Abstract:
Different intermittent phases were introduced during the continuous operation of UASB reactor treating simulated textile wastewater using single dye and optimized combination was operated for mixed dye solution. Initially the reactor was operated at organic loading rate (OLR) of 2 kg COD/m3d OLR and HRT of 24 hrs using single dye feed to optimize the non-feeding period provided to reactor for maximum COD and color removal rates. 12 hrs feeding and 12 hrs non- feeding (12F/12NF) cycle gave suitable COD and color removal rates of 57.50 and 71.04% respectively. The similar cycle was operated using mixed dye feed with increase in dye concentration to 30 mg/L at same operating conditions. Maximum COD and color removal efficiency of 47.80 and 38.35% was obtained. The decreased removal rates for mixed dyes were due to possible presence of intermediate metabolites produced by chromogenic breakdown of dyes. The above condition was extended as consecutive 12 hrs feeding and 12 hrs non-feeding periods (12F/12NF/12F/12NF) at 48 hrs HRT and increased dyes concentration to 50 mg/L. Improved COD and color removal rates of 67.0 and 77.86% were achieved. Minimum VFA/alkalinity ratio of 0.49 was obtained at stable MLSS concentration of 7300 mg/L. Effluent TKN and orthophosphates concentration was maintained at 42.35 and 18 mg/L, respectively.
