Article

Development of the most adequate pre-treatment for high capacity seawater desalination plants with open intake

Authors:
To read the full-text of this research, you can request a copy directly from the authors.

Abstract

Pre-treatment systems in reverse osmosis seawater desalination plants can be relatively simple or complex depending upon the direct function of the physical, chemical and microbiological quality of the water which is fed through the reverse osmosis membranes which separate the salts and the other disperse matter (colloids and micro-organisms) which are present in the processed water which, according to type and quantity, will produce a progressive or accelerated process of fouling of the same. Thus, the less quality of water to be desalinated, the greater or more intensive will be the pre-treatment system. The process water which is the result of systems of open intake is less recommendable since the characteristics are lower in quality, above all, the micro-biological parameters (the worst). All of this has a basic repercussion by increasing the cost per unit of the cubic metre of water produced and supplied to the end consumer or by reducing the profits for the companies exploiting the seawater desalination plant.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

... When presented with a new seawater desalination plant project, after on-site drilling and sampling of observation wells is completed, gathering historical information on the composition of raw seawater is required to understand the conditions of the intake-seawater quality. Table 2 describes common compositions of raw seawater at several sites in the Middle East [9][10][11][12][13][14][15][16][17][18]. Then, depending on the raw seawater quality at various sites, it is necessary to determine individual guidelines for configuring the pretreatment process, RO system design, membrane selection, and chemical cleaning methods [19]. ...
... After screening trash from the intake seawater as an initial pretreatment step, coagulation, flocculation, media filtration, and cartridge filter steps are usually included in the pretreatment process to improve the feed water quality for the RO process. Key issues to be considered in the pretreatment step are as follows [8,15,20,21]: C Preventing bacterial growth and bio-fouling in the RO membrane. C Inhibiting scale formation in the RO membrane. ...
... In order to resolve the problems mentioned above, the following approaches are recommended, respectively [8,15,20,21]: C Sodium hypochlorite (NaOCl), Cl 2 , KMnO 4 , or O 3 can be used to control bio-fouling. H 2 SO 4 can be applied to assist the biocide action of NaOCl. ...
Article
Over 100 papers were reviewed to elucidate factors influencing large-scale seawater desalination plants with reverse osmosis networks (SWRO). This paper consists of subjects such as SWRO systems investigation, system models of pretreatment and RO networks, systems optimization to minimize the total cost of SWRO plant design, and the future direction of SWRO technology. In order to design a large-scale seawater desalination plant, a systematic understanding of SWRO processes should be followed. After investigating all the processes, including site-specific features, seawater intakes, pretreatment systems, RO networks, energy recovery systems, post-treatment systems, brine disposal, and the environmental impact of SWRO desalination, system models are discussed for predicting the performance of each system. Based on the minimal principle of total cost required for a full-scale SWRO plant, optimized results are discussed. Studies needed for developing future SWRO technologies are suggested.
... Flocculants are often high molecular weight (>1 Â 10 7 Da), anionic polymers. Granular media filtration includes materials such as sand, anthracite, pumice, gravel, and garnet (Bonnelye et al., 2004;Elguera and Bá ez, 2005), and often, a combination of materials is used in layers in the filtration bed to take advantage of materials' different effective sizes. Filtration beds can be open to the atmosphere, using gravity to cause permeate flow, or filters can be closed to the atmosphere and pressurized (Elguera and Bá ez, 2005). ...
... Granular media filtration includes materials such as sand, anthracite, pumice, gravel, and garnet (Bonnelye et al., 2004;Elguera and Bá ez, 2005), and often, a combination of materials is used in layers in the filtration bed to take advantage of materials' different effective sizes. Filtration beds can be open to the atmosphere, using gravity to cause permeate flow, or filters can be closed to the atmosphere and pressurized (Elguera and Bá ez, 2005). Although more expensive and energy intensive, pressurized media filtration is more common in RO pretreatment and can typically reduce the feed water SDI by a factor of 2 (Morenski, 1992). ...
