tank volume; chlorine gas detection sensors (electrochemical, 0–10 ppm range) at 6 locations in chlorine room and adjacent corridors; emergency chlorine scrubber (caustic soda spray tower, 50 kg/hr neutralisation capacity); forced exhaust ventilation (20 air changes/hour in chlorine room); emergency shutdown interlocks that close cylinder valves on gas detection >1 ppm; audible/visual alarms and SCADA annunciation. |
| Chemical Dosing Control System | 55F77A18 | Distributed chemical dose control system integrating SCADA with local PLCs and online water quality analysers for automated dose-pacing of all chemical feeds at a 50 ML/d water treatment plant. Implements flow-proportional base dosing for alum, chlorine, caustic, and fluoride with trim from streaming-current analyser (coagulant), chlorine residual analyser (disinfectant), pH analyser (caustic), and fluoride analyser (fluoride). PAC dosing is manually initiated with flow-proportional control. System includes cascade control loops, alarm setpoints for over/under-dosing, chemical inventory tracking via tank level, and automatic switchover logic for duty/standby pumps on flow or pressure fault. All control signals 4–20 mA analog or Modbus RTU to SCADA. |
| Chemical Storage and Dosing Subsystem | DE853219 | Centralised chemical storage facility serving all treatment stages. Aluminium sulphate: 2x 40,000L FRP bulk storage tanks with secondary containment bund (110% capacity), diaphragm metering pumps (4 duty + 2 standby, 0-200 L/h each). Polymer: dry polymer (polyacrylamide) make-up and aging system with 3-stage preparation (wetting, mixing, aging) producing 0.1-0.5% solution, progressing cavity metering pumps. Sodium hypochlorite: 2x 20,000L HDPE tanks with forced ventilation enclosure, peristaltic metering pumps. Lime slurry: lime silo (50 tonne), slaker, and slurry storage with agitator, positive displacement pumps. Sodium bisulphite: 5,000L tank for emergency dechlorination. All chemical areas have spill containment, safety showers, eyewash stations, and gas detection where required. Chemical delivery truck unloading area with spill containment pad. |
| Chlorine Contact Tank | CE851218 | Reinforced concrete baffled contact tank providing minimum 30-minute detention time at peak flow (580 L/s) for chlorine disinfection CT compliance. Over-under baffled design with 10 passes achieving T10/T ratio of 0.65 minimum (validated by tracer study). Two parallel tanks each sized for 50% of peak flow, allowing one tank offline for maintenance. Tank volume approximately 1,050 cubic metres each. Inlet receives chlorinated water from Chlorine Gas Storage and Feed System ejector. Equipped with online chlorine residual analysers at inlet and outlet, and turbidity monitor at inlet for CT calculation. |
| Chlorine Gas Storage and Feed System | 47D73059 | Gaseous chlorine storage, evaporation, and feed system for primary disinfection at a 50 ML/d water treatment plant. Stores chlorine in 900 kg cylinders (6 on-line, 6 reserve) in a dedicated chlorine room with forced ventilation. Two vacuum-operated chlorinators (1 duty, 1 standby) rated 0–50 kg/day each draw chlorine through a vacuum regulator, with water-powered ejector injection into the chlorine contact tank inlet. Residual target 0.5–2.0 mg/L free chlorine after 30-minute CT contact. System includes automatic cylinder switchover, residual analyser feedback loop, and vacuum-fail safety shutdown. Chlorine room maintained at negative pressure relative to adjacent spaces. |
| Coagulation and Flocculation Subsystem | 54953218 | Two-stage chemical treatment process converting dissolved and colloidal contaminants into settleable floc. Rapid mix chamber (G value 300/s, 30-second detention) injects aluminium sulphate coagulant (dose range 5-60 mg/L depending on raw water turbidity) and cationic polymer as coagulant aid (0.1-0.5 mg/L). Three-stage tapered flocculation basins with variable-speed paddle mixers providing G values of 50, 30, and 15/s over 30-minute total detention time. pH correction with lime or caustic soda to maintain optimal coagulation pH of 6.5-7.5. Jar testing laboratory guides daily dose optimisation. Redundant chemical feed pumps (peristaltic for polymer, diaphragm for alum) with calibration tubes. |
| Coagulation pH Control System | 55B73A18 | Dedicated pH monitoring and control loop for optimising alum coagulation in a municipal water treatment plant. Comprises dual-redundant pH analysers (glass electrode type, 0-14 pH range, ±0.05 accuracy) installed at the rapid mix chamber outlet, a PID controller integrated with SCADA, and a trim signal to the caustic soda dosing pump. Maintains coagulation pH within the optimal range of 6.2-7.0 for aluminium sulphate coagulation, adjusting for seasonal alkalinity variations. Includes automatic analyser cleaning (air-blast or ultrasonic) on a 4-hour cycle to prevent electrode fouling by coagulant residue. |
| CT Compliance Monitoring System | 51F77B58 | Automated CT (concentration × time) compliance calculation and recording system for regulatory disinfection verification. Continuously calculates achieved CT value from online chlorine residual (mg/L) at contact tank outlet multiplied by validated T10 contact time (minutes) at current flow rate. Compares achieved CT against required CT from EPA Surface Water Treatment Rule tables based on water temperature and pH. Logs CT values at 15-minute intervals and generates automatic alarms when achieved CT falls below 90% of required CT. Interfaces with SCADA for display and regulatory reporting. |
| Disinfection Residual Analyser Network | 54E77018 | Network of online chlorine residual analysers providing continuous free and total chlorine measurement at key disinfection process points: pre-UV (1 analyser), contact tank inlet (1), contact tank outlet (2 — duty and verification), and clearwell outlet (1). Amperometric membrane-type analysers with range 0-5 mg/L free chlorine, accuracy ±0.02 mg/L at 1.0 mg/L. Each analyser has sample conditioning (constant-head overflow, temperature compensation) and automatic reagent-less calibration. 4-20 mA output to SCADA with sample flow alarm on loss of sample. |
