The Study And Solution Of Tannery Wastewater Impact On Municipal Wastewater Treatment Plant

This project was conducted in a municipal wastewater treatment plant with the mixed sewage from a typical tannery wastewater treatment plant and domestic sewage,to explore the influence of tannery sewage on the operation of municipal wastewater plant and provide corresponding solutions.The results show that the high chemical oxygen demand(COD)and ammonia nitrogen(NH₃-N)pose a significant effect on the operation efficiency of activated sludge in the municipal wastewater treatment plant,and the extremely high COD and NH₃-N could trigger the microbial community disturbance.When the influent C/N ratio was 3.43,the removal efficiency of total nitrogen(TN)and NH₃-N were only44.8%and 54.3%,respectively.To mix the treated tannery sewage with the domestic sewage is a pathway to further reduce the pollution load of the municipal wastewater treatment plant.However,the presence of a large number of dyeing agents which is regarded as the non-degradable COD resulted in the insufficient ratio of biological oxygen demand(BOD)and COD(BOD/COD).The effect of external carbon source and specific denitrifying bacteria on the enhancement in the denitrification efficiency under the condition of activated sludge was studied in this thesis.The results exhibit that the removal efficiency of TN with the addition of specific denitrifying bacteria was 73.76%,while that without the specific denitrifying bacteria was 68.79%,indicating a negligible influence of specific denitrifying bacteria on the TN removal.Whereas,the adjustment and optimization of external carbon source dosage could ensure the TN reaching the discharge standard of15 mg/L.Hence,the addition of external carbon source and the control of the biochemical process should be considered for the removal of TN.Besides,the removal of COD via four-phase catalytic oxidation process and four-stages adsorption of activated coke was investigated in this thesis.The results suggest that these two kinds of advanced oxidation process could promote the removal of COD,with an average removal efficiency of 60%by the four-phase catalytic oxidation process and that of 89%by the four-stages adsorption of activated coke,which can meet the COD discharge standard of 50 mg/L.Meanwhile,four-phase catalytic oxidation process also had an excellent removal effect on SS and chroma.Regarding the four-phase adsorption of activated coke,the adsorption efficiency decreased with the reaction time.Thus,the modification investment of these two processes in the practical application should be strictly analyzed to meet discharge standard with the minimum operational cost.In summary,the TN and COD concentrations in effluent exceed the discharge standard,which is might attributed to that the conventional activated sludge process used in the municipal wastewater treatment plant has a low removal efficiency of COD and NH₃-N of the tannery sewage.The addition of external carbon source could adjust the BOD/COD ratio to ensure high denitrification efficiency,leading to a reduction of TN concentration in the effluent.In addition,four-phase catalytic oxidation process and four-stages adsorption of activated coke have a good effect on the further removal of COD.