Wastewater treatment in a company with advanced demands for water quality

Abstract

The result of the North Sea Conference 1987 in London was the 50% reduction of dangerous and nutritive substances before 1995. To reach that aim the wastewater treatment plants discharging to the river Elbe were subjected to more severe discharge standards. In our case the company could also use the publicly owned treatment plant of Hamburg and so we were in direct competition with that plant. After several conferences with the client and the water authority we began the planning. The treatment plant also includes removal of nitrogen in the last stage and phosphorus in the biological stage (not only with chemicals). Another difficulty was that only a small area between the dam of the Elbe with a street alongside and the offices was available. So we had to plan a very compact treatment plant. To avoid the emission of odours the plant was completely housed. As in other factories we also had the problem that on weekends and during the holidays very little water is flowing to the plant. The sewage system collected the wastewater in one system and stormwater in another. Since the area is flat, several pumpstations transport the water. So we planned a modular system with sieve screen and three SBR reactors to use it further as cascaded activated sludge tanks with predenitrification and enhanced biological phosphorus removal. The sludge treatment was realized as an aerobic thermophilic process in a separate tank. To improve matters we also installed a computer for process control. The influent concentrations are higher than municipal wastewater which is conditioned by the separate system of transportation without infiltration water. For example COD influent concentrations are about 1500 mg/l, NH4-N about 130 mg/l and total phosphorus Ptot about 17 mg/l. The results we obtained in the plant are presented in this paper.