| Disinfection Subsystem | 54F73A58 | Dual-barrier disinfection combining UV irradiation and chlorination. UV system: medium-pressure UV reactors (3 duty + 1 standby) providing minimum 40 mJ/cm2 dose validated to USEPA UV Disinfection Guidance Manual for 3-log Cryptosporidium inactivation. UV transmittance monitoring and dose-pacing based on flow and UVT. Chlorination: sodium hypochlorite (12% NaOCl) dosing at two points — pre-filter (breakpoint chlorination 0-3 mg/L for ammonia removal when present) and post-filter (target 1.0-1.5 mg/L free chlorine residual). Chlorine contact chamber with serpentine baffling (T10/T ratio >0.7) providing minimum 30-minute contact time at peak flow for 4-log virus CT compliance. Online chlorine residual analysers at contact chamber inlet and outlet. Dechlorination capability (sodium bisulphite) for process discharge. |
| Distributed PLC Network | 51B77218 | Network of 8-12 process area PLCs (Allen-Bradley ControlLogix or Siemens S7-1500 class) controlling all treatment process areas in a 50 ML/day water treatment plant. Each PLC handles one or two process areas (intake, coagulation, filtration, etc.) with local I/O racks. PLCs communicate via redundant fibre-optic Ethernet/IP backbone at 100 Mbps. Each PLC executes control logic independently — plant continues operating in degraded mode if SCADA server connection is lost. Scan time <100ms for safety interlocks, <500ms for process loops. |
| Distribution Network Surge Protection System | 56973058 | Hydraulic surge protection system for the treated water distribution header, preventing water hammer damage from rapid pump starts/stops or valve closures. Comprises a hydropneumatic surge vessel (2 m3 capacity, pre-charged to 80% of steady-state pressure) and surge anticipation valves on the pump discharge header. Air compressor maintains vessel pre-charge. Pressure transducers trigger alarms if transient pressures exceed 150% of steady-state. System designed per AWWA M11 guidelines for transmission mains surge analysis. |
| Dual-Media Gravity Filter Cell | CE841018 | Reinforced concrete filter box containing 600mm anthracite over 300mm silica sand media bed on a Leopold-type underdrain. Each cell provides 150 m3/hr at 6 m/hr filtration rate with 2.5m water depth above media. Designed for turbidity reduction from 2 NTU settled water to <0.1 NTU filtered effluent per SDWA Surface Water Treatment Rule. Includes troughs for backwash waste collection, filter gullet for influent distribution, and effluent weir. Typical plant has 6-8 cells for N+1 redundancy. |
| Electrical Power and Emergency Generation Subsystem | 54F73218 | Dual utility power feed (2x 13.8kV from separate distribution feeders) to main switchgear with automatic transfer between feeds. Step-down transformers (2x 2.5 MVA, 13.8kV to 4.16kV for high-lift pumps; 2x 1.5 MVA, 13.8kV to 600V for general plant loads). Emergency standby diesel generator (2.5 MW Caterpillar or MTU unit) with 500L integrated fuel tank plus 20,000L external double-wall tank providing 72-hour operation at essential load. Automatic transfer switch (ATS) with <10 second transfer time. Uninterruptible power supply (UPS) for SCADA, instrumentation, and emergency lighting (30 kVA, 30-minute battery backup). Motor control centres with combination starters and variable frequency drives for major pumps. Power factor correction capacitor bank. Lightning and surge protection. Emergency generator exercises weekly under load via automatic exerciser. |
| Emergency Diesel Generator Set | D7D71018 | Standby diesel generator rated at 1.5 MVA providing emergency power to critical treatment processes during utility outage. Turbocharged diesel engine with 500-litre day tank and 10,000-litre bulk fuel storage providing 72 hours of continuous operation at 75% load. Automatic transfer switch detects utility loss and starts generator within 10 seconds as required by SYS-REQS-006. Includes coolant system, exhaust silencer, vibration isolators, and battery starting system. Located in a dedicated acoustic enclosure adjacent to the main switchroom. |
| Filter Control and Instrumentation Panel | 55F77A18 | Per-filter-cell PLC-based control panel managing filter operation modes: filtering, backwash sequence, filter-to-waste, and offline. Monitors filter headloss via differential pressure transmitter across the media bed (range 0-3m, alarm at 2.5m), individual filtered water turbidity via online laser nephelometer (range 0-10 NTU, alarm at 0.3 NTU, shutdown at 1.0 NTU), filter effluent flow via electromagnetic flowmeter, and water level via ultrasonic level transmitter. Controls influent and effluent motorised butterfly valves, backwash valve, drain valve, and filter-to-waste valve. Communicates with central SCADA via Modbus TCP over plant Ethernet. Implements automatic filter-to-waste on return to service until turbidity falls below 0.15 NTU for 15 consecutive minutes. |
| Filter Underdrain and Support Gravel System | CE851018 | Leopold Type S or equivalent nozzle-less underdrain system installed at the base of each gravity filter cell. Comprises HDPE underdrain blocks with integral orifices for uniform backwash water and air distribution, overlaid with graded gravel support layers (300mm total, 4 layers from 25mm to 3mm). Collects filtered water uniformly across the entire filter floor area at less than 0.3 m/s approach velocity. Must withstand combined air-water backwash at 60 m/hr water plus 50 m/hr air without media migration or gravel disruption. |
| Filter-to-Waste System | 55B73218 | Diverts initial filtered water production to the sludge handling system after each backwash cycle until filtered water turbidity stabilises below 0.15 NTU for 15 minutes. Comprises a motorised butterfly valve on the filter-to-waste header, piped to the backwash waste holding tank. Flow capacity matches full filter production rate of 150 m3/hr per cell. Prevents post-backwash turbidity spike from reaching the clear well and distribution system. Activated automatically by the filter control panel on backwash completion and deactivated on turbidity clearance. Typical waste volume 15-30 m3 per filter-to-waste event. |
| Filtration Subsystem | DFB73218 | Eight dual-media gravity filters (each 6m x 12m bed area) containing 600mm anthracite (1.2mm effective size) over 300mm silica sand (0.5mm effective size) over 300mm gravel support. Design filtration rate 8 m/h, maximum 12 m/h. Filter-to-waste capability after backwash. Automated backwash sequence: air scour (60 m/h for 3 min), combined air-water wash (60 m/h air, 15 m/h water for 3 min), high-rate water wash (40 m/h for 8 min). Backwash water from elevated storage tank or dedicated backwash pumps. Head loss monitoring (0-2.5m differential) triggers backwash. Filtered water turbidity target <0.1 NTU with individual filter effluent turbidimeters. Post-filter granular activated carbon contactors (2 units, 15-minute EBCT) for taste, odour, and organic micropollutant removal. |
