Tracing the limits of organic micropollutant removal in biologicalwastewater treatment

摘要

Removal of organic micropollutants was investigated in 15 diverse biological reactors through short and long-term experiments. Short-term batch experiments were performed with activated sludge from three parallel sequencing batch reactors (25, 40, and 80 d solid retention time, SRT) fed with synthetic wastewater without micropollutants for one year. Despite the minimal micropollutant exposure, the synthetic wastewater sludges were able to degrade several micropollutants present in municipal wastewater. The degradation occurred immediately after spiking (1–5 μg/L), showed no strong or systematic correlation to the sludge age, and proceeded at rates comparable to those of municipal wastewater sludges. Thus, the results from the batch experiments indicate that degradation of organic micropollutants in biological wastewater treatment is quite insensitive to SRT increases from 25 to 80 days, and not necessarily induced by exposure to micropollutants. Long-term experiments with municipal wastewater were performed to assess the potential for extended biological micropollutant removal under different redox conditions and substrate concentrations (carbon and nitrogen). A total of 31 organic micropollutants were monitored through influent-effluent sampling of twelve municipal wastewater reactors. In accordance with the results from the sludges grownon synthetic wastewater, several compounds such as bezafibrate, atenolol andacyclovir were significantly removed in the activated sludge processes fed withmunicipal wastewater. Complementary removal of two compounds, diuron and diclofenac,was achieved in an oxic biofilm treatment. A few aerobically persistentmicropollutants such as venlafaxine, diatrizoate and tramadol were removed underanaerobic conditions, but a large number of micropollutants persisted in allbiological treatments. Collectively, these results indicate that certain improvementsin biological micropollutant removal can be achieved by combining different aerobicand anaerobic treatments, but that these improvements are restricted to a limitednumber of compounds.