游离氨对热水解联合中温厌氧消化处理剩余污泥的影响

The inhibition of free ammonia on combined thermal hydrolysis and mesophilic anaerobic digestion for treating waste activated sludge

热水解预处理强化了污泥厌氧消化过程,但同时增加了微生物受游离氨抑制的风险.对比传统工艺,在有机容积负荷率1.74-4.27g VS/（L·d）条件下,研究了游离氨（FA）对热水解联合中温厌氧消化工艺性能的影响.结果表明,组合工艺甲烷产量较传统反应器提高89%-121%,有机去除率提高1.21-1.46倍.但同时导致系统中游离氨浓度达89-382mg N/L,显著高于传统工艺中37-84mg N/L的范围.游离氨毒性测试显示,传统工艺中FA浓度从43mg N/L升至84mg N/L,没有抑制解乙酸产甲烷途径,而组合工艺中FA升至264mg N/L时,表现出抑制作用,尽管厌氧菌对高浓度FA表现更强的驯化趋势.结合氮负荷试验,FA浓度与基质利用能力,解乙酸产甲烷途径抑制程度和挥发性有机酸积累的关系表明,高有机负荷条件下组合工艺效率可通过控制氮负荷优化.

Thermal hydrolysis facilitates anaerobic digestion process, but raises the possibility of free ammonia inhibition. This study evaluated the effect of free ammonia on the methanogenic ability of the thermal hydrolysis and mesophilic combined process treating waste activated sludge （WAS） with conventional single phase process as comparision. At the volumetric organic loading rates of 1.74-4.27gVS/（L·d）, the combined process had 89%-121% methane production and 1.21-1.46 times volatile solids reduced than the conventional process. But it produced free ammonia （FA） ranging 89-382mgN/L, much higher than that （37-84mgN/L） in the conventional process. Anaerobic microorganisms in both processes acclimated to high FA concentrations. The aceticlastic methanogenesis pathway was barely affected in the conventional process with FA increasing from 43 to 84mgN/L, while the activity of aceticlastic methanogens was inhibited in the combined process with FA concentration higher than 264mgN/L. The interaction of FA concentration, BMP utilization ratio, the inhibition of aceticlastic methanogenesis and volatile fatty acid （VFA） accumulations indicated the combined process was mainly affected by nitrogen loading, which was different from organic loading limited conventional process. At high solid concentration, nitrogen loading rates should be considered as an limiting operational parameter for thermal hydrolysis anaerobic digestion process.