Dual Media Filtration Research Articles

Potential biofoulants in open-ocean SWRO desalination station in Jeddah, KSA

Abstract Currently, water desalination is an essential solution for the high demand for water worldwide. A sea water reverse osmosis (SWRO) facility fulfills the need for pure water. Conventionally, these plants use open-ocean water that is rich with natural organic matter (NOM) and transparent exo-polymers (TEP). Marine flora increases the demand for fouling the membrane in the SWRO facility that raises the pressure and results in the halting of the station. Therefore, water samples were collected from SWRO stages during high-pressure problems to probe the factors that play a key role in membrane biofouling. NOM and TEP particles physically disappeared after the dual-media filter (DMF). However, turbidity significantly increased after the DMF stage, which is indicative of the fragmentation of NOM and TEP particles. Chlorophyll and phycoerythrin disappeared after the DMF stage but were observed in the reject stage (brine). Therefore, NOM and TEP are playing a role indirectly in membrane biofouling. Fifteen potential species of heterotrophic prokaryotes are identified and recorded in all stages of the SWRO. The characteristics of these species imply that they form a cooperative consortium that potentially creates the biofilm in the RO membrane. Therefore, SWRO facilities that use open-ocean water must develop highly sophisticated pretreatment technology to eliminate the seeds of the biofilm that fouls RO membranes.

Modelling clogging dynamism within dual-media pre-treatment rapid filters in seawater desalination

The dual-media rapid filtration is a popular pre-treatment technology in seawater desalination industry. However, it is still difficult for operators to optimize both the filtration and backwashing processes, particularly during the rapid filtering of moderate and high turbid (MHT) influents, due to the lack of a good understanding of the clogging dynamism incurred during operations. In this study, we attempt to model the incurred clogging dynamism via both experimental and computational means. For the former, experimental filtering of MHT influents was carried out within a lab-scale dual-media rapid pressure filter under varying experimental conditions. Concurrently, dimensionless analysis of the particle removal constant (RC) parameter was performed by considering the initial influent conditions and media characteristics. Good agreement was achieved between the predicted values from the dimensionless formulation of RC and the respective experimental values, which renders the likelihood of employing the formulation to improve the design of pre-treatment rapid filters for filtering MHT influents. Lastly, we attempt to model the clogging dynamism with the homogenization upscaling approach, by computationally resolving both the macroscale and microscale hydraulic gradient under clean and increasing clogging filter condition respectively to approximate the total clogging hydraulic gradient (CHG). Good agreement between the computational and semi-empirical values was achieved for the clean filter condition. Developing the solver in an open-source Open Field Operation and Manipulation (OpenFOAM) CFD software to investigate the particles’ interactions with a singular collector grain for approximating the microscale CHG is currently in progress.

Deployment of Recyclable Polycarbonate as Alternative Coarse Media in Dual-media Rapid Filters

Sand and anthracite coal/granular activated carbon are commonly employed in traditional dual-media rapid filters to remove physical impurities present in influents. With increasing emphasis on sustainability, more water treatment facilities worldwide are opting for the use of eco-friendly materials which include recycled crushed glass, wood chips, and coconut shell based carbons. For instance, some filtration facilities of private pools in the United States have adopted recycled glass and obtained high quality effluent. The deployment of eco-friendly filter media in rapid filters deserves attention. In this study, sewed polyester bags which contained recyclable polycarbonate pellets (RPCs) were deployed as an alternative coarse media in a lab-scale dual-media rapid pressure filter setup. By coupling RPCs with sand, the following performance criteria were attained during the experimental runs when compared with the traditional dual-media: (a) similar rate of head loss development while maintaining acceptable effluent quality, and (b) improved clogging distribution within the filter. Life-cycle analysis (LCA) was also carried out with the Gabi Education software to assess the environmental footprint associated with various dual-media combinations. It is hopeful that the obtained LCA results would provide useful insights to industrial decision-makers who wish to improve the company’s environmental performance index.

