新型超高分子量聚乙烯管式微滤膜处理高铁地下水的试验研究

采用新型超高分子量聚乙烯管式微滤膜为过滤介质,研究了预曝气-微滤组合工艺对高铁地下水的处理效果.结果表明:预曝气-微滤组合工艺对铁的去除率达90%以上,比单独微滤提高40%～60%,出水铁浓度小于0.1 mg/L,满足饮用水卫生标准;且有曝气时有毒有害微污染物去除效率高,对TOC、UV_(254)和UV_(410)的平均去除率分别为41.5%、82.1%和88.7%;有无曝气时对浊度的去除影响不大,去除率都大于95%,出水浊度小于0.2 NTU.铁等无机物是造成膜污染的主要原因,用2%～3% HCl清洗管内壁后再用清水反冲洗是处理此类膜污染的简单有效方式.     

庆阳市反渗透苦咸水淡化工程介绍

甘肃省庆阳市属于严重的干旱缺水地区,该市原二水厂出水浊度、总硬度、硫酸盐、溶解性固体超标,为此采用反渗透技术,对二水厂1.92万m3/d的出水进行深度处理,再将反渗透系统出水与V型滤池滤后水进行勾兑,形成了3.8万m3/d的生产规模。工程中采用了反渗透浓水回收装置,使水的回收率达到85%以上。系统运行数据表明,各项技术指标达到了设计要求,水质经检验达到国家《生活饮用水卫生标准》(GB5749—2006)。     

污水再生处理微滤-反渗透工艺运行效果分析

随着高水质要求用户对再生水需求的增加,微滤/超滤(MF/UF)与反渗透(RO)组合而成的双膜过滤工艺在污水再生处理领域的应用受到关注。根据北京市某再生水厂微滤—反渗透(MF—RO)工艺的长期运行数据,评价了COD、NH3—N、TP、SS等水质指标的去除效果。结果表明再生水厂进水(即上游污水处理厂出水)水质总体较好,以生物处理为主的上游污水处理厂可以有效去除污水中的颗粒污染物、有机污染物、NH3—N、TP等,但NH3—N、TP的处理效果存在季节性变化。经MF—RO工艺处理的出水COD平均为0.45mg/L,87.7%的出水NH3—N低于检测限(0.2mg/L),98.8%的出水TP不超过0.01mg/L,出水浊度的平均值为0.064NTU,出水平均TDS为30.8mg/L。出水水质好且稳定,受进水水质和季节变化影响较小,但pH主要分布在5.5～6.0的范围内,需要投加碱调节pH以保证水质稳定性。     

MBR—RO工艺深度处理煤化工废水试验研究

采用膜生物反应器(MBR)—反渗透(RO)组合工艺深度处理煤化工废水,结果表明,原水经MBR系统处理后,可有效去除废水中的COD、NH3—N、浊度和SS,去除率分别达72.6%、85.4%、98.8%和100%。MBR系统出水进入RO系统进行深度处理,硬度的去除率和除盐率分别达到87.7%和95.3%,同时可进一步除去剩余浊度和COD。系统出水水质满足《工业循环冷却水处理设计规范》(GB 50050—2007)中再生水水质指标的要求。同时,根据现场中试结果,提出了煤化工废水的膜组件和生物段的设计、运行参数及布置方案。     

混凝-沉淀+砂滤技术在典型再生水厂中的应用

针对微滤预处理系统不完善的情况,通过在预处理系统前端增加混凝-沉淀+砂滤池,解决微滤运行不稳定的实际情况.运行结果表明:滤池出水COD、浊度和TP的平均值分别为19.31 mg/L、1.68 NTU和0.26 mg/L,滤池对其平均去除率分别为40.79％、85.59％和72.95％,系统出水水质稳定.同时,滤池系统可完全去除大粒径杂质,确保自清洗过滤器正常运行.微滤系统在保持恒定通量生产运行时,滤池的存在使得微滤系统跨膜压差上升幅度大为减缓,约为没有滤池系统时的0.5倍;微滤系统清洗周期也大幅度降低,约为没有滤池系统时的一半.滤池系统的存在,有效地延长了微滤系统的使用时间,保证了微滤系统的稳定运行,在一定程度上延长了微滤膜的使用寿命,为类似工程提供相关解决思路.     

