Thiemo Dunkel
University of Duisburg-Essen, Germany
Title: Towards a specific controlling strategy to prevent filamentous bulking and foaming considered as the last major unsolved problem in operation of activated sludge systems
Biography
Biography: Thiemo Dunkel
Abstract
The succesful operation of activated sludge (AS) processes is ultimatively depending on a sufficient separation of activated sludge from treated water in secondary clarifiers to guarantee a high effluent quality. However, most AS plants suffer from disturbances in the sludge settling process mainly referred to filamentous bulking and foaming which are described as the last major unsolved problem in the operation of AS systems (Soddell and Seviour, 1990). Poor settling biomass may lead to low effluent quality, increased economic costs and potential environmental impacts. Up to now, no reliable specific controlling method to prevent filamentous bulking and foaming exists. Our recent research is focused on the development of a specific controlling strategy to avoid filamentous overgrowth. Alongside fluorescence in situ hybridisation and next generation sequencing were used for the identification of dominant filamentous bulking and foaming bacteria (BFB) in AS systems showing increased abundances of M. parvicella, Gordonia and Chryseobacteria known to cause filamentous foaming. The combination of real-time polymerase chain reaction for the quantification of these BFB and multidimensional gaschromatography for the analysis of wastewater composition revealed a highly singificant linear relationship between long chain fatty acid (LCFA) loadings and the growth of dominant BFB. Based on these findings a specific controlling strategy was developed with regard to the removal of LCFAs from wastewater influents to inhibit the overgrowth of BFB. This controlling strategy was succesfully validated in a pilot-scale trial in an industrial WWTP (Germany).