DETERMINATION OF ORTHOPHOSPHATE IN ACTIVATED SLUDGES FROM WASTE-WATER-TREATMENT SYSTEMS SHOWING ENHANCED BIOLOGICAL PHOSPHATE REMOVAL

A procedure for measuring orthophosphate which employed ascorbic acid as reductant at room temperature was found to be unaffected by the pre sence of pyrophosphate, polyphosphate and two organic phosphates. Unde r the conditions used for extraction of orthophosphate from biological sludges obtained from wastewater-treatment systems, perchloric acid d id not cause hydrolysis of pyrophosphate, polyphosphate or the organic phosphates; however, neutralization of the perchloric acid prior to a nalysis was necessary. The measurement of orthophosphate in the solid phase of sludge directly by extraction was modified so as to take into account the orthophosphate in the liquid phase remaining with the dep osited solid phase. Values for orthophosphate in sludges from laborato ry-scale and full-scale wastewater-treatment systems were not apprecia bly different when determined directly by extraction of the solid phas e of a sludge or indirectly by subtraction of liquid-phase orthophosph ate from total orthophosphate in the sample. However, due to the fewer steps involved, the indirect procedure has an advantage over the dire ct procedure.