Review of trace organic chemicals in urban stormwater: Concentrations, distributions, risks, and drivers.

Urban stormwater, increasingly seen as a potential water resource for cities and towns, contains various trace organic chemicals (TrOCs). This study, conducted through a comprehensive literature review of 116 publications, provides a detailed report on the occurrence, concentration distribution, health, and ecological risks of TrOCs, as well as the impact of land use and rainfall characteristics on their concentrations. The review uncovers a total of 629 TrOCs detected at least once in urban stormwater, including 228 pesticides, 132 pharmaceutical and personal care products (PPCPs), 29 polycyclic aromatic hydrocarbons (PAHs), 30 per- and polyfluorinated substances (PFAS), 28 flame retardants, 24 plasticizers, 22 polychlorinated biphenyls (PCBs), nine corrosion inhibitors, and 127 other industrial chemicals/intermediates/solvents. Concentration distributions were explored, with the best fit being log-normal distribution. Risk assessment highlighted 82 TrOCs with high ecological risk quotients (ERQ > 1.0) and three with potential health risk quotients (HQ > 1.0). Notably, 14 TrOCs (including six PAHs, five pesticides, three flame-retardants, and one plasticizer) out of 68 analyzed were significantly influenced by land-use type. Relatively weak relationships were observed between rainfall characteristics and pollutant concentrations, warranting further investigation. This study provides essential information about the occurrence and risks of TrOCs in urban stormwater, offering valuable insights for managing these emerging chemicals of concern.

Removal of phosphorus by modified bentonite:polyvinylidene fluoride membrane-study of adsorption performance and mechanism.

Enhanced phosphorus management, geared towards sustainability, is imperative due to its indispensability for all life forms and its close association with water bodies' eutrophication, primarily stemming from anthropogenic activities. In response to this concern, innovative technologies rooted in the circular economy are emerging, to remove and recover this vital nutrient to global food production. This research undertakes an evaluation of the dead-end filtration performance of a mixed matrix membrane composed of modified bentonite (MB) and polyvinylidene fluoride (PVDF) for efficient phosphorus removal from water media. The MB:PVDF membrane exhibited higher permeability and surface roughness compared to the pristine membrane, showcasing an adsorption capacity (Q) of 23.2 mgP·m-2. Increasing the adsorbent concentration resulted in a higher removal capacity (from 16.9 to 23.2 mgP·m-2) and increased solution flux (from 0.5 to 16.5 L·m-2·h-1) through the membrane. The initial phosphorus concentration demonstrates a positive correlation with the adsorption capacity of the material, while the system pressure positively influences the observed flux. Conversely, the presence of humic acid exerts an adverse impact on both factors. Additionally, the primary mechanism involved in the adsorption process is identified as the formation of inner-sphere complexes.

Microscale fluid and particle dynamics in filtration processes in water treatment: A review.

The complex filtration processes in water treatment, granular filtration and membrane filtration, often suffer from filter fouling, and the fundamental understanding of microscale fluid and particle dynamics is a key to improving filtration efficiency and stability. In this review, we identify and review several key topics in filtration processes: drag force, fluid velocity profile, intrinsic permeability and hydraulic tortuosity in microscale fluid dynamics, and particle straining, absorption, and accumulation in microscale particle dynamics. The paper also reviews several key experimental and computational techniques for investigating filtration processes at microscale considering their applicability and capability. Then, major findings in previous studies on these key topics are comprehensively reviewed in terms of microscale fluid and particle dynamics. Last, future research is discussed in terms of techniques, scopes and links. The review provides a comprehensive overview of microscale fluid and particle dynamics in filtration processes for water treatment and particle technology communities.

Polymer leachates emulate naturally derived fluorescent dissolved organic matter: Understanding and managing sample container interferences.

