---
name: evolv-biological-process-engineering
description: Engineer biological wastewater process behavior for EVOLV nodes. Use when implementing or reviewing reactor/settler biology, ASM-style kinetics, oxygen demand, nitrification/denitrification, sludge behavior, calibration assumptions, and biologically plausible constraints.
---

# EVOLV Biological Process Engineering

## Mission
Keep EVOLV biological process models physically plausible, calibratable, and operationally useful.

## Harness Execution Contract
- Ground changes in current biology/state variables and connected control topics.
- Define invariants before edits:
  - biological mass-balance intent is preserved
  - model assumptions remain explicit and traceable
  - degraded behavior remains availability-first and bounded
- Validate with deterministic tests and representative operating scenarios.

## Scope
- `nodes/reactor/`
- `nodes/settler/`
- `nodes/pumpingStation/` (where biology interacts with flow/retention assumptions)
- Related reaction modules and utilities under `nodes/*/src/`

## Workflow
1. Identify biological state variables, units, and expected ranges.
2. Map kinetic pathways (growth, decay, transfer, conversion) and rate constraints.
3. Verify oxygen/temperature dependencies and fallback behavior.
4. Check integration stability for configured time-step and resolution choices.
5. Confirm outputs remain interpretable for control and dashboard consumers.

## Standards
- Keep state vectors explicit and index mappings documented.
- Avoid silent clipping/coercion without test coverage and rationale.
- Preserve topic/payload compatibility unless migration is defined.
- Record calibration assumptions and required field data.

## Test Expectations
Cover:
- kinetic branch behavior under representative and boundary conditions
- non-negativity and boundedness safeguards
- temperature and oxygen transfer sensitivity
- time-step/resolution edge behavior and stability warnings

## Deliverables
Return:
- biological assumptions and constraints used
- changed files/tests and evidence
- calibration notes and unresolved biological uncertainties

Decision interview triggers:
- altered biology assumptions that can change plant behavior
- parameter/default changes with startup or compliance impact
- compatibility breaks in biological outputs or topic contracts