Bioremediation Of Arsenic Contaminated Water Using Green Microalgae

This paper studies the effects of arsenite and arsenate on the growth of five microalgae(Selenastrum capricormulum, Chlorella vulgaris, Chlorella minata, Chlorella sp.(100ai) andChlorella sp.(zfsaia)) and their biosorption abilities of arsenic.Five microalgae were exposed to various concentrations of arsenic and cultured forseven days. The toxic effect of arsenic was quantified using physiological parametersincluding cell density and chlorophyll-a. In biosorption experiment, the five microalgae wereexposed to the same arsenic concentrations, and biosorption rates were recorded based on theremaining arsenic concentrations in solutions.Under arsenite effect, the five microalgae showed different tolerability: S.capricormulum> C. minata> C. vulgaris> Chlorella sp.(zfsaia)> Chlorella sp.(100ai).Among the five microalgae, Chlorella sp.(zfsaia) and Chlorella sp.(100ai) were highlysensitive to arsenite, the96h-EC50was17.32mg/L-1and25.79mg/L-1.Similar with arsenite, thetolerance of these microalgae to arsenate based on168h-EC10followed the decending orderof S. capricormulum> Chlorella sp.(zfsaia)> C. vulgaris> C. minata> Chlorella sp.(100ai).Chlorella sp.(100ai) was highly sensitive to arsenate, with an EC10of0.295mg/L. Underarsenite effect, Chl-a concentrations of Chlorella sp.(100ai) was lower than the controltreatments. While under arsenate effect, Chl-a concentrations of S. capricormulum andChlorella sp.(100ai) were lower than the control. It was suggested that the balance ofavailability of nutrients for optimum growth was disturbed at the presence of arsenic.Arsenic accumulation by algal cells was also investigated. After24hours, the arseniteremoval by C. vulgaris reached up to81.36%. The accumulation efficiency of arsenitefollowed the decending order of C. vulgaris> S. capricormulum> C. minata> Chlorella sp.(100ai)> Chlorella sp.(zfsaia). For arsenate, S. capricormulum had the highest removalefficiency (85.45%), followed by C. vulgaris, Chlorella sp.(zfsaia), Chlorella sp.(100ai) andC. minata. The biosorption of arsenic by microalgae was found associated with functionalgroups such as carboxyl (-COOH), amino (-NH), hydroxyl (-OH),-CO,-CH3,C-O-C,phosphate and sulfonic acid groups.Investigation of microalgal tolerance to arsenic and their biosorption abilities is critical to use this technique to treat arsenic contamination in aquatic bodies, which also is significantin understanding of the behavior of arsenic transfer and transformation in association withmicroalgae.