Fluorescence spectroscopy has become a fundamental tool for the qualitative and quantitative fingerprinting of dissolved organic matter. Due to the inherent sensitivity of the technique, a strict sampling protocol should be followed to ensure sample integrity. A literature survey conducted as part of this research determined that 27% of fluorescence sampling has been conducted in polymeric containers, while 52% did not report. Given the potential for fluorescence leachates to arise from plastics commonly used in sampling bottles, a systematic laboratory investigation was undertaken to assess the likelihood of leachate contamination and consequent interferences. It was observed that characteristic fluorescent dissolved organic matter (FDOM) leachates from standard polypropylene sampling containers were produced at environmentally relevant peaks, Peak T (λEx/λEm: 250/349 nm) and B (λEx/λEm: 250/306 nm), commonly attributed to tryptophan-like and tyrosine-like molecular origins. Leachate fluorescence and concentration generally increased with elevated storage temperatures (>4 °C), sample acidification, container steam sterilisation and in new containers, with variability across different manufactured batches. For example, at ambient storage temperatures, the highest observed leachate intensity could contribute an error equivalent to as much as 98% (Peak T) and 2062% (Peak B) for highly treated water or 28% (Peak T) and 398% (Peak B) for surface water. For leachates formed under typical conditions, i.e., 3-day fridge storage, this reduced to 9% (Peak T) and 15% (Peak B) or 3% (Peak T/B) for the same water samples. In addition, PP was found to be typically unsuitable for DOC measurements, except under strict conditions (well-aged containers in short term cold storage). Consequently, we demonstrate the need for container material reporting, refrigerated storage, steam sterilisation avoidance, and the importance of glass usage for low FDOM samples. Future research should investigate the potential for polymer-based pollution as a potential origin of environmentally sampled FDOM.

Impact of Forward Osmosis Operating Pressure on Deformation, Efficiency and Concentration Polarisation with Novel Links to CFD.

Forward osmosis (FO) modules currently suffer from performance efficiency limitations due to concentration polarisation (CP), as well as pressure drops during operation. There are incentives to further reduce CP effects, as well as optimise spacer design for pressure drop improvements and mechanical support. In this study, the effects of applying transmembrane pressure (TMP) on FO membrane deformation and the subsequent impact on module performance was investigated by comparing experimental data to 3D computational fluid dynamics (CFD) simulations for three commercial FO modules. At a TMP of 1.5 bar the occlusion of the draw-channel induced by longitudinal pressure hydraulic drop was comparable for the Toray (16%) and HTI modules (12%); however, the hydraulic perimeter of the Profiera module was reduced by 46%. CFD simulation of the occluded channels indicated that a change in hydraulic perimeter due to a 62% increase in shear strain resulted in a 31% increase in the Reynolds number. This reduction in channel dimensions enhanced osmotic efficiency by reducing CP via improved draw-channel hydrodynamics, which significantly disrupted the external concentration polarization (ECP) layer. Furthermore, simulations indicated that the Reynolds number experienced only modest increases with applied TMP and that shear strain at the membrane surface was found to be the most important factor when predicting flux performance enhancement, which varied between the different modules. This work suggests that a numerical approach to assess the effects of draw-spacers on pressure drop and CP can optimize and reduce investment in the design and validation of FO module designs.

Developing Bayesian networks in managing the risk of Legionella colonisation of groundwater aeration systems.