| Flocculation Basin Train | D6C41218 | Three-stage tapered-energy flocculation basin train in a municipal water treatment plant. Each train consists of three sequential chambers with progressively decreasing mixing intensity: Stage 1 (G=60-80 s⁻¹), Stage 2 (G=30-50 s⁻¹), Stage 3 (G=10-20 s⁻¹). Equipped with horizontal-shaft paddle flocculators driven through reduction gearboxes. Total hydraulic retention time of 20-30 minutes at design flow. Baffled to prevent short-circuiting. The plant has a minimum of 3 parallel trains to allow one train offline for maintenance while maintaining rated capacity. Produces well-formed, settleable floc for downstream sedimentation basins. |
| Flocculator Drive and Gearbox Assembly | DED51018 | Variable-speed flocculator drive system for a municipal water treatment plant. Each flocculation stage has a horizontal-shaft paddle mixer driven by a helical gear reducer and a variable frequency drive (VFD). Motor sizes range from 2.2 kW (Stage 3, low-energy) to 7.5 kW (Stage 1, high-energy). VFDs allow continuous adjustment of paddle tip speed from 0.15 to 0.9 m/s to achieve the required velocity gradient profile. Drives are mounted above the water line on concrete plinths with stainless steel shafts extending through stuffing-box seals. Each drive includes torque monitoring and over-speed protection. |
| Flow Measurement and Control System | 55F77A18 | Raw water flow measurement and control system at the intake of a 50 ML/d municipal water treatment plant. Comprises a full-bore electromagnetic flow meter (DN600-DN900) on the rising main with accuracy of ±0.5% of reading, a modulating butterfly valve for flow throttling, and a flow totaliser integrated with SCADA. Provides the master flow signal used for flow-proportional chemical dosing across the entire plant. Includes redundant flow measurement (duty/standby) to maintain dosing accuracy during meter maintenance. |
| Fluorosilicic Acid Storage and Feed System | D7973059 | Hydrofluorosilicic acid (H2SiF6, 23% w/w) storage and metering system for community water fluoridation. Single 5,000L HDPE day tank with secondary containment rated for 110% volume, supplied from 1,000L IBCs. Two chemical-resistant diaphragm metering pumps (1 duty, 1 standby) rated 0–15 L/hr dose fluoride into the clearwell outlet. Target fluoride residual 0.7 mg/L ±0.1 per public health guidelines. Flow-proportional dosing with online fluoride analyser verification. All wetted parts Hastelloy C-276 or PVDF due to extreme corrosivity of HFS acid. |
| High-Lift Distribution Pump Station | 56F53018 | Variable-speed centrifugal pump station drawing from the clear well and delivering treated water into the distribution network at 350-700 kPa. Four pumps (3 duty, 1 standby) each rated at 200 L/s at 50 m TDH, driven by 132 kW motors with VFDs. Pressure sustaining valves prevent overpressure. Suction-side isolation, non-return valves, and discharge headers with Woltman flow meters. Pump selection and speed controlled by SCADA based on downstream pressure and reservoir levels. Designed for continuous 24/7 operation with pump rotation to equalise wear. |
| Inclined Plate Settler Module | CE841018 | Stacked polypropylene inclined plate packs installed in reinforced concrete sedimentation basins. Plates inclined at 60 degrees from horizontal with 50 mm spacing, providing effective settling area of 2500 m2 per basin. Removes flocculated particles by reducing effective settling depth to 50 mm, enabling surface overflow rates of 8 to 12 m/hr versus 1.5 m/hr for conventional horizontal flow basins. Each basin handles 450 m3/hr with two basins operating in parallel for N+1 redundancy. Plates are modular for removal and cleaning during annual maintenance shutdowns. |
| Industrial Network Infrastructure | 50A57018 | Redundant fibre-optic Ethernet backbone (ring topology with RSTP/MRP for sub-50ms failover) connecting all PLC racks, SCADA servers, and network switches in the water treatment plant. Managed Layer 2/3 switches (Cisco IE or Hirschmann) in each MCC room. DMZ firewall separating the OT network (IEC 62443 zone) from the corporate IT network — only the historian mirror port crosses this boundary. Network monitoring via SNMP with bandwidth and latency alarms. Cybersecurity includes port security, VLAN segmentation per process area, and intrusion detection. |
| Intake Screen and Trashrack Assembly | CE971018 | Combined coarse trashrack (75mm bar spacing) and travelling band screen (6mm aperture) at the raw water intake of a 50 ML/d municipal water treatment plant. The trashrack protects the travelling screen from large debris (logs, branches). The travelling band screen provides fine screening with automatic backwash, removing algae, leaves, and aquatic organisms. Located at the source water body (river or reservoir) intake structure, typically 2-3 metres below minimum water level. Includes a screen differential level sensor to trigger automatic cleaning when headloss exceeds 150 mm. |
| Main Utility Power Switchgear | D6B51018 | 11 kV/415 V main switchboard receiving dual utility power feeds for a 50 ML/day water treatment plant. Total connected load approximately 2.5 MW. Includes incoming circuit breakers, bus-tie, power factor correction capacitor bank, metering, and protection relays. Automatic bus transfer between utility feeds within 100 ms. Supplies power to 6 motor control centres distributed across the plant. Located in the main electrical switchroom with arc-flash rated enclosures. |
| Master SCADA Server and Historian | 50A47218 | Redundant server pair running SCADA/HMI software (e.g., Citect, Ignition, or VTScada) for a 50 ML/day water treatment plant. Provides real-time process visualisation, alarm management, trend logging, and historical data archival. Receives data from ~800 I/O points via OPC-UA from PLCs. Stores 12 months online history at 1-second resolution for critical parameters and 10-second for routine. Hot-standby failover within 5 seconds. Located in the main control room with UPS-backed power. |
