Process and apparatus for treating liquids containing ammonium, phosphate and potassium

摘要

A process treats liquid effluent containing ammonium, phosphate and phosphates and solid particles. The liquid is first treated by mechanical separation and ultra- or micro-filtration, followed by precipitation of ammonium and phosphates as magnesium-ammonium-phosphate. Residual organic matter is then broken down under aerobic conditions and ammonia removed. Further organic residual compounds still present in the water and dissolved salts are then removed from water by reverse osmosis. The first mechanical separation process is a multi-stage operation. The ultra- or micro-filtration is a cross-flow process at a pass rate of 1-4 m/s. The precipitation is driven by the admixture of magnesium oxide, caustic soda and phosphoric acid as required. The Mol ratio of Mg, NH3 and phosphates is in the range (1 to 2) : 1 (0.5 to 1) . The pH value is set at pref. 8 to 10 by the dosed admixture of caustic soda. The biological break-down takes place in an activated membrane unit. Also claimed is a commensurate assembly consisting of a liquid/solids separator, a settlement tank, a sediment holder and an activated membrane unit and a reverse osmosis assembly.