Evaluation of Organic Carbon from Anaerobic Sequencing Batch Reactor Effluent as a Carbon Source for Denitrification

Abstract

The discharge of nitrate-rich effluent has adverse effect on the receiving environment and the public health of the polluted water users. The nitrates are eliminated in a denitrification step that requires reducing power in form of organic carbon. The objective of this study was to evaluate the potential of utilizing organic carbon in effluent from the anaerobic SBR as a carbon source for denitrification. Reactors were operated for one year using meat processing wastewater. Anaerobically treated abattoir wastewater equivalent to 5, 10 and 15% of aerobic SBR hydraulic volume were added to three separate reactors. A 12 h operating cycle consisted of the following periods: (a) filling, 0.30 h; (b) settling, 11 h and (d) decanting, 0.30 h for the anoxic reactor. A comparison between different carbon loads was performed based on biological carbon, nitrogen and phosphorus removal. Sufficient denitrification was achieved with 10% (aerobic SBR hydraulic volume) of anaerobically-treated abattoir wastewater. TCOD, BOD5, TKN, N02 -N, NO3-N, PO43-, TS, EC and temperature and turbidity were reduced by 78, 70, 91, 100, 98, 62, 39, 65,71, 5 and 39% respectively, with effluent mean concentrations of 80 ± 5 mg/L, 54 ± 12 mg/L, 35 ± 4, 00 ± 0, 2 ± 1, 18 ± 1, 254 ± 12, 1.64 ± 0.01, 22.04 ± 0.02 and 738 ± 9 FAU. Organic carbon in effluent from the anaerobic SBR can be used as a carbon source for anoxic denitrification. However, the denitrification rate is affected by the organic carbon load used. Except TKN and o-PO43- mg/L, all other parameters in the denitrified effluent met discharge standards.