Assessing the feasibility of a vertical double submerged membrane modules system for wastewater reclamation under different conditions

Nowadays, water is deteriorating for several reasons, such as an increase in wastewater that flows into rivers and the limitation of water resources. Therefore, we have concentrated our plans on securing water resources by reusing wastewater treatment effluent. In this study the reuse system was organized using a submerged membrane bioreactor (SMBR) consisting of an anoxic, select, and aerobic tank. Our plan to solve the problems mentioned above involved optimizing the operating hydraulic retention time (HRT), which was done by comparing the characteristics of water treatment for several HRTs. Also, the simple and vertical double membrane modules were analyzed to find more effective operating condition in SMBR. The Specific characteristics of the SMBR system were represented as follows. We could know below 10 mg/L of BOD, below 5 mg/L of COD, 0 mg/L of SS without changes of HRT, which was satisfied with the standard of reuse water. Optimized HRT was 2.3 h and by composing the vertical double membrane modules, air flow rate could be reduced by 28.5%, lower than that of the simple membrane module.     

The beneficial role of intermediate clarification in a novel MBR based process for biological nitrogen and phosphorus removal

BACKGROUND: A novel membrane bioreactor (MBR) is described, employing an intermediate clarifier. Unlike the established function of a final clarifier in a conventional biological nutrient removal system, the role of an intermediate clarifier has rarely been studied. Thus, this work focused on explaining the fate of nutrients in the intermediate clarifier, as influenced by the hydraulic retention time (HRT) of the preceding anaerobic bioreactor. RESULTS: The system was tested with two different anaerobic/anoxic/aerobic biomass fractions of 0.25/0.25/0.5 (run 1) and 0.15/0.35/0.45 (run 2) using synthetic wastewater. The major findings of the study were that phosphorus (P) removal was affected by the role of the intermediate clarifier. In run 1, P was removed at a rate 0.16 g d⁻¹ in the intermediate clarifier while in run 2, additional P was released at 0.49 g d⁻¹. The nitrogen (N) removal efficiencies were 74 and 75% for runs 1 and 2 respectively, while P removal was 91 and 96%. P uptake by denitrifying phosphate accumulating organisms (DPAOs) accounted for 41–52% of the total uptake in the MBR. CONCLUSIONS: This study found that the intermediate clarifier assisted chemical oxygen demand (COD), N, and P removal. With respect to the fate of P, the intermediate clarifier functioned as an extended anaerobic zone when the HRT of the preceding anaerobic zone was insufficient for P release, and as a pre‐anoxic zone when the anaerobic HRT was adequate for P release. Copyright © 2008 Society of Chemical Industry     

ABR＆BAF组合工艺处理造纸废水

采用ABR（折流板反应器）＆BAF（曝气生物滤池）组合工艺处理造纸废水。运行结果表明。在进水CODcr,4004-500mg／L,BOD5 200-300mg／L时,处理后出水水质可达到《制浆造纸工业水污染物排放标准》（GB3544—2008）第二时段一级标准之现有企业水污染排放限值：CODcr≤100mg／L,BOD5≤30mg／L。该工艺简单,占地面积小,运行方便,运行费用低。     

水解酸化-膜生物反应器处理化工综合废水

采用水解酸化-浸没式膜生物反应器工艺处理化工综合废水。小试结果表明:在进水CODCr的质量浓度为1500～2400mg/L,BOD5与CODCr的质量比为0.28～0.35,pH值为6～9,水解酸化、膜生物反应器HRT分别为12、18h,膜通量约16L/(m2.d),污泥负荷约为0.38[CODCr]/(kg[MLVSS].d)时,经该工艺处理,CODCr、挥发酚去除率分别达到92%、97%以上,且膜生物反应器出水浊度小于1NTU,未检测到SS。     

膜生物反应器中影响膜透水率的几个因素

本文研究了影响膜 -好氧生物反应器中中空纤维膜透水率的几个因素 ,如组件长度、操作压力、膜面流速、活性污泥浓度和温度。中空纤维膜内 ,压力沿料液流动方向呈抛物线型分布 ,所以在膜内径和膜面流速一定的情况下 ,存在一个最佳的膜组件长度 Llin使得膜利用率最高 ,且最省能 ;操作压力对膜透水率的影响分为三个区域 ,各个区域膜的主要过滤阻力不同 ,不同污泥浓度时 ,为了使中空纤维膜内腔不堵塞 ,膜面流速必须高于某一范围 ,膜透水率随温度呈正比例关系变化。     

