| Description |
[vi], 75 leaves : illustrations ; 28 cm |
| Summary |
"The primary objective of this investigation was to determine the effect of nickel on activated sludge over a comprehensive range of concentrations and to evaluate the ability of the sludge to acclimate and become more tolerant to the metal. Six one-liter fill and draw activated sludge units were fed domestic sewage; five of these units also received constant, increasing, and shock doses of nickel while the sixth was maintained as a control. Treatment efficiency was evaluated in terms of the chemical oxygen demand, suspended solids, and nickel content of the effluent. A Warburg respirometer was also employed and was operated at 20°C; reaction flask mixtures consisting of sewage and either acclimated or nonacclimated activated sludge at constant mixed liquor suspended solids were exposed to different nickel concentrations. Nickel above certain concentrations was found toxic; the toxicity threshold limit was approximately 2 mg/l. Nickel doses in the range of 0.5 to 4.0 mg/l, 1.0 to 8.0 mg/l, and 1.0 to 16 mg/l or higher when added to activated sludge units caused little, moderate, and serious effects. The 24 hour oxygen uptake of acclimated activated sludge in the Warburg respirometer was inhibited by less than 20 per cent when nickel at doses of 12 mg/l or less was added and by more than 70 per cent when 60 mg/l or more were used. Acclimation considerably reduced the toxicity of the metal. Neither the acclimated or the nonacclimated sludge removed appreciable amounts of nickel and significant concentrations of the metal were discharged in the effluent. Pilot plant investigations complemented by Warburg respirometer studies were found to be desirable for comprehensive investigation"--Abstract, leaf [ii]. |
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