Development of Sustainable Approaches to Achieving Low Phosphorus Effluents

In an increasing number of wastewater treatment facilities there is a push towards ever lower effluent phosphorous limits. In order to meet low effluent P concentrations, chemical phosphorus removal is the preferred option for reliable and consistent performance. However, since high molar ratios of Metal/P are required for driving phosphorus to very low levels, large quantities of chemicals are required. These chemicals are costly and have their own environmental impact that is rarely considered when low effluent phosphorous limits are set. Biological phosphorus removal can achieve effluent ortho-P concentrations of less than 0.1 mg/L, but in order to meet very low levels consistently, chemicals are required for standby, for precipitation of residual ortho-phosphorus and for coagulation of the remaining particulate and colloidal phosphorus. Some facilities have investigated the synergy of biological and chemical phosphorus removal, whereby chemicals can be added as a polishing stage or in conjunction with biological phosphorus removal. This paper will discuss proposals and implications of Water Environment Research Foundation (WERF) Study: Development of Sustainable Approaches to Achieving Low Phosphorus Effluents which will look at available information and research needs to determine the optimal and synergistic use of a combination of both processes to reduce the chemical cost while still allowing the recovery of phosphorus from the plant.