Identification of sustainable flux in the process of using flat-sheet membrane for simultaneous thickening and digestion of waste activated sludge

The influences of mixed liquor properties on critical flux were investigated in the membrane for simultaneous thickening and digestion of activated sludge (MSTD) process, and the sustainable operation of the MSTD process was examined by employing sub-critical operation. The critical flux significantly decreased with the increase of operation time due to the variations of sludge properties in the MSTD process. Test results showed that mixed liquor suspended solids (MLSS), capillary suction time (CST), soluble microbial products (SMP) and chemical oxygen demand concentrations of colloids (COD(c)) were found to have significant influences on critical flux while the extracellular polymeric substances (EPS) had mild impacts. MLSS was then chosen as an indicated parameter, and an empirical relationship was established to predict the variation of critical flux in the MSTD process. The variable sub-critical flux operation was proposed to realize the sustainable operation according to the changing law of the critical flux during the MSTD process. The result showed that the membrane fouling potential in the MSTD process could be controlled at an operationally accepted condition by the variable sub-critical flux operation.     

颗粒物质控制膜污染的增强型膜生物反应器工艺的研究

用于废水处理的膜生物反应器工艺(MBR),是指通过膜过滤实现活性污泥与产水的分离的新型生化法处理废水技术.由于MBR具有占地面积小和出水水质好的优点,膜生物反应器成功应用到废水处理中的案例正在迅速增加.膜污染是MBR废水处理工艺面临的主要问题之一.膜污染会导致膜的渗透性能降低,为此必须通过化学清洗才能恢复膜的性能.为了实现无化学清洗的MBR工艺,研究使用持续物理冲刷去除膜污染层的方法.在活性污泥中加入颗粒物质(粉料),通过这些颗粒物质的持续冲刷作用实现去除膜污染层的目的.经过8个多月的实验,膜组件的渗透性能保持不变,通量可以达到40 L/(m2.h)以上.系统安装了在线的浊度仪作为产水质量的检测,在试验过程中,浊度始终没有变化.作为对比,同时也进行了一个参照实验(MBR标准工艺,没有加入颗粒物质),实验结果表明,传统的MBR工艺的膜组件渗透性能会不断下降导致通量下降,需要进行化学清洗.新型MBR工艺高通量和无需化学清洗的优势,将极大地提高MBR工艺的成本效益.     

Evaluation of potential integration of entrapped mixed microbial cell and membrane bioreactor processes for biological wastewater treatment/reuse

The challenge of biological wastewater treatment process is the design and operation of effective retention of mixed microbial cells within the reactor. Entrapped mixed microbial cell (EMMC) technology is designed to entrap the mixed microbial cells in polymeric carriers; membrane bioreactor (MBR) process utilizes membrane sheets/fibers to effectively retain the biomass in the reactor. These two biotechnologies are considered potential alternatives for conventional biological treatment/reuse because of their capability of retaining high concentration of biomass in the reactor, or in other words increasing the solid retention time (SRT). The simultaneous removal of organics and nitrogen were investigated using a modified EMMC system design. The modified EMMC system demonstrated higher organic and nitrogen removal performance due to high SRT. Compared to single-stage MBR process operated at similar conditions, the modified EMMC system was able to achieve slightly lower organic removal, comparable nitrification, and higher total nitrogen removal. One limitation in applying an EMMC only treatment process regime for potential reuse of treated wastewater is that such an operation requires the removal of pathogens and large particles if disinfection and solid/liquid separation were not followed. The major challenge of MBR process to overcome is membrane fouling, and the high energy consumption associated with fouling control. The intrinsic features of EMMC process including high SRT, low, and stabilized effluent suspended biomass concentration may significantly reduce the chance and extent of membrane fouling; while the membrane filtration can further polish the effluent quality from EMMC process. Therefore, integrating MBR and EMMC is strongly recommended because it may be a ??break-through?? for solving the membrane fouling problem and in improving effluent quality for potential reuse.     

