Lower aeration energy and a more stable process. Operators can override the system at any time.

Ekster & Associates' control systems replace the conventional PID control (the feedback control method in general use for about 110 years) of aeration and sludge wasting at your plant. They run on your existing SCADA (plant control) system and your existing blowers. Your operators set the targets and the limits within which the system operates.

What changes at your plant

• Aeration follows the load. DO/Nmaster sets dissolved oxygen and airflow from the measured ammonia load, minute by minute, instead of holding a fixed dissolved oxygen setpoint with a safety margin.
• Sludge age is held on target. SRTmaster calculates the sludge age (SRT) from on-line measurements and sets the waste sludge flow automatically, instead of relying on daily grab samples and manual adjustment.
• Faulty readings are not acted on. Every reading is checked before it is used. Faulty readings are detected and not acted on, and operators are alerted.

Case studies

Pomona Water Reclamation Plant, Los Angeles County Sanitation Districts. In a U.S. Department of Energy funded demonstration, aeration energy fell from 1,300 to 550 kWh/MG. The old blowers were replaced first (34% less blower energy); lowering dissolved oxygen with DO/Nmaster and SRTmaster then saved a further 30% of blower energy. Total inorganic nitrogen removal stayed at about 84% before and after the change. Dissolved oxygen was held within 0.06 mg/L of setpoint on average, against 0.20 mg/L with tuned PID control, and sludge age within 0.13 days. The project received the 2025 CASA Excellence in Innovation and Resiliency Award (awarded to the Los Angeles County Sanitation Districts and Carollo Engineers). BLANKETmaster has been under contract for the plant's secondary clarifiers since October 2026.

City of Chico, California (12 MGD design). A 2018 control project built around DO/Nmaster, with automated valves, airflow and ammonia meters, and improved blower sequencing, and with the existing blowers, reduced aeration energy per pound of oxygen demand by 47.6%, verified under a PG&E energy efficiency program: 1,198,692 kWh a year. The plant's aeration energy is 580 kWh per million gallons treated (kWh/MG), against an industry average of 800–1,500 kWh/MG, both aeration energy only. The activated sludge system operates unattended outside an 8-hour staffed day. SRTmaster has been in service at Chico since 2014, and DO/Nmaster since 2018.

Sludge age control, published record (WEFTEC 2016).

• Sludge age held within 5% of setpoint, and most of the time within 2.5%.
• Daily variation in the mass of sludge wasted reduced from 23% to 3% of the daily average.
• Up to 30% more secondary treatment capacity from better sludge settling (Victor Valley Wastewater Reclamation Authority, 30%).
• Laboratory suspended solids tests for process control reduced by as much as 90%.
• Foaming caused by Nocardia, a filamentous bacterium, significantly reduced at Sacramento Regional and at other plants.
• No recorded incident, in the twenty years to 2016, of the controller acting on an erroneous instrument signal.

How the risk is controlled

• Operators keep authority. Operators set the setpoints and limits within which the system operates, and can override it at any time.
• If the control system stops. If the control system or its communication link stops, the plant's own control system (PLCs or SCADA) responds according to the fallback logic programmed for that plant.
• No new blowers, and no capital project for the control system. The system uses the existing blowers and SCADA system. Where additional instruments are needed, the plant buys them from any supplier, to recommended performance specifications that Ekster & Associates provides.
• No vendor inside your operations. Ekster & Associates sells no hardware, no automation platform and no service contract that places a vendor inside plant operations.
• The estimate comes first. The free plant assessment states the expected savings, the assumptions behind them, any changes required before installation, and a fixed price, before any commitment.
• References. Plant staff at Chico and Pomona are available to speak with other utilities.

Next step: a free plant assessment

Send one year of operating data and energy bills. You will receive a written estimate of savings in kWh and dollars, the assumptions behind it, any changes required before installation, and a fixed price. If your plant is already operating efficiently, the estimate will say so.