Instrumentation, automation and control in municipal wastewater treatment can result in the savings of large resource, cost and energy . Feedforward and feedback control algorithms were implemented with turbidity and phosphorus analysers to control the chemical dose at the tertiary stage of the Nenäinniemi wastewater treatment plant, consisting of coagulation, flocculation and microsieve filtration. This optimization lowered the coagulant dose by 70% and the polymer dose by 36% than manual adjustments of the chemical dosing. Effluent total phosphorus (TP) and total suspended solid (TSS) concentrations were lowered by 20–30%. With the control system in operation, the annual savings in coagulant and polymer were 100 and 1.4 tons, respectively. Conducting automated CIP on the media at an economical breakeven interval of approximately 20 days was also important to further lower energy usage and operational costs.
Online phosphorus analysers and turbidity sensors vastly improve the P-removal performance of disc filters in tertiary treatment.
Feedforward and PI feedback online dosing control reduced the annual chemical consumption by 85–100 tons at the Nenäinniemi WWTP (165,000 PE) tertiary disc filter treatment stage.
20 days of operation between chemical disc filter cleanings is the cost and energy breakeven.