厌氧膜生物反应器(AnMBR)处理高浓度豆制品废水的研究

采用膨胀污泥床反应器与外置管式超滤膜组成厌氧膜生物反应器(AnMBR)处理高浓度豆制品废水,实验连续运行240d,AnMBR平均处理量30～160L/d,研究了反应器的处理效果并获得了最佳水力停留时间(HRT).实验结果表明,AnMBR处理高浓度豆制品废水能够达到较好的效果,当进水COD为10g/L左右时,最佳HRT为18h,COD去除率约90%,此时相对应的有机负荷(OLR,以COD计)为13.6kg/(m3.d);稳定运行期间,单位COD气体产率为0.10～0.25L/g,甲烷含量在70%左右:在0.1MPa操作压力条件下进行膜的运行试验,考察了不同清洗方式的效果,采用最佳清洗方式膜通量可以恢复到新膜的90%左右.     

Simultaneous methane production and wastewater reuse by a membrane-based process: evaluation with raw domestic wastewater

In this study, a membrane-based process was applied to simultaneously reclaim methane and generate reused water from raw domestic wastewater. The system was comprised of up-flow anaerobic sludge fixed bed (UAFB), anoxic sink (AS) and aerobic membrane bioreactor (MBR). The hydraulic retention time of UAFB (HRT(U)) was gradually shortened from 8h to 6h, 3h and to 1h, while the HRT of AS and MBR kept at 8 h. It is found that HRT(U) of 3h was more suitable for the balancing production of biogas and volatile fatty acids (VFAs), and the VFAs served as carbon source for denitrification. The trans-membrane pressure (TMP) of the MBR kept lower than 0.04 MPa without wash or change of membrane sheet, however, the scanning electron microscopy (SEM) analysis indicated that microbes attached to the inner-surface of membrane, causing irreversible fouling after 133-day operation. The denaturing gradient gel electrophoresis (DGGE) profiles of amplified 16S rDNA gene fragments proved that more functional bacteria and higher microbial diversity emerged at HRT(U) of 3h and 1h. Most bacteria belonged to Betaproteobacteria and were responsible for carbon and nitrogen removal.     

淹没式MBR去除有机物动力学模型及其应用

针对淹没式MBR的工艺特点,以反应器内物料衡算为基础,建立了有机物去除的动力学模型——ROM模型,得出淹没式MBR对有机底物的去除速率Uy不仅与进、出水中的有机底物质量浓度S0、Sc和水力停留对间tH有关,还与膜组件去除的有机底物质量浓度Sm、污泥停留时间ts有关．利用ROM模型,可以预测反应器内活性污泥浓度X,确定污泥停留时间ts和不排泥条件下反应器内的最大活性污泥浓度Xmax,试验中以啤酒厂废水为例,对模型进行了验证,试验结果与模型计算结果基本一致．     

厌氧膜-EGSB反应器处理生活污水的研究

厌氧膜-膨胀颗粒污泥床(EGSB)反应器处理生活污水的结果表明,在11～25℃,水力停留时间5,7h、膜出水TOC保持在48mg／L以下,TOC去除率在81％～94％．用高上流速度可以提高出水质量,也有助于减轻膜污染．膜过滤阻力分布测试结果表明滤饼层阻力是主要阻力,     

Integration of microfiltration and nanofiltration to promote textile effluent reuse

This study investigates the application of a hybrid microfiltration–nanofiltration (MF–NF) process for textile wastewater reclamation. Indigo blue dye was efficiently retained by an MF membrane, allowing its recovery from the concentrated stream. NF technology was successfully applied to polish textile effluent. The NF membrane was evaluated under different transmembrane pressure (8–15 bars), crossflow velocities (0.21–0.84 cm s^?1), pH (7–11), and feed temperature (20–40 °C). The best NF performance was provided at a pressure of 12 bar and a crossflow rate of 0.63 cm s^?1. The NF performance (in terms of COD, conductivity, colour, and nitrogen removal) was not influenced by pH; however, higher feed pH values resulted in increased membrane fouling. The principal cause of flux decline was due to concentration polarization. Membrane chemical cleaning was sufficient to regain the initial permeability. The NF permeate met the quality requirements for all water demands within the textile industry, while the NF concentrate could be used to wash equipment, print work screens, print paste containers, and floors. The total capital cost (CapEx) of the MF–NF system was estimated at 58,362.50 US dollars and the total operational cost (OpEx) at 0.31 US dollars per cubic metre of effluent.     

