污泥停留时间对厌氧膜生物反应器处理餐厨废水效能的影响

Effect of sludge retention time on performance of anaerobic membrane bioreactor treating kitchen wastewater

采用中试厌氧膜生物反应器(AnMBR)处理高浓度餐厨废水,多维分析污泥停留时间(SRT为50、30和20 d)对其运行效能的影响。结果显示,An MBR在各SRT工况下均展现出较好的稳定性,消化罐pH维持在7.2(7.8之间,膜出水COD去除率达到96%以上。缩短SRT虽然能够有效提高有机负荷,但是过低的SRT会显著降低COD转化率。An MBR在SRT 30 d工况下可获得最佳处理效能,有机负荷达到(8.7±1.3)kg COD·(m^3·d)^(-1),沼气生产强度达到(4.5±0.8)m^3·(m^3·d)^(-1),COD转化率为(82.1±7.3)%。厌氧消化液中胶体态和溶解性大分子有机质的累积是导致膜过滤效能下降的主要原因,控制SRT 30 d有效削减了其积累量,从而提高了膜通量并减缓了膜污染趋势。Ca^(2+)会沉积在污泥混合液中,其浓度随着SRT缩短显著降低。此外,SRT缩短会降低长链脂肪酸(LCFA)的转化率;但是未降解的LCFA很可能与Ca^(2+)形成沉淀,会减轻游离LCFA对微生物活性的抑制作用,进而有助于AnMBR的稳定运行。

A pilot-scale anaerobic membrane bioreactor（ An MBR） was used to treat high-strength kitchen wastewater,and the effects of sludge retention time（ SRT 20,30,50 days） on operational performance were multi-dimensionally investigated. The results showed that the An MBR provided excellent operational stability at each SRT,with a constant pH of 7. 2—7. 8 in the digester and a high COD removal efficiency of over 96% based on membrane permeate quality. Although decreasing SRT elevated the organic loading rate（ OLR）,an overly low SRT remarkably reduced the COD conversion efficiency. Optimal An MBR performance was observed with a SRT of 30 d. The OLR and biogas productivity reached（ 8. 7 ± 1. 3） kg COD·（ m^3·d）^（-1）and（ 4. 5 ± 0. 8） m^3·（ m^3·d）^（-1）,respectively,while the COD conversion efficiency remained at（ 82. 1 ± 7. 3） %. The accumulation of colloidal and soluble macromolecular organic compounds was the major reason for the decline in membrane filtration performance,and their concentration decreased when the An MBR was operated with a SRT of 30 d.Thus,the membrane flux improved and the propensity for membrane fouling was alleviated. Ca^（2＋）precipitated in the sludge mixed liquor,and its concentration remarkably decreased as the SRT was shortened. Moreover,reducing the SRT lowered the long chain fatty acid（ LCFA） conversion efficiency,but undegraded LCFAs were most likely to form a precipitate with Ca^（2＋）. Thus,the inhibitory effects of free LCFAs on microbial activity were attenuated,further contributing to the stable operation of the An MBR.