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Ushani, U.,Rajesh Banu, J.,Kavitha, S.,Kaliappan, S.,Yeom, Ick Tae Elsevier 2017 CHEMOSPHERE - Vol.175 No.-
<P><B>Abstract</B></P> <P>In this study, an attempt was made to disintegrate waste activated sludge (WAS) in a cost-effective way. During the first phase of this study, effective break down of extracellular polymeric substance (EPS) was performed by deflocculating WAS with 0.1 g/g SS of MgSO<SUB>4</SUB>. Deflocculation rate was 92% with discharge rate of extractable EPS at 185 mg/L. In the second phase, effective bacterial cell disintegration was obtained at 36 h post treatment. Maximum solubilization of deflocculated sludge was approximately 21%, which was higher than that of flocculated sludge (14.2%) or the control (4.5%). Biodegradability studies were assessed through kinetic analysis by non-linear regression modeling. Results revealed that the deflocculated sludge had higher methane generation (at about 235.8 mL/gVs) compared to flocculated sludge (at 146.1 mL/gVs) or the control (at 34.8 mL/gVs). Cost assessment of the present work revealed that the net yield for each ton of the deflocculated sludge was about 32.99 USD.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Optimum floc disruption was occurred at 0.1 g/g SS of MgSO<SUB>4</SUB>. </LI> <LI> COD Solubilization of about 21% is obtained in deflocculated sludge. </LI> <LI> A higher methane generation of 235.8 mL/gVs was achieved for deflocculated sludge. </LI> <LI> A net profit of 32.99 USD was obtained for deflocculated sludge. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Ushani, U.,Rajesh Banu, J.,Tamilarasan, K.,Kavitha, S.,Tae Yeom, Ick Elsevier 2017 Bioresource technology Vol.241 No.-
<P><B>Abstract</B></P> <P>The objective of this study was to evaluate the effect of dioctyl sodium sulphosuccinate (DOSS, a surfactant) on lysis rate of sludge and specific energy required for sonic pretreatment of waste activated sludge (WAS). Different ultrasonic power levels, WAS concentrations, DOSS dosages, and specific energy levels were used to compare pretreatment efficiencies. At an optimum time of 10min with ultrasonic power level of 160W, DOSS coupled sonic pretreatment resulted in better lysis rate (24.7%) of sludge than sonic pretreatment (17.6%). Biodegradability estimation through non-linear regression modeling revealed that DOSS coupled ultrasound pretreatment of sludge showed better biodegradability with higher hydrolysis constant (about 0.25d<SUP>−1</SUP>) than sonic pretreatment (0.19d<SUP>−1</SUP>). Nearly six times less energy was required for DOSS coupled ultrasound pretreatment compared to that required for sonic pretreatment. Therefore, DOSS coupled ultrasound pretreatment makes the pretreatment process energetically positive.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A novel attempt to minimize energy demand of ultrasonication through surfactant. </LI> <LI> Lysis rate of about 24.7% was obtained with 0.05g/gSS of DOSS. </LI> <LI> Biodegradability rate constant of 0.25d<SUP>−1</SUP> was attained for coupled pretreatment. </LI> <LI> Coupled pretreatment saves considerable amount of energy than sonic pretreatment. </LI> <LI> Coupled pretreatment makes the disintegration process energetically positive. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Kavitha, S.,Rajesh Banu, J.,Subitha, G.,Ushani, U.,Yeom, I.T. Elsevier Applied Science 2016 Bioresource technology Vol.219 No.-
The objective of this study was to determine the impact of solubilization during thermo-chemo-sonic pretreatment of waste activated sludge (WAS) on anaerobic biodegradability and cost for biogas production. The results revealed that it was possible to achieve 40-50% of solubilization of WAS when ultrasonic energy input was doubled (11,520-27,000kJ/kgTS). The cost to achieve 30-35% of solubilization of WAS was calculated to be 0.22-0.24USD/L, which was relatively lower than the cost of 0.53-0.8USD/L when 40-50% of solubilisation of WAS was achieved. There was no significant difference in biodegradability (0.60-0.64gCOD/gCOD) for samples with solubilization efficiency of 35-50%. Comparing energetic balance and economic assessment of samples with different solubilization percentages, the results showed that samples with 30-35% of solubilization had lower net cost (7.98-2.33USD/Ton of sludge) and negative energy balance compared to samples with other percentages of solubilization.