System

Sixth system in the decomposition programme. {{entity:Water Treatment Plant}} classified as {{hex:57F73A59}} — a municipal facility processing 50 ML/d of river surface water to potable standard for 200,000 people. Civil domain, first in the programme. Decomposition status: scaffolded. Ten subsystems identified, ten stakeholder requirements and fifteen system-level requirements written with full traceability. Zero orphans at scaffold baseline.

Decomposition

The treatment train drives the architecture. Water flows through {{entity:Raw Water Intake Subsystem}} ({{hex:5E851018}}), {{entity:Coagulation and Flocculation Subsystem}} ({{hex:54953218}}), {{entity:Sedimentation Subsystem}} ({{hex:4C853218}}), {{entity:Filtration Subsystem}} ({{hex:DFB73218}}), and {{entity:Disinfection Subsystem}} ({{hex:54F73A58}}) before reaching {{entity:Treated Water Storage and Distribution Pumping Subsystem}} ({{hex:DEF53018}}). Three support subsystems operate across the train: {{entity:Chemical Storage and Dosing Subsystem}} ({{hex:DE853219}}) feeds coagulant, polymer, lime, and hypochlorite to multiple injection points; {{entity:Sludge Handling Subsystem}} ({{hex:56951218}}) receives waste from sedimentation and filter backwash; {{entity:SCADA and Instrumentation Subsystem}} ({{hex:54E57318}}) provides supervisory control plant-wide. {{entity:Electrical Power and Emergency Generation Subsystem}} ({{hex:54F73218}}) supplies all subsystems with dual-feed utility power and 72-hour diesel backup.

flowchart TB
  RWI["Raw Water Intake"]
  CF["Coagulation and Flocculation"]
  SED["Sedimentation"]
  FIL["Filtration"]
  DIS["Disinfection"]
  CSD["Chemical Storage and Dosing"]
  TWS["Treated Water Storage and Pumping"]
  SLH["Sludge Handling"]
  SCA["SCADA and Instrumentation"]
  EPG["Electrical Power and Emergency Gen"]
  RWI -->|Raw water| CF
  CF -->|Flocculated water| SED
  SED -->|Settled water| FIL
  FIL -->|Filtered water| DIS
  DIS -->|Disinfected water| TWS
  CSD -->|Coagulant and polymer| CF
  CSD -->|Chlorine| DIS
  SED -->|Settled sludge| SLH
  FIL -->|Backwash waste| SLH
  SCA -->|Supervisory control| RWI
  SCA -->|Supervisory control| CF
  EPG -->|Power| RWI
  EPG -->|Power| CF

Analysis

Cross-domain comparison found 93.75% Jaccard similarity between the {{entity:Disinfection Subsystem}} and the nuclear reactor programme’s {{entity:Class 1E Power Supply Subsystem}} ({{hex:54D73858}}). Both are safety-critical subsystems requiring high reliability, redundancy, and continuous monitoring — in one case to prevent core damage, in the other to prevent pathogen passage to the distribution network. The {{entity:Sequential Events Controller}} from the nuclear domain also shares 30 of 32 traits, reinforcing that the disinfection subsystem demands the same rigour in requirements around degraded-mode operation and verification testing that the nuclear programme applies. This should inform subsystem requirement depth in the next session.

Lint returned 2 low-severity findings — both ontological ambiguity between the WTP (abstract compositional entity) and its physical subsystems (filtration, SCADA). These are correct: the plant is a system of systems, while individual subsystems contain tangible physical equipment. Both acknowledged.

Requirements

Ten stakeholder requirements span six stakeholder groups: the utility operator ({{stk:STK-NEEDS-001}}, {{stk:STK-NEEDS-002}}), regulatory authority ({{stk:STK-NEEDS-003}}), plant operators ({{stk:STK-NEEDS-004}}), public health ({{stk:STK-NEEDS-005}}), environmental authority ({{stk:STK-NEEDS-006}}), maintenance ({{stk:STK-NEEDS-007}}), finance ({{stk:STK-NEEDS-008}}), emergency management ({{stk:STK-NEEDS-009}}), and worker safety ({{stk:STK-NEEDS-010}}).

Fifteen system requirements derive from these. Key specifications: finished water turbidity ≤0.3 NTU 95th percentile ({{sys:SYS-REQS-001}}), UV dose ≥40 mJ/cm² with CT ≥6 mg·min/L ({{sys:SYS-REQS-003}}), 1-minute monitoring intervals across all compliance points ({{sys:SYS-REQS-004}}), N−1 redundancy maintaining 35 ML/d ({{sys:SYS-REQS-005}}), emergency power transfer within 10 seconds ({{sys:SYS-REQS-006}}), chlorine gas detection at 1 ppm with 5-second alarm response ({{sys:SYS-REQS-007}}), ISA-18.2 alarm management at ≤6 alarms/operator/hour ({{sys:SYS-REQS-015}}). All 15 system requirements trace to stakeholder requirements. All 25 requirements are baselined as SCAFFOLD-2026-03-16.

Next

The next session should begin Flow B decomposition, prioritising the {{entity:Disinfection Subsystem}} given its safety criticality and the cross-domain insight from nuclear systems. The dual-barrier UV/chlorine architecture needs component-level decomposition, subsystem requirements (particularly degraded-mode performance when one UV reactor is offline), interface requirements between the UV system and the chlorine contact chamber, and verification entries. The {{entity:Filtration Subsystem}} should follow, as it is the second-highest-risk process with complex backwash sequencing and direct impact on pathogen barrier credit.