Pathogen Content of Sewage Sludge Mitigation. Requirement for Agricultural Valorization

Among the main priorities of the EU’s strategy regarding sewage sludge, improving of treatment conditions for waste recovery is of interest. The key factors involved in production of stable biosolid (treated sewage sludge) are advanced disinfection and stabilization, prior to land application. The aerobic composting of anaerobic digested residual organic sludge from urban WWTPs ensures the transformation of waste into a valuable product, compost used as agricultural fertilizer. The biotechnological solutions set up by INCD ECOIND for the post-treatment of stabilized sludge provide high pathogens reduction (fecal Coliforms/99.9%, fecal Streptococcus/99.9%, Escherichia coli/89%) but the residual level of E.coli (over the detection limit) still arises environmental and health concerns. Application of ultrasound process as a pre-treatment step of anaerobic digestion has an important effect on the bacterial mortality, with improving in the same time of activated sludge stabilization and biogas production. Low frequency sonication, based on cavitation effects, can destroy the bacterial cell membrane of E.coli, high susceptible to this treatment. The coupling of advanced oxidation techniques based on sonolysis and ultraviolet irradiation (US/UV) is able to achieve total removal of pathogens.