Influences Of Acid-producing Bacteria In Anaerobic Digestion Of High Temperature Hydrolysis Sludge

With the rapid development of biological wastewater treatment,waste activated sludge(WAS)as a byproduct is produced in abundance every year.WAS contains a lot of poisonous and harmful materials such as organic pollutants and pathogens.If WAS can not get effective disposal,it can cause potential harm to ecological environment.The disposal of reduction and resource utilization about WAS has become the most pressing problems in the process of the urban construction.The high temperature hydrolysis treatment technology,with the advantages of high treatment efficiency,low processing cost and recyclability,has become a primary processing technology of WAS treatment.However,most microbial flora do not adapt in thermophilic anaerobic digestion,and WAS after thermal hydrolysis contains complex toxic substances.Therefore,it is necessary to screen and inoculate thermophilic strains to WAS for enhancing sludge decomposition and fermentation efficiency.On the one hand,acid-producing bacteria are abundant in the WAS and with the advantages of fast metabolism and growth rate,which can be adapted to the high temperature environment.On the other hand,in the process of sludge anaerobic digestion,acid-producing bacteria can convert complex organic substance to soluble organic substances through own life activities,which provides nutrition material such as carbon source for methanogens.And acid-producing bacteria can remove the oxygen that is brought into the mud at the beginning of fermentation,cleave benzene ring and degrade other substances.Therefore,the key to the success of the high temperature hydrolysis treatment technology is to screen and isolate the acid-producing bacteria.In this study,three acid-producing bacteria were isolated from sewage treatment plant.Isolated three acid-producing bacteria were extracted the DNA and made amplification and sequencing,which based on 16 S rRNA,determined the genus through phylogenetic analysis.Moreover,adding acid-producing strains to high temperature anaerobic digestion reactor analyzed the performance of anaerobic digestion.The dominant bacteria would be selected and studied the optimization of dosage of bacterial cells,which provided the information basis for the WAS treatment technology based on the addition of acid-producing bacteria.The research showed that three acid-producing strains,AFB-1,AFB-2 AFB-3,were isolated and adapted to the high-temperature environments.With the help of molecular biology approaches,data of 16 S rRNA method showed that AFB-1 and AFB-2 were Bacillus coagulans,and AFB-3 was Escherichia coli.The newly generated sequences were deposited in GenBank(accession number KY170856,KY170857,KY170858).The experiments of anaerobic digestion showed that the removal for volatile solids(VS)and total chemical oxygen demand(TCOD)maximized 42.7% and 44.7%by inoculating Bacillus coagulans AFB-1.Besides,the optimal inoculum concentration of Bacillus coagulans AFB-1 was 30%(v/v).The solubilization degree experiments performed that solubilization ratio(SR)of WAS reached to 20.8 ± 2.2 %,17.7 ± 1.48%,and 11.1 ± 1.53%,respectively.Volatile fatty acids(VFAs)concentrations and compositions were also explored by a gas chromatograph.The results showed that VFAs improved by 98.5%,53.0% and 11.6% than those in the control,respectively.Biochemical methane potential(BMP)experiments revealed that biogas production increased by 90.7% and 75.3% by inoculating Bacillus coagulans AFB-1 and AFB-2.However,there was no increase in the biogas production of Escherichia coli AFB-3.The inoculation size of Bacillus coagulans AFB-1 was explored ranging from 10% to 40% and the influence of inoculation rates on degradation efficiency by Bacillus coagulans AFB-1 was examined.The results showed that 30% of inoculation size was optimal for Bacillus coagulans AFB-1,in which TCOD,VS removal and productivity of biomass were maximized.The above results show that the acid-producing bacteria can adapt to thermophilic anaerobic digestion and be able to efficiently treat WAS.It should be noted that 30% of inoculation size was optimal for Bacillus coagulans AFB-1,in which productivity of biomass,the removal rate of pollutant,and anaerobic digestion efficiency were maximized.