| Mechanical Sludge Dewatering System | 56D51018 | Belt filter press or centrifuge system dewatering thickened alum sludge from 2-4% to a minimum of 18% solids for the 50 ML/day water treatment plant. Consists of two belt filter presses (one duty, one standby) each rated at 25 m3/hr sludge feed. Includes polymer conditioning (cationic polyelectrolyte), gravity drainage zone, low-pressure and high-pressure squeeze zones. Dewatered cake conveyed to storage hopper. Filtrate returned to plant headworks. Polymer demand approximately 3-5 kg/dry tonne. Housed in an enclosed sludge building with odour control. |
| Motor Control Centres | D4A55018 | Six motor control centres (MCCs) distributed across the water treatment plant process areas (intake, chemical, filters, distribution, sludge, general services). Each MCC contains motor starters (DOL for <7.5 kW, VFD for larger drives), feeder circuit breakers, control transformers, and PLC I/O racks. MCCs rated for 415 V three-phase with form 3b segregation. Typical MCC serves 15-30 motor loads plus auxiliary circuits. Communication to SCADA via Ethernet/IP from local PLC in each MCC. |
| Operator HMI Workstations | D4ED7038 | Three operator workstations in the main control room plus one in the chemical building and one mobile tablet for field rounds. Each workstation runs SCADA client software providing process mimic screens, alarm lists, trend displays, and report generation. Dual-monitor configuration in the control room showing overview and detail screens simultaneously. Role-based access control with operator, supervisor, and engineer levels. Alarm annunciation via on-screen pop-ups and external audible/visual alarm horn. Supports direct setpoint entry and manual override of automatic control loops. |
| Polymer Preparation and Feed System | 56D53218 | Anionic polyacrylamide flocculant aid preparation and dosing system. Dry polymer is loaded into a volumetric dry feeder, hydrated in a three-stage aging tank system (make-up, aging, feed) with 45-minute total aging time, and dosed by two peristaltic metering pumps (1 duty, 1 standby) at 0–8 L/hr. Polymer concentration 0.1–0.5% w/v solution. Applied at flocculation basin inlet to enhance floc formation. Dose range 0.1–0.5 mg/L, adjusted by jar test results and settling performance. |
| Powdered Activated Carbon Feed System | D6D51218 | Powdered activated carbon (PAC) slurry preparation and injection system for seasonal taste-and-odour control during algal bloom events. 20-tonne bulk silo with screw conveyor feeding a gravimetric dry feeder into a slurry mix tank with continuous agitation. Two progressive-cavity slurry pumps (1 duty, 1 standby) inject 5–10% w/v carbon slurry at the raw water intake or rapid-mix basin. Dose range 5–50 mg/L depending on geosmin/MIB concentrations (action threshold 10 ng/L). System is intermittent — activated only during T&O events, typically 30–90 days per year. |
| Power Distribution and Protection Network | 44A53018 | Cascaded protection system including the 11 kV incoming protection, 415 V distribution boards, sub-distribution boards for lighting and small power, and the protection relay coordination scheme. Includes earth fault protection, overcurrent protection with time-graded discrimination, and residual current devices on socket circuits. Cable reticulation uses XLPE/SWA cables in buried duct and above-ground ladder tray. Earthing system uses copper earth grid with electrode resistance below 1 ohm. Lightning protection via air terminals on elevated structures. |
| Process Instrumentation Field Network | 54855018 | Approximately 200 field instruments (turbidimeters, pH analysers, flow meters, level transmitters, pressure transmitters, dissolved oxygen probes, chlorine analysers) distributed across the 50 ML/day water treatment plant. Instruments connect to local PLC I/O via 4-20mA HART, Modbus RTU on RS-485, or Profibus PA depending on area. Includes instrument calibration infrastructure and instrument air supply for pneumatic actuated valves. Field wiring is routed through IP66 junction boxes with surge protection on exposed runs. |
| Rapid Mix Chamber | D6C51018 | Concrete rapid mix chamber at the head of a municipal water treatment plant. Receives raw water from the intake pumping station and coagulant (liquid aluminium sulphate) from the chemical dosing subsystem via injection quills. Equipped with a vertical-shaft, high-speed mechanical mixer (typically 300-900 rpm) providing a velocity gradient (G) of 600-1000 s⁻¹ and a detention time of 15-30 seconds. The chamber ensures instantaneous and uniform dispersion of coagulant throughout the raw water stream, initiating destabilisation of colloidal particles. Designed for a peak flow of 150 ML/d with provision for polymer co-injection during high-turbidity events. |
| Raw Water Intake Subsystem | 5E851018 | Intake structure on river bank with coarse bar screens (75mm spacing) and travelling band screens (6mm mesh) removing large debris and aquatic organisms. Low-lift pumps (3x 50% duty centrifugal, 700 L/s each) draw water from a submerged intake crib located 30m offshore at 3m depth. Includes raw water flow measurement (electromagnetic flowmeter), raw water quality monitoring (turbidity, temperature, pH, conductivity), and intake channel level control. Designed for seasonal flow variation from 0.5 to 5.0 NTU raw turbidity typical, with storm events up to 200 NTU. Fish exclusion screens comply with DFO requirements. |
| Raw Water Pumping Station | DED71018 | Low-lift raw water pumping station for a 50 ML/d municipal water treatment plant. Comprises 3 duty + 1 standby vertical turbine or submersible pumps, each rated at approximately 290 L/s at 15-25m TDH. Pumps are VFD-controlled for flow modulation to match plant demand. The wet well is sized for a minimum 5-minute retention at maximum pump rate. Includes level measurement (ultrasonic), pump vibration monitoring, and automatic duty rotation. Delivers raw water to the rapid mix chamber at the plant headworks via a dedicated rising main. |
| Raw Water Quality Monitoring Station | 54E55218 | Online raw water quality monitoring station at the intake of a 50 ML/d municipal water treatment plant. Continuously measures turbidity (0-4000 NTU, nephelometric), pH (0-14, ±0.05), temperature (0-40°C, ±0.1°C), conductivity (0-2000 µS/cm), and dissolved oxygen. Sampling via a side-stream arrangement with <60 second transport lag from the intake point. All instruments transmit 4-20 mA or Modbus RTU to SCADA. Provides early warning of raw water quality changes (storm events, algal blooms, upstream discharge events) to enable proactive chemical dosing adjustments. |
