According to European agreements, many WWTPs (waste water treatment plants) have to be modified and extended to reach stricter effluent standards with regard to phosphorus and nitrogen. This paper presents the modification of a 300,000 p.e. WWTP. The following steps are distinguished: location/centralization study, process pre-selection, pilot tests and process control.

Most important aspects in the location study are costs and ecological importance of the receiving water. In the process pre-selection study two nitrogen and phosphorus removal processes were selected: a high cost/low risk process and a low cost/high risk process. Final selection of the Bio-Denipho process was based on comparison of both processes in pilot tests. During the six months operation period the process control programs for weekdays/weekends, day hours/night hours, dry weather flows/storm weather flows resulted in low nitrogen concentrations in the effluent.

Biological phosphorus removal, nitrogen removal, nitrification, denitrification, anaerobic tank, Bio-Denipho, Bio-Denitro, pilot plant, process selection, process optimization
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© IWA Publishing 1996
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