投加硅藻土对平板膜通量的影响

实验研究了在不同污泥浓度情况下，投加硅藻土运载平板膜分离性能的影响。结果表明：硅藻土的投加可改善平板膜的分离性能，提高膜的水通量：硅藻土存在最佳的投加量，在此投加量下，水通量最大提高率为：污泥浓度为6g／L时，提高约39．7％：9g／L时，提高约32％；12g／L时，提高约23％；随着污泥浓度的增加，投加硅藻土对改善平板膜通量的效果逐渐变得不明显。     

毛细管膜生物反应器中加沸石对膜污染的影响

通过处理生活污水时毛细管膜污染状况的研究，考察了膜水通量随沸石投加量而变化的情况。在操作压力为0．025MPa，膜面流速为0．8m/s，p(MLSS)为3000mg／L的条件下，与不投加沸石直接处理生活污水相比，沸石的投加使膜水通量上升，总阻力下降；试验还探讨了沸石最佳投加量问题。结果表明，沸石的投加可改善膜面泥饼性质，提高水通量，是一种积极的膜污染防治手段。     

滑石粉减缓膜污染作用的小试研究

膜生物反应器以其突出的优点迅速成为污水处理的新的发展方向,但一直以来膜污染都是其推广应用的障碍.在膜生物反应器中投加滑石粉,主要通过膜通量等参数来研究滑石粉对膜污染的减缓作用,试验结果表明当滑石粉的投加量为1.4 g/L时膜通量下降最为缓慢,污泥沉降性能也相对较好.     

PAC投加量对MBR混合液性质及膜污染的影响

比较了1g／L及2g／L的PAC投加量对膜生物反应器中混合液性质及膜污染速率的差异。发现两系统上清液COD差距不明显,说明1g／L的PAC投加量忆足以吸附小分子的有机物。当PAC从1g／L增至2g／L时,从微生物絮体中提取的多糖平均值分别为：14．92mg／gMLSS、15．38mg／gMLSS;蛋白质平均值分别为18．82mg／gMLSS、17．58mg／gMLSS;且膜丝内部累积的多糖和蛋白质含量基本相同。当PAC投加量为2g／L时,部分破碎的PAC颗粒会进入膜孔内部,引起不可逆污染。     

无纺布膜临界通量及其在洗浴废水处理中的应用研究

以无纺布平板膜生物反应器为试验装置,采用通量阶梯式递增法的临界通量进行了测定,研究了混合液污泥浓度(MLSS)对无纺布膜临界通量的影响,考察了膜通量对无纺布平板膜生物反应器长期运行的影响。试验结果表明,无纺布膜的临界通量与MLSS浓度成反比,当MLSS的质量浓度从3 g/L增长到9 g/L时,无纺布膜临界通量从17 L/(m2·h)下降到13 L/(m2·h)。在MLSS的质量浓度控制为5 g/L,膜通量低于临界通量15 L/(m2·h)的条件下,无纺布平板膜生物反应器可连续稳定运行130 d,且反应器出水各项指标均可满足GB/T 18920—2002《城市污水再生利用城市杂用水水质》标准的要求。     

聚偏氟乙烯平板膜处理MgCl2水溶液的实验研究

采用聚偏氟乙烯平板膜,研究MgCl2水溶液在40g／L时减压膜蒸馏性能。实验结果表明,随着温度的升高,膜的渗透通量明显增大,通量随着膜后真空侧的压力增大而减小。聚偏氟乙烯平板膜表现了很好的疏水性,MgC2。水溶液的截留率在99．9％以上。     

