Pilot-scale anaerobic co-digestion of municipal biomass waste and waste activated sludge in China: Effect of organic loading rate
School of Environment, Tsinghua University, Beijing 100084, China. Electronic address: . Waste Management
(Impact Factor: 3.22).
03/2012; 32(11):2056-60. DOI: 10.1016/j.wasman.2012.03.003
The effects of organic loading rate on the performance and stability of anaerobic co-digestion of municipal biomass waste (MBW) and waste activated sludge (WAS) were investigated on a pilot-scale reactor. The results showed that stable operation was achieved with organic loading rates (OLR) of 1.2-8.0kgvolatile solid (VS)(m(3)d)(-1), with VS reduction rates of 61.7-69.9%, and volumetric biogas production of 0.89-5.28m(3)(m(3)d)(-1). A maximum methane production rate of 2.94m(3)(m(3)d)(-1) was achieved at OLR of 8.0kgVS(m(3)d)(-1) and hydraulic retention time of 15days. With increasing OLRs, the anaerobic reactor showed a decrease in VS removal rate, average pH value and methane concentration, and a increase of volatile fatty acid concentration. By monitoring the biogas production rate (BPR), the anaerobic digestion system has a higher acidification risk under an OLR of 8.0kgVS(m(3)d)(-1). This result remarks the possibility of relating bioreactor performance with BPR in order to better understand and monitor anaerobic digestion process.
Available from: David Bolzonella
- "The different growth rates and pH optima for hydrogen producing microorganisms (between 5.5 and 6.5) and methanogenic microorganisms (around pH 7), have led to the development of the two-stage AD process (De laRubia et al., 2009). This approach has been used to the hydrogen production (HP) in the first phase reactor and methane production (MP) in the second phase reactor, with the final purpose of mixing the two gasses to achieve bio-Hythane (50–55% CH 4 , 5–10% H 2 and 35–40% CO 2 ), a biogas that offers better combustion and reduced greenhouse gas emissions compared to fossil fuels (Cavinato et al., 2011;Liu et al., 2012). Due to the advantages of the AD process, an ample research has been done on the optimization of AD for treating the organic fraction of municipal solid waste (OFMSW), including the interesting option of the co-digestion process. "
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ABSTRACT: In this paper, the microbial community in a two-phase thermophilic anaerobic co-digestion process was investigated for its role in hydrogen and methane production, treating waste activated sludge and treating the organic fraction of municipal solid waste. In the acidogenic phase, in which hydrogen is produced, Clostridium sp. clusters represented 76% of total Firmicutes. When feeding the acidogenic effluent into the methanogenic reactors, these acidic conditions negatively influenced methanogenic microorganisms: Methanosaeta sp., (Methanobacteriales, Methanomicrobiales, Methanococcales) decreased by 75%, 50%, 38% and 52%, respectively. At the same time, methanogenic digestion lowered the numbers of Clostridium sp. clusters due to both pH increasing and substrate reduction, and an increase in both Firmicutes genera (non Clostridium) and methanogenic microorganisms, especially Methanosaeta sp. (208%). This was in accordance with the observed decrease in acetic (98%) and butyric (100%) acid contents. To ensure the activity of the acetate-utilizing methanogens (AUM) and the acetogens, high ratios of H2-utilizing methanogens (HUM)/AUM (3.6) were required.
Available from: ., Zeshan
- "Cumulative biogas production decreased at higher organic loading due to VFAs accumulation in digesters. These results are in accordance with other studies where higher risks of VFA accumulation and low biogas yield at higher organic loading rate have been reported (Alvarez and Lidén, 2008; Liu et al., 2012). Digester at an S/I ratio of 0.25 yielded highest biogas among all other digesters (Fig. 2b). "
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ABSTRACT: Aim of this study was to find out suitable mixing ratio of food waste and rice husk for their co-digestion in order to overcome VFA accumulation in digestion of food waste alone. Four mixing ratios of food waste and rice husk with C/N ratios of 20, 25, 30 and 35 were subjected to a lab scale anaerobic batch experiment under mesophilic conditions. Highest specific biogas yield of 584L/kgVS was obtained from feedstock with C/N ratio of 20. Biogas yield decreased with decrease in food waste proportion. Further, fresh cow dung was used as inoculum to investigate optimum S/I ratio with the selected feedstock. In experiment 2, feedstock with C/N ratio 20 was subjected to anaerobic digestion at five S/I ratios of 0.25, 0.5, 1.0, 1.5 and 2.0. Specific biogas yield of 557L/kgVS was obtained at S/I ratio of 0.25. However, VFA accumulation occurred at higher S/I ratios due to higher organic loadings.
- "Very few reports have discussed in detail the changing process of system controlling indexes (i.e. GP rate, pH, VFA) under increasing OLR s (Liu et al., 2012) and how the changes influence the microbial populations and stability of the AD system is also lacking. As research in molecular microbiology progresses in this area, the scientific community has now pointed out that microorganisms found in anaerobic environments are extremely diverse and that their interactions and metabolic functions and regulation remain to be elucidated in detail (Talbot et al., 2008). "
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ABSTRACT: Different high feed organic loading rates (OLRs) (from 5.7g to 46.0g TVS/l/d) or hydraulic retention times (HRTs) (from 15d to 2d) in single-phase dry-thermophilic anaerobic digestion (AD) of organic fraction municipal solid waste (OFMSW) were investigated. The specific gas production (SGP) values (0.25-0.53m(3)/kg TVS) and the percentages of Eubacteria, Archaea, H2-utilising methanogens (HUMs) and acetate-utilising methanogens (AUMs) were stable within the ranges 80.2-91.1%, 12.4-18.5%, 4.4-9.8% and 5.5-10.9%, respectively. A HUM/AUM ratio greater than 0.7 seems to be necessary to maintain very low partial pressures of H2 required for dry AD process. Increasing OLR resulted in an increase in all the populations, except for propionate-utilising acetogens (PUAs). Optimal conditions were obtained at 3d HRT (OLR=30.7g TVS/l/d), which is lower than the doubling time of acetogens and methanogens. The methane production (MP) was clearly higher than those reported in AD of OFMSW.
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