Field testing and economic evaluation of RO seawater technology

An experimental RO seawater system has been in operation for two years at Eilat on the Red-Sea shore. Simplified seawater pretreatment, comprising only sand filtration and acid dosing was applied. Hollow fiber and spiral wound membranes were tested. Evaluation of pretreatment effectiveness and comparative membrane performances are reported. Investment and water cost analysis of a 4,000 m³/day RO seawater desalting system under various operating conditions is given. The analysis is based on the results of experimental site operation, current technology development and updated industrial quotations. The resulting water production cost from a one-stage system, adequate to produce desalted water acceptable for local drinking water standards, is approximately $ 1.1/m³.     

The performance of the 12,000 m3/day seawater ro plant at Jeddah,Saudi Arabia

This paper outlines the performance of the 12,000 m³/day seawater RO plant at Jeddah, Saudi Arabia. The plant started operation in February 1979 and has been operating since then. The feedwater to the plant has a TDS of 42,000 ppm and the maximum seawater temperature is 32°C. The plant is made up of a first and a second stage. The first stage includes nine units, eight operating and one stand-by, and the second stage containes three units. The nine first stage and the three second stage RO units are each composed of 56 Fiberglass pressure tubes (Model 66 FRP-6) 150 mm diameter by 6.5 m long, each containing six spiral wound elements manufactured by UOP Fluid Systems Division. The plant uses Fluid System's polyamide thin film composite membrane element, Model 1501 TFC. The pretreatment is composed of dual media filtration, acid injection, sodium hexametaphosphate injection and cartridge filtration.The performance from the start of operation till the present time is shown both for the overall plant and for each unit. The product rate of each unit and its water quality throughout its operating period is indicated showing the times when the unit was shut-down and the reason for it. Deterioration in unit performance is analyzed and explained. Actual plant consumption of fuel and chemicals is given and estimates of the plant operating costs are made.     

聚电解质静电沉积改性制备高性能反渗透膜

利用次氯酸钠溶液对商品反渗透膜表面进行氯化处理,然后将聚阳离子电解质壳聚糖通过静电吸附作用沉积在RO膜的表面,系统地研究了氯化过程的pH、氯化时间、次氯酸钠浓度、壳聚糖浓度及其沉积时间对膜性能的影响,以制备出高通量、高截留率的RO膜。在压力1.55 MPa、原料液温度（298±1）K的条件下,测定RO膜处理2000 μg·g^-1氯化钠溶液的水通量和截留率。结果表明,当pH=9、氯化时间为30 min、次氯酸钠浓度为1000 mg·L^-1时,水通量较原膜提高了约19.89%,截留率略有提高;当壳聚糖浓度为0.1%（质量分数）、沉积时间为30 min时,改性膜的接触角降低到34.88°,亲水性提高,水通量较氯化后的RO膜几乎保持不变,为60.55 L·m^-2·h^-1,截留率达到了99.56%。经过氯化和沉积改性后的RO膜水通量和截留率均得到了提高。     

Surface characterization and performance evaluation of commercial fouling resistant low-pressure RO membranes

This paper describes the characterization and evaluation of various RO/NF membranes for the treatment of seasonally brackish surface water with high organic contents (TOC ≈21 mg/L). Twenty commercially available RO and NF membranes were initially evaluated by performing controlled bench-scale flat-sheet tests and surface characterization. Based on the results, four low pressure RO membranes were selected for use in the pilot study. The surface characterization revealed that each of four selected membranes had unique surface characteristics to minimize membrane fouling. Specifically, the LFC1 membrane featured a neutral or low negative surface to minimize electrostatic interactions with charged foulants. The X20 showed a highly negatively charged surface, and thus, was expected to perform well with feed waters containing negatively charged organics and colloids. The BW30FR1 exhibited a relatively neutral and hydrophilic surface, which could be beneficial for lessening organic and/or biofouling. The SG membrane had a smooth surface that made it quite resistant to fouling, particularly for colloidal deposition. In the large-scale pilot study using single element, all of the four membranes experienced a gradual increase in specific flux over time, indicating no fouling occurred during the pilot study. The deterioration of permeate water quality such as TDS was also observed over time, suggesting that the integrity of the membranes might be compromised by the monochloramine used for biofouling control.     