Surgical treatment for Müller–Weiss disease

The safety of drinking water in Australia is ensured using a risk management framework embedded within the Australian Drinking Water Guidelines (ADWG). This framework includes elements for hazard identification, risk assessment, risk mitigation, verification of barrier performance and monitoring for any changes to the hazards that influence source water quality. The next revision of the ADWG will incorporate Health-Based Targets (HBTs) for achieving microbiologically safe drinking water. This incorporates Quantitative Microbial Risk Assessment and the metric of Disability Adjusted Life Year (DALY) to define safety, with a target of 1 × 10− 6 Disability Adjusted Life Year (1 microDALY) set as the maximum tolerable disease burden from drinking water, which in the case of Cryptosporidium is < 1.3 × 10− 5 oocysts/L. The resulting product water specification, in combination with knowledge of pathogen challenges in source waters, allows the determination of the treatment requirements to ensure public safety. The ADWG revision provides default removal values for Cryptosporidium for particular treatment processes, such as conventional coagulation and dual media filtration. However, these values are based on assumptions regarding treatment plant design, operation and water quality. To properly manage risk and demonstrate compliance with the guidelines, water utilities may need to validate treatment performance for Cryptosporidium removal. A particular limitation is the absence of Cryptosporidium surrogates for full-scale filter validation. This paper will provide an overview of risk-based management of drinking water safety in Australia, the development of health-based targets for microbial pathogens and the evaluation of Cryptosporidium surrogates for conventional coagulation and dual media filtration.

Risk-based management of drinking water safety in Australia: Implementation of health based targets to determine water treatment requirements and identification of pathogen surrogates for validation of conventional filtration

The safety of drinking water in Australia is ensured using a risk management framework embedded within the Australian Drinking Water Guidelines (ADWG). This framework includes elements for hazard identification, risk assessment, risk mitigation, verification of barrier performance and monitoring for any changes to the hazards that influence source water quality. The next revision of the ADWG will incorporate Health-Based Targets (HBTs) for achieving microbiologically safe drinking water. This incorporates Quantitative Microbial Risk Assessment and the metric of Disability Adjusted Life Year (DALY) to define safety, with a target of 1×10−6 Disability Adjusted Life Year (1 microDALY) set as the maximum tolerable disease burden from drinking water, which in the case of Cryptosporidium is <1.3×10−5oocysts/L. The resulting product water specification, in combination with knowledge of pathogen challenges in source waters, allows the determination of the treatment requirements to ensure public safety. The ADWG revision provides default removal values for Cryptosporidium for particular treatment processes, such as conventional coagulation and dual media filtration. However, these values are based on assumptions regarding treatment plant design, operation and water quality. To properly manage risk and demonstrate compliance with the guidelines, water utilities may need to validate treatment performance for Cryptosporidium removal. A particular limitation is the absence of Cryptosporidium surrogates for full-scale filter validation. This paper will provide an overview of risk-based management of drinking water safety in Australia, the development of health-based targets for microbial pathogens and the evaluation of Cryptosporidium surrogates for conventional coagulation and dual media filtration.

Effect of engineered environment on microbial community structure in biofilter and biofilm on reverse osmosis membrane

Four dual media filters (DMFs) were operated in a biofiltration mode with different engineered environments (DMF I and II: coagulation with/without acidification and DMF III and IV: without/with chlorination). Designed biofilm enrichment reactors (BERs) containing the removable reverse osmosis (RO) coupons, were connected at the end of the DMFs in parallel to analyze the biofilm on the RO membrane by DMF effluents. Filtration performances were evaluated in terms of dissolved organic carbon (DOC) and assimilable organic carbon (AOC). Organic foulants on the RO membrane were also quantified and fractionized. The bacterial community structures in liquid (seawater and effluent) and biofilm (DMF and RO) samples were analyzed using 454-pyrosequencing. The DMF IV fed with the chlorinated seawater demonstrated the highest reductions of DOC including LMW-N as well as AOC among the other DMFs. The DMF IV was also effective in reducing organic foulants on the RO membrane surface. The bacterial community structure was grouped according to the sample phase (i.e., liquid and biofilm samples), sampling location (i.e., DMF and RO samples), and chlorination (chlorinated and non-chlorinated samples). In particular, the biofilm community in the DMF IV differed from the other DMF treatments, suggesting that chlorination exerted as stronger selective pressure than pH adjustment or coagulation on the biofilm community. In the DMF IV, several chemoorganotrophic chlorine-resistant biofilm-forming bacteria such as Hyphomonas, Erythrobacter, and Sphingomonas were predominant, and they may enhance organic carbon degradation efficiency. Diverse halophilic or halotolerant organic degraders were also found in other DMFs (i.e., DMF I, II, and III). Various kinds of dominant biofilm-forming bacteria were also investigated in RO membrane samples; the results provided possible candidates that cause biofouling when DMF process is applied as the pretreatment option for the RO process.

