Nickel, Copper and Chromium Removal from Contaminated Wastewaters by Serratia plymuthica and Rhodococcus quingshengii strains

Nowadays accumulation of heavy metals in water bodies represents a serious environmental and human health threat. Heavy metals are known for their utility in industrial processes such as industrial welding, dyes and pigments manufacturing, electroplating processes, leather tanning and wood preservation. Among possible remediation strategies, the use of biological systems can be proposed since microorganisms interact with metals by passive adsorption processes and active enzymatic reactions.
In the present study, resistance to heavy metals and ability to reduce their concentration in industrial wastewaters were determined for Serratia plymuthica strains SC3I(2) and As3-5a(5) and Rhodococcus quingshengii strain SC26 . The S. plymuthica strains were tested for Ni(II) and Cu(II) biosorption by filtration. SC3I(2) was able to remove 89.4% of Ni(II) from a 50 mg L−1 solution, and showed maximum biosorption capacity of 33.5 mg g−1. As3-5a(5) removed up to 91.5% of Cu(II) from a 200 mg L−1 solution, yielding maximum biosorption capacity of 80.5 mg g−1. R. quingshengii strain SC26 was characterized for its ability to resist to hexavalent chromium (MIC of 300 mg L-1) and to reduce up to 51.14 mg L-1 hexavalent to trivalent chromium in growing-cell conditions. Bacterial strains ability to adsorb Ni(II), Cu(II) and Cr(VI) was assessed also in planktonic experiments. Trials on electroplating wastewaters were conducted to assess the bioremediation potential of S. plymuthica strains SC3I(2) and As3-5a(5) and R. qingshengii strain SC26 in close-to-real scenarios. Their characterization will provide information regarding possible metal removal and recovery in a full-scale bioremediation system.