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Wastewater of sugar industries has high pollutant load due to presence of organic and inorganic materials. Discharge of untreated or partially treated wastewater has negative effect on environment and on life of human, plants and animals. In our present studies, it is attempted to treat sugar industry effluent (SIE) by electrocoagulation process (ECP) using mild steel (MS) as electrode material. For this purpose, three process parameters namely pH (5-9), current density (j = 34.7-104.46 A m-2) and treatment time (tR = 20-100 min) were selected to optimize process using response surface methodology (RSM). The optimum conditions were pH 6.66, j = 105.16 A m-2 and tR = 100 min. The maximum chemical oxygen demand (COD) removal of 75.98% was achieved from the optimum conditions. The predicted model by RSM showed R2 = 0.9515. After treatment of effluent, the sludge content in treated water was separated effectively by filtration and settling.

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The sugar industry effluent (SIE) is characterized as high organic load. The aim of this study is to treat SIE by bio-aerobic process in batch and continuous mode in bio-aeration reactor. In batch process, effect of hydraulic retention time (HRT) in terms of effluent fill volume, and in continuous process, effect of HRT in terms of effluent feed rate was studied. In batch process, HRT of 2.5 d (fill volume = 0.8 dm3) was found to be the best and in continuous process, HRT of 1.37 d (feed rate = 133 mL/h) was found to be the best. The chemical oxygen demand (COD) reduction by bio oxidation followed first order kinetics with respect to COD and the rate constant (K) was evaluated as 5.197 d−1. The sludge yield coefficient (a) and sludge endogenous oxidation coefficient (b) were also evaluated from sludge formation studies, which are 0.4 (gm VSS produced/g COD removed) and 0.1 (g VSS oxidized/day. g MLVSS in the aeration basin), respectively. In continuous process, the COD reduction of 83.12% of 4800 mg/dm3 and BOD reduction of 88.70% of 1240 mg/dm3 were obtained at HRT = 1.37 d. The results of the experiments show the SBR process to be an effective process for the treatment of SIE.