Direct measurement of ATP in seawater and application of ATP to monitor bacterial growth potential in SWRO pre-treatment systems

The use of adenosine triphosphate (ATP) to monitor bacterial growth potential of seawater is currently not possible as ATP cannot be accurately measured at low concentration in seawater using commercially available luciferase-based ATP detection. The limitation is due to interference of salt with the luciferin–luciferase reaction, which inhibits light production. This research demonstrates that new reagents developed for (i) ATP extraction from microbial cells and (ii) ATP detection in seawater are able to reliably detect Microbial ATP as low as 0.3 ng L–1 in seawater. The luminescence signal of the new detection reagent is significantly higher (>20 times) than the luminescence signal of the freshwater reagent, when applied in seawater. ATP can now be used to monitor bacterial growth potential (BGP) through pre-treatment trains of seawater reverse osmosis (SWRO) plants. The level of detection of the new BGP test is significantly lower than the estimated threshold value required to prevent biofouling in SWRO systems. The new reagents have been used to monitor Microbial ATP in coastal North Sea water. Moreover, Microbial ATP has been applied to monitor the bacterial growth potential (using indigenous bacteria) through the pre-treatment train of an SWRO desalination plant. A significant reduction (>55%) of the bacterial growth potential was found through the dual media filtration with 4.5 mg-Fe(III) L–1 coagulant. Overall, the new reagents can detect low Microbial ATP concentrations in seawater and can be used to monitor bacterial growth potential in seawater desalination plants.

Production of demineralized water for use in thermal power stations by advanced treatment of secondary wastewater effluent

The operation and efficiency of a modern, high-tech industrial full-scale water treatment plant was investigated in the present study. The treated water was used for the supply of the boilers, producing steam to feed the steam turbine of the power station. The inlet water was the effluent of municipal wastewater treatment plant of the city of Bari (Italy). The treatment stages comprised (1) coagulation, using ferric chloride, (2) lime softening, (3) powdered activated carbon, all dosed in a sedimentation tank. The treated water was thereafter subjected to dual-media filtration, followed by ultra-filtration (UF). The outlet of UF was subsequently treated by reverse osmosis (RO) and finally by ion exchange (IX). The inlet water had total organic carbon (TOC) concentration 10–12 mg/L, turbidity 10–15 NTU and conductivity 3500–4500 μS/cm. The final demineralized water had TOC less than 0.2 mg/L, turbidity less than 0.1 NTU and conductivity 0.055–0.070 μS/cm. Organic matter fractionation showed that most of the final DOC concentration consisted of low molecular weight neutral compounds, while other compounds such as humic acids or building blocks were completely removed. It is notable that this plant was operating under “Zero Liquid Discharge” conditions, implementing treatment of any generated liquid waste.

A pilot plant study using conventional and advanced water treatment processes: Evaluating removal efficiency of indicator compounds representative of pharmaceuticals and personal care products

With widespread occurrence of pharmaceuticals and personal care products (PPCPs) in the water cycle, their presence in source water has led to the need to better understand their treatability and removal efficiency in treatment processes. Fifteen indicator compounds were identified to represent the large number of PPCPs reported worldwide. Criteria applied to determine the indicator compounds included PPCPs widely used, observed at great frequency in aqueous systems, resistant to treatment, persistent in the environment, and representative of classes of organics. Through a pilot plant investigation to understand the optimal combination of unit process for treating PPCPs, 12 treatment trains with their additive and synergistic contributions were investigated; processes included dissolved air flotation (DAF), pre- and intermediate-ozonation with and without H2O2, intermediate chlorination, dual media filtration, granular activated carbon (GAC), and UV/H2O2. Treatment trains that achieved the greatest removals involved 1. DAF followed by intermediate ozonation, dual media filtration, and virgin GAC; 2. pre-ozonation followed by DAF, dual media filtration, and virgin GAC; and, 3. DAF (with either pre- or intermediate oxidation) followed by dual media filtration and UV/H2O2. Results revealed significant removal efficiencies for virgin GAC (preceded by DAF and intermediate ozonation) and UV/H2O2 with an intensity of 700 mJ/cm2, where more than 12 of the compounds were removed by greater than 90%. Reduced PPCP removals were observed with virgin GAC preceded by pre-ozonation and DAF. Intermediate ozonation was more effective than using pre-ozonation, demonstrating the importance of this process targeting PPCPs after treatment of natural organic matter. Removal efficiencies of indicator compounds through ozonation were found to be a function of the O3 rate constants (kO3). For compounds with low O3 rate constants (kO3 < 10 M−1s−1), H2O2 addition in the O3 reactor was required. Of the 15 indicator compounds, tri(2-chloroethyl) phosphate (TCEP) and cotinine were observed to be the most recalcitrant. Although UV/H2O2 with elevated intensity (700 mJ/cm2) was effective for PPCP removals, energy requirements far exceed intensities applied for disinfection.

