BIOLOGICAL TREATMENT OF MUNICIPAL WASTEWATER IN BERLIN, USING A 10 m DEEP BASIN AND FLOTATION FOR SECONDARY CLARIFICATION

For municipal treaunent of wastewater, the space-saving 10 m deep basins biological treaunent is an interesting alternative to conventional activated sludge basins of shallow construction. Results of pilot tests in the Berlin-Ruhleben wastewater clarification plant have shown that the biological P-elimination, nitrification and denitrification processes can be implemented as in shallow basins. However, the activated sludge did not settle satisfactorily. So flotation was implemented in the process for secondary clarification and in the meantime has shown to be a big advantage. In a year-long test with the pilot unit, the functional efficiency of the process could be proven. Energy requirements for both systems were found to be approximately the same. A cost estimate based on a preplan revealed a 10% advantage in favour of the 10 m deep biological treaunent basin. For these reasons and for the possibility to further improve this process, three large clarification plants using 10 m biological technology and flotation for secondary clarification will be built in Berlin in the near future.