Produced Water Effluent Research Articles

Quantification and ecotoxicological contribution of volatile compounds in produced water effluents

Produced water (PW) is a significant byproduct of offshore oil and gas production, constituting a major waste stream in the North Sea. Existing regulations address only the dispersed aliphatic hydrocarbon content in PW, and limited attention is given to other potentially hazardous compounds, including benzene, toluene, ethyl benzene and xylene (BTEX), polycyclic aromatic hydrocarbons (PAHs), phenols, water-soluble petroleum constituents as well as production-related chemicals. In this study, Danish oil production PW samples were subjected to purge and trap extraction on granular activated carbon for volatile compounds identification and quantification by GC-MS analysis. The obtained analytical data correlate with toxicity assessments conducted on three trophic levels, bacteria (Aliivibrio fischeri), algae (Skeletonema costatum) and copepods (Acartia tonsa) on the whole effluent as well as on treated samples. The removal of the PW volatile fraction by purging experiments resulted in a decrease in toxicity response from 37% ± 23–65% ± 16 across the tested species. The chemicals identified in this study and their toxicity response enhance the comprehension of the PW effluent composition and inform the development of strategies for offshore reservoir wastewater.

Highly efficient oil-in-water emulsion separation based on innovative stannic oxide/polyvinylchloride (SnO2/PVC) microfiltration membranes

Global awareness has been raised to tackle the impact of produced water effluents from the oil and gas industries on the environment. In this work, innovative stannic oxide/polyvinylchloride (SnO2/PVC) microfiltration membranes were fabricated via the phase inversion method and their properties and performance were studied. Six membranes consisting of a fixed PVC concentration of 15 wt%, and varying loading of SnO2 nanoparticles (SnO2NPs) of 0.1, 0.25, 0.5, 1, and 1.5 wt% were cast. The results showed that embedding SnO2NPs outstandingly increased the pure water flux from 40.03 L/m2.h for the pristine PVC membrane to 104.06 L/m2.h for the 1 wt% SnO2NPs/PVC membrane when the oil in water feed concentration was 100 mg/L. This was attributed to enhancing the comprehensive porosity and hydrophilicity of the membranes as well as improving their grifted negative charge. Additionally, the maximum rejection of oil as COD and NTU removal percent achieved by the 1 wt% SnO2NPs/PVC membrane were around 99.6 % and 99.3 % respectively, compared to 83.29 % and 86.11 % using the pristine PVC membrane. Finally, the surface roughness decreased from 18.45 to 8.59 nm with adding SnO2NPs which positively improved the fouling resistance of the membranes as confirmed by obtaining low relative flux reduction and high flux recovery ratio.

Technical Feasibility of Extraction of Freshwater from Produced Water with Combined Forward Osmosis and Nanofiltration.

This study assesses the technical feasibility of a forward-osmosis-based system for concentrating produced water and extracting freshwater. Forward osmosis was combined with nanofiltration, the latter system used to restore the initial osmotic pressure of the diluted draw solutions while concurrently obtaining the final freshwater product. Three draw solutions, namely, MgCl2, NaCl, and C3H5NaO2, were initially tested against a synthetic water mimicking a pretreated produced water effluent having an osmotic pressure equal to 16.3 bar. MgCl2 was thus selected for high-recovery experiments. Different combinations of draw solution osmotic pressure (30, 40, 60, 80, and 120) and draw-to-feed initial volume ratios (1, 1.6, and 2.2) were tested at the laboratory scale, achieving recovery rates between roughly 35% and 70% and water fluxes between 4 and 8 L m-2h-1. One-dimensional, system-wide simulations deploying the analytical FO water flux equation were utilized to validate the experiments, investigate co-current and counter-current configurations, and understand the system potential. The diluted draw solutions were then transferred to nanofiltration to regenerate their original osmotic pressure. There, the highest observed rejection was 96.6% with an average flux of 21 L m-2h-1, when running the system to achieve 100% relative recovery.