An Australian water utility has developed a Legionella High Level Risk Assessment (LHLRA) which provides a semi-qualitative assessment of the risk of Legionella proliferation and human exposure in engineered water systems using a combination of empirical observation and expert knowledge. Expanding on this LHLRA, we propose two iterative Bayesian network (BN) models to reduce uncertainty and allow for a probabilistic representation of the mechanistic interaction of the variables, built using data from 25 groundwater treatment plants. The risk of Legionella exposure in groundwater aeration units was quantified as a function of five critical areas including hydraulic conditions, nutrient availability and growth, water quality, system design (and maintenance), and location and access. First, the mechanistic relationship of the variables was conceptually mapped into a fishbone diagram, parameterised deterministically using an expert elicited weighted scoring system and translated into BN. The "sensitivity to findings" analysis of the BN indicated that system design was the most influential variable while elemental accumulation thresholds were the least influential variable for Legionella exposure. The diagnostic inference was used in high and low-risk scenarios to demonstrate the capabilities of the BNs to examine probable causes for diverse conditions. Subsequently, the causal relationship of Legionella growth and human exposure were improved through a conceptual bowtie representation. Finally, an improved model developed the predictors of Legionella growth and the risk of human exposure through the interaction of operational, water quality monitoring, operational parameters, and asset conditions. The use of BNs modelling based on risk estimation and improved functional decision outputs offer a complementary and more transparent alternative approach to quantitative analysis of uncertainties than the current LHLRA.

Novel housing designs for nanofiltration and ultrafiltration gravity-driven recycled membrane-based systems.

Ultra-low pressure gravity-driven membrane (GDM) systems have the potential to be significantly less costly and complex than conventional membranes for water treatment applications. To build upon this inherent advantage, this study assesses the reuse of recycled membranes in GDM systems for producing drinking water. Two reverse osmosis spiral-wound modules were recycled into nanofiltration (NF)-like and ultrafiltration (UF)-like membranes via controlled exposure to free chlorine. To operate the recycled membranes, two housing devices, based on a simple fitting and an advanced end-caps design, were developed. The recycled membrane systems were tested under a range of conditions (submerged vs. external system configuration and continuous vs. intermittent filtration mode). Synthetic river water feed solutions were used in the tests where performance, fouling, and clogging were measured. NF-like recycled membranes resulted in poor salt rejection and low permeability (~1.7 L m-2 h-1 bar-1), but also in high rejection (>81%) of dissolved organic carbon. UF-like recycled membranes maintained their capacity to reject biopolymers (BP) (>74%) and featured up to 18-fold higher permeate rate than NF-like recycled membranes. The optimized operating conditions were found when the recycled membranes were housed in the end-caps device and operated intermittently (relaxation time plus forward flushing). Flushing reduced the fouling accumulation inside the membrane (only 12% and 40% of BP accumulation was observed in the NF-like and UF-like, respectively). However, the end-caps-based device was estimated to be more expensive during the economic analysis. To address this techno-economic trade-off, a decision-making tree was developed to select the appropriate configuration based upon the implementation context. Overall, this study concludes that these designs can serve as robust, low-cost (water production cost <1 USD ct. yr. L-1), and light-weight GDM alternatives. This study is beneficial for developing compact GDM systems based on recycled spiral-wound membranes for both rural areas and emergency response.

Forward Osmosis as Concentration Process: Review of Opportunities and Challenges.

In the past few years, osmotic membrane systems, such as forward osmosis (FO), have gained popularity as "soft" concentration processes. FO has unique properties by combining high rejection rate and low fouling propensity and can be operated without significant pressure or temperature gradient, and therefore can be considered as a potential candidate for a broad range of concentration applications where current technologies still suffer from critical limitations. This review extensively compiles and critically assesses recent considerations of FO as a concentration process for applications, including food and beverages, organics value added compounds, water reuse and nutrients recovery, treatment of waste streams and brine management. Specific requirements for the concentration process regarding the evaluation of concentration factor, modules and design and process operation, draw selection and fouling aspects are also described. Encouraging potential is demonstrated to concentrate streams more than 20-fold with high rejection rate of most compounds and preservation of added value products. For applications dealing with highly concentrated or complex streams, FO still features lower propensity to fouling compared to other membranes technologies along with good versatility and robustness. However, further assessments on lab and pilot scales are expected to better define the achievable concentration factor, rejection and effective concentration of valuable compounds and to clearly demonstrate process limitations (such as fouling or clogging) when reaching high concentration rate. Another important consideration is the draw solution selection and its recovery that should be in line with application needs (i.e., food compatible draw for food and beverage applications, high osmotic pressure for brine management, etc.) and be economically competitive.

