Anaerobic digestion of sludges coming from biological wastewater treatment plants

Organic pollutants such as PAHs, PCBs and pesticides tend to accumulate in the primary and secondary sludges of biological plants treating domestic and industrial wastewaters. Thus, those sludges have to be submitted to a dedicated treatment, that generally consists in their thermal destruction. Anaerobic digestion could represent an alternative technology for the decontamination of such sludges. In fact, it can mediate the biodegradation of the occurring contaminants, the depletion of pathogenic microrganisms and the production of a biogas with a high content of methane. The effects of the anaerobic digestion (both under mesophilic and thermophilic conditions) on the final decontamination and disinfection of a sludge coming from a domestic water treatment plant and spiked with a mix of xenobiotics were investigated along with the possibility of enhancing the process by adding yeast extract. Methane production and xenobiotic removal were more efficient under mesophilic conditions while a complete disinfection of the sludge was achieved at 55°C. Yeast extract allowed to obtain better performances under mesophilic conditions both in terms of sludge decontamination and disinfection.