... Cartridge filtration is used as a last pretreatment step in conventional RO pretreatment. The filter cartridges are usually 1-10 mm (Elguera and Bá ez, 2005;Morenski, 1992;Petry et al., 2007) and act as a final polishing step to remove larger particles that passed through media filtration. Particulate matter greater than 5-10 mm can foul the channels used to remove RO concentrate (Morenski, 1992); therefore, filter cartridges are a necessary final step before RO treatment. ...
Article
Reverse osmosis membrane technology has developed over the past 40 years to a 44% share in world desalting production capacity, and an 80% share in the total number of desalination plants installed worldwide. The use of membrane desalination has increased as materials have improved and costs have decreased. Today, reverse osmosis membranes are the leading technology for new desalination installations, and they are applied to a variety of salt water resources using tailored pretreatment and membrane system design. Two distinct branches of reverse osmosis desalination have emerged: seawater reverse osmosis and brackish water reverse osmosis. Differences between the two water sources, including foulants, salinity, waste brine (concentrate) disposal options, and plant location, have created significant differences in process development, implementation, and key technical problems. Pretreatment options are similar for both types of reverse osmosis and depend on the specific components of the water source. Both brackish water and seawater reverse osmosis (RO) will continue to be used worldwide; new technology in energy recovery and renewable energy, as well as innovative plant design, will allow greater use of desalination for inland and rural communities, while providing more affordable water for large coastal cities. A wide variety of research and general information on RO desalination is available; however, a direct comparison of seawater and brackish water RO systems is necessary to highlight similarities and differences in process development. This article brings to light key parameters of an RO process and process modifications due to feed water characteristics.
... The increase of feed water temperhre or pressure results in a recovery ratio increase while the increase of feed water salinity or feed water pH leads to a decrease in recovery ratio. Elguera and Perez Baez, [12] have developed the most adequate' pretreatment for high capacity seawater desaliation plants with open intake. This has been attempted to show how important the adequate system for optimization of the pre-treatment systcm of seawater desalination plants of open intake. ...
... NTU by conventional sand filtration. The filter cartridges are usually 1-10 m [13,236]. Particles larger than five microns can be removed by a classical method. ...
... A wide range of chemicals is used in pretreatment, and chemical choices depend on water quality [49]. For example, chlorine is an effective biocide added to intake water in most desalination plants to control and reduce biofouling throughout the system [23]. ...
Article
Seawater desalination is a potential solution for addressing water shortages. The number of desalination plants projected and constructed in some regions has substantially increased in recent decades. However, desalination process poses some undesirable environmental impacts in terms of energy consumption, land use, and seawater intake, but particularly the most significant impacts are related with effluent disposal and discharge. Thus, the challenge for the desalination industry is to produce new water resources without increasing pressure on the marine environment. The effluent characteristics depend on the feed water and desalination technology used. Negative environmental impacts of brine discharge from a desalination plant can be minimized by appropriate planning. The countermeasures should vary depending on plant size and type, the biological communities in the discharge area, and the area’s hydrogeological features. This study overviews the available information about minimizing the harmful effects of the desalination industry. It highlights that an appropriate discharge location must be selected and the mixing of brine with ambient seawater must be maximized to reduce the environmental impacts of brine. Moreover, it is helpful to establish a carefully designed environmental monitoring program to assess brine plume distribution over time while monitoring biota. Frequent environmental monitoring programs of desalination plants normally show that the impacts are small, localized, and unimportant; however, significant effects have been detected in some cases. In these cases, effects can be mitigated by introducing devices that increase the mixing of effluent and surrounding seawater or/and by diluting the effluent before discharge.
... The Corso station is the object of our study. The works of Elguera and al. [1] showed that the membranes fouling by the biofilm formation and precipitate on the membrane surface led to the increase of the pressure drop in the reverse osmosis system. This was confirmed by the works of Bonnelye et al. [2]. ...