Management of concentrate and waste streams for membrane-based algal separation in water treatment: A review.

Frequent occurrence of harmful algal blooms (HABs) and red tides in freshwater and seawater poses serious threats to water treatment and drives the application of membrane-based technologies in algal separation. Despite the high removal efficiency of algal cells and their metabolites (e.g. organic matter and toxins) by membranes, the generation of concentrate and waste streams presents a major challenge. In this paper, we review the scenarios under which membrane-based processes are integrated with algal separation, with particular attention given to (i) drinking water production and desalination at low algal concentrations and (ii) cyanobacteria-laden water treatment/desalination. The concentrate and waste streams from backwashing and membrane cleaning in each scenario are characterised with this information facilitating a better understanding of the transport of algal cells and metabolites in membrane processes. Current strategies and gaps in managing concentrate and waste streams are identified with guidance and perspectives for future studies discussed in an Eisenhower framework.

Impact of FO Operating Pressure and Membrane Tensile Strength on Draw-Channel Geometry and Resulting Hydrodynamics.

In an effort to improve performances of forward osmosis (FO) systems, several innovative draw spacers have been proposed. However, the small pressure generally applied on the feed side of the process is expected to result in the membrane bending towards the draw side, and in the gradual occlusion of the channel. This phenomenon potentially presents detrimental effects on process performance, including pressure drop and external concentration polarization (ECP) in the draw channel. A flat sheet FO system with a dot-spacer draw channel geometry was characterized to determine the degree of draw channel occlusion resulting from feed pressurization, and the resulting implications on flow performance. First, tensile testing was performed on the FO membrane to derive a Young's modulus, used to assess the membrane stretching, and the resulting draw channel characteristics under a range of moderate feed pressures. Membrane apex reached up to 67% of the membrane channel height when transmembrane pressure (TMP) of 1.4 bar was applied. The new FO channels considerations were then processed by computational fluid dynamics model (computational fluid dynamics (CFD) by ANSYS Fluent v19.1) and validated against previously obtained experimental data. Further simulations were conducted to better assess velocity profiles, Reynolds number and shear rate. Reynolds number on the membrane surface (draw side) increased by 20% and shear rate increased by 90% when occlusion changed from 0 to 70%, impacting concentration polarisation (CP) on the membrane surface and therefore FO performance. This paper shows that FO draw channel occlusion is expected to have a significant impact on fluid hydrodynamics when the membrane is not appropriately supported in the draw side.

Particle-scale modelling of fluid velocity distribution near the particles surface in sand filtration.

Sand filtration is widely used in drinking water treatment processes, yet the hydraulic fundamentals at particle-scale are not well defined, especially the fluid velocity profile near the sand particles surface. In this study, a numerical model is developed by combining the Lattice Boltzmann (LBM) and the Discrete Element Method (DEM), used to describe the fluid flow over the sand particles surface and the micro-structure details of the sand packed bed respectively. The model is validated by comparing the simulation results with the experimental measurements using two systems, showing that the model can describe the fluid velocity distribution around the particles surface. Critical flow velocity is introduced as the balance between hydrodynamic and adhesive torques acting on sand particle surface. Furthermore, a new concept - effective filter surface (EFS), is defined as the area where the velocity near sand particles surface is less than the critical flow velocity, aiming for indirectly evaluating the performance of sand filtration. It is quantitatively demonstrated that increasing the sand particle size or feed flow velocity results in the decrease of both critical flow velocity and EFS under the given tested conditions. The LBM-DEM model provides a useful tool for understanding the fundamentals of liquid flow distribution and also estimating sand filtration performance under different operation conditions.

Toward Portable Artificial Kidneys: The Role of Advanced Microfluidics and Membrane Technologies in Implantable Systems.

