Simultaneous Removal of High Nitrate and Phosphate from Synthetic Waste Water by Prolonged Anoxic Cycle in a Batch Reactor

Abstract

Phosphorus, as well as nitrate, is an essential nutrient for different agricultural activities, but its excess disposals and discharges into natural water sources result in eutrophication. This leads to water quality problems including increased purification costs, interference with the recreational and conservation value of water bodies. In the current study, attempts have been made to remove nutrients from synthetic wastewater using activated sludge under anoxic condition. Enhanced biological nutrient removal is an efficient and sustainable biological technology to remove overall COD from wastewater. It is based on the enrichment of activated sludge with phosphorous accumulating organisms (PAOs) and denitrifying phosphate accumulating organisms (DNPAOs) by introducing alternating anoxic and aerobic conditions, which favour specific bacterial growth over ordinary heterotrophic organisms. In a small reactor, anoxic condition prevails throughout the working time (24 h). In this reactor, the removal rate of phosphate and nitrate is ~75 and >90% respectively. Metagenomic analysis of the sludge confirmed the presence of DNPAOs in the anaerobic reactor. These metagenomic studies further confirmed the presence of DNPAOs. These DNPAOs removed high amount of nutrient in the presence of an optimum amount of carbon source in anaerobic condition using nitrate as electron acceptor.