Conference Paper
Full-text available
To mitigate the deficit in hydrous resources engendered by the situation of drought that our country knew, the sea water desalination in Algeria appears as an alternative solution. The objective of this study is to follow the performances of the Corso desalination plant using the reverse osmosis membranes by proceeding to the physical chemical and bacteriological analysis crude sea water, the pretreated water (the microfiltration) and the permeate reverse osmosis, by the follow-up of the permeate reverse osmosis conductivity with time and by the evolution of the function parameters: the pressure drop, the conversion rate and the permeate flux. To estimate the state of membranes after two years of function, we made an analysis by scanning electron microscopy (SEM) of the membrane surface coupled by an analysis XRD of the fouling deposit. The results obtained, indicated a problem at the plant what incited the person in charge to stop the plant functioning.
... Tahap pertama yang dilakukan dalam pre-treatment adalah melakukan penyaringan sampah yang terbawa, selanjutnya dilakukan koagulasi, flokulasi, filtrasi, dan catridge filter [2]. Hal tersebut perlu dilakukan untuk mencegah pertumbuhan bakteri (bio-fouling), pencegahan pembentukan kerak< pengaturan pH, dan menghilangkan padata-padatan yang terbawa [5,7]. Langkah-langkah tersebut dilakukan untuk meningkatkan kualitas air umpan yang akan masuk ke proses RO. ...
Article
Full-text available
Abstrak Kebutuhan manusia akan air terus bertambah seiring dengan pertumbuhan penduduk dan industri. Namun, jumlah sumber air yang ada saat ini sudah tidak cukup untuk memenuhi kebutuhan manusia yang terus bertambah dengan sangat pesat. Sehingga, air laut yang jumlahnya sangat berlimpah dimanfaatkan untuk mengatasi kekurangan yang ada. Namun, air laut memiliki kandungan garam terlarut yang sangat tinggi. Sehingga, air laut perlu diolah terlebih dahulu sebelum dapat digunakan. Sala satu metode desalinasi air laut yang telah komersial digunakan yaitu sea water reverse osmosis (SWRO). Metode ini terbukti efektif dan menguntungkan di beberapa tempat untuk memproses air laut menjadi air murni. Metode ini menggunakan membran RO untuk merejeksi kandungan garam terlarut agar didapatkan air murni. Proses rejeksi garam terlarut pada air laut dilakukan pada tekanan tinggi, sehingga memerlukan energi yang besar untuk melangsungkan proses ini. Oleh karena itu, perlu diperhatikan setiap sistem pemrosesan dalam SWRO plant agar proses desalinasi dapat berjalan secara maksimal dan ekonomis. Pada paper ini akan dibahas mengenai perancangan sistem pengolahan air laut menggunakan SWRO dan hal-hal yang perlu diperhatikan dalam melakukan perancangan.
... There are many pretreatment methods for desalination of seawater such as conventional pretreatment by using coagulation, flocculation, sedimentation and filter [1,12,[24][25][26][27][28], membrane technology by employing high rate dissolved air flotation, MF & UF ( [1,24,25,[29][30][31], beach well system [24], dead-end backwahable hollow fiber ultrafiltration [32], [33], ozonation followed by microfiltration [34], nanofiltration [35] and ozonation with biological activated carbon [14]. Due to the increasing world population, it is essential to produce the potable water in good quality by using desalination of seawater [28]. ...
