Anaerobic treatment of wastewater with high organic content using a stirred tank reactor coupled with a membrane filtration unit

Using a cross-flow membrane bioreactor, high anaerobic conversion rates of three different types of wastewater with varying organic content were achieved. Loading rates obtained were as follows: 20 g CODL(-1) x d(-1) for artificial wastewater, approximately 8 g CODL(-1) x d(-1) from vegetable processing industry (sauerkraut brine) and 6-8 g CODL(-1) x d(-1) for wastewater from an animal slaughterhouse. At stable conditions, COD-removal rates in all three wastewaters were higher than 90%. Methane yields from the treatment of artificial wastewater, sauerkraut brine, and animal slaughterhouse wastewater were in the range of 0.17-0.30, 0.20-0.34, and 0.12-0.32 L(n) x g(-1) COD(-1) fed, respectively. The complete retention of biomass and suspended solids is a unique feature of this treatment process, which combines a high loading capacity and at the same time, high COD removal rates even for complex wastewater containing high concentrations of particulate matter.     

Fate of hormones and pharmaceuticals during combined anaerobic treatment and nitrogen removal by partial nitritation-anammox in vacuum collected black water

Vacuum collected black (toilet) water contains hormones and pharmaceuticals in relatively high concentrations (μg/L to mg/L range) and separate specific treatment has the potential of minimizing their discharge to surface waters. In this study, the fate of estrogens (natural and synthetical hormones) and pharmaceuticals (paracetamol, metoprolol, propranolol, cetirizine, doxycycline, tetracycline, ciprofloxacin, trimethoprim, carbamazepine, ibuprofen and diclofenac) in the anaerobic treatment of vacuum collected black water followed by nitrogen removal by partial nitritation-anammox was investigated. A new analytical method was developed to detect the presence of several compounds in the complex matrix of concentrated black water. Detected concentrations in black water ranged from 1.1 μg/L for carbamazepine to >1000 μg/L for paracetamol. Anaerobic treatment was only suitable to remove the majority of paracetamol (>90%). Metoprolol was partly removed (67%) during aerobic treatment. Deconjugation could have affected the removal efficiency of ibuprofen as concentrations even increased during anaerobic treatment and only after the anammox treatment 77% of ibuprofen was removed. The presence of persistent micro-pollutants (diclofenac, carbamazepine and cetirizine), which are not susceptible for biodegradation, makes the application of advanced physical and chemical treatment unavoidable.     

Bioaugmented membrane bioreactor (MBR) with a GAC-packed zone for high rate textile wastewater treatment

The long-term performance of a bioaugmented membrane bioreactor (MBR) containing a GAC-packed anaerobic zone for treatment of textile wastewater containing structurally different azo dyes was observed. A unique feeding strategy, consistent with the mode of evolution of separate waste streams in textile plants, was adopted to make the best use of the GAC-zone for dye removal. Dye was introduced through the GAC-zone while the rest of the colorless media was simultaneously fed through the aerobic zone. Preliminary experiments confirmed the importance of coupling the GAC-amended anaerobic zone to the aerobic MBR and also evidenced the efficacy of the adopted feeding strategy. Following this, the robustness of the process under gradually increasing dye-loading was tested. The respective average dye concentrations (mg/L) in the sample from GAC-zone and the membrane-permeate under dye-loadings of 0.1 and 1 g/L.d were as follows: GAC-zone (3, 105), permeate (0, 5). TOC concentration in membrane-permeate for the aforementioned loadings were 3 and 54 mg/L, respectively. Stable decoloration along with significant TOC removal during a period of over 7 months under extremely high dye-loadings demonstrated the superiority of the proposed hybrid process.     

