Technical Study On Treatment Of Acidic Wastewater From Zinc Hydrometallurgy Industry Using Microbial Method

Nonferrous metallurgy industry has always been one of the main source of heavy metal pollution.In the present case,as the demand for environment grows,how to deal with heavy metal wastewater from nonferrous metallurgy industry effectively becomes an urgent problem confronted with the enterprise.This subject studies on a microbiological method dealing with acidic wastewater from zinc hydrometallurgy industry.Acidic wastewater from zinc hydrometallurgy industry has three following characteristics:at first,concentration of SO42-in the water is relatively high,secondly,large amounts of heavy metal ions are dissolved in water;the last but not the least,pH of water is extremely low.Nowadays,for domestic zinc metallurgy factory,a relatively customary method dealing with this kind of wastewater is three-section lime neutralization method.In spite of this method could attain the goal of heavy metal removal in water,huge amount of neutralization sludge is generated in the process.With current environmental protection policy,this kind of dangerous waste sludge undoubtedly would increase tax cost for enterprises.This study used microbiological method to deal with effluent from first-section lime neutralization process,could not only immensely decrease production of neutralization sludge,but also achieve the aim of getting rid of heavy metal.According to lab test scale,an up-flow anaerobic sludge blanket(UASB)reactor was designed and manufactured,and was set up in laboratory.Simulation wastewater was preparated referring to water quality of actual wastewater neutralized to pH 5.5.Sulfate reducing bacteria(SRB)was inoculated and UASB reactor was started.Removal rate of Zn2+ concentration in effluent came to 92%?96%.Three concentrations of carbon source were:500 mg/L?1000 mg/L and 1500 mg/L,on different condition treatment effect of actual wastewater was compared by UASB.Molecular biological method was applied to research microorganism community structure on different carbon source concentration condition.The result shows that richness of SRB is highest when carbon source is 1000 mg/L,comparing impact of three different concentrations of carbon source.While microorganism was made up of a heterogeneous population,of which SRB accounted for 13.86%.By species classification,the actual work of reducing sulfate was Desulfovibrio.A phylogenetic tree was structured according to information biology method and taxonomic position of Desulfovibrio was obtained.On the basis of lab research,pilot enlarge test was conducted in wastewater treatment plant of a domestic zinc metallurgy factory.Pilot scale test system was designed?manufactured and set up according to treatment capacity of 1 m3/d first-section neutralization effluent.Static starting and small flow continuously starting of SRB reaction tower were accomplished,A/O biological tank was started,the whole pilot system was started by gradient flooding acidic wastewater.As pilot test system steady operating,concentration of each heavy metal ion from effluent could get up to lead and zinc industry pollution emission standard,among which concentration of Zn2+×was less than 1.5 mg/L,Cd2+ was less than 0.05 mg/L,Pb2+ was less than 0.5 mg/L.