氨氮浓度对猪粪厌氧消化及产甲烷菌群结构的影响

氨氮抑制是影响高含固厌氧消化推广应用的主要因素之一。通过批式实验，采用外源氨氮投加方式，考察了厌氧消化过程中不同氨氮浓度对鲜猪粪产甲烷效果和产甲烷菌群结构的影响。结果表明：氨氮添加量为2 000 mg·L-1（TAN≈3 596.7 mg·L-1）时，日产甲烷速率及累积产甲烷量均明显下降；添加量大于4 000 mg·L-1（TAN≈5 618.7 mg·L-1）时，氨氮抑制加剧，出现VFAs累积、产甲烷高峰期后移、丙酸降解失败。不同氨氮投加量下猪粪中挥发性固体（VS）产甲烷率分别为（369.0 ± 17.3）、（318.5 ± 7.6）、（234.7 ± 2.5）、（165.4 ± 19.4）mL·g-1，产甲烷效率较对照组分别下降14%、36%和55%。超过4 000 mg·L-1的外源氨氮投加促使产甲烷菌群结构发生显著变化，乙酸利用型产甲烷优势菌Methanosaeta 逐渐被Methanosarcina代替，而氢利用型产甲烷菌属中Methanospirillum的优势性逐渐被Methanoculleus和Methanomassiliicoccus取代，说明后者均有较强的氨氮耐受性。主成分分析和冗余分析表明，高浓度氨氮会促使产甲烷途径由乙酸利用型为主向氢利用型为主转变。

Effects of ammonia concentration on anaerobic digestion of swine manure and community structure of methanogens

Ammonia inhibition is regarded as a main factor that influences the popularization and application of high solid anaerobic digestion. In this study, batch experiments were carried out with exogenous ammonia addition to investigate the effect of ammonia concentration on methane production and methanogenic community during the anaerobic digestion of swine manure. Results showed that the daily and cumulative methane production both decreased obviously when the addition amount was 2 000 mg·L-1 with corresponding TAN about 3 596.7 mg·L-1. Furthermore, extend of ammonia inhibition was further aggravated with the accumulation of VFAs, lag phase of methane production peak and failure of propionic aid degradation when the addition amount of ammonia exceeded 4 000 mg·L-1 with corresponding TAN about 5 618.7 mg·L-1. With the increase of ammonia addition, the methane production of volatile solid in swine manure was (369.0 ± 17.3), (318.5 ± 7.6), (234.7 ± 2.5) and (165.4 ± 19.4) mL·g-1, respectively, resulting in 14%, 38% and 55% reduction of methane production potential compared with control group. The methanogenic community changed significantly when the addition amount exceeded 4 000 mg·L-1. For example, Methanosaeta was outcompeted by Methanosarcina among aceticlastic methanogens, and Methanospirillum was eliminated by Methanoculleus and Methanomassiliicoccus among hydrogenotrophic methanogens, indicating that the latter ones are more tolerant to ammonia. According to the result of PCA and RDA, high concentration of ammonia nitrogen would promote the evolution of methanogenesis from the aceticlastic pathway to hydrogenotrophic pathway gradually.