粕滤慢滤技术在西北村镇集雨窖水处理中的应用研究

针对西北村镇集雨窖水污染现状,采用粗滤慢滤组合净水工艺进行了现场试验研究.通过自然挂膜确定了膜的生物稳定期,并对其影响因素进行了分析.结果表明:粗滤慢滤小型净水装置能有效地处理西北村镇集雨窖水.对窖水的浊度、有机物、氨氮及微生物学指标有良好的去除效果.在粗滤慢滤装置滤速控制在0.1 m/h的情况下,生物膜生长期为40～50 d.在生物膜形成之后,出水氨氮平均0.285 mg/L,氨氮去除率最高达78.35％;出水CODMn平均2.27 mg/L,CODMn去除率最高达到61.58％.出水浊度平均0.56 NTU,浊度去除率最高达到98.99％.该净水技术工艺简单,无需投药,操作管理方便,适用于西北村镇等以户为单位的分散式窖水处理.     

连续微滤应用于印染废水反渗透预处理的研究

采用连续微滤(CMF)作为反渗透(RO)的预处理工艺,对印染废水二级生化出水进行深度处理。结果表明:CMF处理系统运行稳定,对色度、膜污染指数值的去除率均达到RO系统进水的要求。RO系统对盐度的去除率达到98%以上,出水水质优于自来水,各项水质指标满足印染工艺回用的要求。     

印染废水处理及回用实例

某集团印染废水处理采用水解酸化-接触氧化-双膜系统(连续微滤 反渗透),工程运行结果表明:进水CODCr为450～900 mg/L,BOD5为180～350 mg/L、SS为170～340 mg/L,其生化出水CODCr为74～110 mg/L,平均为90 mg/L,BOD5＜20 mg/L,SS＜10 mg/L,优于《污水综合排放标准》(GB 8978-1996)的二级标准;双膜系统(连续微滤 反渗透)出水优于企业染整软水标准,可作为企业染整用水.处理过程不产生固废,实现了废水的零排放.     

人工快速渗滤技术净化微污染水的试验研究

采用人工快速渗滤技术净化河道微污染水,渗滤柱内介质分别为不同厚度的火山岩、粗砂、铁矿砂和直径不等的砾石.粗砂滤柱出水水质NH3-N在0.05mg/L以下,TN在lmg/L以下,CODcr在(15～40)mg/L范围,TP在0.1 mg/L以下,叶绿素a在2mg/L以下;砾石滤柱出水水质NH3-N在0.05mg/以下,TN在1.5 mg/L以下,CODcr在35 mg/L左右,TP在0.1mg/L以下,叶绿素a在(1～5)mg/L范围.粗砂滤柱与砾石滤柱对微污染水的去除效率基本相同,但砾石滤柱渗透系数与粗砂滤柱相比.大了2个数量级.     

混凝-气浮-过滤工艺中粉末活性炭投加效果与投加点研究

对投加粉末活性炭(PAC)预处理黄河原水进行了现场中试研究,确定了PAC适宜的投加位置和投量。结果表明,PAC最佳投加点为混合池,投加PAC使气浮出水浊度提高0.4NTU左右,滤后出水浊度略有升高(<0.1NTU);在絮凝池投加会造成气浮、过滤出水浊度的明显增加;在预氧化前投加PAC较之在混合池投加其有机物去除率略有下降;在混合池投加,当PAC的投加量为10mg/L时,滤后水的CODMn去除率提高15%-20%,可取得满意的结果;滤后水的色、臭和味等指标可完全达到国家饮用水标准的要求。     

一体式膜生物反应器膜污染防治理论研究

从理论上分析了一体式膜生物反应器内曝气量与污水流量、反应器设计高度、主副腔过流面积的关系,膜外污染错流临界流速与抽吸压力及主腔宽度的关系,膜管内污染的临界速度与膜管径、膜壁吸力的关系,并得出采用化学方法消除膜污染的原理。     

Function of dynamic membrane in self-forming dynamic membrane coupled bioreactor.

