The degradation rate of Volatile Fatty Acids (VFAs) produced predominantly in the acidogenesis stage is a key process parameter to be optimised to ensure a successful Anaerobic digestion (AD). Thermodynamically, the o...The degradation rate of Volatile Fatty Acids (VFAs) produced predominantly in the acidogenesis stage is a key process parameter to be optimised to ensure a successful Anaerobic digestion (AD). Thermodynamically, the oxidation of the VFAs are energetically unfavourable, and as such external energy source apart from the energy derived from the hydrolysis of Adenosine Triphosphate (ATP) is needed for the initial activation of the VFAs, initial growth of the methanogens in AD process and improved degradation rate of the VFAs. Thus, this research investigated the influence of polyphosphate hydrolysis on the degradation rate of the VFAs at high concentration. Sodium-propionate, Sodium-butyrate and Sodium-acetate salts were added at the start of experiments in order to increase the concentration of the VFAs. The polyphosphate salts used were;Na-hexametaphosphate, Na-tripolyphosphate and potassium pyrophosphate. The control experiment was polyphosphate free and three process parameters (degradation rate, cumulative biogas production and specific methane content) of anaerobic digestion were investigated. The experiments were carried out at a mesophilic temperature of 37.5°C for 41 days. The results of the investigation showed that the treated reactors with the polyphosphate salt solution in low concentration performed better than the reactors with high concentration of the polyphosphate salts solution. All the treated reactors with poly-P salts performed better than reactor Nr-9 (control experiment), but reactor Nr-1 was outstanding with an improved degradation rate of 47%, cumulative biogas production of 21% and specific methane content of 23%.展开更多
Background Chlorophenoxy compounds represent a group of selective herbicides widely used around the world.Chlorophenoxy herbicides are toxic,chemically stable,and can migrate into groundwater through soil leaching,pos...Background Chlorophenoxy compounds represent a group of selective herbicides widely used around the world.Chlorophenoxy herbicides are toxic,chemically stable,and can migrate into groundwater through soil leaching,posing a significant threat to drinking water safety and human health.Chlorophenoxy herbicides in groundwater aquifers are subject to anaerobic processes;however,the pathway and microbiology involved in the attenuation of chlorophenoxy herbicides under anaerobic condition are largely unknown.Here,the anaerobic degradation process of 2,4,5-trichlorophenoxyacetic acid(2,4,5-T),a typical chlorophenoxy herbicide,was investigated.Results The initial 52.5±2.3μM 2,4,5-T was completely degraded by a sediment-derived microbial consortium,with 3,4-dichlorophenol,2,5-dichlorophenol,3-chlorophenol(3-CP)and phenol being identified as the intermediate products.Reductive dechlorination of 3-CP to phenol and the subsequent elimination of phenol were the key transformation steps in the overall degradation process of 2,4,5-T.Amplicon sequencing suggested that Dehalobacter,Sulfuricurvum,Bacteroides,Acetobacterium,and Clostridium sensu stricto 7 might contribute to the transformation of 2,4,5-T to phenol,and Smithella,Syntrophorhabdus,Methanofollis and Methanosaeta likely cooperated to accomplish the complete mineralization of phenol.Conclusions This study reported the anaerobic degradation of 2,4,5-T via reductive dechlorination and the subsequent syntrophic metabolization of phenol,an intermediate product transformed from 2,4,5-T.Dehalobacter was identified as the organohalide-respiring population catalyzing the reductive dechlorination reaction.Syntrophorhabdus and methanogenic populations were likely involved in anaerobic phenol oxidation and facilitated the complete mineralization of 2,4,5-T.展开更多
文摘The degradation rate of Volatile Fatty Acids (VFAs) produced predominantly in the acidogenesis stage is a key process parameter to be optimised to ensure a successful Anaerobic digestion (AD). Thermodynamically, the oxidation of the VFAs are energetically unfavourable, and as such external energy source apart from the energy derived from the hydrolysis of Adenosine Triphosphate (ATP) is needed for the initial activation of the VFAs, initial growth of the methanogens in AD process and improved degradation rate of the VFAs. Thus, this research investigated the influence of polyphosphate hydrolysis on the degradation rate of the VFAs at high concentration. Sodium-propionate, Sodium-butyrate and Sodium-acetate salts were added at the start of experiments in order to increase the concentration of the VFAs. The polyphosphate salts used were;Na-hexametaphosphate, Na-tripolyphosphate and potassium pyrophosphate. The control experiment was polyphosphate free and three process parameters (degradation rate, cumulative biogas production and specific methane content) of anaerobic digestion were investigated. The experiments were carried out at a mesophilic temperature of 37.5°C for 41 days. The results of the investigation showed that the treated reactors with the polyphosphate salt solution in low concentration performed better than the reactors with high concentration of the polyphosphate salts solution. All the treated reactors with poly-P salts performed better than reactor Nr-9 (control experiment), but reactor Nr-1 was outstanding with an improved degradation rate of 47%, cumulative biogas production of 21% and specific methane content of 23%.
基金supported by the Natural Science Foundation of China(42377133,42177220)with additional support from the Natural Science Foundation(Joint Fund)of Liaoning Province(2023JH2/101700354,2023JH2/101800044).
文摘Background Chlorophenoxy compounds represent a group of selective herbicides widely used around the world.Chlorophenoxy herbicides are toxic,chemically stable,and can migrate into groundwater through soil leaching,posing a significant threat to drinking water safety and human health.Chlorophenoxy herbicides in groundwater aquifers are subject to anaerobic processes;however,the pathway and microbiology involved in the attenuation of chlorophenoxy herbicides under anaerobic condition are largely unknown.Here,the anaerobic degradation process of 2,4,5-trichlorophenoxyacetic acid(2,4,5-T),a typical chlorophenoxy herbicide,was investigated.Results The initial 52.5±2.3μM 2,4,5-T was completely degraded by a sediment-derived microbial consortium,with 3,4-dichlorophenol,2,5-dichlorophenol,3-chlorophenol(3-CP)and phenol being identified as the intermediate products.Reductive dechlorination of 3-CP to phenol and the subsequent elimination of phenol were the key transformation steps in the overall degradation process of 2,4,5-T.Amplicon sequencing suggested that Dehalobacter,Sulfuricurvum,Bacteroides,Acetobacterium,and Clostridium sensu stricto 7 might contribute to the transformation of 2,4,5-T to phenol,and Smithella,Syntrophorhabdus,Methanofollis and Methanosaeta likely cooperated to accomplish the complete mineralization of phenol.Conclusions This study reported the anaerobic degradation of 2,4,5-T via reductive dechlorination and the subsequent syntrophic metabolization of phenol,an intermediate product transformed from 2,4,5-T.Dehalobacter was identified as the organohalide-respiring population catalyzing the reductive dechlorination reaction.Syntrophorhabdus and methanogenic populations were likely involved in anaerobic phenol oxidation and facilitated the complete mineralization of 2,4,5-T.
