A serious foaming incident occurred in a mesophilic food waste digester. The effects of foaming on reactor efficiency parameters were investigated, including specific biogas production (SBP), specific methane production (SMP) and volatile solids (VS) removal rate. The possible causes of foaming were evaluated according to a series of stability parameters including volatile fatty acids (VFAs), the ratio of VFA to total alkalinity (VFA/TA) combined with the ammonia nitrogen concentration (TAN), as well as the bacterial community structure in pre-and post-foaming system. The SBP, SMP and VS removal rate during the stable stage were (0.950±0.104) m3/kg VS, (0.574±0.072) m3CH4/kg VS and (87.14±2.76)%, respectively. However, those parameters decreased to (0.717±0.100) m3/kg VS, (0.432±0.070) m3CH4/kg VS and (84.24±4.44)% with the appearance of the foaming incident, which indicated that the efficiency of the digester had been significantly influenced by the foaming incident. Prior to the foaming, there appeared to be a rapid accumulation of VFAs along with a reduction in the proportion of acetic acid in VFAs. The propionic acid, which is believed to play a major role in enhancing the foaming tendency, increased in its proportion in VFAs as well. The filamentous bacteria Longilinea arvoryzae, Levilinea and the myxobacterium Cytophaga fermentans had stronger band intensities after foaming. Their filamentous structure or mucilage can be a significant contributor to the initiation of foaming to some extent. In conclusion, foaming may be caused by the combination of VFAs accumulation and the proliferation of specific bacteria.
Tanimu M I, Ghazi T I M, Harun M R, et al. Effects of feedstock carbon to nitrogen ratio and organic loading on foaming potential in mesophilic food waste anaerobic digestion [J]. Applied Microbiology and Biotechnology, 2015,99(10):4509-4520.
[2]
Kougias P G, Boe K, O-Thong S, et al. Anaerobic digestion foaming in full-scale biogas plants: a survey on causes and solutions [J]. Water Science and Technology, 2014,69:889-895.
[3]
Moeller L, Görsch K, Müller R A, et al. Formation and suppression of foam in biogas plants-practical experiences [J]. Agricultural Engineering (Landtechnik), 2012,67(2):110-113.
[4]
Boe K, Kougias P G, Pacheco F, et al. Effect of substrates and intermediate compounds on foaming in manure digestion systems [J]. Water Science and Technology, 2012,66(10):2146-2154.
[5]
Ganidi N, Tyrrel S, Cartmel E. Anaerobic digestion foaming causes-A review [J]. Bioresource Technology, 2009,100:5546-5554.
[6]
Ganidi N, Tyrrel S, Cartmell E. The effect of organic loading rate on foam initiation during mesophilic anaerobic digestion of municipal wastewater sludge [J]. Bioresource Technology, 2011,102(12):6637-6643.
[7]
Lienen T, Kleyböcker A, Verstraete W, et al. Foam formation in a downstream digester of a cascade running full-scale biogas plant: Influence of fat, oil and grease addition and abundance of the filamentous bacterium Microthrix parvicella [J]. Bioresource Technology, 2014,153:1-7.
[8]
Kougias P G, Francisci D, Treu L, et al. Microbial analysis in biogas reactors suffering by foaming incidents [J]. Bioresource Technology, 2014,167:24-32.
[9]
Zhang Y, Banks C J, Heaven S. Anaerobic digestion of two biodegradable municipal waste streams [J]. Journal of Environmental Management, 2012,104:166-174.
[10]
APHA. Standard methods for the examination of water and wastewater [M]. Washington, DC: American Public Health Association, America Water Works Association, Water Environment Federation, 1999.
[11]
Casamayor E O, Schäfer H, Bañeras L, et al. Identification of and spatio-temporal differences between microbial assemblages from two neighboring sulfurous lakes: comparison by microscopy and denaturing gradient gel electrophoresis [J]. Applied and Environmental Microbiology, 2000,66(2):499-508.
[12]
Li L, He Q, Wei Y, et al. Early warning indicators for monitoring the process failure of anaerobic digestion system of food waste [J]. Bioresource Technology, 2014,171:491-494.
