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The aerobic microbial treatment of a groundwater contaminated with several organic compounds was investigated. This microbial process was combined with posttreatment by activated carbon. Mixed cultures were immobilised on polyurethane foam carrier material in a fluidised bed reactor. The main contaminants benzene and chlorobenzene were almost completely eliminated. Elimination rates remained high even at hydraulic retention times of about two hours. A complete elimination of the haloorganic compounds resistant to microbial degradation was achieved by subsequent adsorption on activated carbon. On the basis of the elimination rates and hydraulic retention times, established by these investigations, a technical scale plant combining microbial degradation and polishing adsorption can be designed. Due to the high degree of microbial mineralisation the presented process offers economic advantages over conventional methods. The quantity of residual waste products for disposal is also minimised.

Presents the findings of a study conducted to examine the efficiency of the combined anaerobic‐aerobic reactors for the treatment of three different tannery industrial wastewaters, focusing on the fate of chromium and other associated metals. Examines elimination rates of such metals with respect to each successive treatment process. Discusses the correlation between the chemical characteristics of the wastewater influent and effluent along with the level of heavy metals in such wastewater and the produced sludge. Confirms that the use of such sludge in agriculture should be restricted and recommends the recovery of Cr from the tanning sludge.

Describes a study carried out to evaluate the accumulation of heavy metals by two different vascular aquatic plants in the artificial wetlands which were constructed for the treatment of municipal wastewater in Berlin, Germany. The studied plants were Pharagmites australis and Schoenoplectus lacustris. The investigated metals were: Zn, Cr, Cu, Fe, Cd, Ni and Pb. The translocation of such metals in the plant roots, stems and leaves was also determined. The level of metals in the influent and effluent of the wastewater, as well as the sludge, was investigated. The concentration factor of each metal by plants and sludge was further studied. Results revealed that P. australis has a higher tendency for the accumulation of metals than S. Lacustris. The level of metals was higher in roots, followed by leaves, then stems. Metals were more concentrated in the sludge than in the plants. Further study showed that the levels of metals in plants grown in the artificial wetlands were higher than in those grown in a “controlled” area. Concludes that vascular plants can act as scavengers of metals from the municipal wastewater while still maintaining a healthy status.

In this study tannery industrial wastewater was supplied from a leather industry plant in the south of Germany. An anaerobic pilot plant was erected for the treatment of this wastewater. Discusses the effect of such an anaerobic process with special reference to the fate of chronium and the other associated heavy metals throughout the process. The studied metals were Cr, Cd, Pb, Ni, Cu, Fe and Zn. The elimination rate of these metals throughout the anaerobic processes from the wastewater and the increasing rate of metal correlations in the sludge were studied extensively. Levels of Cr, Cu, Fe, Cd, Ni, Pb and Zn in the raw wastewater after acidification were 33.72, 0.13, 1.82, 0.06, 0.19, 0.21 and 1.07 mg/l respectively. In the sludge the levels were 6,296, 16, 141, 31, 12.4, 23 and 94 mg/kg dry weight respectively. The levels of these metals were decreased by stabilization. The overall results revealed that a remarkable decrease has been achieved in the reduction level of metals in the final wastewater. The elimination of such metals reached 98 per cent for Cr, 53.8 per cent for Cu, 81.3 per cent for Fe, 16.7 per cent for Cd, 21.1 per cent for Ni, 72.9 per cent for Zn. On the other hand, such metals were concentrated in the sludge, on the dry weight basis, up to the levels of 13,193 mg Cr/kg, 27.7 mg Cu/kg, 348 mg Fe/kg, 3.2 mg Cd/kg, 13.7 mg Ni/kg, 28 mg Pb/kg and 110 mg Zn/kg. Meanwhile, the studied anaerobic process exhibited significant improvement in the quality of the tannery wastewater to meet the guideline characteristics. However, the partial high level of Cr (III) and the other associated metals in the produced sludge strongly militate against the use of such tannery sludges as manure in agriculture.

Investigates anaerobic two‐stage treatment of tannery wastewater. This results in a mean chemical oxygen demand (COD) removal of 60 per cent for tannery B and more than 70 per cent for tanneries A and C with COD_o = 5,710mg l^‐1 and mean detention time held at 3.5 days. Gas production was small, rating an estimated 75 l kg‐1 COD_o with COD_o = 5,710mg l^‐1. Tests simultaneously the influence of quality and quantity of wastewater on COD removal and gas production (multiple regression). Finds significant inhibitory effects were caused by chloride on gas volume and by sulphate on COD removal. Chromium showed no significant effect. Dosage of ferric chloride for removal of the toxic sulphide effected a decrease in gas volume and had no effect on COD removal (analysis of variance).