| Remote Telemetry and Reporting Gateway | 51E57A18 | Outstation gateway providing remote access and regulatory reporting for the water treatment plant. Transmits key operational parameters (flow, turbidity, chlorine residual, pH) to the utility's central SCADA system and to the state drinking water authority's compliance portal via secure VPN over 4G/fibre WAN link. Generates automated daily compliance reports (CT log, turbidity profile, chemical usage). Supports remote alarm notification via SMS/email to on-call operators. Cellular backup link activates on primary WAN failure within 30 seconds. |
| SCADA and Instrumentation Subsystem | 54E57318 | Supervisory Control and Data Acquisition system providing centralised monitoring and control of all plant processes. Architecture: redundant SCADA servers (hot standby) running on Windows Server with historian database (minimum 5-year data retention at 1-second scan rate for critical parameters). Three operator workstations in central control room with dual 27-inch displays each. Distributed I/O via 8 remote PLCs (Allen-Bradley ControlLogix or Siemens S7-1500) communicating over redundant fibre-optic Ethernet ring (EtherNet/IP or PROFINET). Field instrumentation includes: 45+ turbidimeters, 20+ pH analysers, 15+ chlorine residual analysers, 30+ pressure transmitters, 25+ flow meters, 20+ level transmitters, 10+ dissolved oxygen probes. Alarm management system with ISA-18.2 compliant alarm rationalisation. Remote access via secure VPN for on-call operators. Interface to corporate LIMS (Laboratory Information Management System) for manual sample results. OPC-UA gateway for data exchange with municipal asset management system. |
| Sedimentation Basin Inlet Distribution System | CE853010 | Perforated baffle wall and energy dissipation chamber at the inlet end of each sedimentation basin. Receives flocculated water from the flocculation outlet channel and distributes it uniformly across the full cross-sectional area of the basin to prevent short-circuiting. Baffle wall has 150 mm diameter orifices at calculated spacings to achieve velocity variation of less than 10% across the basin width. Includes a 2 m long energy dissipation zone with submerged weir to reduce inlet velocity from 0.3 m/s to below 0.05 m/s, preventing floc breakup. |
| Sedimentation Effluent Launder and Weir System | CE853010 | V-notch weir plates on multiple collection launders spanning the outlet end of each sedimentation basin above the inclined plate settlers. Launders are spaced at 3 m centres with V-notch weirs at 150 mm spacing providing a maximum weir overflow rate of 10 m3/hr per metre of weir length. Launders discharge to a common outlet channel connecting to the filter influent distribution channel. Weir crests are adjustable plus or minus 10 mm with stainless steel levelling bolts to ensure uniform flow collection and prevent localised high-velocity zones that could carry over settled floc. |
| Sedimentation Subsystem | 4C853218 | Four rectangular horizontal-flow sedimentation basins (each 60m x 15m x 4.5m water depth) with total detention time of 4 hours at design flow. Inclined plate settlers (60-degree angle, 50mm spacing) in the final third of each basin increase effective settling area by factor of 6. Chain-and-flight sludge collectors traverse basin floor at 0.3 m/min, directing settled sludge to hopper at inlet end. Surface overflow rate 1.2 m/h at average flow. Scum collection troughs at outlet weirs. Settled water turbidity target <2 NTU before filtration. Sludge withdrawal via timed valve sequence to sludge handling subsystem. |
| Sludge Cake Storage and Disposal Hopper | CE851058 | Enclosed storage hopper receiving dewatered sludge cake at 18-22% solids from the belt filter press. Capacity of 60 m3 providing approximately 5 days of storage before truck haul-off. Live-bottom screw discharge for loading into hook-lift bins or trucks. Level monitoring and truck loading position indicator connected to SCADA. Sludge is classified as non-hazardous waste and disposed at a licensed landfill or used for land rehabilitation. |
| Sludge Handling Subsystem | 56951218 | Receives waste streams from sedimentation basins (alum sludge at 0.5-2% solids), filter backwash water (0.01-0.05% solids), and chemical drain-down water. Sludge equalization tank (200 m3) with submersible mixers to blend intermittent sludge withdrawals. Gravity thickener (12m diameter circular tank) concentrating sludge from 1% to 3-4% solids, with slow-rotating rake mechanism and supernatant return to plant headworks. Mechanical dewatering: 2x belt filter presses (2m belt width, 250 kg DS/m/h capacity) producing cake at 18-22% solids. Polymer conditioning prior to dewatering (cationic flocculant, 3-6 kg/tonne DS). Dewatered sludge conveyed to covered storage bins (3-day capacity) for truck removal to licensed disposal facility. Filtrate and thickener supernatant returned to plant inlet. Odour control via covered tanks and biofilter. |
| Sludge Holding and Thickening Tank | DE851018 | Concrete sludge holding tank receiving alum sludge from sedimentation basin hoppers and backwash waste from filters at a 50 ML/day water treatment plant. Two-stage design: primary holding with slow-speed paddle stirrer to prevent septicity, and gravity thickening zone with lamella plates. Combined volume of 400 m3 providing 3 days of sludge storage at peak production. Supernatant decanted and returned to plant headworks. Thickened sludge at 2-4% solids feeds the dewatering system. Level and density instrumentation reports to SCADA. |
| Sludge Scraper and Hopper System | DFD71218 | Chain-and-flight sludge collection mechanism operating on the floor of each sedimentation basin. Two parallel chains drive HDPE flights at 0.3 m/min along the basin floor, scraping settled sludge toward pyramidal sludge hoppers at the inlet end. Each basin has 4 hoppers with 60-degree side slopes and pneumatically actuated mud valves. Sludge is withdrawn by gravity and hydrostatic head to the sludge holding tank at 2 to 3% solids concentration. Desludging occurs automatically every 4 hours based on sludge blanket depth measured by ultrasonic sludge level detector. |