Removal of nitrogen from wastewater for reusing to boiler feed-water by an anaerobic/aerobic/membrane bioreactor

The innovative process anaerobic/aerobic/membrane bioreactor (A/O/MBR) was developed to enhance pre-denitrification without the energy consumption of the recirculation pump for reusing wastewater to boiler feed-water. The performance of this bioreactor was investigated. Firstly, the septic tank wastewater with low ratio of COD/TN was disposed by a dynamic membrane bioreactor (DMBR). It was found that, although the high concentration of NO₂⁻–N in the effluent implied the potential ability of DMBR to realize shortcut nitrification and denitrification, the effluent of single DMBR was difficult to reach the criteria of reusing to boiler feed-water. Then, the process A/O/DMBR in disposing the septic tank wastewater was studied. The results indicated that this process not only accomplished the removal of 91.5% COD, 90.3% NH₄⁺–N and 60.2% TN, but also successfully realized pre-denitrification without additional recirculation pump. At last, based on the A/O/DMBR, a pilot plant A/O/MBR was built to dispose the municipal raw sewage. In the stable operation period, the average removal efficiencies for COD, NH₄⁺–N, TP and turbidity reached 90%, 95%, 70% and 99%, respectively. During the tested HRT run of 9.0 h, the effluent of COD, NH₄⁺–N, TP and turbidity was about 10 mg/L, 3 mg/L, below 1 mg/L and 1.2 NTU, respectively, which reached the criteria of the boiler feed-water in China.     

Effects of the sludge reduction system in MBR on the membrane permeability

For the sludge volume reduction, gravity thickening and mechanical thickening processes have been mainly applied. However, these processes usually cause several problems such as large footprint, low thickening efficiency, etc. To solve these problems, a sludge reduction system using submerged membrane in a reactor with excess sludge from a biological nutrient removal (BNR) system was investigated. Both lab and pilot scale experiments for sludge reduction were carried out. The hydraulic retention time (HRT) was in a range of 4.5-6.7 days during the experimental period. A flat-sheet membrane with a mean pore size of 0.08 µm was used and operated at a flux range of 7-20 L/m²·h.During the experimental period, concentrations of BOD and SS were maintained less than 8 mg/L, 3 mg/L, respectively, which indicated the high quality of treated wastewater. While extracellular polymeric substances (EPS) were lowest at a coagulant concentration of 15 ppm, soluble microbial product (SMP) concentrations did not have any correlation with coagulant concentrations. The critical flux was observed in a range of 18-24 L/m²·h.These results suggested that the sludge reduction system using membrane bioreactor (MBR) could be applied as one of suitable processes to overcome problems of conventional processes such as gravity and mechanical thickening.     

Applicability of nanofiltration for the advanced treatment of landfill leachate

Landfill leachates are generated from municipal solid waste landfills under the action of water percolating through the landfilled waste. A treatment system using a combined membrane engineering process was developed to effectively treat the landfill leachate in the Dahanzhuang sanitary landfill (Tianjin, China). The process combines a membrane bioreactor (MBR) and nanofiltration (NF) technology to treat the leachate. The results indicate that the NF system, including the hollow‐fiber NF membrane, is an appropriate advanced treatment alternative for landfill leachates. This system provided good removal of chemical oxygen demand and color. The membrane flux renewal reached over 96% after washing with 0.01 mol/L HCl. As a result, the effluent water quality met effluent discharge standards (GB16889‐2008). © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

New chlorine‐resistant polyamide reverse osmosis membrane with hollow fiber configuration

New asymmetric hollow fiber reverse osmosis (RO) membrane was developed from a new chlorine‐resistant copolyamide [4T‐PIP(30)] with a piperazine moiety by a conventional phase‐separation method. The new 4T‐PIP(30) hollow fiber membrane has the same low‐pressure RO performance as cellulose triacetate hollow fiber membrane (FR = 205 L/m² day, Rj = 99.6%) and superior chlorine resistance as well as pH resistance to conventional aramid RO membranes. Structural analysis and viscoelastic study revealed that the new hollow fiber consisted of a top skin, dense layer, and microporous layer, and that it began to decrease its elasticity at 80°C in water, which is possibly related to its good and stable RO performance around room temperature. Several kinds of RO modules were made from the new hollow fiber membranes, for which RO performances were stable for 2 years in chlorinated feed water desalination (the free residual chlorine ranged from 0.l to 1.1 mg/L). © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 517–527, 2001     

