提高污泥含固率对高温厌氧消化互营产甲烷影响

Effects of the increased solid content of waste activated sludge on syntrophic acetate oxidation for methane production through thermophilic anaerobic digestion

以常规含固率(2%)剩余污泥高温厌氧消化排泥为接种污泥,分析接种污泥在不同氨浓度下厌氧消化各步骤的动力学速率变化,并以热水解预处理的高含固污泥(10%)为基质进行连续试验,探讨高温厌氧消化条件下基质由常规含固率快速切换至高含固率的产甲烷性能变化.结果表明,随着氨浓度上升,接种污泥对乙酸、丙酸、丁酸和热水解污泥的比产甲烷活性均有所下降,但其氢利用速率和互营乙酸氧化速率未受到显著影响.高温厌氧消化基质含固率由2%切换至10%连续运行试验结果表明,在有机负荷高达14g COD/(L·d)时,虽然系统COD去除率不足(27.99±3.66)%,且存在VFAs积累(10.41±2.25)g COD/L,但pH值仍可稳定在(7.74±0.09),说明该切换策略具有可行性.稳定运行系统中产氢产乙酸和互营乙酸氧化功能菌属以Coprothermobacter(15.29%)、Anaerobaculum(8.89%)、Tepidimicrobium(17.99%)和Syntrophomonas(1.60%)为主,切换后乙酸营养型产甲烷菌Methanothrix被淘汰,而参与互营乙酸氧化过程的Methanosarcina和Methanothermobacter相对丰度显著提高,说明体系通过构建互营乙酸氧化产甲烷途径来抵御高温高氨的环境胁迫.因此,以常规含固率高温厌氧消化污泥作为接种泥是实现由常规含固率切换至高含固热水解-高温厌氧消化的有效策略,并且接种污泥的互营乙酸氧化活性是切换成功的关键因素.

This study investigated the kinetic rate variations of each stage involved in anaerobic digestion under different ammonia loadings,in this process,the inoculated sludge was obtained from a thermophilic anaerobic digestion system with solid content of 2%.Furthermore,effects of the quick switch between low solid content(2%)and high solid content(10%)on methane production potentials were explored through feeding thermal hydrolyzed sludge to a continuous flow model.Results showed that with ammonia loading increasing,the specific methanogenic activities of typical substrates like acetic acid,propionic acid,butyric acid,and thermal hydrolyzed sludge were all decreased,while the hydrogen utilization rates(HUR)and syntrophic acetate oxidation(SAO)rates were not significantly affected.With continuous flow model,although the chemical oxygen demand(COD)removal ratio was insufficient(27.99±3.66)%and the VFAs accumulation(10.41±2.25)g COD/L was observed when the organic loading reached 14g COD/(L·d),the pH values remained stable at(7.74±0.09).This result suggested that this switching strategy was feasible in achieving stable operating condition.The predominant hydrogen-producing acetogen and syntrophic acetate oxidizing functional genera were Coprothermobacter(15.29%),Anaerobaculum(8.89%),Tepidimicrobium(17.99%),and Syntrophomonas(1.60%)at stable stage.Moreover,Methanothrix,acetoclastic methanogen,was eliminated,while Methanosarcina and Methanothermobacter,being involved in the syntrophic acetate oxidation process,was significantly enriched.It can be concluded that the above anaerobic digestion system resists the environmental stress of high temperature and ammonia through establishing syntrophic acetate oxidation coupled with hydrogenotrophic methanogenesis(SAO-HM)pathway.Overall,using conventional thermophilic anaerobic digestion sludge as the inoculated sludge is an effective strategy to achieve switching from conventional solid content to high solid thermal hydrolysis pretreatment following thermophilic anaerobic digestion(THP-TAD),and the syntrophic acetate oxidation activity of the inoculated sludge is the key factor for this successful switch.