不同温度下氨对疫病动物尸骸废水厌氧消化的影响

Effects of ammonia on the anaerobic digestion of animal carcass wastewater under different temperatures

采用厌氧折流板反应器处理疫病动物尸骸废水,研究了反应器由中温(35℃)逐步升至高温(55℃)时的运行特性.结果表明,升温至45℃和55℃时,厌氧处理效率显著降低,将有机负荷由35℃时的6.0 kg COD·(m^3·d)^(-1)降至55℃时的2.4 kg COD·(m^3·d)^(-1)并没有得到恢复,高温厌氧COD去除率相比中温下降了24%,甲烷产率下降了33%,出水挥发性脂肪酸(VFAs)增加了1.9倍.升温过程中,厌氧产甲烷菌受到了游离氮(FAN)的抑制导致甲烷产率显著降低.当温度由35℃升至55℃时,反应器p H值由7.63升至8.22,FAN由98 mg·L^(-1)升至340 mg·L^(-1),VFAs由235 mg·L^(-1)积累至684 mg·L^(-1),p H、FAN和VFAs三者的协同作用导致反应器在高温状态下处于"抑制稳态".与中温厌氧相比,高温菌对FAN的耐受性更强.当p H值为8.2时,FAN对中温菌的IC50为324 mg·L^(-1),对高温菌则达到453 mg·L^(-1),但这一优势不能抵消升温所引起的FAN抑制效应.这是疫病动物尸骸废水高温厌氧消化效率显著低于中温的主要原因.

An anaerobic baffled reactor （ABR） was used for the treatment of animal carcass wastewater, and the reactor operation characteristics were investigated as the temperature was increased from 35 ℃ to 55 ℃ gradually. The results showed that the anaerobic treatment efficiency was significantly reduced as the temperature was increased to 45 ℃ and 55 ℃, and it could not be recovered as the organic loading rate decreased from 6.0 kgCOD- （m3- d）-1 at 35 ℃ to 2.4 kgCOD· （m3·d）-1 at 55 ℃. Compared with mesophilic anaerobic digestion, the COD removal rate of thermophilic anaerobic digestion decreased by 24% and the methane yields decreased by 33%. Meanwhile the effluent concentration of VFAs increased by 1.9 times. Anaerobic methanogens were inhibited, which caused a low methane yields in the process of increasing temperature. As the temperature was increased from 35 ℃ to 55 ℃, the reactor pH increased from 7.63 to 8.22, FAN concentration increased from 98 mg· L-· to 340 mg· L-1 , and VFAs concentration accumulated from 235 mg· L-1 to 684 mg· L-1. The synergistic effects of pH, FAN and VFAs led to an ＇ inhibited steady state＇ in the thermophilic reactor. Thermophilic methanogens had stronger tolerance to FAN than mesophilic methanogens. The IC50 of FAN for mesophilic methanogens was 324 mg· L-1 at pH 8.2, while for thermophilic methanogens was 453 mg· L-1 , but this advantage was difficult to offset the FAN inhibition caused by increasing temperature. These were the main reasons that thermophilic anaerobic digestion efficiency was much lower than mesophilic anaerobic digestion.