低浓度溶解氧下猪粪固体有机物水解产酸研究

本文以猪粪为发酵原料,通过批式实验研究不同溶解氧(DO)浓度(0—0.26 mg.L-1)、发酵时间(3—12 d)和挥发性固体(VS)浓度(11.14—111.35 g.L-1)对猪粪固体水解酸化过程的影响,确定了低DO浓度下固体有机物优化水解产酸工艺条件:中温35℃,初始VS浓度37.11 g.L-1,初期的DO浓度0.1—0.26 mg.L-1.在此条件下,发酵时间3 d,DO浓度下降到0.10 mg.L-1以下.猪粪发酵液pH值由7.45±0.10降低到5.86±0.17,VS降解率(25.67±1.20)%,挥发性脂肪酸(VFA)中乙酸(3895±91)mg.L-1、丙酸(2313±82)mg.L-1、正丁酸(1361±17)mg.L-1、正戊酸(540±11)mg.L-1.优化条件下的猪粪水解酸化液进行厌氧产甲烷发酵,发酵10 d内产气停止,低溶解氧水解酸化和厌氧产甲烷发酵累计时间仅为13 d,甲烷体积分数(69.5±0.2)%,VS产气率为(0.282±0.011)L CH.4g-1VS.研究结果表明,适当延长发酵时间能够增加VFA中乙酸的含量,初始VS浓度差异对发酵液VFA浓度和VS降解率的影响较显著,低溶解氧能够促进猪粪固体有机物水解过程.

The process of hydrolysis and acidification of swine manure under limited dissolved oxygen

The processes of hydrolysis and acidification of solid swine manure were investigated.Three factors,dissolved oxygen(DO) concentration(0—0.26 mg · L-1),fermentation time(3—12 days) and initial volatile solids(VS) concentration(11.14—111.35 g · L-1) were studied in batch experiments.The optimum processing conditions were found to be initial DO concentration of 0.1—0.26 mg · L-1,VS concentration of 37.11 g · L-1at 35 ℃ with fermentation time of 3 days.On day 3,DO concentration decreased to below 0.10 mg · L-1.The pH value decreased from 7.45±0.10 to 5.86±0.17,and VS degradation rate was 25.67%±1.20%.The concentrations of acetic acid,propionic acid,butyric acid and valeric acid were(3895±91) mg · L-1,(2313±82) mg · L-1,(1361±17) mg · L-1 and(540±11) mg · L-1,respectively.Biogas production from the swine manure acidified for 3 days at limited dissolved oxygen ceased after 10 days.Total fermentation time of hydrolysis,acidification and methanogenesis was only 13 days.Methane content of biogas was 69.5%±0.2%.The average biogas yield was(0.282±0.011) L CH4 · g-1 VS added.The results show that longer fermentation time increased the concentration of acetic acid.Initial VS concentration had a significant influence on VFA concentration and VS degradation rate.Limited dissolved oxygen enhanced the hydrolysis process of the organic matters.