Comparison of media and membrane filtrations for seawater desalination pretreatment

AbstractWe compared microfiltration (pressurized and submerged) and media filtration as pretreatment to increase the removal of organics and to reduce reverse osmosis (RO) membrane fouling. The studied plant (feed rate = 2,500 m3/d, production rate = 1,000 m3/d) was taking seawater from East Sea of Korea and originally consisted of strainers, coagulation, dissolved air flotation, dual media filters (DMF), and RO membrane processes. A pressurized microfiltration (MF) and a submerged microfiltration (SMF) were installed and compared with DMF as pretreatment to the RO process. Upon pilot test results over one year, MF exhibited higher removal of dissolved organic materials. Average removals of UVA254 were 23, 19, and 13% at MF, SMF, and DMF, respectively. These results were confirmed with molecular weight distribution, and compositions of humic and fulvic acids. Silt density index (SDI) values were lower in membrane processed waters, and the SDI results correlated with transparent exopolymer particles (r = 0...

Effect of filtration rate on coal-sand dual-media filter performances for microalgae removal

ABSTRACTThis study tested the efficiency of granular filtration using a bilayer sand filter for microalgae removal from culture dilutions ranging from 10,000 to 17,000 cells/mL. The objective is to evaluate the removal capacity of the filter without chemical coagulation. Two filter media, sand and anthracite, with mean grain sizes of 0.395 and 1.2 mm, respectively, were used in constant-flow-rate experiments (down-flow mode) with suspensions containing Heterocapsa triquetra microalga. The conventional rapid filtration which usually operates at a constant rate of approximately 5 m3/m2 h is compared to high-rate filtration. Two filtration velocities (5 and 10 m/h) were investigated with bed depth of 1100 mm. Average microalgal cell removal rates were 90% at 5 m/h and 68% at 10 m/h. Turbidity removal was more than 71% at 5 m/h but just 57% at 10 m/h. Head losses did not increase significantly, and values measured at process end were 32 mbar at 5 m/h and 78 mbar at 10 m/h. Retention probabilities were calculated from experimental data. A theoretical model was used to evaluate the contributions of the different drivers of microalgae removal. Hypotheses are developed on the understanding of change in the mechanisms of retention as a function of filtration velocity.

Technology development trajectory for drinking water treatment: a comparative study between South Korea, Thailand, and Lao PDR

This paper reports on a study to compare the technological trajectory of drinking water treatment for the past 30 years, from the 1980s to the 2010s, in South Korea, Thailand, and Lao PDR. There are significant differences in water treatment technology in the three countries, resulting from factors such as national regulations, economic conditions, and water policies. These act either as drivers or as barriers for water service development in the three countries. South Korea has introduced various new treatment technologies since the 1990s for meeting stringent regulations and for improving tap water quality and safety. Thailand and Lao PDR maintained similar treatment methods without great changes, because they focused more on quantity expansion for meeting water demand than on quality improvement. In addition, lax regulations and financial constraints acted as barriers to the development of water treatment technology in the two countries. Thailand is now trying to apply new treatment technologies, such as online monitoring, mechanical sludge collector, and dual-media filter, as water quality has grown in importance, and Lao PDR has developed new water supply systems for increasing water supply coverage. This study explored changing patterns of treatment technology in the three countries, and offered lessons for developing water treatment technology in the region.

Advanced organic and biological analysis of dual media filtration used as a pretreatment in a full-scale seawater desalination plant

Dual media filter (DMF) is being used as a primary pretreatment to remove particulate foulants at seawater desalination plants. However, many plants experience organic and biological fouling. The first part of this paper focuses on the monitoring of organic and biological foulants using advanced analytical techniques to optimize functioning of DMF at Perth Seawater Desalination Plant (PSDP) in Western Australia. In addition, microbial community analysis in DMF filtered seawater, and on DMF media (DMF-M) and cartridge filter (CF) was conducted using terminal restriction fragment length polymorphism (T-RFLP) and 454-pyrosequencing. In the full-scale DMF system, the bacterial community structure was clustered along with the filtration time and sampling positions. For the DMF effluent samples, the bacterial community structure significantly shifted after 4h of filtration time, which corresponded with the permeability reduction trend. The dominant bacterial communities in the DMF effluent were OTU 13 (Phaeobacter) and OTU 19 (Oceaniserpentilla). The different biofilm-forming bacteria communities were found in the biofilm samples on DMF-M and CF. In the second part of the study, semi-pilot scale DMF columns were operated on-site under same operating conditions used in PSDP. It demonstrated the advantage of operating DMF at the biofiltration mode for improving the reduction of biofoulants.