Engineering design of outer‐selective tribore hollow fiber membranes for forward osmosis and oil‐water separation

Outer‐selective thin‐film composite (TFC) hollow fiber membranes offer advantages like less fiber blockage in the feed stream and high packing density for industrial applications. However, outer‐selective TFC hollow fiber membranes are rarely commercially available due to the lack of effective ways to remove residual reactants from fiber's outer surface during interfacial polymerization and form a defect‐free polyamide film. A new simplified method to fabricate outer‐selective TFC membranes on tribore hollow fiber substrates is reported. Mechanically robust tribore hollow fiber substrates containing three circular‐sector channels were first prepared by spinning a P84/ethylene glycol mixed dope solution with delayed demixing at the fiber lumen. The thin wall tribore hollow fibers have a large pure water permeability up to 300 L m^?2 h^?1 bar^?1. Outer‐selective TFC tribore hollow fiber membranes were then fabricated by interfacial polymerization with the aid of vacuum sucking to ensure the TFC layer well‐attached to the substrate. Under forward osmosis studies, the TFC tribore hollow fiber membrane exhibits a good water flux and a small flux difference between active‐to‐draw (i.e., the active layer facing the draw solution) and active‐to‐feed (i.e., the active layer facing the feed solution) modes due to the small internal concentration polarization. A hyperbranched polyglycerol was further grafted on top of the newly developed TFC tribore hollow fiber membranes for oily wastewater treatment. The membrane displays low fouling propensity and can fully recover its water flux after a simple 20‐min water wash at 0.5 bar from its lumen side, which makes the membrane preferentially suitable for oil‐water separation. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4491–4501, 2015     

Hydrophilic hollow fiber membranes for water desalination by the pervaporation method

Hydrophilic ion-exchange membranes based on sulfonated polyethylene hollow fibers were manufactured, and their suitability for a water pervaporation process was studied for possible application in water desalination systems. The effects of the following parameters on the average water flux were determined: membrane properties (diameter (0.4–1.8 mm) and wall thickness (0.05–0.18 mm)); charge density (0.6–1.2 meq g⁻¹); and operating conditions (brine inlet temperature (30–68°C), air sweep velocity (0–6 m s⁻¹), and salt concentration in the feed brine (0–3 M)). A water flux of 0.8–3.3 kg m⁻² h⁻¹ was obtained using this type of hollow fiber with an inlet brine temperature of 25–65°C. It was found that, for our application, the optimal specifications for the ion-exchange hollow fibers were an outside diameter of 1.2 mm, a wall thickness of 0.1 mm, and an ion-charge density of about 1.0 meq g⁻¹. This information is required as basic data for the design of a prototype water desalination system based on a pervaporation system that uses this type of ion-exchange hollow fiber membrane.     

Preparation and characterization of alumina hollow fiber membranes

With the rapid development of membrane technology in water treatment, there is a growing demand for membrane products with high performance. The inorganic hollow fiber membranes are of great interest due to their high resistance to abrasion, chemical/thermal degradation, and higher surface area/volume ratio therefore they can be utilized in the fields of water treatment. In this study, the alumina (Al₂O₃) hollow fiber membranes were prepared by a combined phase-inversion and sintering method. The organic binder solution (dope) containing suspended Al₂O₃ powders was spun to a hollow fiber precursor, which was then sintered at elevated temperatures in order to obtain the Al₂O₃ hollow fiber membrane. The dope solution consisted of polyethersulfone (PES), Nmethyl-2-pyrrolidone (NMP) and polyvinylpyrrolidone (PVP), which were used as polymer binder, solvent and additive, respectively. The prepared Al₂O₃ hollow fiber membranes were characterized by a scanning electron microscope (SEM) and thermal gravimetric analysis (TG). The effects of the sintering temperature and Al₂O₃/PES ratios on the morphological structure, pure water flux, pore size and porosity of the membranes were also investigated extensively. The results showed that the pure water flux, maximum pore size and porosity of the prepared membranes decreased with the increase in Al₂O₃/PES ratios and sintering temperature. When the Al₂O₃/PES ratio reached 9, the pure water flux and maximum pore size were at 2547 L/m²·h and 1.4 μm, respectively. Under 1600dgC of sintering temperature, the pure water flux and maximum pore size reached 2398 L/(m²·h) and 2.3 μm, respectively. The results showed that the alumina hollow fiber membranes we prepared were suitable for the microfiltration process. The morphology investigation also revealed that the prepared Al₂O₃ hollow fiber membrane retained its’asymmetric structure even after the sintering process.     

