Pilot study on municipal wastewater treatment by a modified submerged membrane bioreactor.

A pilot-scale modified submerged membrane bioreactor (SMBR) with the capacity of 18.1 m3d(-1) was developed on the basis of the principle of air-lift internal-loop reactor. Economical aeration intensity of the SMBR was determined as 96 m3m(-2)h(-1) according to hydrodynamic investigation. Corresponding economical air-flow rate was selected as the working air-flow rate in the long-term run. Under economical aeration intensity, the critical flux zone of the modified SMBR was as high as 30-35 Lm(-2)h(-1) when MLSS was less than 13 gL(-1). Therefore, a sub-critical flux of 30 Lm(-2)h(-1) was selected as the working membrane flux in the long-term run. Membrane fouling was effectively controlled by sub-critical flux operation and periodic on-line chemical cleaning in the long-term run. When the average influent CODCr, NH3-N and turbidity were 310 and 44.3 mgL(-1) and 161 NTU, respectively, the average permeate were 38.5 and 19.5 mgL(-1) and 0.96 NTU under hydraulic retention time (HRT) was only 2.8 h. Corresponding removal was 86, 58.2 and 99.4%. DO deficiency caused by high MLSS was demonstrated as the main reason for low NH3-N removal.     

Domestic wastewater reclamation by submerged membrane bioreactor with high concentration powdered activated carbon for stream restoration.

This study focuses on the practical application of high concentration powdered activated carbon coupled membrane bio-reactor to domestic wastewater reclamation. The study was conducted in three parts, such as analysis of secondary domestic wastewater effluent, design and operation parameter evaluation and reclaimed water quality estimation for stream restoration. The organic concentration was 25.2-80.2 mgCOD(Cr)/L for the effluent of three domestic wastewater treatment plants. Around 50-75% of the COD was low molecular substances less than 1,000 which were quite biodegradable. The sawdust PAC was estimated to be proper adsorbent for the organics in the secondary effluents. Its Freundlich constant, K value was 5.847 and 1/n, 0.36. Using a system consists of single reactor with high concentration PAC (80 g/L) and submerged hollow fiber MF membrane module with nominal pore size of 0.1 microm, design and operation parameters were obtained, such as HRT of the bioreactor (2.5 hr), PAC concentration (80 g/L), the initial flux (less than 0.5 m/day) and intermittent suction cycle (12 min. suction and 3 min. idling). Organic removal by the system was high enough to produce reclaimed water for urban stream restoration The effluent organic concentration was at the level of 2 mg/L in terms of TOC (around 5 mg/L as COD(Cr)). Substances with molecular weight cut off < 1,000 were removed mostly by adsorption and biodegradation. Those above 1,000 were rejected at PAC cake layer on the membrane and gradually degraded by microorganisms during extended contact.     

MBR在医院污水处理领域中的应用分析

对我国各大城市医院污水处理系统中病原微生物状况的调查表明:膜生物反应器将减少出水中悬浮物、降低后续消毒剂投加量、减少污泥的产量及气溶胶的排放三大特点结合起来,适用于我国医院污水的处理.现有工程实践表明:MBR与传统的医院污水处理工艺相比,可以有效节约消毒剂用量(投氯量可降低到1 mg/L),缩短接触时间(＞1.5 min即可),微生物灭活效果好,对于降低消毒工艺的运行费用,减少消毒剂残留对自然生态环境的影响具有积极意义.     

Treatment of toilet wastewater for reuse in a membrane bioreactor.

Toilet wastewater is treated and reused on site at Europe's highest membrane bioreactor (MBR), located in a cable car mountain station in the ski resort of Zermatt. Negative impacts on the sensitive mountain environment are minimised by reusing close to 100% of the treated wastewater for toilet flushing. Besides 100% nitrogen removal, 80% of phosphorus was also eliminated. This paper presents operational results, optimisations of sludge management, decoloration and long-term maintenance of biomass in the very low-loaded summer season. From a global view the experiences and results of the project are of great importance, proposing a solution to a problem existing 100-fold in the Alps as well as in arid regions all over the world: reducing water consumption for sanitation by reuse.     