Article
Feed water that need to be pre-treated before using methods such as, microfiltration, Ultrafiltration, nanofiltration and reverse osmosis is characterized by containing turbidity, bacterial content and total dissolved solid which causes fouling and scaling in membrane performance. Thus, it is necessary to develop a method which is cost effective. Pre-treatment has been shown as a good method to enhance the performance and reducing the cost of replacement for membrane of the RO/NF as it helps to remove turbidity, bacteria and TDS (Total dissolve solid), COD and Colour. In this paper, a brief review on the pretreatment in different industry will be clarified such as pretreatment of seawater, and wastewater treatment. Basically, methods of pretreatment can be categorized as coagulation, flocculation, sedimentation, microfiltration, ultrafiltration, ozonation and etc. Therefore, this review can provide a better alternative in solving the membrane fouling and scaling problem.
... Adding to the membrane pre-treatment discussion, Halpern et al. [49] observed that membrane pre-treatment worked well for source waters of low bio-fouling potential, namely for subsurface or deep open ocean intakes. Plants with dissolved air flotation, described by Bonnelye et al. [50,51] or other pre-treatments [52][53][54][55][56] apart from microfiltration and ultrafiltration membranes have shown satisfactory operation even during unstable intake water quality. ...
Article
Full-text available
In this paper, modern large-scale industrial water desalination technologies are briefly reviewed and a comparison between their technological characteristics and field of application is presented to indicate possible areas for technology advancement. In addition, recent developments in distillation processes and new desalination methods are introduced for relevant technologies, offering more accessible water supplies. The research was based on both work with analytic materials from large information agencies involved in the desalination industry and research carried out by individual authors and research institutions. The authors discuss the possibility of applying their own technology for water distillation, so called supercavitating evaporation. Analysis of the current situation indicates an increasing trend for reverse osmosis technology for water desalination, the rise of newer technologies and further limitation of thermal methods for heat utilization purposes.
... Figure 1 shown the main steps of pretreatment , it includes: - Dosage of 6-9 ppm of Sodium hypochlorite in order to control the membrane biofouling. - Injection of Sulphuric acid (H 2 SO 4 ), in order to regulate the water pH, about 62 ppm of Sodium Metabisulfit (NaHSO 3 ) (reducing agent) to neutralize completely the residual active chlorine [21]. - Injection of a commercial scale inhibitor (antiscalant) with a dosage level at 9 ppm in order to attenuate the risk of salt precipitations. ...
Article
Desalinated brackish water is becoming an important water source for agricultural irrigation. In Brackish water desalination, pretreatment of reverse osmosis is the key step in designing the plants to avoid membrane fouling and scaling. It is enormously important to carry out a study designed at ensuring the optimization of the pretreatment system for brackish desalination plant in order to optimize the quality of the water fed through the reverse osmosis membranes, to guarantee the highest performance and to minimize the number of shutdowns for chemical cleaning. In this paper, performance evaluation carried out for a brackish water reverse osmosis plant for agricultural application, located in Dokkala Region in Morocco. This plant showed poor performances after few months of operating and frequent shutdown. The operating pressure increased significantly and the permeate conductivity decreased surprisingly. To identify the causes for the poor performance, different investigations were carried out. Thus, the pretreatment scheme was thoroughly reviewed to find out the causes of anomalies. The problem was resolved by removing chlorination and sodium bisulfate steps from the pretreatment.
... Conventional packed-bed filters using granular media such as sand, anthracite, pumice, gravel, and garnet with different effective sizes are beneficial in terms of regeneration, since hydraulic backwashing has proven to be effective in conventional water treatment in restoring capacity [18,40,41]. For constant physicochemical conditions, the granular media filtration process is effective at removing particles significantly larger than a few micrometers or smaller than 0.1 µm [42]. ...