生物沥浸法改善污泥脱水性能及反应参数优化

在微生物功能菌定量条件下探讨不同污泥含量条件下营养剂投加量对生物沥浸改善剩余污泥脱水性能的影响,并采用响应面分析法对生物沥浸改善剩余污泥脱水性能的反应参数进行优化设计。结果表明,在生物沥浸过程中,不同污泥含量、不同营养剂投加量条件下系统pH均呈现出先下降后保持稳定的趋势,污泥比阻在反应初期显著减小,然后逐渐回升。随着营养剂投加量的增加,反应后期污泥脱水性能恶化越严重。响应面分析法得出,当污泥的质量浓度为20 g/L、营养剂投加量为2 g/L、生物沥浸功能菌质量浓度为0.25 g/L,即污泥、营养剂投加量和功能菌量的质量比为80:8:1,反应时间为1 d时,生物沥浸法改善污泥的脱水性能为佳。     

浸没式管式膜MBR处理含酚废水的工艺条件

采用浸没式管式膜生物反应器处理含酚废水,对不同操作条件下的出水通量进行研究,结果表明,随着膜管内曝气量的增加膜通量衰减程度降低,能保持更高的膜通量;随着污泥浓度的增加,膜仍有较高的通量,当污泥浓度为15.2g·L-1时,膜通量可维持在60L·m-2·h-1;通过连续和间歇出水运行试验对比,发现间歇出水运行膜通量相对较高,通量衰减较慢,运行8h后通量仍能维持在70L·m-2·h-1以上.     

PAC延缓一体式MBR膜污染与膜通量恢复的对比试验

在处理洗浴废水的一体式微滤膜膜生物反应器内,投加粉末活性炭,以减缓反应器膜污染速度,延长膜生物反应器工作周期。试验结果表明,在98天试验运行期间,投加70-100目活性炭1g/L,膜通量10 L/m2·h,投炭膜只在第89 d化学清洗1次,而对照膜分别在第27 d和第81 d各清洗1次,投炭膜的工作周期延长。采用空曝气方法恢复膜过滤性能,投炭膜过滤阻力下降幅度大于对照膜。经化学清洗后,投炭膜的通量恢复效果好于对照膜。而且,投炭反应器内活性污泥的沉降性能得到提高。因此,投加适宜粒径的粉末活性炭,可有效减缓膜污染,改善膜污染层的状态,提高活性污泥的沉降性能。     

管式膜MBR处理垃圾渗滤液过程中膜的性能研究

采用管式膜MBR工艺处理垃圾焚烧场渗滤液,考察了长时间运行下管式膜通量的变化及操作压力、循环流量、温度、污泥含量等对管式膜性能的影响.结果表明,当循环体积流量达到1 000L·h-1、操作压力0.13 MPa时,膜通量达到48.02 L·m-2·h-1,膜通量随着操作压力升高而升高;随着温度的升高膜通量呈上升趋势,当温度达到32.7℃时,平均膜通量达到107.5 L·m-2·h-1;污泥含量对膜通量影响不大,污泥质量浓度在30～45 g·L-1时,膜通量仍能维持在75～100 L-m2·h-1;通过适当的膜清洗(NaClO溶液清洗),管式膜能保持在较高的通量(≥75 L·m-2·h-1,温度27.4～32.1℃)下长时间稳定运行.     

Effect of Sludge Retention Time on Membrane Bio‐Fouling Intensity in a Submerged Membrane Bioreactor

Abstract

The submerged membrane bioreactor (sMBR) is being increasingly applied for municipal and industrial wastewater treatment. This paper examines the role of sludge retention time (SRT), an important operating parameter of the MBR as it affects the biological characteristics of the sludge and therefore influences membrane fouling. Well controlled runs were carried out at short SRT (10days) and moderate SRT (30days) in a 30 L submerged MBR equipped with KUBOTA flat‐sheet membranes. At steady operation, the mixed liquor suspended solids (MLSS) stabilized at approximately 5–6 g/L and 8.5–10 g/L for SRT 10 and 30days respectively. The DGGE profiles suggested a shift in the dominant bacterial community with the prolonged SRT. The soluble microbial products (SMP) were 9.3 mg/L and 5.4 mg/L at the SRTs of 10days and 30days respectively. The total amount of extracellular polymeric substance (EPS) extracted from the floc and the supernatant was approximately constant at the two SRTs under the same organic loading rate. However, the polysaccharide concentration in the supernatant was about 100% higher for the SRT of 10days than that for 30days. The viscosity of the biomass increased with the prolonged SRT, while the estimated average air induced water velocity was similar for the two SRTs. The results of flux stepping tests showed that the membrane fouling rate (dTMP/dt) at SRT 10days was always higher than that at 30days at each flux step. Similarly, long term experimental runs at a constant flux of 20 L/m²·h clearly showed more severe membrane fouling for the SRT of 10days than that at 30days. This implies that fouling is more influenced by the concentration of SMP and Polysaccharides than the MLSS.     

