Electroprecipitation of Phosphate from Sewage

A study of phosphate removal from secondary sewage effluent was conducted using a two-step method of electroprecipitation followed by lanthanum chloride precipitation. In the first step, a sacrificial low-carbon steel anode and a stainless steel cathode were used. This step removed 80% of the orthophosphate, reduced chemical oxygen demand by 23%, and lowered total dissolved solids by 9%. In the second step, colloids persisting from the first step were flocculated by addition of lanthanum chloride, which also removed additional phosphate. Two-stage removal of soluble orthophosphate was 99.4%, and chemical oxygen demand was diminished by 50%. No increase in total dissolved solids occurred in the second step.