| Streaming Current Detector | 54F54218 | Online streaming current detector (SCD) for real-time coagulation control in a municipal water treatment plant. Installed downstream of the rapid mix chamber, continuously measures the streaming current index (SCI) of coagulated water as a proxy for particle surface charge. Output range typically -3 to +3 SCI units. The instrument provides feedback to the SCADA system to trim coagulant dose in response to raw water quality changes (turbidity spikes, pH shifts, seasonal NOM variation). Sampling via a continuous side-stream with <30 second transport lag. Requires daily calibration against jar test results. |
| Supernatant and Filtrate Return System | 55D71008 | Pumping system returning supernatant from sludge thickening and filtrate from dewatering back to the plant headworks for re-treatment. Designed to limit return flow to less than 10% of plant inflow to avoid overloading the treatment train. Includes flow measurement, equalization sump (20 m3), and variable-speed submersible pumps (2 duty, 1 standby). Return quality monitoring includes turbidity and pH to detect abnormal sludge conditions before re-introduction to the process. |
| Treated Water Clear Well | CE851018 | Below-ground reinforced concrete clear well reservoir storing disinfected treated water downstream of the chlorine contact tank at a 50 ML/day water treatment plant. Two cells (each 5 ML effective volume) with common inlet and independent outlets to distribution pumps. Provides CT contact time buffer, equalisation between treatment rate and distribution demand, and fire reserve storage. Baffled internally to prevent short-circuiting. Level measurement via guided wave radar. Overflow to stormwater with chlorine neutralisation. Hatches, ventilation, and access per AS/NZS 3500 for potable water structures. |
| Treated Water Quality Monitoring Station | 54E75058 | Online water quality monitoring station on the clear well outlet and distribution header measuring final treated water quality before entering the distribution network. Instruments include online turbidimeter (<0.1 NTU range), free chlorine residual analyser, pH analyser, fluoride ion-selective electrode, and temperature sensor. All instruments provide 4-20 mA output to the distribution area PLC and SCADA trending. Auto-sampler for composite and grab samples to satisfy regulatory reporting. Sample conditioning panels with constant head overflow to maintain representative sample flow. |
| Treated Water Storage and Distribution Pumping Subsystem | DEF53018 | Two below-ground reinforced concrete clearwells (each 5 ML capacity, 10 ML total) providing minimum 4-hour storage at average demand. Clearwells are divided into cells with baffling to prevent short-circuiting and maintain chlorine contact time. Level monitoring with ultrasonic level transmitters. High-lift pump station: 4x vertical turbine pumps (2x 500 L/s at 60m TDH for Zone 1, 2x 350 L/s at 85m TDH for Zone 2) with variable frequency drives. Surge protection via combination air/vacuum valves and surge anticipation valves on discharge headers. Pressure sustaining valves for multi-zone distribution. Flow measurement on each discharge header (electromagnetic flowmeters). Emergency interconnection with neighbouring utility via bidirectional metered connection. |
| Uninterruptible Power Supply System | D5D71218 | Online double-conversion UPS system providing clean, uninterrupted power to SCADA servers, PLC racks, critical instrumentation, and emergency lighting during the 10-second transfer gap between utility loss and diesel generator start. Rated at 60 kVA with sealed lead-acid battery bank providing 30 minutes of autonomy at full load. Includes static bypass switch, input/output isolation transformers, and battery monitoring with predictive failure alerting. Feeds critical 415V and 240V distribution boards. |
| UV Disinfection Reactor | D7F73058 | Medium-pressure ultraviolet disinfection reactor system providing minimum 40 mJ/cm2 validated dose for 4-log Cryptosporidium inactivation per USEPA UV Disinfection Guidance Manual. Four reactors (3 duty, 1 standby) each rated for 200 L/s, installed in series-parallel configuration in a dedicated UV building downstream of the filters and upstream of the chlorine contact tank. Each reactor contains multiple medium-pressure amalgam UV lamps with automatic intensity monitoring (UV sensors at 254nm), automatic sleeve cleaning (mechanical wiper system), and dose-pacing based on flow rate and UV transmittance. UVT range 85-98% for treated surface water. |
| Water Treatment Plant | 57F73A59 | Municipal water treatment facility processing raw surface water from a river intake to potable drinking water quality. Capacity 50 million litres per day serving approximately 200,000 population. Treatment train: raw water intake with screening, coagulation/flocculation with chemical dosing, sedimentation basins, rapid sand and activated carbon filtration, UV and chlorine disinfection, treated water storage and high-lift pumping to distribution network. Includes sludge handling (thickening, dewatering, disposal), SCADA supervisory control and data acquisition system, on-site chemical storage, laboratory for water quality analysis, and emergency power generation. Regulated under Safe Drinking Water Act with continuous turbidity, chlorine residual, and pH monitoring. Operates 24/7 with redundant treatment trains for maintenance without service interruption. |
| Component | Belongs To |
|---|---|
| Raw Water Intake Subsystem | Water Treatment Plant |
| Coagulation and Flocculation Subsystem | Water Treatment Plant |
| Sedimentation Subsystem | Water Treatment Plant |
| Filtration Subsystem | Water Treatment Plant |
| Disinfection Subsystem | Water Treatment Plant |
| Chemical Storage and Dosing Subsystem | Water Treatment Plant |
| Treated Water Storage and Distribution Pumping Subsystem | Water Treatment Plant |
| Sludge Handling Subsystem | Water Treatment Plant |
| SCADA and Instrumentation Subsystem | Water Treatment Plant |
| Electrical Power and Emergency Generation Subsystem | Water Treatment Plant |
| Alum Bulk Storage and Metering System | Chemical Storage and Dosing Subsystem |
| Polymer Preparation and Feed System | Chemical Storage and Dosing Subsystem |
| Chlorine Gas Storage and Feed System | Chemical Storage and Dosing Subsystem |
| Caustic Soda Storage and Feed System | Chemical Storage and Dosing Subsystem |
| Fluorosilicic Acid Storage and Feed System | Chemical Storage and Dosing Subsystem |
| Powdered Activated Carbon Feed System | Chemical Storage and Dosing Subsystem |
