Characteristics of volatile fatty acids production and microbial succession under acid fermentation via anaerobic membrane bioreactor treating kitchen waste slurry

In this study, two anaerobic membrane bioreactors (AnMBRs) were proceeded to produce volatile fatty acids (VFAs) from kitchen waste slurry under acidic conditions of pH 5 and pH 6. Higher fermentation potential and VFAs quality were obtained at pH 6, with VFAs production, yield and CODVFAs/CODeffluent ratios of 42.0 g/L, 0.35 g/g-CODinfluent and 80% respectively. The alkali dosages at pH 5 and pH 6 were 0.028 g-NaOH/g-VFAs and 0.081 g-NaOH/g-VFAs respectively, far lower than that of pH 9 (0.4 g-NaOH/g-VFAs). The microbial community presented marked differences between pH 5 and pH 6. In addition, chemical cleaning and sludge discharge could alleviate membrane fouling and ensure the stable membrane operation at pH 6, while these control strategies had no obvious improvement for fouling at pH 5 due to higher H+ toxicity.In summary, this study indicates that under acidic conditions, pH 6 is more suitable for VFA production using AnMBR and is associated with lower alkali consumption.

本研究采用两台厌氧膜生物反应器（AnMBRs），以厨余垃圾浆液为底物，在pH 5与pH 6的酸性条件下开展挥发性脂肪酸（VFAs）的生产实验。结果表明，pH 6条件下可获得更高的发酵效能与VFAs产物品质，其挥发性脂肪酸产量、产率以及CODVFAs/CODeffluent比值分别可达42.0 g/L、0.35 g/g-CODinfluent与80%。pH 5与pH 6条件下的碱投加量分别为0.028 g-NaOH/g-VFAs与0.081 g-NaOH/g-VFAs，远低于pH 9条件下的0.4 g-NaOH/g-VFAs。两组体系的微生物群落结构呈现显著差异。此外，在pH 6条件下，化学清洗与排泥可缓解膜污染并保障膜组件稳定运行；而在pH 5条件下，由于氢离子毒性更强，上述调控策略对膜污染的改善效果并不显著。综上，本研究表明，在酸性条件下，pH 6更适用于采用厌氧膜生物反应器制备挥发性脂肪酸，且碱消耗量更低。