Abstract
The degradation of micropollutants (pesticides) absorbed in agro-food industrial sewage sludge was investigated during its excess reduction by disintegration with ultrasound treatment. Sludge sonication (24kHz and 323W) was performed in batch mode in a stainless steel ultrasonic flow-through reactor connected to a recirculation tank. The maximum sludge disintegration was reached by supplying 0.87MJL−1 ultrasound dose (UD) giving rise to 68.7% solubilisation of the carbon content in the disintegrated biomass. The sonicated sludge was biodegradable, thus able to be returned as feed in the secondary wastewater treatment. The ultrasound (US) treatment resulted in a significant reduction in the sludge pesticide content (90% of the total pesticide mass was removed), therefore preventing pollutant accumulation in the sludge. Investigation into the sono-degradation of three characteristic pesticides (thiabendazole, acetamiprid and imazalil) revealed the formation of transformation products (TPs) already reported in studies on the degradation of these compounds by advanced oxidation processes, thus confirming that ultrasonication involves hydroxyl radical reactions. Our results show that this US treatment for the excess sludge reduction is also efficient for pesticides and their TPs removal.
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