Hydrogen-dependent denitrification of water in an anaerobic submerged membrane bioreactor coupled with a novel hydrogen delivery system

Hydrogen-dependent denitrification has gained significant attention due to its potential economic advantage over heterotrophic denitrification. However, effective hydrogen delivery and biomass retention under anaerobic conditions are significant challenges to implementation of this process. An innovative hydrogenotrophic denitrification system, that addresses these challenges, consisting of an anaerobic submerged membrane bioreactor (MBR) and a novel hydrogen delivery unit, was evaluated for removal of nitrate from a synthetic groundwater feed. The hydrogen delivery unit was designed to release hydrogen-supersaturated water to the reactor and was efficient in hydrogen delivery, providing complete mass transfer. The anaerobic submerged MBR was successful in both reducing nitrate from 25 mg NO(3)-Nl(-1) to below detection and separating biomass from treated water to produce effluent free of suspended solids. Nitrogen gas produced during denitrification was internally recycled to effectively achieve membrane scouring and reactor mixing. The total organic carbon was similar to that of the incoming feed water, averaging approximately 6 mgl(-1).     

Effect of disintegrated sludge recycling on membrane permeability in a membrane bioreactor combined with a turbulent jet flow ozone contactor

We have combined a turbulent jet flow ozone contactor (TJC) with a membrane bioreactor (MBR) to establish a zero-discharge system in terms of excess sludge in the MBR. The TJC-MBR system was compared with the conventional MBR (Control-MBR) with respect to i) the size and zeta potential of the sludge particles, ii) the loosely bound extra-cellular polymeric substances (EPSs) and tightly bound EPS of the microbial flocs, iii) the porosity and biovolume of the bio-cake accumulated on the membrane, and iv) the membrane permeability. The TJC system generated the ozonated sludge with a negligible amount of loosely bound EPS and a positive zeta potential. As a result, when such ozonated sludge was recycled, the average size of the sludge particles (e.g., microbial flocs) increased in the TJC-MBR. Consequently the bio-cake formed in the TJC-MBR had greater porosity than that in the Control-MBR, giving rise to higher membrane permeability in the TJC-MBR.     

Membrane coagulation bioreactor (MCBR) for drinking water treatment

In this paper, a novel submerged ultrafiltration (UF) membrane coagulation bioreactor (MCBR) process was evaluated for drinking water treatment at a hydraulic retention time (HRT) as short as 0.5h. The MCBR performed well not only in the elimination of particulates and microorganisms, but also in almost complete nitrification and phosphate removal. As compared to membrane bioreactor (MBR), MCBR achieved much higher removal efficiencies of organic matter in terms of total organic carbon (TOC), permanganate index (COD(Mn)), dissolved organic carbon (DOC) and UV absorbance at 254nm (UV(254)), as well as corresponding trihalomethanes formation potential (THMFP) and haloacetic acids formation potential (HAAFP), due to polyaluminium chloride (PACl) coagulation in the bioreactor. However, the reduction of biodegradable dissolved organic carbon (BDOC) and assimilable organic carbon (AOC) by MCBR was only 8.2% and 10.1% higher than that by MBR, indicating that biodegradable organic matter (BOM) was mainly removed through biodegradation. On the other hand, the trans-membrane pressure (TMP) of MCBR developed much lower than that of MBR, which implies that coagulation in the bioreactor could mitigate membrane fouling. It was also identified that the removal of organic matter was accomplished through the combination of three unit effects: rejection by UF, biodegradation by microorganism and coagulation by PACl. During filtration operation, a fouling layer was formed on the membranes surface of both MCBR and MBR, which functioned as a second membrane for further separating organic matter.     

纳滤用于饮用水深度处理的研究

采用纳滤膜对某市自来水进行深度处理试验,研究了纳滤对自来水中有机物及离子等的去除效果.结果表明,采用一级纳滤工艺,在回收率为70%的情况下,能有效去除自来水中的有机物、离子、内分泌干扰物和细菌等.对CODMn浊度、Cr6+和阿特拉津的平均去除率分别为81.06%,85.47%,77.20%和83.90%;对总硬度和阴离子的去除率保持在一个适中的水平;出水中未检测出细菌.     

