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Investigation of methane production potential of industrial sludges mixed with domestic sludge during anaerobic digestion

Aksu Bahçeci, Hazal
Anaerobic digestion has been established as a sludge stabilization and biogas production method for domestic sludge. However, anaerobic digestion has limited success in industrial sludge applications. In this thesis sludge from two different Organized Industrial Districts (OIDs) and textile industry are mixed with urban wastewater sludge with and without ultrasound pretreatment to investigate their energy production potential by using BMP tests. Sludges were digested alone (A for industrial, D for domestic sludge) or in mixtures (B: 2:1 industrial: municipal; C: 1:2 industrial: municipal; E: 0.5:2.5 industrial: municipal). During the operation biogas amount and methane percentage were measured. At the end of reactor operation, removals of total solids (TS), total suspended solids (TSS), volatile solids (VS) and volatile suspended solids (VSS) as well as pH were measured. TS removal for OID I, OID II and textile sludges were found as 11%, 11%, 8%, respectively for industrial sludge samples only (reactor A). On the other hand, VS removal were found as 20%, 20%, 11%, respectively for the same reactors. COD removal for OID I, OID II and textile sludges alone were found as 17%, 15%, 6.5%, respectively. When the municipal sludge was digested its average TS, VS and COD removals were 23%, 46% and 36%, respectively. The co-digestion reactors performed in accordance with the proportion of sludge that they contained. The methane amount produced per g of COD destroyed for only the industrial sludges were 0.11 L/g, 0.13 L/g and 0.12 L/g, respectively. The industrial sludges co-digested with the domestic sludge have biogas production potentials. Even though adding industrial sludge reduced the observed biogas amount to lower than that expected, results show that it is possible to co-digest industrial sludge with municipal sludge together.