Treatment of Oilfield Produced Water Using Three Electrochemical Processes: Comparative Study

Although various techniques exist for remediation of wastewater, electrochemical technology and electrochemical advanced oxidation processes are the most promising and innovating methods for destroying and eliminating a broad-range of organic and inorganic contaminants presented in the produced water effluents. This study presents integrated electrochemical treatment techniques including electrocoagulation process, electrooxidation process and electro-Fenton process for a real produced water, supplied by an oil company. The electrocoagulation method was conducted by iron and aluminum electrodes, electrooxidation method by graphite electrodes and the electro-Fenton method by iron and graphite electrodes. The experiments were performed in the same electrolytic batch cell with the same spacing between electrodes and electrode surface. The feasibility of treatment processes was monitored by the removal of total organic carbon (TOC) and chemical oxygen demand (COD).As a result of the study, the most efficient technology was the electrooxidation process where the removal efficiencies of TOC and COD were 93.5 % and 94 %, respectively. Additionally, electro-Fenton process led to higher removal efficiencies reaching 85 % and 87 % for TOC and COD, respectively. The electrocoagulation treatment of produced water by using iron and aluminum electrodes was moderately efficient for removal of TOC. However, it was inefficient for removal of COD. Furthermore, electrocoagulation remediation was proved to be an effective method for removal of inorganic species such as calcium, magnesium and sulfate. It can be concluded that electrochemical methods could be used for effective produced water treatment where it can be safely disposed of or effectively reused for injection and irrigation.

Optimization of electro‐oxidation and electro‐Fenton techniques for the treatment of oilfield produced water

AbstractElectrochemical advanced oxidation processes are the most promising methods for destroying and degrading organic and inorganic pollutants present in produced water effluents. This study presents the electro‐oxidation process using graphite electrodes and electro‐Fenton process using iron electrodes for the treatment of real produced water. The effect of operating parameters such as current density on chemical oxygen demand (COD) removal efficiency was addressed. The result showed that electro‐Fenton process was more efficient than electro‐oxidation process where it gave 98% as maximum COD removal efficiency with energy consumption of 1.9 kWh/dm3 at H2O2 concentration of 12 mM, current density of 10 mA/cm2, temperature of 25°C, pH of 3, and treatment time of 80 min compared with 96.9% as maximum COD removal efficiency with energy consumption of 3 kWh/dm3 at pH of 6, current density of 10 mA/cm2, temperature of 40°C, and reaction time of 80 min when using electro‐oxidation process. These results demonstrated that electrochemical technologies are very promising methods for the treatment of produced water from oil/gas industry, so it can be safely disposed of or effectively reused for injection and irrigation.

Culturing strategy for producing levan by upcycling oil produced water effluent as base medium for Zymomonas mobilis

Three distinct reported media were tested as organic and inorganic supplementation of produced water (PW) from mature oil wells with the aim of producing levan. This effluent is generated at high amounts during oil extraction and are often associated to significant environmental impact and treatment costs. PW may display significant amounts of salts that can hinder microbial growth. Using a high saline PW (8%) this research identified that higher sucrose concentrations in association with ammonium and magnesium sulfates mitigated the negative effect of high salts concentrations on Zymomonas mobilis production of levan. Using neat supplemented PW as medium generated within 24 h 10 g L−1 of levan. The highest production of 31.9 g L−1 was obtained with dialyzed pretreated PW. Dialysis pretreatment may be an important standardization of PW prior to full-scale application. FT-IR characterization shows no significant differences between the produced levan and the commercial counterpart.

Acute toxicity assessment of produced water effluent stream on selected local organisms in Delta state, Nigeria.

This study evaluated toxicity level of produced water effluent on indigenous organisms in Delta state, Nigeria. Four test organisms, Vibrio fischeri, Palaemonetes africanus, Tympanosomas fuscatus, and Tilapia guineensis, were selected for toxicity assessment using effluent streams from treated produced water and water from the produced water recipient environment. Representative samples of treated produced water effluent were collected from the bulk header within the oil terminal and within the discharge environment. Acute toxicity tests were carried out using the Microtox® Model 500. The results of the acute toxicity tests on V. fischeri revealed that the average inhibitive concentration (IC50) for treated produced water at 5 min and 15 min was 22.20% and 31.17% and the no effect concentration (NOEC) and low effect concentration (LOEC) at 5 min and 15 min was 5.63% and 5.63%, respectively. In the recipient water, at 5 min and 15 min, IC50 estimate was of 33.57% and 47.02% while the NOEC and LOEC were 5.63% and 5.63%, respectively. The average IC50, NOEC, LOEC, toxicity unit-acute (TUa), toxicity unit-chronic (TUc), and toxicity factor (TF) toxicity values for P. africanus were 80.606%, 66.990%, and 73.13%; 1.24, 1.49, and 2066.82; 42.24%, 6.165%, and 11.936%; 2.37, 16.21, and 25.54 in treated and recipient water, respectively. In T. guineensis, average IC50, LOEC, NOEC, TUa, TUc, and TF were 4.86%, 1.786%, 1.059%, 20.60, 94.34, and 269.72 and 5.090%, 1.828%, 1.070%, 19.65, 93.46, and 282.78 for treated produced water and recipient environment, respectively. There was no mortality in T. fuscatus var radula exposed to both treated produced water and recipient water.

