The use of selected purple nonsulfur bacteria to remove heavy metals and salts from sediment and water collected from contaminated areas to decrease their phytotoxicity

Abstract

The potential of the purple nonsulfur bacteria (PNSB), NW16 and KMS24, to remove heavy metals (HMs) and salts was investigated in a synthetic solution (62.63 Pb²⁺, 34.60 Cu²⁺, 58.5 Zn²⁺ and 0.75 Cd² mg/L) containing 3% NaCl, sediment, and water collected from contaminated post cultured shrimp ponds and seed germination of 2 plants were used to assay their plant toxicities after bioremediation. Both light metal ions (85 mg/L Ca²⁺ and 160 mg/L Mg²⁺ to the synthetic HMs solution) significantly decreased the HMs removal efficiency and the mixed culture gave the highest efficiency to remove HMs (removal percentages; 85 Pb²⁺, 74 Cu²⁺, 47 Zn²⁺ and 28 Cd²⁺). The best set for the treatment of contaminated water from shrimp ponds (Cu²⁺, Zn²⁺; 0.043, 0.057 mg/L and salinity, 10.23%0) under the conditions of aerobicdark and microaerobic-light was a set of native with added mixed culture with a decrease of roughly 75, 31 and 77% for Cu²⁺, Zn²⁺ and salinity, respectively. For the sediment samples, a set of native with added mixed culture also produced the highest efficiency to remove HMs (initial concentrations in mg/kg dry weight; 23.15 Pb²⁺, 15.05 Cu²⁺, 22.16 Zn²⁺ and 0.29 Cd²⁺) and salinity (0.84%0) under aerobicdark conditions with the removal percentages of HMs; 84.29, 62.52, 43.33 and 40.95, and 100% salinity. Consequently, this set produced the most effective treatment as the germination index was 34.50 and 35.29% for rice seed (Oryza sativa) and water spinach (Ipomoea aquatic) respectively in the treated water and 115.70 and 139.33% for rice and water spinach respectively in the treated sediment.

Keywords: Bioremediation, contaminated shrimp ponds, heavy metals, photosynthetic bacteria, salinity, seed germination index

African Journal of Biotechnology Vol. 11(29), pp. 7434-7444, 10 April, 2012