纳滤膜分离技术在矿井水处理中的研究

介绍了用纳滤膜处理含悬浮物矿井水的工艺流程,考察了纳滤膜不同操作特性对膜过滤性能的影响及组合工艺对矿井水的处理效果.试验结果表明:纳滤膜在过滤周期为30min采用逆料液回流冲洗,化学清洗周期5天,能够有效减少膜污染,恢复膜通量,稳定运行4周的试验数据表明,该工艺对矿井水的处理效果明显,出水稳定,出水达到国家饮用水标准,是一种高效、经济的处理工艺.     

Study on zeolite enhanced contact-adsorption regeneration-stabilization process for nitrogen removal

Utilizing preferential ion exchange of zeolite to ammonium, the conventional contact stabilization activated sludge process (CS) can be upgraded to a new type nitrogen removal process, zeolite enhanced contact-adsorption regeneration-stabilization process (ZCS). For municipal wastewater, the effluent ammonium concentration of the ZCS process was around 6.83 mg/L, indicating that ammonium removal efficiency was enhanced over 27% when the influent ammonium concentration was between 24.7 and 50.5 mg/L in the same hydraulic retention time (HRT) and sludge retention time (SRT) conditions as those of the CS process. The results of PCR-DGGE technology showed that the microbial diversity, uniformity and abundance of the ZCS process were all higher than that of the CS process. In addition, anoxic/oxic (A/O) process with the volumetric ratio of oxic tank to anoxic tank being 2:1 was preferred for the regeneration process. The pilot scale ZCS process with the capacity to treat up to 72 m(3)/d of municipal wastewater was also monitored. The test results revealed that ammonium saturated zeolite could be biologically regenerated effectively and in time. The daily zeolite powder addition was limited to the amount that made up the loss due to the sludge excluding. Furthermore, the orthogonal experiments results showed that the most significant effects on nitrogen and ammonium removal were zeolite powder dose and external recycle ratio, respectively.     

Digestion of thermally hydrolyzed sewage sludge by anaerobic sequencing batch reactor

Laboratory experiments were conducted to investigate the performance of an anaerobic sequencing batch reactor (ASBR) for the digestion of thermally hydrolyzed sewage sludge. Both mesophilic ASBR and continuous-flow stirred tank reactors (CSTR) were evaluated with an equivalent loading rate of 2.71 kg COD/m(3)day at 20-day hydraulic retention time (HRT) and 5.42 kg COD/m(3)day at 10-day HRT. The average total chemical oxygen demand (TCOD) removals of the ASBR at the 20-day and 10-day HRT were 67.71% and 61.66%, respectively. These were 12.38% and 27.92% higher than those obtained by CSTR. As a result, the average daily gas production of ASBR was 15% higher than that of the CSTR at 20-day HRT, and 31% higher than that of the CSTR at 10-day HRT. Solids in thermally hydrolyzed sludge accumulated within ASBR were able to reach a high steady state with solid content of 65-80 g/L. This resulted in a relatively high solid retention time (SRT) of 34-40 days in the ASBR at 10-day HRT. However, too much solid accumulation resulted in the unsteadiness of the ASBR, making regular discharge of digested sludge from the bottom of the ASBR necessary to keep the reactor stable. The evolution of the gas production, soluble chemical oxygen demand (SCOD) and volatile fatty acids (VFAs) in an operation cycle of ASBR also showed that the ASBR was steady and feasible for the treatment of thermally hydrolyzed sludge.     

超滤膜生物反应器处理生活污水的试验研究

用外压一体化中空纤维超滤膜生物反应器（ＵＭＢＲ）进行了处理生活污水的试验．结果表明,当水力停留时间（ＨＲＴ）为５ｈ、膜通量在４４２～１１０Ｌ／ｈ时,ＵＭＢＲ对生活污水中ＣＯＤ、浊度、ＳＳ的去除率分别可达９０％、９８％、１００％,出水ＣＯＤ＜６０ｍｇ／Ｌ、浊度＜３、ＳＳ为０,污泥质量浓度ρＭＬＳＳ、污泥负荷Ｆｒ、反应器容积负荷ＦＷ分别为６２ｋｇ／ｍ３、０４６ｋｇ／（ｋｇ·ｄ）、１８２ｋｇ／（ｍ３·ｄ）．初步探讨了超滤膜的堵塞机理,通过杀菌清洗可使超滤膜通透能力恢复到新膜的９７％以上．ＵＭＢＲ出水浊度低,水质稳定,宜于回用     