Novel De-Oiling of Oil-Water

The study anchors on developing a mechanistic model for oil-water separation. Over the years, researchers have been working on how to improve the quality of produced water effluent especially from oil and gas operations sent to the receiving waters. Despite the standard set for compliance by regulatory bodies like united nation agency, ministry, departments and other agencies both state and federal government including non governmental agencies the problem of meeting stipulated bench marks still persist. This study however looks into some variables perceived as being relative to improving or affecting produced water effluent from oil-water separator. Modeling of oil-water separation was based on the philosophy that a mathematical model can be established for the physical problems under investigation. These mathematical problems formulated were based on laws of conservation. Solving the model equation analytically however pose some problems. Hence they were solved by simulation using a computer soft ware SIMULINK a graphical extension of MATLAB with positive outcome since it has the ability to model non-linear systems. From the simulated analysis, increased flow rate creates turbulence in the system with resultant poor effluent quality, whereas also, from the simulated analysis, gradual increases in temperature improves oil-water separation from lower temperature of the fluid upstream thereby aiding improvement in effluent quality.

Microbiological Strategies for Sustainable Production of Bioactive Compounds Using Oil Produced Water Effluent with Sucrose and Crude Glycerine as Carbon Sources

Biopolymers and biosurfactants are bioactive compounds of great commercial interest. They are used for changing fluids viscosity and emulsifying properties of several types of solutions, characteristics necessary for the performance of enhanced oil recovery (EOR) strategies applied at distinct rock formations. The present work evaluated the production of Enterobacter amnigenus exopolysaccharide (EPS) of the strain grown alone or in consortium with Pseudomonas aeruginosa. Culturing was carried out using produced water amended with a mixture of crude glycerin and sucrose as carbon sources. E. amnigenus exopolysaccharide production was low when grown on pure culture, on the other hand, in the presence of P. aeruginosa, the amount of EPSwas of 14.74 gL-1. The produced biopolymer and biosurfactant exhibited excellent viscosity and emulsifyingactivity characteristics for the application in EOR strategies, and better pseudoplastic rheological behavior (was detected) than conventional chemicals used for this purpose. Statistical analysis showed that EPS production was influenced by the interaction between sucrose and glycerin amendments. Infrared absorption spectroscopy showed similar molecular structure to the E. amnigenus FucoPoL. This research shows that a recovering oil fluid can be prepared using produced water as main medium, contributing for reducing costs and increasing environmental gains.

Experimental Study of the Separation of Oil in Water Emulsions by Tangential Flow Microfiltration Process. Part 1: Analysis of Oil Rejection Efficiency and Flux Decline

Management of produced water is a major issue offshore. Microfiltration has emerged as a useful alternative for treating the oil-water emulsions to meet the regulatory limit for disposal. In this work, tangential flow (cross flow) microfiltration of oil-water mixture was studied. The tangential flow microfiltration process was investigated using a ceramic membrane of 0.5 μm pore size. For this phase of work, medium viscosity paraffin oil was used as substitute to crude oil. Using oily water feed of 500-1000 ppm oil concentration, a microfiltration ceramic membrane of 0.5 μm pore size was proven capable of producing a high purity filtrate lower than the threshold required for offshore produced water effluent, typically 29 mg/l residual oil, in the Gulf of Mexico. However, membrane has a major drawback in the form of fouling. Decline in permeation flux should be expected over time of operation. This limitation has certainly impeded the large scale applications of microfiltration process in the field of oil and gas processing industry. An optimized cleaning process is needed to restore membrane performance.

