Treatment of easily biodegradable wastewater avoiding bulking sludge.

The presence of easily degradable compounds from food industries frequently leads to bulking problems. The paper describes a new process that has been developed for a dairy in Austria. Because of the increase in production the treatment plant receiving the wastewater up to now was not able to handle the increased loads. Therefore detailed studies for treatment alternatives have been undertaken which led to a completely new concept. The excess sludge of the urban treatment plant is contacted with the concentrated dairy waste in a separate contact tank. In this tank the easily degradable substrate from the industrial waste is mainly adsorbed to the biological sludge and after a mechanical dewatering transferred to the anaerobic digester where it yields an increased gas production. The filtrate of the dewatering process is completely free from biodegradable material and can without danger of bulking be fed to the aeration tank. The process has been in operation for more than one year and has fulfilled all expectations.