Sewage-treatment under substantial load variations in winter tourism areas--a full case study.

The sewage-load variations in winter tourism areas are characterized by sudden increases - in the range of a factor two to three - within only a few days at the start and the end of the tourist season, especially at Christmas. The sudden load increases occur during periods of low wastewater temperatures, which is an additional demanding factor with respect to nitrogen removal. A full case study was carried out at WWTP Saalfelden, which is located near one of Austria's largest skiing resorts. The plant is designed for 80,000 PE and built according to the HYBRID(R)-concept, which is a special two stage activated sludge process for extensive nutrient removal.