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Zhuo G.,Tongji University | Yan Y.,Tongji University | Yan Y.,Research and Service Center for Environmental Protection Industry in Yancheng | Tan X.,Shanghai Municipal Engineering Design Institution | And 2 more authors.
Journal of Biotechnology | Year: 2012

The effect of temperature on the hydrolysis and acidification of ultrasonic-pretreated waste activated sludge (WAS) under alkaline conditions was investigated in this study. The experiment temperatures were set at 10, 20, 37, and 55 °C. Experimental results showed that the hydrolysis of ultrasonic-pretreated WAS under alkaline conditions increased significantly with temperature from 10 to 55 °C, while the volatile fatty acid (VFA) accumulation was not augmented as temperature increased. Among the four temperatures tested, 37 °C was the point with the highest VFA accumulation after 72. h fermentation. VFA accumulation decreased markedly at 55 °C compared to 37 °C. Mechanism investigation revealed that among all the temperatures tested, 37 °C was the temperature at which consumptions of WAS protein and carbohydrate, activities of key enzymes related to VFA formation and ratio of Bacteria to Archaea all reached the maximum. Due to activities of related microorganisms inhibited by higher temperature (55 °C), VFA accumulation decreased at 55 °C. © 2012 Elsevier B.V. Source


Yan Y.,Tongji University | Yan Y.,Research and Service Center for Environmental Protection Industry in Yancheng | Chen H.,Tongji University | Xu W.,Tongji University | And 2 more authors.
Biochemical Engineering Journal | Year: 2013

Excess sludge with low organic content always led to the failure of anaerobic digestion for methane production. Recently, the mild thermal pretreatment, which is usually operated at temperatures below 120 °C, has drawn much attention due to less energy consumption and no chemical addition. In this study the effect of mild thermal pretreatment (50-120 °C) on the solubilization and methane potential of excess sludge with a low concentration of organic matters was investigated. Experimental results showed that the concentration of soluble organic matters increased gradually with temperature during the mild thermal pretreatment of excess sludge. Biochemical methane potential experiments demonstrated that the potential of methane production from excess sludge was greatly enhanced by mild thermal pretreatment, and under the conditions of pretreatment temperature 100 °C and digestion time 20 d the methane yield was as high as 142.6 ± 2.5. mL/g of volatile solids. Mechanism investigation on the enhancement of methane production from excess sludge exhibited that the consumptions of sludge protein and carbohydrate, the adenosine 5'-triphosphate content of anaerobic microorganisms, the activities of key enzymes related to anaerobic digestion, and the amount of methanogens were all improved by mild thermal pretreatment, in correspondence with the production of methane. © 2012 Elsevier B.V. Source


Feng L.Y.,Tongji University | Feng L.Y.,Research and Service Center for Environmental Protection Industry in Yancheng | Yang L.Q.,Tongji University | Zhang L.X.,Tongji University | And 2 more authors.
Water Science and Technology | Year: 2013

Sludge with low organic content always results in an unsatisfactory performance, even failure of anaerobic digestion. The alkaline pretreatment effect on anaerobic digestion of sludge with low organic content has seldom been studied although it gives many benefits for sludge with high organic content. In this study the influence of alkaline pretreatment (pH 10, an effective alkaline pH) on the solubilization and methane production from waste activated sludge (WAS) with low organic content was investigated. Results from biochemical methane potential (BMP) experiments showed that anaerobic biodegradability of WAS was greatly improved by alkaline pretreatment at pH 10. Methane production from the current WAS under conditions of pretreatment time 4 h and digestion time 15 d was 139.6 mL/g VS (volatile solids), much higher than that from the unpretreated WAS with digestion time of 20 d (75.2 mL/g VS). Also, the solubilization of WAS was significantly accelerated by alkaline pretreatment. Mechanism exploration indicated that the general activities of anaerobic microorganisms, specific activities of key enzymes and the amounts of methanogens were enhanced by alkaline pretreatment at pH 10, showing good agreement with methane production. © IWA Publishing 2013. Source

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