Engineering Practice For Upgrading And Rebuilding Of Treatment Of Printed Circuit Board (PCB) Synthetic Wastewater By MBR And Fenton Combined Process

Specific effluent limitation due to the Emission Standard of Pollutants for Electroplating?ESPE??GB 21900-2008?exert new challenge to the treatment of wastewater from Printed Circuit Board?PCB?industries,furthermore,regarding the environmental capacity,effluent from the PCB industrial for the COD_Cr and ammonia nitrogen shall meet the Class IV of Environment Quality Standard for Surface Water?EQSSW??GB 3838-2002?,meaning COD_Cr less than 30 mg/L,and ammonia nitrogen less than 1.5 mg/L.Therefore,it is necessary to upgrade the treatment of PCB wastewater.Recently,Combined Technique of Membrane Bioreactor?MBR?and Fenton?“CTMF”?had been successfully applied in the treatment of PCB wastewater.Summarization of technique characteristics,impact factors,optimization of operation and economic evaluation could promote the upgrade of PCB wastewater treatment using the MF technique.Optimal process parameters were determined through the lab test for the removal of COD_Cr and ammonia nitrogen.The CTMF was applied in the treatment of 6000 m³/d PCB wastewater in the upgrading treatment in one of Guangdong PCB manufacture;the characteristics and the economic efficiency of the combined technique were analyzed and summarized.The results of using the MBR technique in lab test scale showed that the optimal process parameters followed: aeration gas water ratio 20 to 30,intermittent discharge pattern,meaning stop for 3 minutes after every 8 minutes' of continuous discharge,supplement nutrient salts to make C: N: P ratio reach to 100:5:1.After MBR treatment,the ammonia nitrogen in effluent was less than 1.5 mg/L and COD_Cr less than 30-50 mg/L for PCB complex wastewater.The results of using the Fenton technique in lab test scale showed that the Fenton technique could remove COD_Cr well.Regarding the cost of reagent and the removal efficiency of COD_Cr,the optimal process parameters were: reaction time 60 to 90 minutes,initial p H in the range between 3.0 and 4.0,dose of H₂O₂ in the range between 0.03 and 0.036 ml/L?between 0.10 and 0.12 ml/L equal to 30% H₂O₂?,mole ratio of H₂O₂ and Fe²⁺ in the range between 1.0 and2.0.The COD_Cr in effluent was less than 30 mg/L when using the above process parameters to the treatment of PCB complex wastewater.To test the removal of ammonia nitrogen and COD_Cr in the treatment of PCB wastewater using the CTMF,the CTMF was applied in the upgrading treatment of 6000 m³/d PCB wastewater.The results data from the adjust monitoring and retained monitoring showed that the COD_Cr in the effluent was in range between 10 and 20 mg/L,less than 30 mg/L,meeting the discharge limit of ESPE?GB 21900-2008?for specific pollutants and Class IV of EQSSW?GB 3838-2002?,and the ammonia nitrogen in the effluent was in the range between 0.5 and1.4 mg/L,less than 1.5 mg/L,meeting the Class IV of EQSSW?GB 3838-2002?.The characteristics of the CTMF in the application of upgrading wastewater treatment includes high quality of effluent,less cover area,strong impact resistance,flexible operation,effective response to the changes in the wastewater quality.The unit investment for CTMF was calculated,including operational fee of 29297.63 Yuan per day,and 5.072 Yuan per ton of wastewater.