SBR system for phosphorus removal: Linear model based optimization

Using a linear model, an optimization scheme for a sequencing batch reactor (SBR) system for phosphorus removal was investigated. The objective was to minimize energy consumption by reducing the aeration cycle time (t_air), while meeting the permit requirement (monthly average PO₄^3- of 0.5 mg P/L). Based on the model prediction and error feedback information, the proposed scheme controlled the SBR system well both in the simulation and the real application by adjusting the t_air to meet the effluent PO₄^3- constraint. Mismatch between the model prediction and the measured data was compensated for. In the simulation, the average aeration cycle time was calculated to be 2.8 h, while in the real system it was 3.5 h. The actual optimized system provided excellent removal of phosphorus, COD, and ammonia with efficiencies of 93% (7.4 to 0.5 mg P/L). 90% (420 to 43 mg COD/L), and 98% (22.1 to 0.4 mg N/L), respectively. However, the effluent nitrate concentrations were relatively high (10 mg N/L), due to a slower endogenous nitrate respiration rate.