Forward-osmosis strategy and chemical cleaning of seawater desalination reverse osmosis membranes

In order to settle the membrane fouling of reverse osmosis membranes in seawater desalination process, this study reported a novel strategy based on forward-osmosis process and discussed the effects of different factors like different cleaning combination among reverse osmosis product, simulated reverse osmosis concentrate and simulated seawater, as well as cleaning time on the membrane permeate flux and salt rejection. For irreversible fouling, the effects of different chemical cleaning agents, immersion time and concentration were also investigated in this study. The results exhibited that the cleaning combination between diluted water and simulated reverse osmosis concentrate possessed the best cleaning performance in the process of forward-osmosis cleaning. Such approach also enhanced normalized flux from 9.48 L/(m²·h·MPa) to 13.6 L/(m²·h·MPa) and enhanced NaCl rejection from 80.59% to 92.80%. Furthermore, the normalized flux was enhanced from 9.48 L/(m²·h·MPa) to 14.3 L/(m²·h·MPa) and NaCl rejection was also enhanced from 80.59% to 96.27% after soaking in 2%(mass) citric acid solution for 2h, soaking with 1%(mass) ethylenediamine tetra-acetic acid tetrasodium salt and 0.3%(mass) sodium tripolyphosphate solution for 1.5 h. According to the result of SEM images and AFM images, the forward-osmosis cleaning strategy could not cause the damage of selective layer of membrane surface and caused the drop of inorganic and organic fouling on the membrane surface. Hence, cleaning fouled RO membranes by such approach could prolong the chemical cleaning cycle and reduce the amount of chemical cleaning agent, which has certain industrial application perspectives.     

Nitrate removal with reverse osmosis in a rural area in South Africa

The nitrate-nitrogen concentration (>6 mg/l) and the salinity (>1000 mg/l TDS) of many borehole waters in rural areas in South Africa are too high for human consumption. Therefore, an urgent need for water denitrification and water desalination exists in these areas. Reverse osmosis (RO), electrodialysis (ED), ion-exchange (IX) and certain biological technologies can be very effectively applied for water denitrification. Each of these technologies, however, has its own advantages and disadvantages. Reverse osmosis technology, however, has been selected for this study because the technology is well known in South Africa and because it can be very effectively applied for water desalination. The objectives of this study were: (a) to transfer RO technology through process demonstration performance for water denitrification and water desalination to people living in rural areas; (b) to build capacity regarding the operation and maintenance of an RO application in a rural area; (c) to produce a preliminary operational and maintenance manual for the operation of an RO unit in a rural environment; (d) to train local operators to operate and maintain an RO plant in a rural environment; (e) to evaluate stock watering as brine disposal option; and (f) to determine the preliminary economics ofthe process. The following conclusions were drawn. It was demonstratedthatthe RO process could be very effectively applied for water denitrification and water desalination in a rural area. Nitrate-nitrogen was reduced from 42.5 mg/l in the RO feed to only 0.9 mg/l in the RO product water. The TDS of the RO feed was reduced from 1292 mg/l to 24 mg/l in the RO permeate. Therefore, an excellent quality water could be produced for potable purposes. The RO brine at approximately 50% water recovery should be suitable for stock watering if the conditions for stock watering are met in terms of nitrate-nitrogen concentration, TDS and other constituent concentrations. The capital cost for an approximately 50 m³/d output RO plant is approximately US $29,900. Preliminary cost estimates have shown that the operational cost for water denitrification is approximately US $0.50/m³. This cost, however, should be significantly reduced by optimisation of the chemical dosing and by blending borehole water with RO product water.     

Membrane application for recovery and reuse of water from treated tannery wastewater

Secondary treated tannery wastewater contains high concentrations of Total Dissolved Solids (TDS) and other residual organic impurities, which cannot be removed by conventional treatment method. A pilot plant membrane system with a designed processing capacity of 1 m³/h, comprising of nano and reverse osmosis (RO) membrane units, accompanied by several pre-treatment operations, was evaluated in order to further treat and reuse the tannery wastewater. The maximum TD S removal efficiency of the polyamide RO membrane was more than 98%. The permeate recovery of about 78% was achieved. The water recovered from the membrane system, which had very low TDS concentration, was reused for wet finishing process in the tanneries. The reject concentrate obtained from the operation was sent to solar evaporation pans. It was evident from the study that the membrane system can successfully be applied for recovery of water from secondary treated tannery effluent, provided a suitable and effective pretreatment system prior to membrane system is employed. Combining nano and RO membranes improved the life of the membranes and permeate recovery rate.     

高回收率反渗透海水淡化工艺

目前反渗透海水淡化的回收率小于40％。本文研究开发死端超滤预处理技术和反渗透一纳滤联合脱盐相结合的膜集成海水淡化新工艺,与传统工艺比较,具有装置体积小,产水回收率高等优点。文章介绍了采用新工艺的海水淡化装置样机的试制情况及现场运行结果。沿岸海水为料液,操作压力1为5．1MPa条件下,操作压力2为2.0MPa条件下,装置脱盐率99．21％,产水量3971.3L/h,产水回收率55％。海水淡化装置对海水中Ca^2 、Mg^2 、Na^ 、HCO3^-、Cl^-、SO4^2-、TDS,总碱度,总硬度的脱除率分别为99％,99．6％,99．21％,95％,99．35％,98．48％,99.21％,95％,99．42％。     

