Effects of an Activated Primary Settling Tank on Biological Phosphorus Removal Available to Purchase

This poster describes results and experiences gained at the wastewater treatment plant of the city of Hirblingen to improve the biological phosphorus removal. Investigations were carried out to study the accumulation of volatile fatty acids in an activated primary settling tank (PST), and in the Extended Anerobic Sludge Contact (EASC) Process. The effluent of the activated primary settling tank provided no higher concentrations of VFA compared with the efffluent of of regular settling tank. Laboratory batch-tests confirmed these results. The elimination of N_tot and P_tot was marginally improved, the gas production in the digester decreased. In batch tests the production of VFA was examined in correlation of organic load, pH value and temperature.