Biological nutrient removal from domestic wastewater utilizing organic wastes

Abstract

In order to treat domestic wastewater, a sequencing batch reactor (SBR) system operated in the sequence of anaerobic (3 hr) - aerobic (3 hr) - anoxic (2 hr) phases was used. Because of the exhaust of organic materials at the anaerobic phase, external carbon addition was indispensable for denitrification. Although methanol has been used for denitrification due to its inexpensive cost, it is urgent to find a new alternative carbon compound for the methanol, as an effort to reduce operation cost in the wastewater treatment plants. Acetate is known to be the most efficient electron donor for nitrogen removal, and other volatile fatty acids (VFAs) such as propionate and butyrate are reported to be more favorable than methanol. Furthermore, short-chain fatty acids, especially acetate, are recognized as the most suitable carbon substrates for the biological phosphorus removal process. Therefore, Korean food wastes which contain a higher percentage of fermentable components with less N- and P- than any other wastes were anaerobically fermented in batch reactor, and the VFA solution obtained in the fermentation was added in the biological nutrient removal (BNR) of municipal wastewater using the SBR process in order to promote the denitrification and P removal processes. The removal rates of nitrogen and phosphorus improved from 44 and 37% to 92 and 73%, respectively when the VFA solution was added. The concentrations of nitrogen and phosphorus were maintained below 3 and 1mg/L, respectively. The N- and P- content of the VFA solution was low enough not to influence the final N- and P- concentrations of the wastewater. Each VFAs showed different efficiencies in denitrification and phosphate removal. In the case of denitrification, acetate was the most effective source, followed by butyrate, propionate and valerate. Mean specific denitrification rate of acetate was ca. 2 times higher than those of other VFAs. Other VFAs showed similar efficiency. The best P-release and upt...