Article
Full-text available
Reverse osmosis (RO) technology has developed over the past 40 years to control a 44% market share in the world desalting production capacity and an 80% share in the total number of desalination plants installed worldwide. The application of conventional and low-pressure membrane pretreatment processes to seawater RO (SWRO) desalination has undergone accelerated development over the past decade. Reliable pretreatment techniques are required for the successful operation of SWRO processes, since a major issue is membrane fouling associated with particulate matter/colloids, organic/inorganic compounds, and biological growth. While conventional pretreatment processes such as coagulation and granular media filtration have been widely used for SWRO, there has been an increased tendency toward the use of ultrafiltration/microfiltration (UF/MF) instead of conventional treatment techniques. The literature shows that both the conventional and the UF/MF membrane pretreatment processes have different advantages and disadvantages. This review suggests that, depending on the feed water quality conditions, the suitable integration of multiple pretreatment processes may be considered valid since this would utilize the benefits of each separate pretreatment.
... The feed variability of contaminants will be transferred to the RO if the pretreatment fails, either in design or operation [7]. Furthermore, the cleaning frequency and operating conditions will affect the membrane structure in various ways and cleaning treatments generally have varying degrees of success [2,8,9]. Exposure of polyamide active layer to chlorine alters its structure and morphology, resulting in increase of water permeability and decrease of selectivity [10]. ...
... However, a major issue with the use of RO membranes in seawater desalination is membrane fouling that can occur by the presence of particulate matter [14], dissolved organic matter [14], and organic compounds [15]. To reduce membrane fouling, pretreatment is often conducted, using methods such as coagulation and flocculation [16], packed bed filtration [17,18], and precipitation processes [19]. ...
Article
Recent studies have shown the presence of endocrine disrupting compounds (EDCs) in seawater and brackish water, which could potentially complicate various seawater desalination treatment processes. In this study, the adsorption of bisphenol A (BPA) and 17α-ethinyl estradiol (EE2) by single walled carbon nanotubes (SWCNTs) was investigated. Solutions of artificial seawater, brackish water, and a combination of these two waters were prepared, in accordance with previously published composition data. Overall, the removal efficiency for EE2 (95–98%) was higher than BPA (75–80%), possibly because of its higher log KOW value. The adsorptive capacity of the SWCNTs remained relatively constant for the artificial source waters used in this study, suggesting that the changes in the composition of the water did not affect the overall adsorption of the EDCs. Adjusting the pH of the solutions from 3.5 to 11 showed a 22–26% decrease in the adsorption of BPA, whereas no notable changes were found in the adsorption of EE2. Changes in the ionic strength of the solutions by increasing the concentrations of Na+ and Ca2+ did not significantly affect the adsorption of BPA or EE2. The concentration of dissolved organic carbon (DOC), represented in this study by humic acid, had noticeable effects on the adsorption of BPA and EE2. As the concentration of DOC increased, the removal of BPA and EE2 decreased by 5–15%, which could possibly be explained by competitive adsorption between the EDCs and humic acid. With increasing concentrations of SWCNTs, adsorption of DOC occurred with removal efficiencies of up to 95%. Hydrophobic interactions and π–π electron donor–acceptor (EDA) interactions among the EDCs, the DOC, and the SWCNTs have been hypothesized as the potential adsorption mechanisms for BPA and EE2.
... Water quality parameters of seawater such as temperature, total dissolved solids and biological quality have affected the pretreatment regimes of numerous desalination plants [4][5][6]. Previous studies widely reported development [7], evaluation [8,9] and performance [10] of pretreatment of a SWRO system. Specifically, microfiltration employment prior to RO made filtrate quality good [8] by removing impurities larger than 0.1 m. ...
Article
In order to assess the biofouling propensity of Bacillus sp. and Pseudomonas sp. isolated from the seawater intake of a desalination system, the effect of chlorination and microfiltration pretreatment processes on these organisms was investigated. The removal efficiency of Bacillus sp. Sea-3 was higher than that of Pseudomonas sp. Sea-5 in the hollow-fiber microfiltration. However, Bacillus sp. Sea-3 had a stronger resistance against chlorination and also showed increase in active cell numbers at 24 h after chlorination, whereas the viability of Pseudomonas sp. Sea-5 decreased rapidly during the same time. The spo0A gene (which makes the regulatory protein Spo0A to enter the development process of sporulation) expression assay of Bacillus sp. Sea-3 in different chlorination conditions showed that sporulation gene transcription level varied in 0 and 24 h after chlorination. Increase in the number of spo0A gene at 0 h after chlorination was positively related with the increased numbers of cells during 24 h incubation since lysed cells were utilized by Bacillus sp. during its reproduction and adaptation of 24 h made vegetative growth of spores active. Sporulation gene assay of Bacillus sp. in the chlorination of seawater showed one of the selective options for pretreatment design in order to reduce the risk of biofouling.
