The survival of pathogenic bacteria and plant growth promoting bacteria during mesophilic anaerobic digestion in full‐scale biogas plants     

Guangdou Qi  Zhifei Pan  Yuki Yamamoto  Fetra Jules Andriamanohiarisoamanana  Takaki Yamashiro  Masahiro Iwasaki  Ikko Ihara  Suchon Tangtaweewipat  Kazutaka Umetsu 《Animal Science Journal》2019,90(2):297-303

The introduction of biogas plants is a promising way to recycle organic wastes with renewable energy production and reducing greenhouse gas. Application of anaerobic digestate as a fertilizer reduces the consumption of chemical fertilizers. In this study, the survival of pathogenic bacteria and plant growth promoting bacteria (PGPB) in two full‐scale biogas plants operated at mesophilic condition were investigated. Feedstock and anaerobic digestate samples were collected from biogas plants and bacteria load in samples were detected using standard dilution plate method. Pathogenic bacteria were reduced to not detected level through mesophilic digestion tank except for Campylobacter. However, it could be reduced by 98.7% through a sterilization tank. Bacillus was detected at 8.00 and 7.81 log₁₀ CFU/g dry matter in anaerobic digestates, and it was also resistant to sterilization tank. Bacillus spp. is considered to be the safe bacteria that hold remarkable abilities for promoting plant growth. The results showed that treatment at biogas plants is effective to reduce pathogenic bacteria in dairy manure, and sterilization could further reduce the sanitary risks of pathogenic bacteria relating to anaerobic digestate application. Anaerobic digestates could also be utilized as bio‐fertilizer as the high load of plant growth promoting bacteria.  相似文献   

The survival of multidrug‐resistant bacteria in thermophilic and mesophilic anaerobic co‐digestion of dairy manure and waste milk     

Nilmini Beneragama  Masahiro Iwasaki  Suraju A. Lateef  Takaki Yamashiro  Ikko Ihara  Kazutaka Umetsu 《Animal Science Journal》2013,84(5):426-433

Anaerobic digestion is considered as a promising method to manage animal waste with antibiotic‐resistant bacteria. Current research was conducted to investigate the survival of multidrug‐resistant bacteria (MDRB) resistant to three groups of antibiotics: (i) cefazolin, neomycin, vancomycin, kanamycin (group 1); (ii) penicillin, oxytetracycline, ampicillin, streptomycin (group 2); and (iii) cefazolin, neomycin, vancomycin, kanamycin, penicillin, oxytetracycline, ampicillin, streptomycin (group 3), in anaerobic digestion of dairy manure and co‐digestion of dairy manure and waste milk at 37°C and 55°C for 22 days, respectively. The population densities of three groups of MDRB on peptone, tryptone, yeast and glucose agar plates incubated at 30°C for 7 days before and after digestion showed 100% destruction in both digestates at thermophilic temperature. Overall reduction of more than 90% of three groups of MDRB was observed in mesophilic digestion with no significant differences (P > 0.05) between manure and milk mixture. Co‐digestion of dairy manure and waste milk always produced significantly (P < 0.05) higher total gas and methane gas than digestion of manure alone at both temperatures. Gas production in each case was significantly (P < 0.05) higher in thermophilic digestion than in mesophilic digestion. The results demonstrate that thermophilic co‐digestion of dairy manure and waste milk offers more benefits in terms of the environment and economy.  相似文献   

The effect of temperature on survival of pathogenic bacteria in biogas plants     

Masahiro IWASAKI  Takaki YAMASHIRO  Nilmini BENERAGAMA  Takehiro NISHIDA  Katsuya KIDA  Ikko IHARA  June‐ichi TAKAHASHI  Kazutaka UMETSU 《Animal Science Journal》2011,82(5):707-712

The paper deals with the hygienic advantages of sanitation to treat dairy manure in full‐scale biogas plants. The slurry samples were collected from two thermophilic biogas plants (55°C) and two mesophilic biogas plants (38°C) in Hokkaido Japan. A detectable number of Coli‐aerogenes group and Enterococcus in the slurries after anaerobic digestion (AD) could not be found in either thermophilic biogas plants. However, in both mesophilic biogas plants the viable numbers of Coli‐aerogenes group and Enterococcus were detected in the slurries even after anaerobic digestion. The mean decimation reduction time (T₉₀) values of the Coli‐aerogenes group and Enterococcus in the slurries during mesophilic digestion were 13.3 days and 16.7 days, respectively.  相似文献   

Effect of solid–liquid separation on anaerobic digestion of dairy manure in semi‐continuous stirred tank reactors: Process performance and digestate characteristics     

Guangdou Qi  Zhifei Pan  Fetra J. Andriamanohiarisoamanana  Takaki Yamashiro  Masahiro Iwasaki  Ikko Ihara  Kazutaka Umetsu 《Animal Science Journal》2020,91(1)

The objective of this study was to investigate the effect of solid–liquid separation on anaerobic digestion of dairy manure in semi‐continuous stirred tank reactors. Reactors fed with liquid fraction of dairy manure (screened liquid manure) were kept in water baths at mesophilic (Run 1) and thermophilic (Run 3) temperatures, respectively, while reactors fed with water diluted manure and kept at mesophilic (Run 2) and thermophilic (Run 4) temperatures as control reactors. The performances of reactors were compared in terms of biogas and methane production, and digestate characteristics. The methane yields obtained from screened manure were higher than those from diluted manure at both mesophilic and thermophilic temperatures, while the highest methane yield was 185 L/kg VS_added under thermophilic temperature. Solid–liquid separation also had improved the effect on digestate fertilizer characteristics. Among four digestates from reactors, the highest contents of nutrients, N (4.12 g/kg) and P (2.36 g/kg) were found in Run 3, while the highest content of K (3.42 g/kg) was found in Run 1. These results showed the benefits of solid–liquid separation of dairy manure on process performance and digestate characteristics.  相似文献