Anaerobic membrane bioreactor for treatment of synthetic municipal wastewater at ambient temperature.

Non-woven fabric filter and poly-tetrafluoroethylene (PTFE) composite membrane were investigated to determine their applicability to treat low strength wastewater in an anaerobic membrane bioreactor (AMBR). Sludge cake resistance of the membrane was quantified using pure water flux of anaerobic sludge cake accumulated on the glass fiber filter of similar pore size. It is hypothesized that the formation of thin cake layer on the porous medium, e.g. non-woven and PTFE acts as a dynamic membrane. Thus, the capture of thin sludge cake inside the non-woven fabric matrix and accumulation on the PTFE membrane surface forms a membrane system equivalent to a commercial membrane system. The permeate quality was found to improve as the cake became more dense with filtration time. The PTFE composite membrane coated with thin PTFE film on the non-woven fabric filter enhanced the filtration performance by improving flux and minimizing the propensity of bio-fouling. The membrane flux was restored by back-flushing with permeate. The AMBR coupled with PTFE laminated membrane was operated continuously during the experiment at a cross flow velocity (CFV) of 0.1-0.2 m/sec and a transmembrane pressure (TMP) of 0.5-3 psi. Although about a month of acclimation was required to reach steady state, the effluent chemical oxygen demand (COD), volatile fatty acids (VFAs) as acetic acid, and suspended solids (SS) concentrations were below 30, 20 and 10 mg/L, respectively, during 90 days of operation with intermittent back washing. The lower operation TMP and CFV were subjected to less shear stress on the microbial community during continuous AMBR operation. In addition, thin sludge film accumulated on the membrane surface also acted as a biofilm bioreactor to remove additional COD in this study.     

Evaluation of a hybrid vertical membrane bioreactor (HVMBR) for wastewater treatment

A new hybrid membrane bioreactor (HMBR) has been developed to obtain a compact module, with a small footprint and low requirement for aeration. The aim of this research was to assess its performance. The system consists of a single vertical reactor with a filtration membrane unit and, above this, a sponge fixed bed as support medium. The aeration system is located under the membrane unit, allowing for membrane cleaning, oxygenation, biofilm thickness control and bulk liquid mixing. Operated under continuous aeration, a bench-scale reactor (70 L) was fed with pre-treated, raw (unsettled) municipal wastewater. BOD(5) and suspended solids removal efficiencies (96 and 99% respectively) were comparable to those obtained with other membrane bioreactors (MBRs). Total nitrogen removal efficiencies of 80% were achieved, which is better than those obtained in other HMBRs and similar to the values reached using more complex MBRs with extra anoxic tanks, intermittent aeration or internal deflectors.     

一体式膜生物反应器处理焦化废水

介绍了用一体式膜生物反应器(M BR)处理焦化废水的技术,讨论了对焦化废水中的COD,NH3-N和浊度的去除效果及影响因素。实验结果表明,一体式膜生物反应器用于处理焦化废水在技术上是可行的,调整合适的操作参数,其对焦化废水中的COD,NH3-N和浊度的平均去除率分别达到80%、95%、90%以上,操作简单,出水水质好,稳定,且优于国家一级排放标准,有一定的推广意义。     

Comparison of the behaviour of selected micropollutants in a membrane bioreactor and a conventional wastewater treatment plant.

Micropollutants as pharmaceutical active compounds (PhACs), residuals of personal care products or endocrine disrupting chemicals are of increasing interest in water pollution control. In this context the removal efficiencies of sewage treatment plants (STPs) are of importance, as their effluents are important point sources for the release of those substances into the aquatic environment. Activated sludge based wastewater treatment is the worldwide prevalently used treatment technique. In conventional plants the separation of treated wastewater and sludge occurs via sedimentation. A new development is the application of membrane technology for this separation step. The studies focus on the influence of the solids retention time (SRT) on the removal efficiency, as the SRT is the most important parameter in the design of STPs. A conventional activated sludge plant (CASP) and a membrane bioreactor (MBR) were operated at different SRTs. The substances selected are the antiepileptic carbamazepine, the analgesics diclofenac and ibuprofen, the lipid regulator bezafibrate, the polycyclic musks tonalide and galaxolide and the contraceptive 17alpha-ethinylestradiole. No significant differences in the removal efficiency were detected. Due to the absence of suspended solids in the MBR effluent, substances with high adsorption potential could be retained to slightly higher amounts.     