Article
Reverse osmosis (RO) membrane process has become the most promising technology for desalination to produce purified water. Among numerous polymeric materials used to fabricate RO membranes, aromatic polyamide thin film composite (TFC) membranes are dominant in commercial RO membrane processes because of their high salt rejection and water permeability as well as their excellent chemical, thermal, and mechanical stability. However, the major hindrance to the effective application of polyamide TFC RO membranes is membrane fouling. Furthermore, polyamide TFC RO membranes have limited stability to chlorine, which is commonly used as disinfect to control membrane biofouling. These two factors deteriorate membrane performance and shorten membrane life span. Membrane fouling depends strongly on membrane surface morphology and properties. Up to now, many physical or chemical surface modifications have been reported to alter the surface properties so as to improve the fouling resistance of the RO membranes. In this paper, different kinds of RO membranes fouling, chlorine effects, factors that influence RO membranes fouling, and the ways for reduction of fouling in RO membranes were discussed. Moreover, as a main part of this paper, all physical and chemical surface modification methods for fabricated polyamide TFC RO membranes were completely reviewed.
Chapter
Introduction Membrane Fouling Strategies for Mitigation of Membrane Fouling and Scaling Membrane Surface Structuring via Graft Polymerization Summary References
Article
Full-text available
In this work, problems related to the corrosion and sedimentation in cooling tower and the decrease in the amount of evaporation rate are investigated experimentally, using loop test which is similar to the cooling tower system. The input and output water stream in the loop test are analyzed in different time intervals, different amount of evaporation, different amount of the outlet water and make up water stream. The first analyzes indicate on the increase in the amount of dissolved material, concentration cycle and also the increase in the amount of evaporation rate and consequent corrosion problems and sedimentation. However, adjusting the amount of makeup water and the water outlet provides the acceptable results. Changes in conditions due to each analyze are illustrated in curves.
Article
In reverse osmosis demineralization processes, spiral wound modules are used and after approximately 5 years are discarded, since they lose their performance. These modules could be reused for other treatments that do not require a final permeate with so high quality, but still have limitations for feed water quality. The aim of this study is to propose a pretreatment configuration to a membrane filtration system that uses discarded membranes to treat the stream of a cooling tower for reuse as make-up water. Steps of coagulation/flocculation, sand filtration, sorption with GAC and combinations of these were proposed. Parameters as pH, electrical conductivity, turbidity, total hardness, COD, silica content and SDI were analyzed. The pretreated effluent was tested in a bench scale membrane filtration system. Permeate flux, salt retention and hydraulic permeability were evaluated to identify fouling. The best results were obtained coupling coagulation/flocculation with sand filtration. The RO discarded membranes presented high salt retention, about 97% and analysis of permeates indicates the possibility of reuse. MEV and EDS of SDI membranes showed a decrease of silica and total hardness scale, which are the main causes of fouling and the pretreated stream seems to present suitable characteristics to feed the RO filtration system.
