Effect of deflocculation on photo induced thin layer titanium dioxide disintegration of dairy waste activated sludge for cost and energy efficient methane production

In the present study, the deflocculated sludge was disintegrated through thin layer immobilized titanium dioxide (TiO2) as photocatalyst under solar irradiation. The deflocculation of sludge was carried out by 0.05 g/g SS of sodium citrate aiming to facilitate more surface area for subsequent TiO2 mediated disintegration. The proposed mode of disintegration was investigated by varying TiO2 dosage, pH and time. The maximum COD solubilization of 18.4% was obtained in the optimum 0.4 g/L of TiO2 dosage with 5.5 pH and exposure time of 40 min. Anaerobic assay of disintegrated samples confirms the role of deflocculation as methane yield was found to be higher in deflocculated (235.6 mL/gVS) than the flocculated sludge (146.8 mL/gVS). Moreover, the proposed method (Net cost for control - Net cost for deflocculation) saves sludge management cost of about $132 with 53.8% of suspended solids (SS) reduction.