Application of a membrane bioreactor for the treatment of low loaded domestic wastewater for water re-use.

This paper describes the demonstrative scale application of a membrane biological reactor (MBR) for low loaded domestic wastewater with low attitude to biological treatment (carbon/nitrogen approximately 5). The biological process was managed by the automatically controlled alternate cycles allowing for re-use purposes with a remarkable reduction of the operational costs. The global process evaluation revealed the system capability of obtaining high nitrogen removal (effective nitrogen removal of 69%) thanks to its high flexibility related to the hourly loading fluctuation. Moreover, high removal of heavy metals and polycyclic aromatic hydrocarbons (PAH) was obtained due to the perfect retention capability of the membranes. In-depth studies were conducted to determine the process behaviour for activated sludge over aeration and with addition of exogenous carbon. Limitation of sludge over aeration and energy savings were observed with a gradient air supplying method. The addition of exogenous carbon (acetic acid up to carbon/nitrogen approximately 9) led to complete nitrogen removal (Ed = 96%) and permitted biological phosphorus uptake. In conclusion, it was been found that the coupled process alternated cycles-MBR had the capacity to remove COD, BOD, N, P and suspended solids, as well as heavy metals and organic micropollutants, resulting in high quality effluent suitable for re-use purposes.     

Enhancement of oxygen transfer and nitrogen removal in a membrane separation bioreactor for domestic wastewater treatment.

Biological nitrogen removal in a membrane separation bioreactor developed for on-site domestic wastewater treatment was investigated. The bioreactor employed hollow fiber membrane modules for solid-liquid separation so that the biomass could be completely retained within the system. Intermittent aeration was supplied with 90 minutes on and off cycle to achieve nitrification and denitrification reaction for nitrogen removal. High COD and nitrogen removal of more than 90% were achieved under a moderate temperature of 25 degrees C. As the temperature was stepwise decreased from 25 to 5 degrees C, COD removal in the system could be constantly maintained while nitrogen removal was deteriorated. Nevertheless, increasing aeration supply could enhance nitrification at low temperature with benefit from complete retention of nitrifying bacteria within the system by membrane separation. At low operating temperature range of 5 degrees C, nitrogen removal could be recovered to more than 85%. A mathematical model considering diffusion resistance of limiting substrate into the bio-particle is applied to describe nitrogen removal in a membrane separation bioreactor. The simulation suggested that limitation of the oxygen supply was the major cause of inhibition of nitrification during temperature decrease. Nevertheless, increasing aeration could promote oxygen diffusion into the bio-particle. Sufficient oxygen was supplied to the nitrifying bacteria and the nitrification could proceed. In the membrane separation bioreactor, biomass concentration under low temperature operation was allowed to increase by 2-3 times of that of moderate temperature to compensate for the loss of bacterial activities so that the temperature effect was masked.     

Application of membrane bioreactor system with full scale plant on livestock wastewater.

A full-scale plant of an MBR system treating livestock wastewater has shown impressive results. The Cheorwon County Environmental Authorities adopted the MBR process with UF membrane for retrofitting the old plant, which removes organic matter, nitrogen and phosphorus at a high level. According to 6 months operation data, BOD and SS removal were about 99.9% and COD(Mn), TN and TP removal were 92.0%, 98.3% and 82.7%, respectively. It is considered that the temperature at the bioreactor has to be controlled to be below 40 degrees C so as to ensure sufficient nitrification. It appeared that the MBR system is competitive with other conventional technologies for treatment of livestock wastewater such as piggery waste.     