Globally, around 2.6 million people receive renal replacement therapy (RRT), and a further 4.9-9.7 million people need, but do not have access to, RRT [1]. The next generation RRT devices will certainly be in demand due to the increasing occurrence of diabetes, atherosclerosis and the growing population of older citizens. This review provides a comprehensive, yet concise overview of the cleared and remaining hurdles in the development of artificial kidneys to move beyond traditional dialysis technology-the current baseline of renal failure treatment. It compares and contrasts the state-of-the-art in 'cell-based' and 'non-cell-based' approaches. Based on this study, a new engineering perspective on the future of artificial kidneys is described. This review suggests that stem-cell-based artificial kidneys represent a long-term, complete solution but it can take years of development due to the limitations of current cell seeding technology, viability and complicated behaviour control. Alternatively, there is much potential for near- and medium- term solutions with the development of non-cell-based wearable and implantable devices to support current therapies. Based on recent fundamental advances in microfluidics, membranes and related research, it may be possible to integrate these technologies to enable implantable artificial kidneys (iAK) in the near future.

Assessment of membrane photobioreactor (MPBR) performance parameters and operating conditions.

Membrane photobioreactor (MPBR) technology is an emerging algae-based wastewater treatment system. Given the limitations due to the general use of conventional analytical approaches in previous research, this study aims to provide a more comprehensive assessment of MPBR performance through advanced characterisation techniques. New performance parameters are also proposed, encompassing five important aspects of MPBR system efficiency (i.e. biomass concentration, composition, production, nutrient uptake and harvesting potential). Under initial standard operating conditions, performance parameters, such as cell count/MLSS ratio, cell viability, proportion of bacteria and biomass yield coefficient, were found to offer new insights into the operation of MPBR. These parameters were then used, for the first time, to systematically investigate MPBRs operated under different hydraulic retention times (HRTs) and solids retention times (SRTs). Applying shorter HRT and SRT was observed to increase cell viability and productivity (up to 0.25 × 107 cells/mL·d), as anticipated due to the higher nutrient loading. It was noted that the faster growing algal cells featured lower requirement for nutrients. On the other hand, extending HRT and SRT resulted in a more heterogeneous culture (lower cell count/MLSS ratio and higher proportion of bacteria), achieving a higher degree of autoflocculation and greater NO3-N and PO4-P removals of up to 79% and 78% respectively. The results demonstrate the trade-off between applying different HRTs and SRTs and the importance of fully characterising system performance to critically assess the advantages and limitations of chosen operating conditions.

Augmenting water supply by combined desalination/water recycling methods: an economic assessment.

Dry coastal communities increasingly need to consider non-traditional methods of augmenting their water supply. This study presents a preliminary economic comparison of three alternatives for increasing the water supply by 50% for a hypothetical baseline coastal scenario: increasing desalination (Scenario A), direct potable water reuse (DPWR) (Scenario B), and a novel retrofitted configuration of a hybrid forward osmosis-reverse osmosis (FO-RO) plant (Scenario C). The latter used the dilution of the seawater feed to increase the recovery and overall output water of the original RO step. To account for the time value of money, levelised cost (LC) was used as the primary economic metric. The hybrid FO-RO configuration had a comparable LC to DPWR (0.59 vs. 0.61 $ m-3) and was 12% cheaper than desalination (0.67 $ m-3). Furthermore, hybrid FO-RO was 7% more energy efficient than conventional desalination due to reduced intake and pretreatment flows. Sensitivity analyses demonstrated that incremental reductions in LC were possible for increased FO membrane flux, including in pressure-assisted osmosis scenarios with applied pressure ranging from 2 to 6 bar. These findings validate the examination of hybrid FO-RO configurations that deviate from the energy-reduction paradigms typically studied.

Efficiently Combining Water Reuse and Desalination through Forward Osmosis-Reverse Osmosis (FO-RO) Hybrids: A Critical Review.