Characterization of effluent water qualities from satellite membrane bioreactor facilities

Membrane bioreactors (MBRs) are often a preferred treatment technology for satellite water recycling facilities since they produce consistent effluent water quality with a small footprint and require little or no supervision. While the water quality produced from centralized MBRs has been widely reported, there is no study in the literature addressing the effluent quality from a broad range of satellite facilities. Thus, a study was conducted to characterize effluent water qualities produced by satellite MBRs with respect to organic, inorganic, physical and microbial parameters. Results from sampling 38 satellite MBR facilities across the U.S. demonstrated that 90% of these facilities produced nitrified (NH₄-N <0.4 mg/L-N) effluents that have low organic carbon (TOC <8.1 mg/L), turbidities of <0.7 NTU, total coliform bacterial concentrations <100 CFU/100 mL and indigenous MS-2 bacteriophage concentrations <21 PFU/100 mL. Multiple sampling events from selected satellite facilities demonstrated process capability to consistently produce effluent with low concentrations of ammonia, TOC and turbidity. UV-254 transmittance values varied substantially during multiple sampling events indicating a need for attention in designing downstream UV disinfection systems. Although enteroviruses, rotaviruses and hepatitis A viruses (HAV) were absent in all samples, adenoviruses were detected in effluents of all nine MBR facilities sampled. The presence of Giardia cysts in filtrate samples of two of nine MBR facilities sampled demonstrated the need for an appropriate disinfection process at these facilities.     

Low-pressure membrane integrity tests for drinking water treatment: A review

Low-pressure membrane systems, including microfiltration (MF) and ultrafiltration (UF) membranes, are being increasingly used in drinking water treatments due to their high level of pathogen removal. However, the pathogen will pass through the membrane and contaminate the product if the membrane integrity is compromised. Therefore, an effective on-line integrity monitoring method for MF and UF membrane systems is essential to guarantee the regulatory requirements for pathogen removal. A lot of works on low-pressure membrane integrity tests have been conducted by many researchers. This paper provides a literature review about different low-pressure membrane integrity monitoring methods for the drinking water treatment, including direct methods (pressure-based tests, acoustic sensor test, liquid porosimetry, etc.) and indirect methods (particle counting, particle monitoring, turbidity monitoring, surrogate challenge tests). Additionally, some information about the operation of membrane integrity tests is presented here. It can be realized from this review that it remains urgent to develop an alternative on-line detection technique for a quick, accurate, simple, continuous and relatively inexpensive evaluation of low-pressure membrane integrity. To better satisfy regulatory requirements for drinking water treatments, the characteristic of this ideal membrane integrity test is proposed at the end of this paper.     

Effects of chemical sludge disintegration on the performances of wastewater treatment by membrane bioreactor

A new wastewater treatment process combining a membrane bioreactor (MBR) with chemical sludge disintegration was tested in bench scale experiments. In particular, the effects of the disintegration treatment on the excess sludge production in MBR were investigated. Two MBRs were operated. In one reactor, a part of the mixed liquor was treated with NaOH and ozone gas consecutively and was returned to the bioreactor. The flow rate of the sludge disintegration stream was 1.5% of the influent flow rate. During the 200 days of operation, the MLSS level in the bioreactor with the disintegration treatment was maintained relatively constant at the range of 10,000-11,000 mg/L while it increased steadily up to 25,000 mg/L in the absence of the treatment. In the MBR with the sludge disintegration, relatively constant transmembrane pressures (TMPs) could be maintained for more than 6 months while the MBR without disintegration showed an abrupt increase of TMP in the later phase of the operation. In conclusion, a complete control of excess sludge production in the membrane-coupled bioreactor was possible without significant deterioration of the treated water quality and membrane performances.     

High-concentration food wastewater treatment by an anaerobic membrane bioreactor

The viability of treating high-concentration food wastewater by an anaerobic membrane bioreactor (AMBR) was studied using polyethersulfone (PES) ultrafiltration membranes PES200, PES300, PES500 and PES700 with norminal molecular weight cutoff (MWCO) ranging from 20,000 to 70,000 Da. Hydraulic and solid retention time significantly affected the treatment performance of the AMBR kept at 60 h and 50 days in the study. The four membranes exhibited a similar efficiency in removal of suspended solids, color, chemical oxygen demand (COD) and bacteria. When the volumetric loading rate was below 4.5 kg/m3d, COD removal rate was in the range of 81-94% and the gas yield stabilized at 0.136 m3/kg COD. The effect of membrane properties including MWCO, hydrophobicity and surface morphology on membrane fouling and cleaning was evaluated. The PES200 membranes with the smallest MWCO and smoothest surface exhibited a serious initial flux decline, whereas the PES700 membranes with the largest MWCO and roughest surface were observed related to the highest flux decline and the lowest recoverable flux rate during long-term operation. Membrane autopsy revealed that the significant flux decline was caused by the formation of a thick biofouling layer onto the membrane surfaces.     