Treatment of slaughterhouse plant wastewater by using a membrane bioreactor

The use of a membrane bioreactor (MBR) for removal of organic substances and nutrients from slaughterhouse plant wastewater was investigated. The chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) concentrations of slaughterhouse wastewater were found to be approximately 571 mg O2/L, 102.5 mg/L, and 16.25 mg PO4-P/L, respectively. A submerged type membrane was used in the bioreactor. The removal efficiencies for COD, total organic carbon (TOC), TP and TN were found to be 97, 96, 65, 44% respectively. The COD value of wastewater was decreased to 16 mg/L (COD discharge standard for slaughterhouse plant wastewaters is 160 mg/L). TOC was decreased to 9 mg/L (TOC discharge standard for slaughterhouse plant wastewaters is 20 mg/L). Ammonium, and nitrate nitrogen concentrations of treated effluent were 0.100 mg NH4-N/L, and 80.521 mg NO3-N/L, respectively. Slaughterhouse wastewater was successfully treated with the MBR process.     

Wastewater treatment with anaerobic membrane bioreactor and reverse osmosis.

Domestic wastewater from a new city district in Stockholm has been treated by an anaerobic membrane bioreactor (AMBR) followed by reverse osmosis (RO). The main objectives were to study the gas production, the reduction of organic matter and nutrient recovery. The AMBR was operated at 22 degrees C (equal to the average temperature in the influent) and a hydraulic retention time of 0.6 d. The results show that the reduction of organic matter, nitrogen and phosphorus over the AMBR was approximately 92, 9 and 9%, respectively. A stable gas production was registered throughout the evaluation period. The overall removal efficiency, i.e. including the RO, was >99% for TOC, >91% for Kj-N and about 99% for P. Adding a reverse osmosis (RO) unit to the AMBR makes it possible to produce a concentrated, nutrient rich product well suited for agricultural use. The quality of the concentrate is, in terms of nutrient concentration and heavy metal content, similar to source separated human urine, i.e. nitrogen content about 3 g N/L and <2 mg Cd/kg P. However, addition of acid is required to prevent precipitation/fouling of the RO. The total electricity use for operation for the system, including the RO-unit, is estimated to be 3-6 kWh/m3.     

Evaluation of a long-term operation of a submerged nanofiltration membrane bioreactor (NF MBR) for advanced wastewater treatment.

Nanofiltration (NF) is considered as one of the most promising separation technologies to obtain a very good-quality permeate in water and wastewater treatment. A submerged NF membrane bioreactor (NF MBR) using polyamide membranes was tested for a long-term operation and the performance of the NF MBR was compared with that of a microfiltration MBR (MF MBR). Total organic carbon (TOC) concentration in the permeate of the NF MBR ranged from 0.5 to 2.0 mg/L, whereas that of the MF MBR showed an average of 5 mg/L. This could be explained by the tightness of the NF membrane. Although the concentration of organic matter in the supernatant of the NF MBR was higher than that in the permeate due to high rejection by the NF membrane, the NF MBR showed excellent treatment efficiency and satisfactory operational stability for a long-term operation.     

Effectiveness of flow stabilization in small-scale wastewater treatment facilities.

Household type Johkasous which have a flow stabilization function were surveyed on their performance. The water level, flow velocity and SS were measured after the maximum flow entering the anaerobic filter chamber with or without flow stabilization operation. In operation without the flow stabilization, the flow peak directly reached the biofiltration chamber and the flow rate kept at 1 cm/sec during 3-4 min in the connection baffle between the two anaerobic chambers. This suggested the possibility of sludge transfer from the first anaerobic chamber. Moreover the increase of SS in the second anaerobic chamber indicated sludge transfer from the second anaerobic chamber to the biofiltration chamber. In contrast, in operation with flow stabilization the relaxation of the water flow in the second anaerobic chamber and the biofilm chamber was verified. By the increase of the water level in the first anaerobic chamber, the flow stabilization performance was satisfactorily obtained. A model describing the change of the water level was developed and the calculated values and the measured value agreed well. The model will be useful in the design of the flow stabilization function.     

Optimal performance of an immersed membrane bioreactor equipped with a draft tube for domestic wastewater reclamation.