Toxicity Screening of Produced Water Extracts in a Zebrafish Embryo Assay

Produced water is the largest effluent discharge from oil and gas/condensate production facilities in the North Sea. There is concern that contaminants originating from the reservoir and chemicals used in the production process may affect marine organisms. Developmental toxicity of extractable organic compounds in produced water effluents from oil and gas/condensate production platforms in the Norwegian sector of the North Sea was assessed in a temporal and spatial manner using zebrafish (Danio rerio) embryos. Large-scale solid-phase extraction (SPE) and on-column fractionation of water-soluble fraction (WSF) and an oil/particulate fraction was used in a rapid screening bioassay for embryotoxicity. Exposure to produced water extracts increased rate of mortality and reduced pigmentation and heart rate, as well as delaying time to hatch. The oil/particulate fraction was 10-fold less toxic than WSF, indicating that toxicity was predominantly produced by moderately polar and bioavailable compounds. Large spatial and temporal variation in produced water toxicity was observed, displaying considerable variability in the reservoir, oil well, and effluent composition over time. The noted toxicity did not correlate well with either reported produced water composition or parameters such as total hydrocarbons, thus challenging chemical measurements as a reliable source of information for predicting complex effects. Although embryotoxicity was observed following exposure to the extracts, dilution and transformation of produced water in the recipient are expected to rapidly reduce the concentrations of compounds in the effluents to levels below the thresholds of observed effects.

Modelling produced water dispersion and its direct toxic effects on the production and biomass of the marine copepod Calanus finmarchicus

Zooplankton is a key group in North Atlantic and Arctic food chains, and assessment and minimization of adverse effects from petroleum activities to this resource are important. The potential direct effects of produced water discharges on the biomass of Calanus finmarchicus were evaluated using a fully coupled, high resolution 3D hydrodynamic-ecological model system (SINMOD). Several scenarios with varying effects of produced water concentrations were considered. In order to reduce numerical dilution of the produced water effluents, a “sub grid” model component of higher resolution (80 m horizontal resolution vs 800 m for the main model grid) was developed and implemented. The results show that dilution and dispersion of produced water varies between locations. In general, realistically simulated concentrations of produced water were too low to have significant effects on the C. finmarchicus biomass and reproduction according to the toxicity-dilution profiles used, even when the toxicity of the produced water was increased 10-fold. The decrease in C. finmarchicus biomass was partially compensated by a slight increase in production.

Analysis of bacterial diversity and metals in produced water, seawater and sediments from an offshore oil and gas production platform

Produced water is one of the largest waste products routinely discharged into the ocean from offshore oil and gas platforms. This study analyzed bacterial communities and metals in the produced water, surrounding seawater, and sediment around the Thebaud platform. The bacterial community within the produced water was different from the seawater (SAB=13.3), but the discharge had no detectable effect on the bacterial communities in the seawater (SAB>97). In contrast, genomic analysis of sediments revealed that the bacterial community from 250m was different (SAB=70) from other locations further from the discharge, suggesting that the produced water had a detectable effect on the bacterial community in the sediment closest to the discharge. These near-field sediments contained elevated concentrations of manganese and iron that are associated with the produced water effluent. The results suggested that the discharge of produced water has influenced the bacterial community structure of sediments adjacent to the platform.

Effect-Directed Identification of Naphthenic Acids As Important in Vitro Xeno-Estrogens and Anti-Androgens in North Sea Offshore Produced Water Discharges

Produced water from offshore oil production platforms represents the largest direct discharge of effluent into the offshore environment. Produced water effluents contain a complex mixture of substances which are known to bind to the estrogen receptor (ER) and antagonize the androgen receptor (AR). Short-chain petrogenic alkylphenols have been identified as responsible for around 35% of the ER agonist activity measured in vitro while the compounds responsible for antagonizing the androgen receptor are unknown. For the first time we report that petrogenic naphthenic acids are weak ER agonists that account for much of the 65% of the "unknown" ER agonist potency in North Sea produced waters while also disrupting the binding of AR agonists to the AR ligand receptor. We also report other known petrogenic components such as polycyclic aromatic hydrocarbons (PAHs) and alkylphenols as environmental AR antagonists. Our investigation shows that these petrogenic components are responsible for the majority of the ER and AR receptor mediated activity in produced waters. This hypothesis is supported by data from an effects-directed analysis of produced water using normal-phase high-performance liquid chromatography (HPLC) fractionation in combination with the yeast estrogen and androgen assays as well as androgen receptor binding assays of commercially available mixtures of naphthenic acids.

