Isolation Of Copper Resistant Microorganism And Their Bioaugmentation Efficiency In Electroplating Wastewater Containing Copper

In recent years, more and more surface processing industrial parks are under building and their construction is increasingly perfect. However, due to the uncertainty of water quality, complexity of water quantity, and incomplete treatment of chemical pretreatment unit for heavy metals, the biological treatment unit of surface processing industrial park sewage treatment plant always being exposed to the influence of heavy metals. In order to enhance the biological treatment of organic matter in electroplating wastewater under heavy metal stress efficiency, reduce the content of heavy metals in waste water, to ensure the stable operation of biological treatment system, this paper adopted the bioaugementation technology. Cu²⁺, which is the most common cations in electroplating wastewater, was chosen as the research object. Five bacteria strains that have strong tolerance ability to Cu²⁺ were isolated and named as L1–L5, respectively. The tolerance and adsorption capacity for Cu²⁺, and the ability to remove organic pollutants of each bacterium were investigated, the strains with better performance were selected, the copper tolerant flora was constructed and their augmented performance in a sequencing batch reactor（SBR） were investigated.Minimum inhibition concentration of Cu²⁺ in different medium and the influence of different environmental factors were investigated. Results showed that in LB medium and wastewater medium, L2 to L4 showed a high Cu²⁺ tolerance and good adsorption capacities, better than those of L1 and L5. Minimum inhibition concentrations of Cu²⁺ in LB medium were as high as 200 mg/L, 300 mg/L, 450 mg/L, respectively for L2 to L4. Under the optimal p H and temperature, the maximum Cu²⁺ adsorption capacities were 34.15, 45.68 and 26.72 mg/g, respectively, for L2 to L4. They showed a quick and efficient removal in heavy metals.Little effects in COD removal were investigated when the influence initial COD concentration ranged from 0 to 350 mg COD/L for L2- L4 strains, however, the effcts were relatively obvious after 72 h for L2 and L3 within 0-72 h. The influence of p H value（4–7） on the COD removal were obvious for L2- L4 strains within 0-72 h. The maximum COD removal efficiency of 79.0% was achieve3 d by L4 strain after 72 h. In addition, more Cu²⁺ added resulted in lower COD removal. Within 0-72 h, the average COD removal efficiency of L2 strain(10 mg/L Cu²⁺ in medium), L3 strain(15 mg/L Cu²⁺ in medium) and L4 strain(10 mg/L Cu²⁺ in medium) can reach 65.69±10.89%, 61.54±6.67%, 71.63±5.98%. respectively. The minimum inhibition concentrations of Cu²⁺ of L2- L4 strains were 15, 25 and 25 mg/L, respectively, in the electroplating wastewater（200 mg COD/L） medium. After addition of glucose, the inhibition concentration of Cu²⁺ increased. Therefore, the carbon source is an important factor for bacteria to Cu²⁺ inhibition.Bacteria stains of L2, L3 and L4 were selected to construct Cu²⁺ tolerant flora usded for bioaugmentation research. Augmented effects under different dosage were investigated. The bioaugmented system show a better performance when the inoculum was 400 mg/L（dry biomass） in the biofilm reactor compared with that in the suspended reactor. The COD and Cu²⁺ concentration in the effluent can meet the discharge standard for electroplating wastewater. This flora is anticipated to be used in the practical electroplating wastewater treatment.