One of the options to prevent membrane fouling is to implement air lifting that can improve the cake removal from the membrane surface. This study presents the results of tests that were carried out at the Institutes for Desert Research, Kiryat Sde-Boker, Israel, and focused on the influence of hydrodynamic conditions on fouling in a pilot-scale immersed membrane bioreactor (IMBR) using a hollow fiber membrane module of ZW-10 (Zenon Environmental, Canada) under ambient conditions. In this system, the cross-flow velocities across the membrane surface were induced by one conical and four cylindrical draft-tubes. The relationship between the crossflow velocity and the aeration intensity, the influence of the crossflow on fouling rate under various hydrodynamic conditions were investigated and optimal operating conditions were obtained. Optimal operating conditions were reached during the long-term experiment period (70 days) for the treatment of domestic wastewater. The system was stable without external chemical cleaning. The results showed that the permeate was of high quality, and the removal of COD and BOD was 94.0% and 98.8%, respectively.The crossflow near the membrane surface reveals a major contribution for minimizing membrane fouling, and could offer guidelines for future design of similar systems.     

Occurrence of EPS in activated sludge from a membrane bioreactor treating municipal wastewater.

EPS are supposed to be among the causes of membrane fouling in membrane bioreactors (MBR). In this work they are measured as total proteins and total polysaccharides. Theoretical and empirical considerations of biomass membrane filtration lead to the conclusion that EPS in the water phase is decisive for the filterability of activated sludge. In this study therefore different ways of separating the water phase from the biomass are investigated, where a simple filtration over a paper filter turned out to be sufficient. Subsequently, a simple batch test set up was used to investigate the influence of substrate conditions on the amount of EPS in the water phase. Dilution of the biomass does not result in changes. Dilution together with substrate addition leads to an increase both in proteins and polysaccharides. Replacement of the water phase leads to no significant changes in protein concentration, but polysaccharide concentration may vary considerably. This phenomenon is more pronounced after replacement of the water phase and substrate addition.     

Alternate anoxic/aerobic operation for nitrogen removal in a membrane bioreactor for municipal wastewater treatment

A large pilot-scale membrane bioreactor (MBR) with a conventional denitrification/nitrification scheme for municipal wastewater treatment has been run for one year under two different aeration strategies in the oxidation/nitrification compartment. During the first five months air supply was provided according to the dissolved-oxygen set-point and the system run as a conventional predenitrification MBR; then, an intermittent aeration strategy based on effluent ammonia nitrogen was adopted in the aerobic compartment in order to assess the impact on process performances in terms of N and P removal, energy consumption and sludge reduction. The experimental inferences show a significant improvement of the effluent quality as COD and total nitrogen, both due to a better utilization of the denitrification potential which is a function of the available electron donor (biodegradable COD) and electron acceptor (nitric nitrogen); particularly, nitrogen removal increased from 67% to 75%. At the same time, a more effective biological phosphorus removal was observed as a consequence of better selection of denitrifying phosphorus accumulating organisms (dPAO). The longer duration of anoxic phases also reflected in a lower excess sludge production (12% decrease) compared with the standard pre-denitrification operation and in a decrease of energy consumption for oxygen supply (about 50%).     

Integrated airlift bioreactor system for on-site small wastewater treatment.

An integrated airlift bioreactor system was developed, which mainly consists of a multi-stage loop reactor and a gas-liquid-solid separation baffle and possesses dual functions as bioreactor and settler. This integrated system was used for on-site treatment of industrial glycol wastewater in lab-scale. The strategy of gradually increasing practical wastewater concentration while maintaining the co-substrate glucose wastewater concentration helped to accelerate the microbial acclimation process. Investigation of microbial acclimation, operation parameters evaluation and microbial observation has demonstrated the economical and technical feasibility of this integrated airlift bioreactor system for on-site small industrial wastewater treatment.     

一体式厌氧平板膜生物反应器处理酒厂废水的研究

研究了容积负荷、水力停留时间对一体式厌氧平板膜生物反应器处理高浓度酒厂废水效果的影响。试验结果表明,CODCr负荷为5．2～8 kg／(m3·d),水力停留时间3～5 d时,CODCr平均去除率为95％。正常运行时的碱度与VFA的比为2．5～4．5。当CODCr负荷超过10 kg／(m3·d),系统 VFA出现累积,COD去除率下降。水力停留时间对一体式厌氧平板膜生物反应器处理效果有重要影响,水力停留时间应大于70 h。