Cu(II) biosorption by living biofilms: Isothermal, chemical, physical and biological evaluation

Dissolved copper in stormwater runoff is a significant environmental problem. Biosorption of dissolved metals using microorganisms is known as a green, low-cost and efficient method. However, the role of live biological agents in the remediation of dissolved copper in Sustainable Drainage (SuDS) has not been reported. In this study, the effect of pH, initial concentration and temperature, on bacteria in different stages of biofilm development on a geotextile, along with Cu(II) removal efficiencies, were evaluated. Maximum Cu(II) removal efficiency (92%) was observed at pH 6. By decreasing the pH from 6 to 2, a log 5 reduction in bacteria was observed and Carboxyl groups transformed from -COO- to -COOH. The maximum biosorption capacity (119 mg g(-1)) was detected on day 1 of biofilm development, however, maximum removal efficiency (97%) was measured on day 21 of biofilm incubation. Exteracellular Polymeric Substance (EPS) showed a better protection of CFUs in more mature biofilms (day 21) with less than 0.1 log decrease when exposed to 200 mL(-1) Cu(II), whereas, biofilm on day 1 of incubation showed a 2 log reduction in CFUs number. Thermodynamic studies showed that the maximum Cu(II) biosorption capacity of biofilms, incubated for 7 days (117 mg g(-1)) occurred at 35 degrees C. Thermodynamic and kinetic modelling of data revealed that a physical, feasible, spontaneous and exothermic process controlled the biosorption, with a diffusion process observed in external layers of the biofilm, fitting a pseudosecond order model. Equilibrium data modelling and high R-2 values of Langmuir model indicated that the biosorption took place by a monolayer on the living biofilm surface in all stages of biofilm development.

Automated summary

The study evaluated the effects of pH, initial concentration, and temperature on bacteria in different stages of biofilm development in removing Cu(II) from stormwater runoff. The maximum removal efficiency was observed at pH 6. EPS protected CFUs in mature biofilms, while the CFUs number significantly decreased in biofilms on day 1 of incubation.