Heavy metal removal in primary sedimentation I. The influence of metal solubility

Abstract Heavy metal removal in the primary sedimentation process is primarily influenced by metal solubility and the settleability of insoluble forms. The fraction of the total metal in soluble form in raw sewage was investigated over a range of suspended solids (SS) concentrations and chemical oxygen demand (COD) values, obtained by adding primary sludge and a soluble synthetic sewage, respectively, to raw sewage samples. The soluble fraction in raw sewage was influenced to a greater extent by suspended solids than by COD. Increasing the suspended solids concentration caused marked decreases in the soluble fraction of Cd, Cr, Cu and Tl. The addition of soluble heavy metals in order to achieve concentrations typical of mixed industrial/domestic sewage did not in general have a significant effect on solubility. Thus, the removal of heavy metals could be assessed at these elevated concentrations in a pilot scale primary sedimentation plant. The plant was operated at four different influent suspended solids concentrations at each of four different hydraulic loadings covering the range from 0.5 to 5 dry weather flow (DWF) equivalents. Increases in influent suspended solids concentrations caused higher metal removals, whereas increasing the hydraulic loading had the opposite effect.

[1]  Barry G. Oliver,et al.  The efficiency of heavy metal removal by a conventional activated sludge treatment plant , 1974 .

[2]  J. Lester,et al.  Atomic-absorption spectrophotometric determination of antimony, arsenic, bismuth, tellurium, thallium and vanadium in sewage sludge. , 1982, Talanta.

[3]  John N. Lester,et al.  A study of the factors which influence metal removal in the activated sludge process , 1980 .

[4]  John N. Lester,et al.  Heavy metal removal in primary sedimentation II. The influence of metal speciation and particle size distribution , 1987 .

[5]  Robert Smith.  Preliminary Design of Wastewater Treatment Systems , 1969 .

[6]  T.H.Y. Tebbutt,et al.  Performance relationships for primary sedimentation , 1975 .

[7]  John N. Lester,et al.  Significance and behaviour of heavy metals in waste water treatment processes I. Sewage treatment and effluent discharge , 1983 .

[8]  John N. Lester,et al.  The balance of heavy metals through a sewage treatment works II. Chromium, nickel and zinc , 1979 .

[9]  R. M. Harrison,et al.  The balance of heavy metals through a sewage treatment works I. Lead, cadmium and copper , 1979 .

[10]  John N. Lester,et al.  The influence of flow conditions on the removal of heavy metals in the primary sedimentation process , 1983, Water, Air, and Soil Pollution.

[11]  John N. Lester,et al.  The influence of process parameters on the removal of heavy metals in activated sludge , 1982 .

[12]  John N. Lester,et al.  Atomic absorption spectrophotometric analysis of the metal content of waste water samples , 1980 .

[13]  D. Laxen,et al.  Comparison of filtration techniques for size distribution in freshwaters , 1982 .