Acclimatization And Bioaugmentation Of Methanogenic Propionate Degrading Microbial Consortia

Anaerobic digestion(AD),a well-accepted technology for simultaneous organic waste management and renewable energy,has been developed quickly in China,however,poor operational stability and low economic benift still prevent the AD process from being widely applied.Volatile fatty acids accumulation,which leads to inhibition of biogas production is an urgent problem to be solved in high loading rate AD.In order to enhance the degradation of propionic acid and acetic acid,the study enriched several different function of methanogenic propionate degrading microbial consortia for bioaugmenting three metabolic steps of AD including propionic acid degrade to acetic acid,methane production from acetic acid and H2+CO2.The bioaugmentation efficiency and the mechanism of bioaugmentation were studied as well.The main conclusions are as follows:High propionate degradation ability of methanogenic propionate degrading microbial consortia is obtained after a long term(more than 300 d)acclimatization,which can running stable with OLR of 2.5 gHpr L-1d-1,the average volume of methane production rate was 1.20 LL-1d-1,the tolerance of propionic acid concentration is more than 11 g L-1.The dominant microbial groups are Syntrophobacter,Methanoculleus and Methanothrix.Low pH tolerance methanogenic propionate degrading microbial consortia is also obtained,which can survive and produce methane under low pH condition of 4.8-6.0.The groups of Smithella,Syntrophobacter,Pelotomaculum,Syntrophomonas and Methanothrix,Methanolinea,Methanospirillum are the predominant microbes.Bioaugmentation were successfully conducted both with high propionate degradation ability of methanogenic propionate degrading microbial consortia and low pH tolerance methanogenic propionate degrading microbial culture.The results show that bioaugmentation is not only able to prevent the further deterioration of a poor performing digester,but can also recover from anaerobic digestion failure under the double stress from propionate and ammonia accumulation.The organic load rate of anaerobic digestion was enhanced 2 times with bioaugmentation.Moreover,after bioaugmentation the reactors showed better performance in terms of volume of methane production rate volumeic methane production rate and VS methane production rate,which were increased by 24.04%(76.54%),0.22 L L-1 D-1,(366.67%)and 0.23 Lg-1VSd-1(287.50%),respectively.This study also demonstrates that bioaugmentation can also recover overloading anaerobic digestion from failure whin one week.In addition,the volume methane production rate increased by 30-35%after bioaumention.With 3.0 g N L-1 of ammonia stress,one dose(0.3 g cell dry weight L-1d-1)bioaugmentation can prevent the reactor against further deterioration and 2 dose of bioaugmentation can recover the anaerobic digestion inhibited with 8500 mg L-1 of propionic acid and 3000 mg L-1 of acetic acid.After bioaugmentation,the volumic methane producton,methane recover rate and propionic acid degradation rate were increased by 158 mL L-1 d-1,48%and 62%,respectively.The investigation of mechanism of the bioaugmentation reveals that bioaugmentation can reconstruct the microbial community,enhance the biomass of beneficial functional bacteria,using high concentration of propionic acid methanogens for bioaugmentation,In addition,at the genetic level,bioaugmentation can enhanced the role of genes involved in membrane transport and cell moility.This study provides a method for microbial culture acclaimization for enhancing the volatile fatty acids degradation and the different functions of bioaugmentation seeds.In addition,it is confirmed that methanogenic propionate degrading microbial consortia can relieve VFA inhibition,promote recovery of the failure AD system and alleviate ammonia inhibition,and thus improve anaerobic digestion performance,which enriched the understanding of the mechanism of bioaugmentation and provided experimental and theoretical basis for the application of bioaugmentation technology in anaerobic digestion,and promoted its practical process.