Changes in characteristics of soluble microbial products in membrane bioreactors associated with different solid retention times: Relation to membrane fouling

A membrane bioreactor (MBR) is a promising wastewater treatment technology, but there is a need for efficient control of membrane fouling, which increases operational and maintenance costs. Soluble microbial products (SMP) have been reported to act as major foulants in the operation of MBRs used for wastewater treatment. In this study, SMP in MBRs operated with different sludge retention times (SRTs) were investigated by means of various analytical techniques and their relations to the evolution of membrane fouling were considered. Bench-scale filtration experiments were carried out in a laboratory with synthetic wastewater to eliminate fluctuations that would occur with the use of real wastewater and that would lead to fluctuations in compositions of SMP. Three identical submerged MBRs were operated for about 50 days under the same conditions except for SRT (17, 51 and 102 days). Accumulation of SMP in the MBRs estimated by conventional analytical methods (i.e., the phenol-sulfuric acid method and the Lowry method) was significant in the cases of short SRTs. However, the degrees of membrane fouling in the MBRs were not directly related to the concentrations of SMP in the reactors estimated by the conventional analytical methods. Non-conventional analytical methods such as excitation-emission matrix (EEM) fluorescence spectroscopy revealed that characteristics of SMP in the three reactors considerably differed depending on SRT. Foulants were extracted from the fouled membranes at the end of the operation and were compared with SMP in each MBR. It was clearly shown that characteristics of the foulants were different depending on SRT, and similarities between SMP and the extracted foulants were recognized in each MBR on the basis of results of EEM measurements. However, such similarities were not found on the basis of results obtained by using the conventional methods for analysis of SMP. The results of this study suggest that the use of conventional methods for analysis of SMP is not appropriate for investigation of membrane fouling in MBRs.     

Combination of one-dimensional TiO2 nanowire photocatalytic oxidation with microfiltration for water treatment

This paper proposed the fabrication of two different diameter one-dimensional TiO₂ nanowires, 10 nm TNW₁₀ and 20-100 nm TNW₂₀, via hydrothermal process using different alkaline sources. TNW₁₀ and TNW₂₀ were used as photocatalysts for the degradation of humic acid (HA), the major natural organic matters (NOMs) in surface and ground water, followed by microfiltration. The evaluation of photocatalytic activities of them showed that TNW₁₀ was superior to the commercial P25 TiO₂ while TNW₂₀ was as good as P25. The membrane filtration verified that the two types of nanowires could be completely reclaimed. The membrane fouling caused by TNW₁₀ and TNW₂₀ was much less than that of P25 due to more porous cake and less pore plugging. No apparent decrease on their photocatalytic activity was observed in repeated reuse experiments. These one-dimensional TiO₂ nanowires would provide a new route for the combination of photocatalytic oxidation and membrane filtration for water treatment.     

Denitrification from drinking water using a membrane bioreactor: chemical and biochemical feasibility

Interest is growing in developing membrane bioreactors (MBRs) to replace ion exchange for nitrate removal from drinking water. However, few published studies have successfully managed to retain exogenous or biologically derived carbon. This study determined an optimum C:N by substrate breakthrough rather than maximum nitrate removal. By dosing 相似文献   

Characterization of biofilm structure and its effect on membrane permeability in MBR for dye wastewater treatment

Two membrane bioreactors were operated at aerobic (DO=6.0mg/L) and anoxic (DO<0.3mg/L) conditions for the treatment of synthetic dye wastewater to determine the effect of dissolved oxygen on membrane filterability. The rate of membrane fouling for the anoxic MBR was five times faster than that for the aerobic MBR. Differences in the nature of the biofilm that was formed on the membrane surface as the result of different DO level was the main factor in the different fouling rates. The biofilm structure was characterized using digital image analysis techniques. Biofilm images were obtained using confocal laser scanning microscopy (CLSM) at various operation points. Structural parameters were then computed from these images using an image analysis software (ISA-2). The structural parameters indicated that the anoxic biofilm was thinner than the aerobic biofilm but the anoxic biofilm was spread out on the membrane surface more uniformly and densely, resulting in the higher membrane fouling. Based on the extracellular polymeric substances (EPS) visualization and quantification, it was also found that EPS, key membrane foulants were spread out more uniformly in the anoxic biofilm in spite of lower amount of EPS compared to that in the aerobic biofilm.     

