Anaerobic digestion found limited use in sludges from industrial wastewater treatment plants (WWTPs). So, it is of interest to assess the biodegradability and co-digestion performance of industrial sludges of biological origin alone and when mixed with municipal sludge. In this study, sludge from two different organized industrial districts (OIDs) and textile industry WWTPs are individually mixed with municipal sludge with and without ultrasound pretreatment to investigate their energy production potential and digestibility using biochemical methane potential tests. Sludges were used at different mass ratios in reactors with F/M ratio of 1. During operation, biogas amount and methane percentage were measured. Before and after reactor operation, total solids (TS), volatile solids (VS), chemical oxygen demand (COD) and pH were measured as performance indicators of digestion. Methane production potential was highest in reactors containing only municipal sludge and lowest containing only industrial sludge. The specific methane production normalized with COD removed for OID I, OID II and textile sludges were 0.13 L/g, 0.11 L/g and 0.11 L/g, respectively; whereas average specific methane production for municipal sludge was 0.31 L/g. COD, TS and VS reductions were lower in industrial sludges compared to domestic sludge. The co-digestion reactors with mixed industrial and municipal sludge performed in accordance with the proportion of two sludges. Ultrasonication improved the digestion performance. Although adding industrial sludge reduced the observed biogas amount to lower than that expected, results show that it is possible to co-digest some industrial sludges with municipal sludge in closely coordinated additions (about < 20%).

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