Phosphorus release from excess activated sludge to sludge liquide under aerobic and anaerobic sludge stabilization

Abstract

A limited number of known reserves of phosphorus and avoiding eutrophication of water bodies are the driving forces to search and study ways to extract phosphorus from wastewater and sludge treatment plants. It is shown that the phosphorus of excess activate d sludge can release into sludge water during sludge treatment. This water is returned to the head of wastewater treatment plant, thereby increasing the phospho-rus load to the biological treatment system. The aim of this study was to establish patterns of phosphorus transition in sludge water under diff erent condition of activated sludge stabilization. The object of the study was the suspension of thickened activated sludge from Minsk treatment plant (MTP). The modeling process treatment of excess active sludge was carried out in laboratory settings of volume 2.5–6.0 dm{3}. There were established the dependences of phosphorus content and pH value during prolonged thickening of aerobic and anaerobic stabilization. It is shown that the most insensitive phosphorus release from excess active sludge to supernatant takes plac e under anaerobic treatment during first three days. Under these conditions the concentration of phosphorus in sludge water increased up to 300 mg P/dm{3}. During prolonged anaerobic treatment the release of phosphorus depends on hydrodynamic conditions. Up to 80% of the total phosphorus content in the excess activated sludge is released without stirring. Under aerobic conditions, the yield of phosphorus in the sludge water is determined by the air flow rate and processing time and can be up to 387 mg P/dm{3}.