The reduction processes at four advanced sewage treatment plants in Baden-Württemberg were evaluated with regard to virus elimination and the elimination of indicator organisms from wastewater. The results of virus elimination were compared with the reduction of somatic and male specific bacteriophages and of E. coli. In total, 222 water samples were examined. The results obtained for the different treatment plants show reduction rates from 80.0% to 99.9% for enteroviruses, enumerated as PFU l−1 on BGM cell line, and reduction rates from 59.4% to 99.9% for other enteric viruses, enumerated as MPN l−1 on MA-104 cell line. Identification of the isolated enteroviruses yielded 88.3% for Coxsackie virus B (1-5), 18.3% were positive for Polio (1-3) and 8.3% for Echo virus (1+11). The reduction rates of somatic bacteriophages ranged from 76.4% to 99.90%, for male specific bacteriophages from 87.5% to 99.9% and for E. coli. from 75.0% to 99.9% respectively. Two of the plants use standard chemical precipitation and the other two employ combinations of chemical and biological elimination techniques to reduce the concentrations of phosphorus and nitrogen. A correlation between the amount of precipitators and the elimination rates of the tested microorganisms could not be demonstrated, perhaps due to the fact that the treatment conditions could not be modified by the investigators. It is concluded that the tested treatment plants using combinations of chemical and biological techniques for P and N removal show equal or higher elimination rates than conventional treatment processes using chemical elimination techniques.

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