| Chemical Containment and Emergency Safety System | Chemical Storage and Dosing Subsystem |
| Chemical Dosing Control System | Chemical Storage and Dosing Subsystem |
| Chlorine Contact Tank | Disinfection Subsystem |
| UV Disinfection Reactor | Disinfection Subsystem |
| CT Compliance Monitoring System | Disinfection Subsystem |
| Disinfection Residual Analyser Network | Disinfection Subsystem |
| Dual-Media Gravity Filter Cell | Filtration Subsystem |
| Filter Underdrain and Support Gravel System | Filtration Subsystem |
| Backwash Supply System | Filtration Subsystem |
| Air Scour Blower System | Filtration Subsystem |
| Filter Control and Instrumentation Panel | Filtration Subsystem |
| Filter-to-Waste System | Filtration Subsystem |
| Inclined Plate Settler Module | Sedimentation Subsystem |
| Sludge Scraper and Hopper System | Sedimentation Subsystem |
| Sedimentation Basin Inlet Distribution System | Sedimentation Subsystem |
| Sedimentation Effluent Launder and Weir System | Sedimentation Subsystem |
| Rapid Mix Chamber | Coagulation and Flocculation Subsystem |
| Flocculation Basin Train | Coagulation and Flocculation Subsystem |
| Flocculator Drive and Gearbox Assembly | Coagulation and Flocculation Subsystem |
| Streaming Current Detector | Coagulation and Flocculation Subsystem |
| Coagulation pH Control System | Coagulation and Flocculation Subsystem |
| Intake Screen and Trashrack Assembly | Raw Water Intake Subsystem |
| Raw Water Pumping Station | Raw Water Intake Subsystem |
| Flow Measurement and Control System | Raw Water Intake Subsystem |
| Raw Water Quality Monitoring Station | Raw Water Intake Subsystem |
| Master SCADA Server and Historian | SCADA and Instrumentation Subsystem |
| Distributed PLC Network | SCADA and Instrumentation Subsystem |
| Process Instrumentation Field Network | SCADA and Instrumentation Subsystem |
| Operator HMI Workstations | SCADA and Instrumentation Subsystem |
| Industrial Network Infrastructure | SCADA and Instrumentation Subsystem |
| Remote Telemetry and Reporting Gateway | SCADA and Instrumentation Subsystem |
| Main Utility Power Switchgear | Electrical Power and Emergency Generation Subsystem |
| Emergency Diesel Generator Set | Electrical Power and Emergency Generation Subsystem |
| Motor Control Centres | Electrical Power and Emergency Generation Subsystem |
| Uninterruptible Power Supply System | Electrical Power and Emergency Generation Subsystem |
| Power Distribution and Protection Network | Electrical Power and Emergency Generation Subsystem |
| Sludge Holding and Thickening Tank | Sludge Handling Subsystem |
| Mechanical Sludge Dewatering System | Sludge Handling Subsystem |
| Sludge Cake Storage and Disposal Hopper | Sludge Handling Subsystem |
| Supernatant and Filtrate Return System | Sludge Handling Subsystem |
| Treated Water Clear Well | Treated Water Storage and Distribution Pumping Subsystem |
| High-Lift Distribution Pump Station | Treated Water Storage and Distribution Pumping Subsystem |
| Treated Water Quality Monitoring Station | Treated Water Storage and Distribution Pumping Subsystem |
| Distribution Network Surge Protection System | Treated Water Storage and Distribution Pumping Subsystem |
| From | To |
|---|---|
| Chemical Dosing Control System | Alum Bulk Storage and Metering System |
| Chemical Dosing Control System | Polymer Preparation and Feed System |
| Chemical Dosing Control System | Chlorine Gas Storage and Feed System |
| Chemical Dosing Control System | Caustic Soda Storage and Feed System |
| Chemical Dosing Control System | Fluorosilicic Acid Storage and Feed System |
| Chemical Dosing Control System | Powdered Activated Carbon Feed System |
| Chemical Containment and Emergency Safety System | Chlorine Gas Storage and Feed System |
| Chemical Containment and Emergency Safety System | Chemical Dosing Control System |
| Chemical Dosing Control System | SCADA and Instrumentation Subsystem |
| Alum Bulk Storage and Metering System | Coagulation and Flocculation Subsystem |
| Polymer Preparation and Feed System | Coagulation and Flocculation Subsystem |
| Chlorine Gas Storage and Feed System | Disinfection Subsystem |
| Caustic Soda Storage and Feed System | Treated Water Storage and Distribution Pumping Subsystem |
| Fluorosilicic Acid Storage and Feed System | Treated Water Storage and Distribution Pumping Subsystem |
| UV Disinfection Reactor | Chlorine Contact Tank |
| CT Compliance Monitoring System | Chlorine Contact Tank |
| Disinfection Residual Analyser Network | CT Compliance Monitoring System |
| Disinfection Residual Analyser Network | SCADA and Instrumentation Subsystem |
| UV Disinfection Reactor | Filtration Subsystem |
| Backwash Supply System | Dual-Media Gravity Filter Cell |
| Air Scour Blower System | Filter Underdrain and Support Gravel System |
| Filter Control and Instrumentation Panel | Dual-Media Gravity Filter Cell |
| Filter Control and Instrumentation Panel | Backwash Supply System |
| Filter Control and Instrumentation Panel | Air Scour Blower System |
| Filter Control and Instrumentation Panel | Filter-to-Waste System |
| Filter-to-Waste System | Sludge Handling Subsystem |
| Filter Control and Instrumentation Panel | SCADA and Instrumentation Subsystem |
| Sedimentation Subsystem | Dual-Media Gravity Filter Cell |
| Dual-Media Gravity Filter Cell | Treated Water Storage and Distribution Pumping Subsystem |
| Sludge Scraper and Hopper System | Sludge Handling Subsystem |
| Sedimentation Basin Inlet Distribution System | Coagulation and Flocculation Subsystem |
| Sedimentation Effluent Launder and Weir System | Filtration Subsystem |
| Sedimentation Basin Inlet Distribution System | Inclined Plate Settler Module |
| Inclined Plate Settler Module | Sedimentation Effluent Launder and Weir System |
| Sludge Scraper and Hopper System | Inclined Plate Settler Module |
| Rapid Mix Chamber | Flocculation Basin Train |
| Flocculator Drive and Gearbox Assembly | Flocculation Basin Train |
| Streaming Current Detector | Rapid Mix Chamber |
| Streaming Current Detector | SCADA and Instrumentation Subsystem |
| Coagulation pH Control System | Rapid Mix Chamber |
| Coagulation pH Control System | Chemical Storage and Dosing Subsystem |
| Intake Screen and Trashrack Assembly | Raw Water Pumping Station |
| Raw Water Pumping Station | Flow Measurement and Control System |
| Flow Measurement and Control System | Rapid Mix Chamber |