[13]
Gupta P, Ahammad S Z, Sreekrishnan T R. Improving the cyanide toxicity tolerance of anaerobic reactor: Microbial interactions and toxin reduction [J]. Journal of Hazardous Materials, 2016,315:52-60.
Supaphol S, Jenkins S N, Intomo P, et al. Microbial community dynamics in mesophilic anaerobic co-digestion of mixed waste [J]. Bioresource Technology, 2011,102(5):4021-4027.
[16]
Sorokin Y, Tourova T P, Mußmann M, et al. Dethiobacter alkaliphilus gen. nov. sp. nov., and Desulfurivibrio alkaliphilus gen. nov. sp. nov.: two novel representatives of reductive sulfur cycle from soda lakes [J]. Extremophiles, 2008,12(3):431-439.
[17]
Sorokin Y, Panteleeva A N, Tourova T P, et al. Natronoflexus pectinivorans gen. nov. sp. nov., an obligately anaerobic and alkaliphilic fermentative member of Bacteroidetes from soda lakes [J]. Extremophiles, 2011,15(6):691-696.
[18]
Zhao C, Gao Z, Qin Q, et al. Mangroviflexus xiamenensis gen. nov., sp. nov., a member of the family Marinilabiliaceae isolated from mangrove sediment [J]. International Journal of Systematic and Evolutionary Microbiology, 2012,62(8):1819-1824.
[19]
Zhao B, Chen S. Alkalitalea saponilacus gen. nov., sp. nov., an obligately anaerobic, alkaliphilic, xylanolytic bacterium from a meromictic soda lake [J]. International Journal of Systematic and Evolutionary Microbiology, 2012,62(11):2618-2623.
[20]
Grabowski A, Tindall B J, Bardin V, et al. Petrimonas sulfuriphila gen. nov., sp. nov., a mesophilic fermentative bacterium isolated from a biodegraded oil reservoir [J]. International Journal of Systematic and Evolutionary Microbiology, 2005,55(3):1113-1121.
[21]
Weon H Y, Kim B Y, Lee C M, et al. Solitalea koreensis gen. nov., sp. nov. and the reclassification of [Flexibacter] canadensis as Solitalea canadensis comb. nov [J]. International Journal of Systematic and Evolutionary Microbiology, 2009,59(8):1969-1975.
[22]
Bachmann B J. Studies on Cytophaga fermentans, n. sp., a facultatively anaerobic lower myxobacterium [J]. Microbiology, 1955,13(3):541-551.
[23]
Yamada T. Anaerolinea thermolimosa sp. nov., Levilinea saccharolytica gen. nov., sp. nov., and Leptolinea tardivitalis gen. nov., sp. nov., novel filamentous anaerobes, and description of the new classes Anaerolineae classis nov., and Caldilineae classis nov. in the bacterial phylum Chloroflexi [J]. International Journal of Systematic and Evolutionary Microbiology, 2006,56(Part 6):1331-1340.
[24]
Yamada T, Imachi H, Ohashi A, et al. Bellilinea caldifistulae gen. nov., sp. nov. and Longilinea arvoryzae gen. nov., sp. nov., strictly anaerobic, filamentous bacteria of the phylum Chloroflexi isolated from methanogenic propionate-degrading consortia [J]. International Journal of Systematic and Evolutionary Microbiology, 2007,57(6):2299-2306.
[25]
Liu F H, Wang S B, Zhang J S, et al. The structure of the bacterial and archaeal community in a biogas digester as revealed by denaturing gradient gel electrophoresis and 16S rDNA sequencing analysis [J]. Journal of Applied Microbiology, 2009,106(3): 952-966.
[26]
Kougias P G, Kotsopoulos T A, Martzopoulos G G. Effect of feedstock composition and organic loading rate during the mesophilic co-digestion of olive mill wastewater and swine manure [J]. Renewable Energy, 2014,69:202-207.
[27]
Ali Shah F, Mahmood Q, Maroof Shah M, et al. Microbial ecology of anaerobic digesters: the key players of anaerobiosis [J]. The Scientific World Journal, 2014.
[28]
Subramanian B, Pagilla K R. Anaerobic digester foaming in full-scale cylindrical digesters-Effects of organic loading rate, feed characteristics, and mixing [J]. Bioresource Technology, 2014,159:182-192.