重力出流式膜生物反应器污泥浓度的优化控制

采用重力出流式膜生物反应器(Membrane Bioreactor, MBR)工艺对生活污水进行了实验研究. 重力出流式MBR是利用液位水头重力驱动出水,整个系统结构紧凑,操作简便. 结果表明,随着污泥浓度增大(3.9~18.4 g/L),同样的曝气强度对膜表面滤饼层的剪切能力降低,膜通量下降;污泥粘度从5.4 mPa×s上升到680 mPa×s,相应的污泥中的传氧系数与清水中的传氧系数之比a从0.89降到0.10. 因此,从提高膜通量、氧传递速率和降低能耗的角度出发,将MBR的污泥浓度控制在适当范围是非常必要的. 此外,当污泥浓度大于4.8 g/L,污泥浓度的提高对有机物的去除、硝化以及反硝化速率的提高没有明显的贡献. 因此,从MBR的处理能力和运行能耗的双重影响确定MBR的最佳处理污泥浓度值为4~6 g/L,在该浓度区间,生物反应器系统对冲击负荷有较好的抵御能力,同时系统的运行能耗也较低.     

运行停抽时间对平板膜分离效果的影响

通过理论计算分析了PVDF截留分子量140000的平板膜和300目金属平板膜的最佳运行／停抽时间关系,并通过试验验证了理论计算结果。实验结果表明,对于平板膜存在最佳运行／停抽时间关系,但是在污泥浓度过高时,影响平板膜运行通量的主要因素已经不再是运行／停抽时间,而是累计抽吸时间．     

动态无机膜处理污泥后的清洗条件

对动态无机膜处理污泥混合液后的膜清洗进行了研究。实验先用涂膜后的无机膜管处理污泥混合液,在膜管污染后再进行清洗实验。清洗过程中测量了高速冲洗、反冲、碱洗、酸洗后的膜管通量的恢复率,主要考察了酸碱洗顺序、时间、浓度对清洗效果的影响,在选择的清洗条件下还进行了涂膜后的反复清洗实验和与未涂膜的对比实验。结果表明：最佳清洗工艺为：高速冲洗-自来水反冲-碱洗（0．2mol／LNaOH）1h-酸洗（0．1mol／LHCl）1h;反复清洗后,涂膜后的膜管通量恢复均在90％左右：对比实验证明,涂膜后的膜管通量恢复率更高。     

淹没式MBR处理啤酒废水的净化效能研究

在投加营养物质,保持COD:TN:TP=100:5:1的条件下,淹没式MBR对啤酒废水中的COD、NH 4-N有着较好的去除效果,系统稳定时COD与NH 4-N的平均去除率均在90%以上,而且MBR工艺对进水有机负荷的冲击具有较强的短时适应能力,当COD污泥负荷由0.27g/g·d突然增加至0.54g/g·d时,出水COD浓度未出现明显的波动。通过GC/MS分析得出,膜组件出水中剩余的有机物主要为高分子量的烷烃类,膜组件对于保证系统的最终出水水质起到了关键的作用。     

Preparation and properties of PVDF-fabric composite membrane for membrane distillation

