Control Strategies of Phosphorus Removal in Wastewater Treatment Plants

The paper deals with the phosphorus removal in a wastewater treatment plant in accordance with the legislation. The treatment plant in question is one that supplies a city with a population of 250,000–300,000 inhabitants. At the same time, the phosphorus removal must also keep the other components of the wastewater (ammonium, organic substances) within legal limits. The treatment plant was modeled with the ASM2d. The authors make an analysis of methods of reducing the total phosphorus concentration below the limit required by law, considering the two components: inorganic phosphorus and organic phosphorus. The first strategy proposed in the paper is the control of the inorganic phosphorus concentration by addition of ferric chloride. In the second strategy, a control loop of suspended solids concentration (TSS) measured at the output of biological reactors is added. The third strategy introduces in addition a control loop of ammonium concentration in the effluent. The results are obtained in numerical simulation.