净水供水一体化设备处理高藻低浊水库水研究

采用净水供水一体化设备对珠海市唐家水厂水库原水进行净化处理。结果表明,一体化净水供水设备对浊度、藻类、有机物和细菌均有较好的处理效果,运行期间浊度和CODMn的平均去除率分别为97％和46％,藻类去除率大于99％,细菌的截留率达到100％,出水水质满足《生活饮用水卫生标准》（GB5749--2006）限值要求。     

Submerged anaerobic membrane bioreactor for low-strength wastewater treatment: Effect of HRT and SRT on treatment performance and membrane fouling

Three 6-L submerged anaerobic membrane bioreactors (SAnMBRs) with solids retention times (SRTs) of 30, 60 and infinite days were setup for treating synthetic low-strength wastewater at hydraulic retention times (HRTs) of 12, 10 and 8 h. Total COD removal efficiencies higher than 97% were achieved at all operating conditions. Maximum biogas production rate was 0.056 L CH₄/g MLVSS d at an infinite SRT. A shorter HRT or longer SRT increased biogas production due to increased organic loading rate or enhanced dominancy of methanogenics. A decrease in HRT enhanced growth of biomass and accumulation of soluble microbial products (SMP), which accelerated membrane fouling. A drop in carbohydrate to protein ratio also inversely affected fouling. At 12-h HRT, the effect of SRT on biomass concentration in SAnMBRs was negligible and membrane fouling was controlled by variant surface modification due to different SMP compositions, i.e., higher carbohydrate and protein concentrations in SMP at longer SRT resulted in higher membrane fouling rate. At 8 and 10-h HRTs, infinite SRT in SAnMBR caused highest MLSS and SMP concentrations, which sped up particle deposition and biocake/biofilm development. At longer SRT, lower extracellular polymeric substances reduced flocculation of particulates and particle sizes, further aggravated membrane fouling.     

Mixing characterisation of full-scale membrane bioreactors: CFD modelling with experimental validation

Membrane Bioreactors (MBRs) have been successfully used in aerobic biological wastewater treatment to solve the perennial problem of effective solids-liquid separation. The optimisation of MBRs requires knowledge of the membrane fouling, biokinetics and mixing. However, research has mainly concentrated on the fouling and biokinetics (Ng and Kim, 2007). Current methods of design for a desired flow regime within MBRs are largely based on assumptions (e.g. complete mixing of tanks) and empirical techniques (e.g. specific mixing energy). However, it is difficult to predict how sludge rheology and vessel design in full-scale installations affects hydrodynamics, hence overall performance. Computational Fluid Dynamics (CFD) provides a method for prediction of how vessel features and mixing energy usage affect the hydrodynamics. In this study, a CFD model was developed which accounts for aeration, sludge rheology and geometry (i.e. bioreactor and membrane module). This MBR CFD model was then applied to two full-scale MBRs and was successfully validated against experimental results. The effect of sludge settling and rheology was found to have a minimal impact on the bulk mixing (i.e. the residence time distribution).     

MBR技术处理高氨生活污水的研究

根据MBR技术的优点,采用连续式MBR反应器处理高氨生活污水,介绍了MBR反应器装置及试验用水水质,并对MBR去除COD,NH4^＋-N效果进行了分析,实验结果表明,系统处理效果稳定且没有每天在线清洗的必要性。     

预涂层-超滤膜联用工艺用于应急给水的应用研究

针对应急供水特点,进行了粉末高岭土预涂层-膜过滤联用工艺处理应急水源的生产试验。结果表明,该工艺能够有效去除有机物,出水浊度、CODMn的平均值分别为0．01NTU和3．15mg／L,去除率分别达到98．76％和30．83％。工艺连续运行21d,膜压差增长缓慢,实现了长期稳定运行,水量和水质均适合应急供水的需求。