EFFECTS OF 4-CHLOROPHENOL LOADINGS ON ACCLIMATION OF BIOMASS WITH OPTIMIZED FIXED TIME SEQUENCING BATCH REACTOR

Chlorinated phenols in many industrial effluents are usually difficult to be removed by conventionalbiological treatment processes. performance of the aerobic sequencing batch reactor treating 4-chlorophenol containing wastewater at different loadings rates from 0.0075 to 1.2 g4cp/l.d wasevaluated. the sequencing batch reactor was operated with fill, react, settle and decant phases in the orderof 10:370:90:10 min, respectively, for a cycle time of 8 h at 10 days solid retention time and 16 hhydraulic retention time in the stable period. the effects of 4-chlorophenol loadings on the 4-chlorophenol and chemical oxygen demand removal percents, yield coefficient (y), biomass variation andsludge volume index were investigated. high chemical oxygen demand removal efficiencies (95±3.5%)and approximately complete 4-chlorophenol removal (>99%) were observed even in the absence ofgrowth substrate. the degradation of 4-chlorophenol led to formation of 5-chloro-2-hydroxymuconicsemialdehyde, which was more oxidized, indicating complete disappearance of 4-chlorophenol via metacleavagepathway. a compact sludge with excellent settleability (sludge volume index=47±6.1 ml/g)developed during entire acclimation period. high removal efficiencies with sequencing batch reactor maybe due to enforced short term unsteady state conditions coupled with periodic exposure of themicroorganisms to defined process conditions which facilitate the required metabolic pathways fortreating xenobiotics containing wastewater.