Enhancement of sludge anaerobic biodegradability by combined microwave-H2O2 pretreatment in acidic conditions

Eswari, Parvathy; Kavitha, S.; Kaliappan, S.; Yeom, Ick-Tae; Banu, J Rajesh

Enhancement of sludge anaerobic biodegradability by combined microwave-H2O2 pretreatment in acidic conditions

2016

Eswari, Parvathy | Kavitha, S. | Kaliappan, S. | Yeom, Ick-Tae | Banu, J Rajesh

The aim of this study was to increase the sludge disintegration and reduce the cost of microwave (MW) pretreatment. Thermodynamic analysis of MW hydrolysis revealed the best fit with a first-order kinetic model at a specific energy of 18,600 kJ/kg total solids (TS). Combining H₂O₂ with MW resulted in a significant increment in solubilization from 30 to 50 % at 18,600 kJ/kg TS. The pH of H₂O₂-assisted MW-pretreated sludge (MW + H₂O₂) was in the alkaline range (pH 9–10), and it made the sludge unfavorable for subsequent anaerobic digestion and inhibits methane production. In order to nullify the alkaline effect caused by the MW + H₂O₂ combination, the addition of acid was considered for pH adjustment. H₂O₂-assisted MW-pretreated sludge in acidic conditions (MW + H₂O₂ + acid) showed a maximum methane production of 323 mL/g volatile solids (VS) than others during anaerobic biodegradability. A cost analysis of this study reveals that MW + H₂O₂ + acid was the most economical method with a net profit of 59.90 €/t of sludge.

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