The Self-Forming Dynamic Membrane Coupled Bioreactor (SFDMBR), which uses coarse pore-sized material to separate solid and liquid in bioreactors, has some advantages compared with MBR using micro-/ultra-filtration membranes, for example, low module cost and high flux. The cake layer and gel layer formed on the surface and in the pores of the material during filtration played an important role, called self-forming dynamic membrane (DM), which mainly consisted of activated sludge. In this study, the function of DM in pollutant removal was investigated. It was found that DM could remove some organic matter (12.6 mg L(-1) on average) and total nitrogen (3.01 mg L(-1) on average) in the supernatant. Colloids and organic nitrogen were partly removed by DM while DOC, ammonia nitrogen and nitrate nitrogen removal by DM varied from negative to positive, which resulted from the combination of various biological activities, e.g. nitrification, biological utilization and so on. DO concentration in DM decreased with the depth and reached zero at about 1.5-2.5 mm depth. The organic degradation activity and nitrification activity of the biomass suspended in the bioreactor were higher than those of the biomass in the cake layer, which might be caused by the low DO concentration and low organic pollutant content in DM.     

Application of PTFE membrane for ammonia removal in a membrane contactor

The feasibility of a membrane contactor system for ammonia removal was studied. The mass transfer coefficient was used to quantitatively compare the effect of various operation conditions on ammonia removal efficiency. Effective removal of ammonia was possible with a Polytetrafluoroethylene (PTFE) membrane contactor system at all tested conditions. Among the various operation parameters, contact time and solution pH showed significant effect on the ammonia removal mechanism. The overall ammonia removal rate was not affected by influent suspended solution concentration unlike other pressure driven membrane filtration processes. Also the osmotic distillation phenomena which deteriorate the mass transfer efficiency can be minimized by preheating of influent wastewater. A membrane contactor system can be a possible alternative to treat high strength nitrogen wastewater by optimizing operation conditions such as stripping solution flow rate, influent wastewater temperature, and influent pH.     

Quantitative analysis of biological effect on membrane fouling in submerged membrane bioreactor.

The objective of this study is to investigate solids concentration and extracellular polymeric substance (EPS) effects on the membrane fouling in the submerged membrane bioreactor. The relationship between the solids retention time (SRT) and the amount of EPS is observed in three lab-scale MBRs. Additionally, the EPS effect on membrane fouling is quantified by calculating the specific cake resistance (alpha) using an unstirred batch cell test. By observing the sludge over a long period under various SRT scenarios, a wide range of EPS and membrane fouling data is obtained. These observations provide sufficient evidence of the functional relationship between SRT, EPS and alpha. As SRT decreases, the amount of EPS bound in sludge floc becomes higher in the high MLSS condition (> 5,000 mg/L). The amount of EPS in the sludge floc has positive influence on alpha. A sigmoid trend between EPS and alpha is observed and the functional relationship obtained by dimensional analysis is consistent with the experimental results.     

延缓膜生物反应器膜污染的技术措施探讨

膜生物反应器(MBR)是膜分离技术和污水生物处理技术有机结合产生的一种新型污水处理工艺,与传统污水处理工艺相比具有很多优点,但膜污染是限制膜生物反应器广泛应用的关键因素.介绍了膜污染的定义,系统论述了膜污染的研究进展,着重从改良膜的性质,改善污泥混合液的特性和优化膜分离操作条件3个方面介绍了国内外有效延缓膜污染的技术措施.     

Characteristics of membrane fouling in submerged membrane bioreactor under sub-critical flux operation.

Recently, the membrane bioreactor (MBR) process has become one of the novel technologies to enhance the performance of biological treatment of wastewater. Membrane bioreactor process uses the membrane unit to replace a sediment tank, and this can greatly enhance treatment performance. However, membrane fouling in MBR restricts its widespread application because it leads to permeate flux decline, making more frequent membrane cleaning and replacement necessary, which then increases operating and maintenance costs. This study investigated the sludge characteristics in membrane fouling under sub-critical flux operation and also assessed the effect of shear stress on membrane fouling. Membrane fouling was slow under sub-critical flux operation. However, as filamentous microbes became dominant in the reactor, membrane fouling increased dramatically due to the increased viscosity and polysaccharides. A close link was found between membrane fouling and the amount of polysaccharides in soluble EPS. The predominant resistance was the cake resistance which could be minimized by increasing the shear stress. However, the resistance of colloids and solutes was not apparently reduced by increasing shear stress. Therefore, smaller particles such as macromolecules (e.g. polysaccharides) may play an important role in membrane fouling under sub-critical flux operation.     