Forward osmosis (FO) is a promising membrane technology to combine seawater desalination and water reuse. More specifically, in a FO-reverse osmosis (RO) hybrid process, high quality water recovered from the wastewater stream is used to dilute seawater before RO treatment. As such, lower desalination energy needs and/or water augmentation can be obtained while delivering safe water for direct potable reuse thanks to the double dense membrane barrier protection. Typically, FO-RO hybrid can be a credible alternative to new desalination facilities or to implementation of stand-alone water reuse schemes. However, apart from the societal (public perception of water reuse for potable application) and water management challenges (proximity of wastewater and desalination plants), FO-RO hybrid has to overcome technical limitation such as low FO permeation flux to become economically attractive. Recent developments (i.e., improved FO membranes, use of pressure assisted osmosis, PAO) demonstrated significant improvement in water flux. However, flux improvement is associated with drawbacks, such as increased fouling behaviour, lower rejection of trace organic compounds (TrOCs) in PAO operation, and limitation in FO membrane mechanical resistance, which need to be better considered. To support successful implementation of FO-RO hybrid in the industry, further work is required regarding up-scaling to apprehend full-scale challenges in term of mass transfer limitation, pressure drop, fouling and cleaning strategies on a module scale. In addition, refined economics assessment is expected to integrate fouling and other maintenance costs/savings of the FO/PAO-RO hybrid systems, as well as cost savings from any treatment step avoided in the water recycling.

Temporal changes in extracellular polymeric substances on hydrophobic and hydrophilic membrane surfaces in a submerged membrane bioreactor.

Membrane surface hydrophilic modification has always been considered to mitigating biofouling in membrane bioreactors (MBRs). Four hollow-fiber ultrafiltration membranes (pore sizes ∼0.1 µm) differing only in hydrophobic or hydrophilic surface characteristics were operated at a permeate flux of 10 L/m(2) h in the same lab-scale MBR fed with synthetic wastewater. In addition, identical membrane modules without permeate production (0 L/m(2) h) were operated in the same lab-scale MBR. Membrane modules were autopsied after 1, 10, 20 and 30 days of MBR operation, and total extracellular polymeric substances (EPS) accumulated on the membranes were extracted and characterized in detail using several analytical tools, including conventional colorimetric tests (Lowry and Dubois), liquid chromatography with organic carbon detection (LC-OCD), fluorescence excitation - emission matrices (FEEM), fourier transform infrared (FTIR) and confocal laser scanning microscope (CLSM). The transmembrane pressure (TMP) quickly stabilized with higher values for the hydrophobic membranes than hydrophilic ones. The sulfonated polysulfone (SPSU) membrane had the highest negatively charged membrane surface, accumulated the least amount of foulants and displayed the lowest TMP. The same type of organic foulants developed with time on the four membranes and the composition of biopolymers shifted from protein dominance at early stages of filtration (day 1) towards polysaccharides dominance during later stages of MBR filtration. Nonmetric multidimensional scaling of LC-OCD data showed that biofilm samples clustered according to the sampling event (time) regardless of the membrane surface chemistry (hydrophobic or hydrophilic) or operating mode (with or without permeate flux). These results suggest that EPS composition may not be the dominant parameter for evaluating membrane performance and possibly other parameters such as biofilm thickness, porosity, compactness and structure should be considered in future studies for evaluating the development and impact of biofouling on membrane performance.

Seasonal variations in fate and removal of trace organic chemical contaminants while operating a full-scale membrane bioreactor.

