Advanced Treatment of Municipal Wastewater with High Content of Printing and Dyeing Wastewater and Tannery Wastewater

The proportion of printing and dyeing wastewater and tannery wastewater was over 80% in the influent of a wastewater treatment plant in Haining.The effluent could not meet the first level B criteria specified in GB 18918-2002.Based on this situation,Fenton reagent,Fenton reagent + biochemistry,ozonation,ozonation + biochemistry were used to undergo advanced treatment.The results showed that the effluent quality from processes using Fenton reagent,ozonation and ozonation + biochemistry could not meet the first level B criteria.When the optimum conditions were: pH=3,Fenton reaction time=1 h,COD ∶ Fe2+ ∶ H2O2=8 ∶ 1 ∶ 2 and HRT of biochemistry tank=6 h,the concentrations of COD,BOD5,SS,NH3-N and TP in the effluent from the Fenton reagent + biochemistry process were 57.32,9.85,8.17,0.87 and 0.36 mg/L respectively,and the effluent pH=7.12,which could meet the first level B criteria.Besides,the treatment cost could reduce from 0.627 yuan/m3 to 0.481 yuan/m3 when pH was adjusted by Ca(OH)2 instead of NaOH.