Primary Studies On Biological Removal Of Cr(Ⅵ) With Activated Sludge

chromium(VI) is a highly toxic heavy metal,which is one of the 129 priority pollutants recognized by the EPA of the United States, and is also China's key anti pollutants. Chromium-containing wastewater has become more and more as one of the issues of concern in world.Conventional ways are difficult to meet requirements for total discharge amount and puremicroorganism is too complicated. Activated sludge treatment was studied to deal with chromium-contained wastewater.Under the long-term cultured conditions, the influences of lower Cr(VI) concentrations on the aerobic, anaerobic and anaerobic/aerobic SBR were investigated by measuring COD, SS, VSS, SVI, microbial activity, and effluent turbidity. Also, the chromium removal was studied. It was found that the presence of Cr(VI) inhibited the aerobic SBR, and the Cr(VI) removal was negligible,achieving less than 8% for wastewater effluent. In the anaerobic SBR , the sludge growth was slowly although the Cr(VI) was removed. At Cr(VI) level less than 10mg/L, the long-term experiments results indicated that the growth and metabolism of activated sludge microorganism were not significantly affected by Cr(VI), and an good Cr(VI) removal was observed, achieving 98% for wastewater effluent.On this basis, this research highlights on a higher concentration of Cr(VI) impacting on material metabolism of the anaerobic/aerobic SBR. Further, in anaerobic/aerobic SBR relations of the Cr(VI) and material metabolism are defined. under the low concentration of Cr(VI) anaerobic/aerobic SBR can stably run, and metabolism of acetic acid, PHA and glycogen is normal. Only when Cr(VI) level is more than 4mg/L, phosphate's release become Less.It indicate that anaerobic/aerobic SBR is ideal biological system of removing Cr(VI).In end, the removal mechanism of Cr(VI) in anaerobic/aerobic SBR is discussed by comparative study in conditions of acetic acid andα-ketoglutarate. It Show that a major role of the activated sludge microorganisms is to deoxidize Cr(VI), and the adsorption is only supporting role in removal of Cr(VI). In deed activated sludge microorganisms provide reducing power and energy generated by materialmetabolism in removal of Cr(VI).