Estrogen receptor (ER) agonists and androgen receptor (AR) antagonists in effluents from Norwegian North Sea oil production platforms

The in vitro estrogen receptor (ER) agonist and androgen receptor (AR) antagonist potencies of offshore produced water effluents collected from the Norwegian Sector were determined using recombinant yeast estrogen and androgen screens. Solid phase extraction (SPE) concentrates of the effluents showed E2 agonist activities similar to those previously reported for the United Kingdom (UK) Continental Shelf (<0.1–4 ng E2 L −1). No activity was detected in the filtered oil droplets suggesting that produced water ER activity is primarily associated with the dissolved phase. Targeted analysis for methyl- to nonyl-substituted alkylphenol isomers show the occurrence of known ER agonists in the analysed samples. For the first time, AR antagonists were detected in both the dissolved and oil associated phase at concentrations of between 20 and 8000 μg of flutamide equivalents L −1. The identity of the AR antagonists is unknown, however this represents a significant input into the marine environment of unknown compounds that exert a known biological effect. It is recommended that further analysis using techniques such as bioassay-directed analysis is performed to identify the compounds/groups of compounds that are responsible in order to improve the assessment of the risk posed by produced water discharges to the marine environment.

The stable aryl hydrocarbon receptor agonist potency of United Kingdom Continental Shelf (UKCS) offshore produced water effluents

The in vitro aryl hydrocarbon receptor (AhR) agonist potency of offshore produced water effluents, collected from the United Kingdom Continental Shelf, was determined using the dioxin responsive (DR)-chemically activated luciferase expression (CALUX) assay. Octadecylsilane (C18) solid phase extraction (SPE) extracts of produced water were exposed to DR-CALUX cells for 24 h in order to investigate the contribution in potency from compounds that are stable to metabolism by the CALUX cells during exposure. The stable AhR agonist potency determined over 24 h was highly variable and ranged from 1 to 430 ng TCDD TEQ CALUX l −1. These data reflect the highly variable composition of produced water discharges from different production fields. It is recommended that further work be performed to characterise the full range of stable dioxin like AhR agonists present in offshore produced water discharges using techniques such as bioassay-directed analysis.

Bio-analytical and chemical characterisation of offshore produced water effluents for estrogen receptor (ER) agonists

The in vitro estrogen receptor (ER) agonist potency and C1 to C9 alkyl substituted phenol content of offshore produced water effluents collected from the UK sector of the North Sea were determined using a combination of bio-analytical and chemical analysis techniques. An in vitro reporter gene assay was used to determine ER agonist potency, whilst gas chromatography coupled to mass spectrometry (GC-MS) was used to quantify the concentration of alkylphenols. The in vitro ER agonist potency was highly variable and ranged from less than the limit of detection (theoretically 0.03 ng 17beta-estradiol (E2) l(-1)) to 91 ng E2 l(-1). C1 to C5 alkylphenol concentrations were also highly variable ranging from 5 to 1600 microg l(-1) with a median concentration of 206 microg l(-1). These data reflect the highly variable composition of produced water discharges from different fields. The observed poor correlation of the alkylphenol isomer content and ER agonist activity suggests that other compounds present in the produced water discharges may be responsible for the ER agonist activity observed. It is recommended that further work be performed to characterise the full range of ER agonists present in offshore produced water discharges.

Toxicity identification evaluations of produced-water effluents

Toxicity identification evaluations (TIEs) were performed on 14 produced-water (PW) samples of various salinities from inland and offshore oil- and gas-production facilities operated by different companies in Wyoming, Texas, California, and Louisiana (USA) to evaluate the efficacy of TIE procedures in determining potential toxicants in PW effluents. The research involved acute (24- and 48-h) freshwater and marine toxicity tests on whole PW and PW fractions generated by standard U.S. Environmental Protection Agency and PW-specific fractionation schemes. Factors influencing PW TIEs were investigated, such as the effect of salinity in selecting fractionation manipulations, the effect of toxicity test replication (i.e., reproducibility) in distinguishing changes in toxicities between whole PW and its fractions, and the suitability of different test species in PW TIEs. The results obtained and lessons learned from conducting these PW TIEs are presented in this article. Components, or fractions, contributing to toxicity differed for each PW with no specific fraction being consistently toxic. For most PW samples, toxicity attributed to any one fraction represented only part of the toxicity of the whole sample. However, no more than two fraction types were identified as potential toxicants in any sample. Potential toxicants identified during this study, besides salinity, included acidic and basic organic compound class fractions, particulates removed by filtration at pH 11, ammonia, hydrocarbons, hydrogen sulfide, material removed by pH change, and volatile compounds.