The flat sheet PVDF-fabric composite membrane used for membrane distillation was prepared by coating and wet phase inversion process. The composite membrane consisted of a PVDF porous membrane layer and a fabric layer. The thin polyester filament woven fabric with water-and-oil repellent finish was used as the support of composite membrane. The effects of fabric texture, PVDF concentration in casting solution and functional finishing of fabric on the preparation and properties of the composite membrane were investigated. The experimental results showed that fabric texture, PVDF concentration and functional finishing of fabric had great influence on the preparation and properties of the composite membrane. When the PVDF concentration in casting solution was 10-12% and the support fabric, with 435 warps/10 cm and 273 wefts/10 cm and the area weight of 79 g/m², was finished with 2 g/L water-and-oil repellent agent FK-501, the prepared composite membrane exhibited better performance in tensile strength, peeling strength and water vapor permeability, with mean pore size of 0.63 μm and overall porosity of 57.6%.     

Fouling Control in a Submerged Flat Sheet Membrane System: Part I – Bubbling and Hydrodynamic Effects

Abstract

Submerged flat sheet membranes are mostly used in membrane bioreactors for wastewater treatment. The major problems for these modules are concentration polarization and subsequent fouling. By using gas‐liquid two‐phase flow, these problems can be ameliorated. This paper describes a study of the use of gas‐liquid two‐phase flow as a fouling control mechanism for submerged flat sheet membrane bioreactors. The effect of various hydrodynamic factors such as airflow rate, nozzle size, intermittent filtration, channel gap width, feed concentration, imposed flux, and the use of membrane baffles were investigated. Experiments conducted on model feeds showed that fouling reduction increased with air flow rate up to a given value and beyond this flowrate no further enhancement was achieved. The effect of bubbling was also found to increase with nozzle size at constant airflow. Using intermittent filtration as an operating strategy was found to be more effective than continuous filtration and it also reduced energy requirements. The study showed the importance of the size of the gap between the submerged flat sheet membranes. As the gap was increased from 7 mm to 14 mm, the fouling became worse and the degree of fouling reduction by two‐phase flow decreased by at least 40% based on suction pressure rise (dTMP/dt). This is the first study which has reported the effects of baffles in improving air distribution across a flat sheet submerged membrane. It was found that baffles could decrease the rate of fouling by at least a factor of 2.0 based on the dTMP/dt data, and significantly increase critical flux.     

水中天然有机物对超滤膜污染研究

对超滤膜受天然有机物污染的特性进行研究,同时考查无机矿物质成分对污染的协同影响。采用PES平板膜进行膜污染试验,模拟地表水研究腐殖酸以及钙离子的影响并进行了化学清洗试验。研究结果表明,在pH值为7.8,腐殖酸质量浓度为15 mg/L,操作压力0.1 MPa下,当钙离子浓度为4 mmol/L时,膜污染最为严重,10 min后膜通量降到起始膜通量的60%以下。先用0.1 mol/L的NaOH,再用0.5%的盐酸清洗后,膜通量可恢复至起始膜通量的98%。     

Short-term fouling propensity and flux behavior in an osmotic membrane bioreactor for wastewater treatment

The short-term fouling behavior of forward osmosis (FO) membrane in an osmotic membrane bioreactor (OMBR) was investigated, using NaCl or MgCl₂ as the draw solutions. The effect of membrane orientation, mixed liquor suspended solids (MLSS) concentration and draw solution (DS) osmotic pressure on water flux and membrane fouling behaviors was examined, along with the effects of simulated elevated salinity on sludge properties and on membrane fouling. Water flux and membrane fouling were not significantly affected by both MLSS concentration (4.91–12.60 g/L) and osmotic pressure (3.0–15.0 MPa), but were severely affected by elevated salinity, due to changes in activated sludge properties, in particular the increase in extracellular polymeric substances (EPS) and sludge hydrophobicity. MgCl₂ as the DS showed more significant influence on activated sludge properties and membrane fouling than NaCl but gave rise to lower salt accumulation. Analyses of the membrane foulants showed that small sludge floc/particles and EPS (in particular, proteins) were enriched in the fouling layer. UPLC–MS/MS analyses of the proteins showed that hydrophobic proteins were the main cause of membrane fouling.