| Raw Water Quality Monitoring Station | SCADA and Instrumentation Subsystem |
| Flow Measurement and Control System | SCADA and Instrumentation Subsystem |
| Process Instrumentation Field Network | Distributed PLC Network |
| Distributed PLC Network | Industrial Network Infrastructure |
| Industrial Network Infrastructure | Master SCADA Server and Historian |
| Master SCADA Server and Historian | Operator HMI Workstations |
| Master SCADA Server and Historian | Remote Telemetry and Reporting Gateway |
| Operator HMI Workstations | Industrial Network Infrastructure |
| Main Utility Power Switchgear | Motor Control Centres |
| Main Utility Power Switchgear | Uninterruptible Power Supply System |
| Emergency Diesel Generator Set | Main Utility Power Switchgear |
| Motor Control Centres | Distributed PLC Network |
| Power Distribution and Protection Network | Main Utility Power Switchgear |
| Uninterruptible Power Supply System | Distributed PLC Network |
| Uninterruptible Power Supply System | Master SCADA Server and Historian |
| Sludge Holding and Thickening Tank | Mechanical Sludge Dewatering System |
| Mechanical Sludge Dewatering System | Sludge Cake Storage and Disposal Hopper |
| Sludge Holding and Thickening Tank | Supernatant and Filtrate Return System |
| Mechanical Sludge Dewatering System | Supernatant and Filtrate Return System |
| Treated Water Clear Well | High-Lift Distribution Pump Station |
| High-Lift Distribution Pump Station | Distribution Network Surge Protection System |
| Treated Water Clear Well | Treated Water Quality Monitoring Station |
| Chlorine Contact Tank | Treated Water Clear Well |
| Powdered Activated Carbon Feed System | Rapid Mix Chamber |
| Component | Output |
|---|---|
| Alum Bulk Storage and Metering System | metered alum solution at 0-120 L/hr |
| Polymer Preparation and Feed System | aged polymer solution at 0.1-0.5% w/v |
| Chlorine Gas Storage and Feed System | chlorine solution via vacuum ejector at 0-50 kg/day |
| Caustic Soda Storage and Feed System | metered caustic soda solution at 0-60 L/hr |
| Fluorosilicic Acid Storage and Feed System | metered fluoride solution at 0-15 L/hr |
| Powdered Activated Carbon Feed System | PAC slurry at 5-10% w/v concentration |
| Chemical Containment and Emergency Safety System | safety alarms and emergency shutdown signals |
| Chemical Dosing Control System | dose setpoints and pump speed commands via 4-20mA/Modbus |
| Chlorine Contact Tank | disinfected water with minimum CT compliance |
| UV Disinfection Reactor | UV-treated water at minimum 40 mJ/cm2 dose |
| CT Compliance Monitoring System | real-time CT compliance status and 15-min logged records |
| Disinfection Residual Analyser Network | continuous chlorine residual readings at 5 process points |
| Dual-Media Gravity Filter Cell | filtered water at less than 0.1 NTU from settled water at 2 NTU nominal |
| Filter Underdrain and Support Gravel System | uniform flow collection across filter floor and uniform backwash distribution |
| Backwash Supply System | backwash water at 60 m/hr rising rate for 20-minute automated backwash sequence |
| Air Scour Blower System | low-pressure scour air at 50 m/hr for media agitation during backwash |
| Filter Control and Instrumentation Panel | valve commands, turbidity alarms, headloss data, and filter status to SCADA |
| Filter-to-Waste System | diverted post-backwash water to waste until turbidity stabilises below 0.15 NTU |
| Inclined Plate Settler Module | settled water with turbidity below 2 NTU |
| Sludge Scraper and Hopper System | concentrated sludge at 2 to 3 percent solids to sludge holding tank |
| Sedimentation Effluent Launder and Weir System | settled water to filter influent channel at max 10 m3/hr/m weir loading |
| Rapid Mix Chamber | coagulated water with destabilised colloids |
| Flocculation Basin Train | well-formed settleable floc at 2-5 mm diameter |
| Raw Water Pumping Station | screened raw water at 580-870 L/s |
| Raw Water Quality Monitoring Station | multi-parameter water quality data at 60s intervals |
| Master SCADA Server and Historian | real-time process visualisation, alarm management, and 12-month historical data archive at 1s resolution |
| Distributed PLC Network | autonomous process control with <100ms safety interlock scan time and <500ms process loop execution |
| Process Instrumentation Field Network | continuous measurement data from ~200 field instruments via 4-20mA HART, Modbus RTU, and Profibus PA |
| Operator HMI Workstations | process mimic displays, alarm annunciation, trend analysis, and operator control interface |
| Industrial Network Infrastructure | redundant Ethernet backbone with sub-50ms failover and IEC 62443 cybersecurity zone segmentation |
| Remote Telemetry and Reporting Gateway | regulatory compliance reports, remote alarm notification, and central SCADA telemetry via secure VPN |
| Main Utility Power Switchgear | 415V three-phase power from dual 11kV utility feeds with <100ms bus transfer |
| Emergency Diesel Generator Set | 1.5 MVA emergency power within 10 seconds of utility loss for 72 hours continuous |
| Motor Control Centres | controlled motor starting, VFD speed control, and local I/O integration for 6 process areas |
| Uninterruptible Power Supply System | 60 kVA clean power for SCADA, PLCs, and critical instrumentation with 30-minute battery autonomy |
| Power Distribution and Protection Network | coordinated overcurrent and earth fault protection with <1 ohm earthing resistance |
| Sludge Holding and Thickening Tank | thickened sludge at 2-4% solids and decanted supernatant for return to headworks |
| Mechanical Sludge Dewatering System | dewatered sludge cake at minimum 18% solids and polymer-conditioned filtrate |
| Sludge Cake Storage and Disposal Hopper | stored sludge cake for truck haul-off at 5-day buffer capacity |
| Supernatant and Filtrate Return System | metered return flow at less than 10% of plant inflow to headworks |
| Treated Water Clear Well | 10 ML buffered treated water storage with CT contact time compliance and fire reserve |
| High-Lift Distribution Pump Station | treated water at 350-700 kPa to distribution network at up to 600 L/s total capacity |
| Treated Water Quality Monitoring Station | continuous final water quality data for turbidity, chlorine residual, pH, and fluoride |
| Distribution Network Surge Protection System | transient pressure attenuation limiting surges to below 150% of steady-state |