Membrane separation of produced water

Each time regulatory agencies initiate more stringent environmental controls, treatment technologies are refined to meet the updated standards. Centrifuges and hydrocyclones are, by and large, producing satisfactory effluents for meeting current quality requirements for the offshore petroleum industries. The European standard for effluent from onshore petroleum activities, however, requires less than 5 mg/l total hydrocarbons (HC) and less than 10 mg/l suspended solids. Such low concentrations are out of reach for the above classical separation processes. The amount of produced water in the North Sea is projected to increase by a factor of 6 from 1990 to the year 2000; from 16 to 90 million cubic meters each year. Produced water is the predominant source for oil discharges. The synergistic effects of chemicals, oil and dissolved components in the produced water effluent are given increased attention, with expectations of tougher effluent criteria. Microfiltration (MF) and ultrafiltration (UF) pilot trials with produced water from the Snorre field in the North Sea showed that UF, but not MF, could meet more stringent effluent standards for total HC, suspended solids and dissolved constituents. Total HC in the produced water was typically 50 mg/l and was reduced to 2 mg/l in the UF permeate (96% removal). The aromatics benzene, toluene and xylene (BTX) were similarly reduced by 54% and the heavy metals copper (Cu) and zinc (Zn) by 95%. UF trials were performed with organic tubular membranes with typical transmembrane pressures between 6 and 10 bars. The feed velocities through the tubes were between 2 and 4 m/s. Flux varied from 140 to 550 l/m2/h (lmh) at a produced water temperature of 60°C and membrane molecular weight cut-off between 100,000 and 200,000 daltons. By recirculating UF retentate as membrane feed, a volume reduction (VR) of 24 was obtained in the trials; i.e., 96% permeate recovery. The limited volume of produced water available in the feed tank negated further volume reduction. Full-scale design is based on permeate recovery of 99%. No irreversible fouling of the membrane surface was experienced. The cleanwater flux was restored after chemical cleaning. The alkaline detergent Ultrasil 11 was chosen as the optimal cleaning agent.

Membrane separation of produced water

Each time regulatory agencies initiate more stringent environmental controls, treatment technologies are refined to meet the updated standards. Centrifuges and hydrocyclones are, by and large, producing satisfactory effluents for meeting current quality requirements for the offshore petroleum industries. The European standard for effluent from onshore petroleum activities, however, requires less than 5 mg/1 total hydrocarbons (HC) and less than 10 mg/1 suspended solids. Such low concentrations are out of reach for the above classical separation processes.The amount of produced water in the North Sea is projected to increase by a factor of 6 from 1990 to the year 2000; from 16 to 90 million cubic meters each year. Produced water is the predominant source for oil discharges. The synergistic effects of chemicals, oil and dissolved components in the produced water effluent are given increased attention, with expectations of tougher effluent criteria.Microfiltration (MF) and ultrafiltration (UF) pilot trials with produced water from the Snorre field in the North Sea showed that UF, but not MF, could meet more stringent effluent standards for total HC, suspended solids and dissolved constituents. Total HC in the produced water was typically 50 mg/1 and was reduced to 2 mg/1 in the UF permeate (96% removal). The aromatics benzene, toluene and xylene (BTX) were similarly reduced by 54% and the heavy metals copper (Cu) and zinc (Zn) by 95%.UF trials were performed with organic tubular membranes with typical transmembrane pressures between 6 and 10 bars. The feed velocities through the tubes were between 2 and 4 m/s. Flux varied from 140 to 550 l/m2/h (lmh) at a produced water temperature of 60°C and membrane molecular weight cut-off between 100,000 and 200,000 daltons.dBy recirculating UF retentate as membrane feed, a volume reduction (VR) of 24 was obtained in the trials; i.e., 96% permeate recovery. The limited volume of produced water available in the feed tank negated further volume reduction. Full-scale design is based on permeate recovery of 99%.No irreversible fouling of the membrane surface was experienced. The cleanwater flux was restored after chemical cleaning. The alkaline detergent Ultrasil 11 was chosen as the optimal cleaning agent.