Influence of Returned Water from Sludge Treatment and Return Activated Sludge on 2-Methylisoborneol and Geosmin Behaviors and Concentrations during Wastewater Treatment

Abstract

Compounds such as 2-methylisoborneol (2-MIB) and geosmin present in the final effluents of wastewater treatment plants may affect water treatment in downstream areas. To reduce the concentrations of 2-MIB and geosmin, we investigated the influence of the returned water from sludge treatment on their concentrations and behaviors during wastewater treatment in the reactor. The inflow of returned water from sludge treatment increased the geosmin concentration in the primary effluent (PE) making it higher than that in the influent. The dissolved 2-MIB concentration in the mixed liquor was higher than that in the PE. However, the geosmin concentration in the mixed liquor tended to be lower than that in the PE as the biological treatment progressed. Laboratory experiments indicated that the 2-MIB and geosmin concentrations varied in the reactor due to their release from activated sludge and removal by aeration and agitation. Our analyses revealed that the return activated sludge substantially impacts 2-MIB concentrations in secondary effluents. Moreover, the geosmin concentration in the reactor decreased, possibly due to removal by aeration and agitation.