臭氧-膜生物反应器深度处理印染废水的研究

采用臭氧-膜生物反应器工艺深度处理达标排放印染废水。研究结果表明:在O3与COD的质量比为0.06,MBR停留时间为4h的条件下,经臭氧氧化后废水的可生化性大幅提升,BOD5与COD的质量比从0.19上升到0.42,废水COD的质量浓度从100mg/L降至25mg/L,色度从35倍降至15倍以下。直接运行费用0.45元/t。     

A study on submerged rotating MBR for wastewater treatment and membrane cleaning

A submerged rotating membrane bioreactor (SRMBR), with a rotatable, rounded, flat-sheet Poly(vinyldiene fluoride) (PVDF) membrane module fixed on hollow axes and moved by an electromotor, was used for wastewater reclamation. It was found that the effluent COD became stable and lower than 20 mg/L after one day running. The equilibrium permeate flux increased from 42.5 to 47.5 L/m²·h with the rotation speed increasing from 15 r/min to 25 r/min. Prolonging relaxation time could alleviate membrane fouling and enhance the flux. Finally, membrane cleaning was studied. The results showed that flushing the membrane surface with water, water/NaOH and water/NaOH/HCl recovered permeate flux to 48.4%, 83.5% and 90.2% of that of the initial operation, respectively.     

生物膜法厌氧-好氧处理腈纶废水的中试研究

采用生物膜法厌氧-好氧处理腈纶废水,试验研究了不同工况条件下,工艺对腈纶废水的处理效果。试验结果表明,当厌氧水力停留时间(HRT)控制在30 h时,COD与BOD5的去除率分别为23.22%、37.57%,BOD5/COD降低17.96%。当好氧的HRT控制在24 h、气水体积比为40:1时,COD去除率58.92%。当工艺总HRT控制在54 h时,COD去除率达60%以上,BOD5去除率达95%以上,特征污染物二甲基乙酰胺(DMAC)和丙烯腈(AN)的去除率接近100%,系统运行稳定可靠。针对此腈纶废水建议厌氧HRT控制在30 h,好氧HRT控制在24 h,气水体积比控制在40:1。     

膜生物反应器工艺处理炼油废水中试研究

采用中空纤维膜生物反应器(MBR)工艺处理炼油废水,了解膜生物反应器在炼油废水处理中的性能.研究结果表明,采用膜生物反应器工艺可有效地处理炼油废水,COD、氨氮和油去除率分别为91.5%、96.7%、84.7%,MBR出水COD为64 mg/L,氨氮为1.85 mg/L,油含量<3.0 mg/L,出水水质达到国家一级排放标准.     

浸没式厌氧膜生物反应器处理乳品有机废水的研究

采用浸没式厌氧膜生物反应器(SABMR)处理乳品有机废水,通过研究不同水力停留时间(HRT)对处理效果的影响确定了最佳的HRT为2 d。并在最佳的HRT条件下,研究微生物和SAMBR对COD_(Cr)和BOD_5的去除效果、反应器内和出水的pH和VFA浓度的变化、沼气的产量、运行前后污泥粒径的变化、膜污染的原因和膜通量的恢复措施及效果。结果表明:在进水COD_(Cr)浓度不超过2 500 mg/L,微生物和SAMBR对COD_(Cr)的去除率分别达到38.6%和80.2%以上;进水BOD_5浓度不超过1 500 mg/L时,微生物和SAMBR对BOD_5的去除率分别达到79.2%和96.6%以上;反应器内和出水pH分别稳定在7.0和7.3左右;反应器内和出水VFA浓度分别稳定在500 mg/L和200 mg/L以下;甲烷气的产量与被除去COD_(Cr)成线形关系,被除去COD_(Cr)量增加,甲烷气的产量相应的增加,甲烷气的体积占总沼气体积的60%左右;系统运行49d后污泥出现明显颗粒化;膜污染主要是由膜表面吸附的有机物和胶体物质以及无机盐在膜表面的结垢作用引起的,物理清洗和化学清洗对膜通量的恢复分别达到60%和85%左右。     

