[Quantitative studies of the elimination of coliphages and other fecal indicators during wastewater treatment].

Concentrations of coliphages, coliforms, enterococci and fluorescent Pseudomonas were monitored in several wastewater purification steps of the treatment plant Wolfenbüttel during one year. Their number varied widely during the investigation period, but was independent of seasons. In the course of sewage treatment, including primary settling, activated sludge purification, simultaneous precipitation, trickling filters and oxidation pond, the concentration of indicators decreased gradually. The coliphages were most resistant, exhibiting only a decimal elimination value of 1.7 log10 units as compared to the bacterial indicators with elimination values ranging between 2.4 and 2.8 log10 units in the whole process. The most efficient purification step revealed to be the activated sludge procedure including simultaneous phosphate precipitation with iron hydroxides and sedimentation. On an average 1.7% of the coliphages present in raw sewage or 9.8.10.11 phages were discharged into the river Oker everyday, 0.64% remained in the sludge. Numbers of indicators in the water of the oxidation pond and those seeded into river water were continuously reduced during 3 days. Also in these laboratory experiments, the coliphages were more resistant than the bacteria, but no evidence was found to support the view that coliphages play a role in the reduction of the number of coliform bacteria. Even after addition of peptone which stimulated growth of E. coli the coliphages were inactivated more rapidly. The behaviour of coliphages during the purification process is compared with literature data about enteroviruses.