Study On Microbiological Treatment Of Electroplating Wastewater Containing Chromium

Hexavalent chromium-containing wastewater, which was harmful to natural environment and human being health, has widespread sources and great toxicity. At present, physicochemical methods are the major ones to treat this wastewater. However, these methods will produce secondary pollution and own the shortcoming of high cost. In recent years, people started to adopt microbiology methods to deal with hexavalent chromium-containing wastewater, and have gained lots of research results on the mechanism and static experiment of treating HCCWW with microbiology methods. But most of the research is the stage of laboratory research, there are little report about engineering experimental study about it.This paper research used the combined process of"Expanded Granular Sludge Bed(EGSB)+Aerobic Activated Sludge"to treatment of electroplating wastewater containing Chromium, and sought out the technological feasibility of this combine process.The Sulfate- reducing bacteria (SRB) was optimum cultured in the EGSB, and the Cr(Ⅵ) was converted to Cr(Ⅲ) by the sulfide which produced during the suflate was reduced by SRB.Most of Cr(Ⅲ) is adsorbed. by the anaerobic sludge to remove.Following, the residuals of COD, Cr(Ⅲ) and SS which generated in the EGSB are completely removed through the aerobic activated sludge process. The result of this research show: (1)Through advantage cultivation of SRB bacteria and in the condition of influent pH was 6~7, COD/SO4 2-=1.5～2.5,HRT=12h, SRB reached the highest rate of sulfate reduction, and produced the most amount sulfide, However, when the volume load was greater than 10 kgSO 4 2-/ (m3?d) , the Sulfide content of effluent would be more than 200mg/L, then the activity of SRB Bacteria was restrained; (2) EGSB Reactor was be used to treat Chromium (Ⅵ) electroplating wastewater Continuously, the return water could reduce toxicity to the microorganisms that from Cr(Ⅵ) in influent water , while concertration of Cr(Ⅵ) of influent was 30～50mg/L, in the context of Sulfide output enough, the reactor could achieve high Cr(Ⅵ) removal efficiency, the removal rate could reach 95%, the average Cr(Ⅵ) content of effluent was lower than 0.5mg/L; Cr(Ⅲ) ions accumulated in the reactor during operation, VSS / SS ratio of sludge decreased continuously, Through regular discharging, the sludge activity of the reactor could be restored in a certain degree.(3)The effluent of EGSB reactor was furtherly treated through using the aerobic activated sludge process, adding ferrous sulfate to avoid the inhibition phenomenon caused by sulfide.Adjusting the pH to 8,the aerobic activated sludge process continuously operated for 30 days, the average COD concentration of effluent is 78.5mg/L, the total chromium is 0.61mg/L, the SS is 64.3mg/L.The effluent quality can satisfiethe discharge standard.The treatmen effect of aerobic activated sludge process will be invalidure if the chromium are greatly accumulated when the reactor is operating lastingly.