Decision question
How would an IED-related change to sludge treatment affect ammonia loading, process headroom and the future role of the ASP and N.BAFF?
Granular process evidence challenged assumed capacity constraints and informed a lower-cost site strategy
An Industrial Emissions Directive (IED) related review of sludge treatment required the client to understand how reduced digester throughput could affect ammonia loading and future asset needs. Five temporary Optimisers challenged earlier capacity assumptions, confirmed the continuing role of the N.BAFF and informed a controlled four-of-six-cell strategy with potential annual OPEX savings of approximately £275,000.
Site / asset snapshot
Site context
Large regional wastewater treatment works
Main treatment
Primary settlement, carbonaceous ASP, final settlement and six-cell nitrifying N.BAFF
Project stage
IED-related sludge strategy and whole-site capacity assessment
Monitoring scope
Five Optimisers across primary settlement, ASP and N.BAFF locations
Process and monitoring points
Five Optimisers and mapped site instruments aligned ammonia loading and removal across primary settlement, the ASP and N.BAFF.
Works inlet
Primary settlement
Carbonaceous ASP
Final settlement
Nitrifying N.BAFF
Final effluent
Five optimisers spanning works inlet, primary settlement, carbonaceous ASP and N.BAFF monitoring points
Project need
Primary driver
Understand how IED-related sludge-treatment changes would affect the liquid process and future asset strategy
Evidence gap
Earlier assessments overstated digester liquor loads and did not resolve the actual role or capacity of the ASP and N.BAFF
Why it mattered
The strategy risked unnecessary capital or the wrong asset decision if it relied on unverified loading assumptions
Approved evidence: asset context and control opportunity
Granular monitoring and revised process modelling changed the understanding of loading, capacity and the future asset strategy
BI-Zen delivery
Deployment
Five Optimisers across primary settlement, the carbonaceous ASP and N.BAFF
Measured
COD, ammonia, nitrate, nitrite, DO and supporting process parameters
Aligned with
Flow, SCADA, return-liquor assumptions, existing ammonia instruments and supplier design data
Service provided
Live dashboards, sensor QA, mass balance and whole-site process headroom assessment
What became clearer
Measured return liquors contributed less than 10% of the ammonia load, challenging earlier assumptions about the benefit of reducing digester throughput. Converting the carbonaceous ASP to nitrification was not practical without significant investment, so the N.BAFF remained essential. Revised loading and supplier design data indicated that four of six cells could meet the duty under robust control.
Decision informed
The evidence supported retaining the N.BAFF, reinstating divert control and targeting maintenance before major investment. Improved sensor-led control and a four-of-six-cell strategy provided a route to meet future demand with potential annual OPEX savings of approximately £275,000.