In-depth analyses of organic matters in a full-scale seawater desalination plant and an autopsy of reverse osmosis membrane

Abstract In order to facilitate the global performance of seawater reverse osmosis (SWRO) systems, it is important to improve the feed water quality before it enters the RO. Currently, many desalination plants experience production losses due to incidents of organic and biofouling. Consequently, monitoring or characterizing the pretreatment step using more advanced organic and biological parameters are required for better operation to lessen fouling issues. In this study, the performance of pretreatment processes (including coagulation, dual media filtration (DMF), polishing with cartridge filter (CF) coupled with anti-scalant) used at Perth Seawater Desalination Plant (PSDP) located in Western Australia were characterized in terms of organic and biological fouling parameters. These analyses were carried out using liquid chromatography with organic carbon detector (LC-OCD), three dimensional-fluorescence excitation emission matrix (3D-FEEM) and assimilable organic carbon (AOC). Furthermore, the used (exhausted) RO membrane and CF were autopsied so that the fates and behaviors of organic foulants in these treatment systems could be better understood.

The Study on the Operating Characteristics of Algae-Contaminated Reservoir Water Using GAC-sand Dual Media Filter Flofilter

The problem of reservoir water quality caused by massive algae pollution keeps going serious, and the traditional solid-liquid separation technology generally fails to meet water quality standards. In the present study, GAC-sand-double-filtration flofilter was built to treat reservoir water derived from the Yellow River that has been polluted by high levels of algal biomass, with the running characteristics and operating results specifically investigated. The experimental results showed that, running effect was relatively superior when the dosage of PAFC was 4 mg/L (Al3+), the pressure of dissolved air was 0.4 Mpa, and the reflux ratio was 8%. Algal biomass fixed onto GAC and sand filter layer was mainly found in the carbon layer, which accounted for 97.4% of the total biomass (the highest value was 50.2 nmol p/g), and the biomass fixed onto carbon layer was 16.7 times of that fixed onto the sand layer (3.0 nmol p/g). Clearly, the removal of pollutants mainly occurred in the carbon layer. Also, the removal efficiency of particulate matter such as blue-green algae, turbidity, CODMn, UV254, NPOC, ammonia nitrogen was 96.48%, 92.40%, 92.56%, 57.40%, 52.50%, 51.60% and 75.67%, respectively. The odor was reduced from 4 to 0, and the content of geosmin and methylisoborneol was less than their detection limit, with the removal efficiency of chloroform and chlorodibromomethane as 60% and 55.1%, respectively. In general, the results showed that the flofilter process had imposed an efficient effect on the removal of algal biomass, odor substances and disinfection byproducts precursors.

Removal of organic matter from drinking water by single and dual media filtration: a comparative pilot study

This pilot-scale research was conducted at Ahvaz water treatment plant to investigate the performance of a dual-media filter with anthracite and silica sand layers for the removal of total organic carbon (TOC) and chemical oxygen demand (COD) as the measuring indices of organic matter in water. In addition, the performance of this dual-media filter was compared with a control single-media filter with a conventional layer. The hydraulic loading rate or water flux during the filtration was in the range of 7–14 m/h. All the experiments were carried out according to the standard methods, and the obtained results were analyzed using statistical tests such as paired-samples t-test. The average concentration of COD and TOC in the input water into the pilot was 7.93 and 2.73 mg/L, respectively. The average efficiency for TOC removal in the single-media and dual-media pilot filters at the loading rate of 7 m/h was 34.10 and 65.59%, respectively, whereas the corresponding values for COD removal in the single-media and dual-media pilot filters were 28.26 and 63.95%, respectively. Furthermore, the mean efficiency for TOC removal in the single-media and dual-media pilots at the loading rate of 14 m/h was 30.25 and 64.56%, respectively. At this loading rate, the corresponding efficiencies for COD removal in the single-media and dual-media pilot filters were 25.51 and 62.23%, respectively. The results of this research showed that the use of anthracite as a layer of dual-media filter increases the efficiency of organic matter removal compared with the single-media filter.