用混凝-超滤法处理低温低浊水

考察了采用混凝-超滤法处理低温低浊时期松花江水的中试试验效果,并与水厂常规处理水质进行了比较.试验结果表明:混凝-超滤法出水浊度恒低于0.3 NTU;投加20 mg/L聚合氯化铝,超滤膜对CODMn去除率达到50%~58%,膜出水色度为6~8度;此外,投加混凝剂可以使膜渗透性能得以改善.因此混凝-超滤法可以作为低温低浊水处理的有效方法.     

Combined advanced oxidation and biological treatment of tannery effluent

During leather processing in tanneries, considerable amount of wastes with organic and inorganic pollutants are generated. For removal of these pollutants and recovery of water, biological treatment methods and reverse osmosis (RO) based membrane technologies are adopted. While recovering water from treated tannery effluent using RO membranes, presence of residual organics, dye molecules, and other impurities in the effluent have been reported as the major drawback which leads to membrane fouling and failure. In this study, an attempt was made to improve the quality of the treated tannery effluent by subjecting the secondary treated tannery effluent by ozonation alone and ozonation of primary and secondary treated tannery effluent followed by aerobic biological Sequential Batch Reactor (SBR). Maximum color reduction of 98% at pH value of 12 with ozonation alone was observed for secondary treated tannery effluent. Ozonation of secondary treated tannery effluent followed by further biological treatment in aerobic SBR increased the chemical oxygen demand (COD) removal rate and resulted in COD values less than 300 mg/L. In case of primary treated tannery effluent, maximum COD reduction of 64% was achieved in SBR.     

Comparison of UASB and EGSB reactors performance, for treatment of raw and deoiled palm oil mill effluent (POME)

Anaerobic digestion of palm oil mill effluent (POME) and deoiled POME was investigated both in batch assays and continuous reactor experiments using up-flow anaerobic sludge blanket (UASB) and expanded granular sludge bed (EGSB) reactors. The methane potential determined from batch assays of POME and deoiled POME was 503 and 610 mL-CH(4)/gVS-added, respectively. For the treatment of POME in continuously fed reactors, both in UASB and EGSB reactors more than 90% COD removal could be obtained, at HRT of 5 days, corresponding to OLR of 5.8 gVS/(L-reactor.d). Similar methane yields of 436-438 mL-CH(4)/gVS-added were obtained for UASB and EGSB respectively. However, for treatment of deoiled POME, both UASB and EGSB reactors could operate at lower OLR of 2.6 gVS/(L-reactor.d), with the methane yield of 600 and 555 mL-CH(4)/gVS-added for UASB and EGSB, respectively. The higher methane yield achieved from the deoiled POME was attributed to lower portion of biofibers which are more recalcitrant compared the rest of organic matter in POME. The UASB reactor was found to be more stable than EGSB reactor under the same OLR, as could be seen from lower VFA concentration, especially propionic acid, compared to the EGSB reactor.     

膜生物反应器用于城市污水处理与回用的试验研究

采用规模为40m^3／d的膜生物反应器对城市污水处理回用进行了试验研究．试验结果表明：膜生物反应器具有较强的抗冲击负荷能力，活性污泥对污染物的去除起主要作用，膜分离对维持稳定的出水起重要作用．膜生物反应器出水稳定，水质良好，优于生活杂用水水质标准(CJ25．1—89)．     

Anaerobic stabilisation of sludge produced during municipal wastewater treatment by electrocoagulation

