BIOPRECIPITATION OF SOME TOXIC METAL-IONS BY SEWAGE BACTERIA

The presence of sulphate-reducing bacteria (Desulfoibriodesulfuricans) in the domestic sewage sludge has been experimentally confirmed. The bacterial count is found to be 7.5 x 10(6)/g sewage sludge. Treatment of solutions of Pb(II), Cu(II), Ce(IV), Mn(II), Hg(II), Ni(II), Co(II) and Zn(II), each containing 500 mg of the cations in 250 mL solution, with 10g of the sewage sludge in presence of 1 g sulphur powder and I g glucose as nutrient, indicates the extent of bioprecipitation of the metal ions in the order: Pb(II) > Cu(II) = Ce(IV) > Mn(II) > Hg(II) > Ni(II) > Co(II) > Zn(II). The effects of experimental conditions and extraneously added materials on the rates of bioprecipitation has also been studied.