Article
A new class of surface-structured ROmembranes was developed with a hydrophilic brush layer of terminally anchored polymer chains resulting in fouling resistant membranes of low mineral scaling propensity and high permeability. The approach is based on free-radical graft polymerization of a suitable monomer, onto the active polyamide (PA) layer of a thin film composite (PA-TFC) membrane, post-surface activation with an impinging atmospheric pressure plasma source. Two types of nano-structured (SNS) ROmembranes (SNS-PA-TFC) were synthesized based on methacrylic acid (MAA-SNS-PA-TFC) and acrylamide (AA-SNS-PA-TFC) graft polymerization. The poly(methacrylic acid) and poly(acrylamide) brush layers, on the PA surface, resulted in ROmembranes of significantly lower mineral scaling propensity, evaluated with respect to the mineral scalant calcium sulfate dihydrate, compared with commercial ROmembrane (LFC1) of about the same salt rejection (95%) and surface roughness (70 nm). Direct membrane surface imaging indicated that the rate of nucleation and thus mineral scaling were reduced owing to the polymer brush layer. Fouling resistance of the SNS-PA-TFCmembranes was also demonstrated with respect to model foulants (the protein BSA and alginic acid). The MAA-SNS-PA-TFC and AA-SNS-PA-TFCmembranes had a negatively charged and near neutral surfaces, respectively, with water contact angles somewhat lower for the former and higher for the latter membranes relative to the LFC1 membrane. The AA-SNS-PA-TFCmembrane displayed lower mineral scaling propensity than the MAA based membrane, although its alginic acid fouling resistance was inferior, despite its lower surface roughness (25–33 nm) relative to the MAA-SNS-PA-RFC (60–80 nm) and LFC1 (73 nm) membranes.
Article
CEDEX (Centro de Estudios y Experimentacion de Obras Publicas) and EMALSA (Empresa Mixta de Aguas de Las Palmas, S.A.) had been performing experimental tests for seawater desalination at Las Palmas, Gran Canaria Is., Spain, using a TOYOBO hollow-fiber membrane. A Hollosep HM10255FI module made by TOYOBO is used in the largest desalination plants around the world, especially in the Middle East. CEDEX and EMALSA confirm that the Hollosep module can produce stable water production and high-quality water for long-term operation without any chemical cleanings during 4600h operation thanks to the its high chlorine resistance and anti-biofouling tolerance.
Article
The sorption of two marine bacteria to surfaces involved an instantaneous reversible phase, and a time-dependent irreversible phase. Reversible sorption of the non-motile Achromobacter strain R8 decreased to zero as the electrolyte concentration decreased, or as the thickness of the electrical double-layer increased. The electrolyte concentration at which all bacteria were repelled from the glass surface depended on the valency of the cation. The reversible phase is interpreted in terms of the balance between the electrical double-layer repulsion energies at different electrolyte concentrations and the van der Waals attractive energies. Even at the electrolyte concentration of seawater, the bacteria probably are held at a small distance from the glass surface by a repulsion barrier. Reversible sorption often led to rotational motion of the motile Pseudomonas sp. strain R3 at a liquid-glass interface. Pseudomonas R3 produced polymeric fibrils in artificial seawater; these may be concerned in the irreversible sorption of the bacteria to surfaces. Sorption and polymer production were stimulated by 7 mg./l. glucose but higher levels inhibited irreversible sorption. Omission of Ca2+ and Mg2+ from the artificial seawater prevented growth, polymer production, and sorption to surfaces by Pseudomonas R3.
Article
Adhesion of selected bacteria to cellulose acetate (CA) reverse osmosis (RO) membranes used in wastewater reclamation processes was investigated to determine its role in membrane fouling and reduced process efficiency. Adhesion of a Mycobacterium sp. previously isolated from an early stage of RO membrane biofouling was relatively unaffected by large variations in the ionic strength or pH of the buffer system. However, trace quantities of a polyoxyethylene ether nonionic detergent almost completely inhibited attachment. The mycobacteria were found to adhere to the CA membrane surface (or to a CA-affinity column) approximately 25-fold more effectively than a wild-type strain of Escherichia coli. The ability of Mycobacterium and E. coli to adhere to the membrane was correlated with their relative surface hydrophobicities as determined by their affinities for (n)-hexadecane. A similar correlation was established between a hydrophilic wild-type strain of Acinetobacter phosphadevorus containing a single 17.8 mega-Dalton plasmid (PYG1) and a more hydrophobic isogenic derivative strain (P7P-) lacking the PYG1 plasmid. Unlike the P7WT parent strain, the P7P- derivative produced more fimbrialike appendages, which may account for its enhanced hydrophobic and adhesive properties. The results suggest that hydrophobic interactions between bacterial cell surface components and the CA membrane surface play an important role in the initial stages of bacterial adhesion and RO membrane biofilm formation.