Anaerobic digestion of sludge from small electrocoagulation wastewater treatment plant (SEWWTP) is described. The sludge for digestion (SEWWTP sludge) was taken from pilot-scale SEWWTP with the capacity of about 200-population equivalent (25 m3 of municipal wastewater per day). Due to the technology of wastewater treatment, the characteristics of SEWWTP sludge was different from sludge produced in conventional mechanical-biological wastewater treatment plant. Therefore, experiments were focused on possibilities of anaerobic sludge digestion and determination of conditions and parameters (amount and quality of the sludge, biogas production, etc.). Average COD removal efficiency in the pilot-scale SEWWTP exceeded 80%. Organic content of excess sludge (volatile suspended solids (VSS)) was in the range of 52.1-59.2% (these values are much lower compared to VSS content in raw sludge from conventional municipal wastewater treatment plant, where VSS is about 75%). Biogas production from anaerobic digestion of SEWWTP sludge was approximately three times lower compared to standard production in conventional municipal wastewater treatment plant. Low pH (6.5-6.7), high concentration of iron (up to 1400 mg/L) and aluminium (up to 1300 mg/L) and very low (almost zero) concentration of dissolved phosphorus in sludge water were the main factors limiting the rate of anaerobic processes. Based on these results, anaerobic digestion of SEWWTP sludge was not recommended as an appropriate stabilisation method.     

Optimizing aeration rates for minimizing membrane fouling and its effect on sludge characteristics in a moving bed membrane bioreactor

In MBR processes, sufficient aeration is necessary to maintain sustainable flux and to retard membrane fouling. Membrane permeability, sludge characteristics, nutrient removal and biomass growth at various air flow rates in the membrane and moving bed biofilm reactor (MBBR) compartments were studied in a pilot plant. The highest nitrogen and phosphorous removal rates were found at MBBR aeration rates of 151 and 85 L h(-1) and a specific aeration demand per membrane area (SAD(m)) of 1.2 and 0.4 m(air)(3) m(-2) h(-1), respectively. A linear correlation was found between the amount of attached biofilm and the nutrient removal rate. The aeration rate in the MBBR compartment and SAD(m) significantly influenced the sludge characteristics and membrane permeability. The optimum combination of the aeration rate in the MBBR compartment and SAD(m) were 151 L h(-1) and 0.8-1.2 m(air)(3) m(membrane)(-2) h(-1), respectively.     

Study of hydrolysis and acidification process to minimize excess biomass production

In this paper, a new wastewater treatment process has been presented to minimize excess biomass production in which both excess sludge digestion and wastewater treatment are conducted simultaneously in the system. The process is modification of conventional activated sludge process with insertion of two facultative basins in the sludge return line. The excess biomass in the aeration tank is recirculated to the first facultative tank. It was observed that: (1) The amount of excess biomass is reduced to nearly aero when 5.95 g/day excess sludge is recirculated from the aeration tank to the first facultative tank at COD(Cr) loading of 2.31 kg/m(3)day. A biomass experiment of 1000 mg/L was maintained at 2.31 kg-COD(Cr)/m(3)day without drawing excess sludge for 6 months of experiment period. Inert organic substances did not seem to accumulate. The effluent quality has been well below the discharge limit. (2) On the basis of infrared spectroscopy proved that dye molecule in wastewater were firstly absorbed on the sludge, and then the bond energy of was gradually weakened and decomposed and eliminated lastly.     

Performance of a hybrid-loop bioreactor system in biological treatment of 2,4,6-tri-chlorophenol containing synthetic wastewater: effects of hydraulic residence time

A hybrid-loop bioreactor system consisting of a packed column biofilm and an aerated tank bioreactor with effluent recycle was used for biological treatment of 2,4,6-tri-chlorophenol (TCP) containing synthetic wastewater. Effects of hydraulic residence time (HRT) on COD, TCP and toxicity removal performance of the reactor were investigated for the HRT values between 5 and 30 h, while the feed COD (2700+/-100 mgl(-1)), TCP (300+/-10 mgl(-1)) and the solids retention time (sludge age, SRT, 20 d) were constant. Percent TCP, COD and toxicity removals increased with increasing HRT resulting in more than 90% COD, TCP and toxicity removals at HRT values above 25 h. Biomass concentrations in the packed column and in the aeration tank increased with increasing HRT resulting in low reactor TCP concentrations and therefore high TCP, COD and toxicity removals at high HRT values. Volumetric and specific rates of TCP and COD removals decreased with increasing HRT due to increased biomass and decreased flow rates at high HRT levels. Volumetric and specific removal rates of COD and TCP were maximum at an HRT of 5 h.