VEAS - English
Vestfjorden Avløpsselskap, VEAS WWTP, is serving a large part of the city of Oslo and three neighbouring communities, and was put in operation in 1982. It was originally a pre-precipitation plant for phosphorous removal. The removal rate for phosphorous was by the end of the 1980`s 97 %, at a total retention time of 3 hours.
The North Sea Agreement and the low oxygen levels in the deep water in the inner Oslofjord led to new effluent demands. A new treatment concept was developed; “The VEAS Concept for Nitrogen Removal”. It is a very compact process, and it had to be, since the plant was located in rock caverns with limited space for expansion. In January 1994 the first line with biological treatment was put in operation. Late in1995 the water treatment process was completed, but the sludge and return stream treatment was not finished.
Sludge digestion was put in operation in 1993, and from late1994 one of the four digesters was used for biological hydrolysis as a pre-treatment before methane production. In 1996, the original gravity thickeners were replaced with drum thickeners. The treatment of the filtrate from the filter presses, with ammonia stripping, started in 1997. Testing and implementation of thermal vacuum drying of sludge is going on.