Article
Several potential additives and the use of influent pH adjustment were examined to remediated the biofouling problem of the ETF reverse osmosis (RO) system. Tests were conducted with simulated RO feed containing salt, metal hydroxides and bacteria. The addition of sodium hexametaphosphate (SHMP), sodium bisulfite, and adjusting the influent pH to 3 were each successful in reducing the RO biofouling. Little or no benefit was found from the use of a biofilm remover (Filmtec Alkaline Cleaner) or the use of surfactants (Surfynol or sodium lauryl sulfate). In addition, Surfynol use resulted in irreversible fouling and necessitated membrane replacement. At the water recoveries used in the ETF (>90%), sodium bisulfite addition resulted in the recovery of 70--90% of the flux and almost complete restoration of the DF to prefouled conditions. Based on the bench-scale tests completed, IWT would recommend that sodium bisulfite addition be tested at the ETF. This testing would involve optimizing the amount of bisulfite required. In addition, it is recommended that the addition of SHMP or influent pH adjustment be evaluated since the relative differences in labscale tests were small and scale-up effects could be present. The ETF operating permit allows each to be added.
Article
To determine the mode of action of free chlorine in inactivating coliforms, acid-fast bacteria and yeasts, the uptake of radioactive chlorine was determined. Cell-associated chlorine could be modeled by the Freundlich relationship, with either free available chlorine or hypochlorous acid as an independent variable. Candida parapsilosis and Mycobacterum fortuitum exhibited greater uptake of chlorine at pH 7.0 than at pH 9.14; an opposite effect of pH on uptake was noted with Escherichia coli and may be ascribed to losses in cellular material. This study confirmed that cell-associated chlorine is responsible for the inactivation of vegetative microorganisms by free available chlorine.
Argo (Orange Country Researchers, California, USA); Biofilm on Reverse Osmosis Membranes. Water Waste Treatment
  • H F Ridgway
  • D M Rodger
H.F. Ridgway, D.M. Rodger and D.G. Argo (Orange Country Researchers, California, USA); Biofilm on Reverse Osmosis Membranes. Water Waste Treatment, March 1986.
Evaluacio´ Econo´ del Intercambio Io´ Versus la O ´ smosis Inversa
  • A M Elguera
A.M. Elguera, Evaluacio´ Econo´ del Intercambio Io´ Versus la O ´ smosis Inversa, Tesina del Master de Desalacio´ -tilizacio´ Aguas Residuales, Universidad de Las Palmas de Gran Canaria, Marzo de 1997.
Orange Country Researchers
  • H F Ridgway
  • D M Rodger
  • D G Argo
Evaluación Técnico Económico del Intercambio Iónico Versus la Ósmosis Inversa
  • A M Elguera
Ventajas económicas al optimizar los productos químicos en el pretratamiento de plantas desaladoras de osmosis inversa
  • A M Elguera
  • S O Báez
Inconvenientes de Realizar Dosificación Intermitente de Hipoclorito de Sodio, en línea de Pretratamiento de una Planta Desaladora por Ósmosis Inversa
  • A M Elguera
  • J Alday
  • A Gotor
  • S O Báez
Understanding Desalination Technology: ‘Water Microbiology
  • David H Paul
Chorine dynamics during inactivation of coliforms, acid fast bacteria and yeast
  • Hass