Conventional drinking water treatment and direct biofiltration for the removal of pharmaceuticals and artificial sweeteners: A pilot-scale approach

The presence of endocrine disrupting compounds (EDCs), pharmaceutically active compounds (PhACs) and artificial sweeteners are of concern to water providers because they may be incompletely removed by wastewater treatment processes and they pose an unknown risk to consumers due to long-term consumption of low concentrations of these compounds. This study utilized pilot-scale conventional and biological drinking water treatment processes to assess the removal of nine PhACs and EDCs, and two artificial sweeteners. Conventional treatment (coagulation, flocculation, settling, non-biological dual-media filtration) was compared to biofilters with or without the addition of in-line coagulant (0.2–0.8mgAl3+/L; alum or PACl). A combination of biofiltration, with or without in-line alum, and conventional filtration was able to reduce 7 of the 9 PhACs and EDCs by more than 50% from river water while artificial sweeteners were inconsistently removed by conventional treatment or biofiltration. Increasing doses of PACl from 0 to 0.8mg/L resulted in average removals of PhACs, EDCs increasing from 39 to 70% and artificial sweeteners removal increasing from ~15% to ~35% in lake water. These results suggest that a combination of biological, chemical and physical treatment can be applied to effectively reduce the concentration of EDCs, PhACs, and artificial sweeteners.

Performance of biofilters in GAC-sand and anthracite-sand dual-media filters in a water treatment plant in Abadan, Iran

Biological water treatment using granular activated carbon (GAC) and anthracite improves water quality by reducing total organic carbon (TOC), colour, nitrogen content and turbidity. This study investigated the operation of aerobic biofilm on two pilot biofilters designed to remove turbidity, TOC, NO3- and NH4+ in water. The results show that the GAC-sand pilot filter at a low hydraulic loading rate (HLR) increased the empty bed contact time and recorded the highest production of heterotrophic bacteria and biofilm, which increased the efficiency of treatment. Breakthrough occurred in the GAC-sand pilot filter at 72 h and low HLR, but occurred sooner for medium and high HLRs at 48 and 24 h, respectively. The run-time for the anthracite-sand pilot filter at high, medium and low HLRs was 70, 46 and 22 h, respectively. The microorganisms Pseudomonas, Bacillus and Citrobacter were identified in the GAC-sand filter.

Effectiveness in chlorite removal by two activated carbons under different working conditions: a laboratory study

Activated carbon is used in many drinking water facilities because it can remove a broad spectrum of contaminants (e.g., herbicides, pesticides, heavy metals, etc.) or to replace anthracite coal in dual media filters. In recent years, liquid chlorine has been substituted by chlorine dioxide (ClO2) because, for instance, it can remove natural organic matter in raw water without formation of harmful disinfection by-products. Interest in chlorine dioxide is due to formation of chlorite (ClO−2), which can be potentially toxic for humans. In this study, the authors investigated the applicability of two activated carbons coming from different matrices (coconuts and bituminous) as technology for chlorite removal. The activated carbons were tested at different conditions (virgin and pre-loaded with some substances) in order to simulate full-scale working situations, and their Freundlich isotherms were determined. The results show a good affinity of virgin carbons in chlorite removal (about 80%), but the pre-loading significantly affected the efficiency of the chlorite removal process, reducing it to only 19%. An investigation into the main removal mechanism used by the carbons for chlorite removal was also done. Results show that activated carbons used both reduction and adsorption processes.

Practical use of standard pore blocking index as an indicator of biofouling potential in seawater desalination

A practical approach to evaluate the biofouling potential of feed waters for seawater reverse osmosis (SWRO) was investigated. Assimilable organic carbon (AOC) and modified fouling index through an ultrafiltration 10kDa membrane (MFI-UF10) were measured for seawater and pretreated seawater. The pretreatments adopted were dual media filtration (DMF) coupled with coagulation and submerged membrane adsorption bioreactor (SMABR). Low molecular weight neutrals (LMW-N) responsible for biological growth (or biofouling) constituted the major component in seawater and pretreated seawater. A very good linear relationship was observed between AOC concentration and LMW-N concentration. A detailed study on various fouling indices revealed that standard blocking index (Ks) calculated from MFI-UF10 correlated with AOC concentration. This indicates that MFI-UF10 test can serve as a preliminary indicator of AOC and LMW-N (which are biofouling precursors). MFI-UF10 can also be used directly in desalination plants.