Application of Vibratory System to Improve the Critical Flux in Submerged Hollow Fiber MF Process

Submerged hollow fiber membrane system is widely used in water and wastewater treatment plants. One of the major problems of the microfiltration/ultrafiltration (MF/UF) process is membrane fouling. Few techniques have been developed to reduce membrane fouling and increase critical flux of the filtration process. In this study, membrane vibration was applied to improve the critical flux in a submerged hollow fiber MF system. A bench scale unit was especially built for this purpose and different vibrating speed was tested. The effect of the feed concentration and vibrating speed on the critical flux measurement were investigated. The critical flux was measured at different vibrating speeds varied from 0–500 oscillation per minute (opm) (5.83 Hz). The lowest critical flux was 15 L·m^?2·h^?1 when no membrane vibration was used and then increased gradually from 27 to 56 L·m^?2·h^?1 when the vibrating speed increased from 100 to 500 opm (8.35 Hz). A sharp drop in the critical flux was noticed when the concentration of feed suspension doubled from 5 g/L to 10 g/L. However, the increase in the critical flux was insignificant at higher feed concentration even when a high membrane vibrating speed was applied. This signifies that there is a limit for flux improvement in a vibratory system which is strongly dependent on the feed concentration.     

A Pilot Study on Performance of a Membrane Bio‐Reactor in Treating Fresh Water Sewage and Saline Sewage in Hong Kong

Abstract

The results of two pilot studies of an immersed membrane bioreactor (MBR) treating fresh water and saline sewage in Hong Kong are presented. The objectives were to demonstrate suitability of the MBR technology to the treatment of Hong Kong sewage and its ability to achieve total nitrogen removal effectively. When operated in nitrification/denitrification mode, the MBR was able to achieve 98% BOD removal, 90–93% COD removal and 82–84% total nitrogen removal with a HRT of 6.8 hours and 300% internal flow recirculation. Very low effluent NH₄ ⁺‐N levels were observed throughout the study suggesting complete nitrification. The MBR was able to achieve full denitrification utilizing organic matter in the raw sewage as a carbon source. The nitrogen removal capacity of the MBR was limited by nitrogen loadings rather than the biological activity in the reactor. The results did not indicate any significant differences in treatment performances with fresh water and saline sewage except that a higher frequency of membrane cleaning was required for the latter.     

Characteristics of simultaneous nitrogen and phosphorus removal in a pilot-scale sequencing anoxic/anaerobic membrane bioreactor at various conditions

This study was conducted to evaluate the performance of pilot-scale sequencing anoxic/anaerobic membrane bioreactor (SAM) process under various real situations. During the pilot experiment, the effect of three important operational parameters, such as hydraulic retention time (HRT), solids retention time (SRT) and internal recycling time mode were estimated and the long-term membrane fouling behaviour was also investigated. During the operation period, the COD removal efficiency was higher than 95% regardless of change of operational conditions because the membrane significantly contributed to remove COD by the complete retention of all particulate COD and macromolecular COD components. The change of Ax/An ratio representing internal recycling time mode significantly affected on nitrogen and phosphorus removal. As increasing Ax/An ratio, nitrogen removal efficiency increased but phosphorus removal efficiency decreased. As HRT decreased, phosphorus removal efficiency increased and nitrogen removal efficiency also increased until a certain limit of HRT (6.5 h in this study). However, when HRT decreased over the limit, nitrogen removal efficiency decreased because of insufficient nitrification. Relation between phosphorus removal efficiency and SRT was a little bit complex because SRT determined both the phosphorus content in the sludge and the sludge wasting rate. However, in this study, the shorter SRT resulted in the higher phosphorus removal efficiency. The effect of changes in all operational conditions was sensitive on phosphorus rather than on nitrogen removal efficiency. The increasing in influent flowrate resulted in the increase of flux and caused a rapid membrane fouling. Thus, the flux of 7.7 L/m²/h was more desirable compared to the 10.7 or 15.4 L/m²/h in this study.