Effect of a suspended carrier on membrane fouling in a submerged membrane bioreactor.

In an attempt at membrane fouling control, a kind of cylindrical plastic suspended carrier was added in a submerged membrane bioreactor (SMBR) and its effect was investigated in this study. According to the transmembrane pressure (TMP) profiles and the sludge characteristics in comparative runs with and without suspended carriers, it was found that the suspended carriers added in SMBR had two effects on membrane fouling: one was the positive effect of mechanically scouring the membrane surface and the other was the negative effect of breaking up sludge flocs. Sludge particle size distribution change was mainly responsible. It was suggested to apply the suspended carrier at higher MLSS concentration and lower carrier dose based on the consideration for retarding sludge breakage caused by the carrier. The experiment was conducted under higher MLSS (8 gL(-1)) and lower carrier dose (carrier volume/total volume = 10/). The TMP increase was effectively retarded by added suspended carriers compared to the system without addition of the carriers. The effect of suspended carriers on membrane fouling at high MLSS concentration was verified.     

Three-dimensional numerical study of flow characteristics and membrane fouling evolution in an enzymatic membrane reactor

In order to enhance the understanding of the membrane fouling mechanism, the hydrodynamics of the granular flow in a stirred enzymatic membrane reactor is numerically investigated in the present paper. A three-dimensional Euler-Euler model, coupled with the k-? mixture turbulence model and the drag function proposed by Syamlal and O'Brien(1989) for the interphase momentum exchange, is built to simulate the two-phase(fluid-solid) turbulent flow. Numerical simulations of single-or two-phase turbulent flows at various stirring speeds are carried out. The numerical results agree very well with the published experimental data. Results include the distributions of the velocity, the shear stress and the turbulent kinetic energy. It is shown that the increase of the stirring speed not only enlarges the circulation loops in the reactor, but also increases the shear stress on the membrane surface and accelerates the mixing process for the granular materials. The time evolution of the volumetric function of the granular materials on the membrane surface can qualitatively explain the evolution of the membrane fouling.     

Influence of total solids concentration on membrane permeability in a submerged hollow-fibre anaerobic membrane bioreactor

The main aim of this work was to study the influence of the mixed liquor total solids (MLTS) concentration on membrane permeability (K(20)) in a submerged anaerobic membrane bioreactor (SAnMBR) pilot plant, which is equipped with industrial hollow-fibre membranes and treats urban wastewater. This pilot plant was operated at 33 °C and 70 days of SRT. Two different transmembrane fluxes (13.3 and 10 LMH) were tested with a gas sparging intensity of 0.23 Nm(3) m(-2)h(-1) (measured as Specific Gas Demand referred to membrane area). A linear dependence of K(20) on MLTS concentration was observed within a range of MLTS concentration from 13 to 32 g L(-1) and J(20) of 10 LMH. K(20) was maintained at sustainable values (about 100 LMH bar(-1)) even at high MLTS concentrations (up to 20 g L(-1)). In addition, several short-tests were carried out when the membranes were operated at high MLTS concentrations in order to assess the effect of the physical cleaning strategies (relaxation and back-flush) on membrane performance. It was observed that, with the applied gas sparging intensity, the duration of the relaxation stage did not critically affect the membrane performance. On the other hand, the required back-flush frequency was considerably affected by the MLTS concentration.     

Comparison of membrane biofouling in nitrification and denitrification for the membrane bioreactor (MBR).

Batch filtration tests were conducted to compare the characteristics of membrane biofouling with regard to nitrification and denitrification. A Modified Fouling Index (MFI) was obtained using a stirred cell tester. The denitrification assays showed higher membrane fouling rates than the nitrification assays. The fouling became worse, not only due to pore blocking resistance, but also from cake layer resistance after denitrification. The Extracellular Polymeric Substances (EPS) concentration and relative hydrophobicity were decreased after denitrification, resulting in floc deterioration. The floc deterioration was assumed to have increased the cake layer resistance in the filtration test. The protein Soluble Microbial Products (SMP) concentration, portion of high molecular weight in carbohydrate SMP and relative hydrophobicity were increased after denitrification, which was assumed to cause membrane pore blocking. The changes in the EPS and SMP characteristics were the main fouling parameters in denitrification.