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Lin Y.,Tongji University | Lu F.,Tongji University | Shao L.,Center for the Technology Research and Training on Household Waste in Small Towns and Rural Area | He P.,Tongji University
Bioresource Technology | Year: 2013

To investigate the influence of bicarbonate on the metabolic pathway of methanogenesis, different concentrations of bicarbonate (0-0.2mol/L) were applied during thermophilic anaerobic digestion of 2.5 and 5g/L glucose. The stable carbon isotopic results demonstrated that, as the bicarbonate concentration increased, the proportion of total CH4 generated from hydrogenotrophic methanogenesis generally increased. Furthermore, methane production rates and acetate degradation rates were seriously reduced under high levels of bicarbonate (0.15 and 0.2mol/L). Meanwhile, carbon isotope fractionation was more prominent in treatments with 5g/L glucose than that of 2.5g/L glucose. Increased concentrations of bicarbonate altered the dominant methanogens and bacteria and increased the microbial diversity. The inhibitory effects of high concentrations of bicarbonate suggested that bicarbonate should be used cautiously as a buffer salt in anaerobic processes, especially when methanogenetic pathways were studied. © 2013 Elsevier Ltd. Source


Lu F.,Tongji University | Li T.,Tongji University | Wang T.,Tongji University | Shao L.,Center for the Technology Research and Training on Household Waste in Small Towns and Rural Area | He P.,Tongji University
Applied Microbiology and Biotechnology | Year: 2014

The sludge digestate stabilized by mesophilic anaerobic digestion was further degraded through thermophilic anaerobic digestion using 0-10 % (v/v) of thermophilic, proteolytic Coprothermobacter proteolyticus, and/or methanogenic granular sludge. The results demonstrated that the temperature shift to thermophilic condition promoted abiotic solubilization of proteins and reactivated the fermentative bacteria and methanogens indigenous in the sludge digestate, resulting in a final methane yield of 6.25 mmol-CH 4/g-volatile suspended solid (VSS) digestate. The addition of C. proteolyticus accelerated the hydrolysis and fermentation of proteins and polysaccharides in the digestate during the early stage of thermophilic anaerobic digestion and stimulated methane production by syntrophic cooperation with methanogenic granular sludge. In the treatment with granular sludge and inoculated with 10 % (v/v) of C. proteolyticus, a final methane yield of 7 mmol-CH4/g-VSS digestate was obtained, and 48.4 % proteins and 27.0 % polysaccharides were degraded. The dissolved proteins were contributed by abiotic factor, C. proteolyticus, and indigenous digestate bacteria, respectively, by around 16, 28, and 56 %. © 2013 Springer-Verlag Berlin Heidelberg. Source


Lu F.,Tongji University | Luo C.,Tongji University | Shao L.,Tongji University | Shao L.,Center for the Technology Research and Training on Household Waste in Small Towns and Rural Area | And 2 more authors.
Water Research | Year: 2016

This investigation evaluated the effectiveness of biochar of different particle sizes in alleviating ammonium (NH4+) inhibition (up to 7 g-N/L) during anaerobic digestion of 6 g/L glucose. Compared to the control treatment without biochar addition, treatments that included biochar particles 2-5 mm, 0.5-1 mm and 75-150 μm in size reduced the methanization lag phase by 23.9%, 23.8% and 5.9%, respectively, and increased the maximum methane production rate by 47.1%, 23.5% and 44.1%, respectively. These results confirmed that biochar accelerated the initiation of methanization during anaerobic digestion under double inhibition risk from both ammonium and acids. Furthermore, fine biochar significantly promoted the production of volatile fatty acids (VFAs). Comparative analysis on the archaeal and bacterial diversity at the early and later stages of digestion, and in the suspended, biochar loosely bound, and biochar tightly bound fractions suggested that, in suspended fractions, hydrogenotrophic Methanobacterium was actively resistant to ammonium. However, acetoclastic Methanosaeta can survive at VFAs concentrations up to 60-80 mmol-C/L by improved affinity to conductive biochar, resulting in the accelerated initiation of acetate degradation. Improved methanogenesis was followed by the colonization of the biochar tightly bound fractions by Methanosarcina. The selection of appropriate biochar particles sizes was important in facilitating the initial colonization of microbial cells. © 2015 Elsevier Ltd. Source


Shao L.-M.,Tongji University | Shao L.-M.,Center for the Technology Research and Training on Household Waste in Small Towns and Rural Area | Zhang C.-Y.,Tongji University | Wu D.,Tongji University | And 4 more authors.
Waste Management | Year: 2014

The effects of rice straw addition level on odorous compounds emissions in a pilot-scale organic fraction of municipal solid waste (OFMSW) composting plant were investigated. The cumulative odorous compounds emissions occurred in a descending order of 40.22, 28.71 and 27.83. mg/dry. kg of OFMSW for piles with rice straw addition level at ratio of 1:10, 2:10 and 3:10 (mixing ratio of rice straw to OFMSW on a wet basis), respectively. The mixing ratio of rice straw to OFMSW had a statistically significant effect on the reduction of malodorous sulfur compounds emissions, which had no statistically significant effect on the reduction of VFAs, alcohols, aldehydes, ketones, aromatics and ammonia emissions during composting, respectively. The cumulative emissions of malodorous sulfur compounds from piles with the increasing rice straw addition level were 1.17, 1.08 and 0.88. mg/dry. kg of OFMSW, respectively. The optimal mixing ratio of rice straw to OFMSW was 1:5. Using this addition level, the cumulative malodorous sulfur compounds emissions based on the organic matter degradation were the lowest during composting of OFMSW. © 2014 Elsevier Ltd. Source


Shao L.,Center for the Technology Research and Training on Household Waste in Small Towns and Rural Area | Wang T.,Tongji University | Li T.,Tongji University | Lu F.,Tongji University | And 2 more authors.
Bioresource Technology | Year: 2013

Aerobic and anaerobic digestion are popular methods for the treatment of waste activated sludge. However, the differences in degradation of sludge during aerobic and anaerobic digestion remain unclear. In this study, the sludge degradation during aerobic and anaerobic digestion was investigated at mesophilic temperature, focused on protein based on the degradation efficiency and degree of humification. The duration of aerobic and anaerobic digestion was about 90. days. The final degradation efficiency of volatile solid was 66.1. ±. 1.6% and 66.4. ±. 2.4% under aerobic and anaerobic conditions, respectively. The final degradation efficiency of protein was 67.5. ±. 1.4% and 65.1. ±. 2.6% under aerobic and anaerobic conditions, respectively. The degradation models of volatile solids were consistent with those of protein under both aerobic and anaerobic conditions. The solubility of protein under aerobic digestion was greater than that under anaerobic digestion. Moreover, the humification index of dissolved organic matter of aerobic digestion was greater than that during anaerobic digestion. © 2013 Elsevier Ltd. Source

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