膜生物反应器(MBR)处理不同浓度高硫酸盐有机废水污泥性质和膜污染研究

Sludge properties and membrane fouling of aerobic membrane bioreactor(MBRs)in treating organic wastewater with different concentrations of sulfate

针对食品加工过程中产生的高SO_(4)^(2-)的高浓度有机物废水,采用膜生物反应器(MBR)工艺对其进行处理研究,分别考察了1.6%和2.6%SO_(4)^(2-)浓度下反应器运行性能、污泥性质和膜污染变化情况.经过110d的运行时间对比发现,1.6%SO_(4)^(2-)浓度下MBR获得的最大有机负荷为1.0kg(md)COD,其化学需氧量(COD)、氨氮和总氮的去除率分别为97.2%、92.5%和89.5%.2.6%SO_(4)^(2-)浓度下微生物受到的抑制更强,其获得的最大有机负荷仅为0.5kg(m^(3)·d)^(-1)COD,其COD、氨氮和总氮的去除率分别为96.3%、82.6%和80.7%.此外,SO_(4)^(2-)浓度为1.6%的反应器在更高的膜运行通量下,膜污染速率反而比2.6%系统更慢.进一步分析其污泥性质发现SO_(4)^(2-)浓度为1.6%系统内的混合液悬浮固体浓度(MLSS)和挥发性悬浮固体浓度(MLVSS)稳定在7.1g·L^(-)和5.9gL左右,MLVSS/MLSS值较初始污泥有所提高,从80.2%升高到83%.SOO_(4)^(2-)浓度为2.6%体系内MLSS和MLVSS稳定在6g·L^(-)和4.5g·L^(-)左右,MLVSS/MLSS较初始污泥有所降低,最终稳定在75%左右.较低的MLSS和MLVSS/MLSS加速了膜表面滤饼层的形成,导致2.6%SO_(4)^(2-)系统膜污染更快.经过长期的高盐环境驯化后,1.6%SO_(4)^(2-)和2.6%SO_(4)^(2-)系统成熟污泥的溶解性微生物产物(SMP)和结合性的胞外聚合物(BEPS)均有所上升,SMP从13.5mg:g VSS上升到20.4mgglVSS和65.3mgglVSS,BEPS从36.9mgglVSS上升到181.8mggVSS和227.3mg·g^(-1)VSS.2.6%SO_(4)^(2-)系统的SMP和BEPS的值均大于1.6%SO_(4)^(2-)系统,从而使得2.6%SO_(4)^(2-)系统的TMP上升加快,膜污染加剧.1.6%系统MBR中污泥粒径从接种时的82.3μm增加至125.84μm,而2.6%SO_(4)^(2-)系统中污泥粒径降至78.23μm.相较于1.6%SO_(4)^(2-)系统,2.6%SO_(4)^(2-)系统的污泥粒径更小,更容易堆积于膜表面,使得滤饼层更加紧致,加速了膜污染的形成.两套装置的膜阻力都主要来源于外部阻力,但2.6%SO_(4)^(2-)系统的内部阻力占比较1.6%SO_(4)^(2-)系统更高.综上,不同盐度对MBR体系的运行效能、污泥性质及膜污染情况具有显著的影响.因此本研究可为MBR应用于高盐高浓度有机物废水的处理提供理论基础和实践指导.

tThe organic wastewater with high SO_(4)^(2-)concentration produced in the food processing plant was treated by aerobic membrane bioreactor(MBR)process,and the performance,sludge properties and membrane fouling of the MBR were investigated at different SO concentrations of 1.6%and 2.6%respectively.For the operation period of 110 days,it was found that the maximum organic loading rate(OLR)of the MBR at the concentration of 1.6%SO_(4)^(2-)was 1.0 kg·(m^(3)·d)^(-1)COD,and the removal efficiencies of chemical oxygen demand(COD),ammonia nitrogen and total nitrogen were 97.2%,92.5%and 89.5%respectively.However,at the concentration of 2.6%SO_(4)^(2-),the maximum OLR was only 0.5 kg·(m^(3)·d)^(-1) COD,and removal efficiencies of COD,ammonia nitrogen and total nitrogen were 96.3%,82.6%and 80.7%respectively.In addition,the membrane fouling rate of the reactor with 1.6%SO_(4)^(2-)concentration was slower than that of the 2.6%system,although the reactor with 1.6%SO_(4)^(2-)concentration operated at higher membrane flux than the 2.6%system.Further analysis of the sludge properties showed that the MLSS and MLVSS in the system with 1.6%SO_(4)^(2-)concentration were stable at about 7.1 g:L-'and 5.9 g L-1,and the MLVS/MLSS was 83%with higher than that of the initial sludge.The MLSS and MLVSS in the system with 2.6%SO_(4)^(2-)concentration were stable at 6 g:L-'and 4.5 g·L-,and the MLSS/MLVSS was only 75% with lower than that of the initial sludge.Lower MLSS and MLVSS/MLSS accelerated the formation of cake layer on the membrane surface,resulting in a serious membrane fouling of 2.6%SO_(4)^(2-)system.After long-term acclimation in high-salt environment,SMP and BEPS of mature sludge for 1.6%SO_(4)^(2-)and 2.6%SO_(4)^(2-)systems increased.SMP increased from 13.5 mg·g^(-1)VSS to 20.4 mg:g'VSSand 65.3 mg·g^(-1) VSS,and BEPS increased from 36.9 mg·g^(-1) VSS to 181.8 mg·g^(-1)VSS and 227.3 mg·g^(-1)VSS respectively for 1.6% SO_(4)^(2-)and 2.6% SO_(2) systems.The SMP and BEPS in 2.6%SO2 system were both higher than that of 1.6% SO_(4)^(2-) system,thus the TMP of 2.6% SO_(2) system increases rapidly and the fouling aggravated.Compared with inoculated sludge,the particle size of MBR in 1.6%system increased from 82.3μm to 125.84μm respectively,while that of 2.6%SO_(4)^(2-)system decreased from 82.3μm to 78.23μm.Compared with 1.6% SO_(2) system,the smaller particle size in 2.6%SO_(4)^(2-)system was easier to accumulate on the membrane surface,which made the cake layer more compact and accelerated the membrane fouling.The membrane resistances of both the two MBRs mainly composed of the external resistance.However,the internal resistance of 2.6% SO_(2) system was higher than that of 1.6% SO_(4)^(2-)system.In short,different salinity had significant influence on the operation efficiency,sludge properties and membrane fouling of MBR system.Therefore this study can provide theoretical basis and practical guidance for the application of MBR in the treatment of high-salt and high-concentration organic wastewater.