Trace organic chemical (TrOC) contaminants are of concern for finished water from water recycling schemes because of their potential adverse environmental and public health effects. Understanding the impacts of seasonal variations on fate and removal of TrOCs is important for proper operation, risk assessment and management of treatment systems for water recycling such as membrane bioreactors (MBRs). Accordingly, this study investigated the fate and removal of a wide range of TrOCs through a full-scale MBR plant during summer and winter seasons. TrOCs included 12 steroidal hormones, 3 xeno-estrogens, 2 pesticides and 23 pharmaceuticals and personal care products. Seasonal differences in the mechanisms responsible for removing some of the TrOCs were evident. In particular the contribution of biotransformation and biomass adsorption to the overall removal of estrone, bisphenol A, 17ß-estradiol and triclosan were consistently different between the two seasons. Substantially higher percentage removal via biotransformation was observed during the summer sampling period, which compensated for a reduction in removal attributed to biomass adsorption. The opposite was observed during winter, where the contribution of biotransformation to the overall removal of these TrOCs had decreased, which was offset by an improvement in biomass adsorption. The exact mechanisms responsible for this shift are unknown, however are likely to be temperature related as warmer temperatures can lower sorption efficiency, yet enhance biotransformation of these TrOCs.

Impact of operating conditions on the removal of endocrine disrupting chemicals by membrane photocatalytic reactor.

This study focuses on the performance of a submerged membrane photocatalytic reactor for the removal of 17beta-oestradiol (E2) in the presence of humic acid (HA). In addition to the impact of operating parameters, such as membrane pore size, ultraviolet (UV) intensity and hydraulic retention time (HRT), the influence of long-term operation was also assessed by advanced characterization of the fouling layer formed on the membrane. The tighter (0.04 microm) hollow fibre polyvinylydene fluoride (PVDF) membrane was found to exhibit not only higher HA removal than the (0.2 microm) module (85% and 75%, respectively), but also greater transmembrane pressure (TMP) values and higher irreversible fouling. Long-term operation conditions have been simulated by conducting an ageing catalyst process and demonstrated a decrease in performance obtained with time. The artificially aged TiO2 resulted in higher TMP values and lower HA removals (about 10-20% decrease) compared with the non-aged catalyst. For E2 removal in the presence of HA, the passive adsorption of the oestrogen onto the organic matter was found to be significant (40% of the E2 adsorbed after I h), demonstrating the importance of the nature of the water matrix for this type of treatment process. An increase in the UV light intensity was observed to favour the E2 elimination, leading to more than 90% removal when using 64 W combined with PVDF membrane and an HRT of 3 h.

Validation of a full-scale membrane bioreactor and the impact of membrane cleaning on the removal of microbial indicators.

The removal of microbial indicators through a full-scale membrane bioreactor (MBR) was characterised. The overall log reduction of Escherichia coli and total coliforms were in the range of 5.0-5.9log10 units, while the reduction of clostridia was marginally less at 4.9log10 units. Removal of bacteriophage was in excess of 4.6log10 units. The impact of membrane cleaning on the elimination of microbial indicators was also assessed since this had been identified by pilot-scale studies as a potential hazardous event. Membrane cleaning temporarily reduced the log removal values of E. coli and total coliforms each by 1log10 unit, but did not affect the removal of bacteriophage or clostridia. Very little research has previously examined the consequences of hazardous events on the performance of full-scale MBRs, and thus the findings presented here will facilitate improvements for the risk assessment and management of MBRs used in water recycling schemes.

Removal of trace organics by anaerobic membrane bioreactors.

The biological removal of 38 trace organics (pharmaceuticals, endocrine disruptors, personal care products and pesticides) was studied in an anaerobic membrane bioreactor (AnMBR). This work presents complete information on the different removal mechanisms involved in the removal of trace organics in this process. In particular, it is focused on advanced characterization of the relative amount of TO accumulated within the fouling layers formed on the membranes. The results show that only 9 out of 38 compounds were removed by more than 90% while 23 compounds were removed by less than 50%. These compounds are therefore removed in an AnMBR biologically and partially adsorbed and retained by flocs and the deposition developed on the membranes, respectively. A total amount of 288 mg of trace organics was retained per m(2) of membrane, which were distributed along the different fouling layers. Among the trace organics analyzed, 17α-ethynylestradiol, estrone, octylphenol and bisphenol A were the most retained by the fouling layers. Among the fouling layers deposited on the membranes, the non-readily detachable layer has been identified as the main barrier for trace organics.