Enhancement of A/O process by hydrocyclone

Abstract

A modified anoxic/oxic (A/O) process was represented by coupling suspended-growth activated sludge and hydrocyclone, simply termed "AOH" process. The nitrate mixture liquid was firstly transported into hydrocyclone and then returned into the anoxic zone in AOH process. Sludge flocs were disrupted and organic carbon substances including extracellular polymeric substances (EPS) and cytoplasm were released into aquatic phase by the effects of pressure gradient, shear stress, cavitation, turbulence and impingement of hydrocyclone. These soluble organic carbon substances were consumed as complementary carbon sources for denitrification reaction, and also consumed by the heterotrophic aerobic bacteria. The end products were carbon dioxides and water. The denitrification reaction was enhanced because of the addition of complementary carbon sources and the removal efficiency of nitrogen (N) was improved. The cryptic growth of sludge was achieved by hydrocyclone, and the production of sludge was reduced. The results of this study showed that the average effluent N concentration of AOH was decreased 14.1 mg/L, the average N removal efficiency was improved 21.5%, the average observed biomass yield (Y obs) of AOH was decreased 0.110 mg MLSS/mg COD , and the total excess sludge production of AOH was decreased mg TSS, compared with A/O.