Biological Nutrient Removal from Synthetic Wastewater Containing 2,4 Dichlorophenol in a Sequencing Batch Reactor

Nutrient removal from synthetic wastewater was investigated using a four-step sequencing batch reactor (SBR) at different 2,4 dichlorophenol (DCP) concentrations. The nutrient removal process consisted of anaerobic, oxic, anoxic, and oxic phases with hydraulic residence times (HRT) of 1/ 3/ 1/1 h and a settling phase of 45 min. Solids retention time (SRT) was kept constant at 10 days in all experiments. Initial dichlorophenol concentrations were varied between 0 and 240 mg/L at eight different levels. Effects of dichlorophenol on removal of COD, NH₄-N, and PO₄-P and on effluent nutrient concentrations were investigated. Dichlorophenol was almost completely degraded up to 123 mg/L influent concentration. Adverse effects of dichlorophenol on COD removal were almost negligible for DCP concentrations below 123 mg/L. About 96% COD, 46% NH₄-N, and 22% PO₄-P removals were obtained at a DCP concentration of 123 mg/L. The sludge volume index (SVI) changed in a range of 59 to 93 mL/g for DCP concentrations below 123 mg/L, which increased to 142 mL/g at a DCP level of 240 mg/L.