Salbukh reverse osmosis plant on stream

An inspection test on the RO plant at Salbukh treatment plant was carried out during a period of operation of 96 hours, October 9–13, 1979. According to the results, the RO plant has been successfully brought into operation. The requirements on water quality, water production and water losses have been satisfied.Based on the performance test, VBB recommends that the RO installation be accepted. Raw water cooling in the pretreatment plant is, however, not acceptable at present. The temperature of the RO feed water was about 38–40°C instead of about 35°C due to the lower efficiency of the coolers than calculated. This failure must be rectified by the Contractor.During the last few months the pretreatment of raw water from Well 54 at Buwayb has been investigated by Ames Crosta Babcock by means of final operation of a pilot plant. Based on these results, the use of 140 mg/l lime and 100 mg/l soda for chemical softening has been recommended by VBB. The high TDS of the raw water in Well 54 indicates, that the final blended water at the same water production rate as originally designed, will contain around 750 mg/l total dissolved solids. However, there is now an indication that the average TDS with all the deep wells in operation will be around 650 mg/l in blended water due to the lower average TDS in the raw water.The pretreatment plant at Buwayb was partly brought into operation in October/November, and the pretreated water is discharged into the water distribution net and blended with desalinated water from Salbukh.     

集成膜技术深度回用处理精对苯二甲酸废水研究

近两年来,膜法回用石化废水备受重视,利用集成膜技术对炼油和乙烯化工废水进行深度回用处理,目前已有相对成熟的经验,但集成膜技术用于精细化工产品精对苯二甲酸废水回用处理的研究尚少。在试验基本工况为超滤系统采用全量过滤方式,运行周期30min,内压式超滤运行通量不大于75L/(m2.h),超滤系统前加入絮凝剂PAC(投加量为5mg/L),低污染反渗透膜运行通量不大于19L/(m2.h),试验中系统回收率为70%,反渗透进水的COD含量小于40mg/L的条件下,精对苯二甲酸达标废水深度回用处理稳定运行,产水水质稳定可靠。     

Spiral-wound new thin film composite membrane for a single-stage seawater desalination by reverse osmosis

New thin film composite membrane system, designated PEC-1000, formed by the acid catalyzed polymerization on the surface of a reinforced-porous supporting membrane, make it possible to produce potable water from seawater by reverse osmosis in a single-stage with a high recovery operation. TDS rejection over 99.9% and stable water fluxes of 0.20–0.30 m³/m²-day (5.0–7.4 gal/ft²-day) have been attained with 3.5% synthetic seawater at an applied pressure of 56Kg/cm²(800psi). For brackish water, sodium chloride rejections of 99.6–99.9% and fluxes of 0.61–0.81m³/m²-day(15.0-20.0 gal/ft²-day) have been attained with 5000 ppm sodium chloride feed at an applied pressure of 40Kg/cm² (571psi). TDS rejection of 99.8% and water flux of 0.30 m³/m²-day (7.4 gal/ft²-day) have been attained with two- or four-inch diameter PEC-1000 composite membrane elements at an applied pressure of 56Kg/cm²(800psi) in a single-stage synthetic seawater desalination test. This performance is kept for more than 1500 hours in PEC-1000 thin film composite membrane and two-inch diameter element. 280 ppm in TDS and water flux of 0.11 m³/m² day (2.7 gal/ft²-day) are observed at an applied pressure of 56Kg/cm²-40% water recovery with one four-inch diameter spiral-wound PEC-1000 composite membrane element in a single-stage seawater desalination. This membrane shows high selectivity for low molecular weight valuable organic materials such as ?-caprolactam, dimethylsulfoxide, dimethylformamide. The thickness of ultrathin salt barrier of the composite membrane is found to be 300Å by the Electron Microscopy with special ultrathin section techniques.     

Nanofiltration and reverse osmosis thin film composite membrane module for the removal of dye and salts from the simulated mixtures

Nanofiltration (NF) and reverse osmosis (RO) thin film composite polyamide membrane modules were used to remove the color from the contaminated solution mixture. The feasibility of membrane processes for treating simulated mixture by varying the feed pressures (100-400 psi) and feed concentrations was studied to assess the separation performance of both NF and RO membranes. It was found that the efficiency of NF and RO membranes used in the treatment of colored water effluents was greatly affected by the presence of salts and dyes in the mixture. Color removal by NF with a high rejection of 99.80% and total dissolved solids (TDS) of 99.99% was achieved from RO by retaining significant flux rate compared to pure water flux, which suggested that membranes were not affected by fouling during the simulated wastewater process operation. The effect of varying concentrations of Na₂SO₄ salt and methyl orange (MO) dye on the performance of spiral wound membranes was determined. Increasing the dye concentration from 500 to 1000 mg/L resulted in a decrease of salt rejection at all operating pressures and for both concentrations of 5000 and 10,000 mg/L as the feed TDS. Increasing the salt concentration from 5000 to 10,000 mg/L resulted in a slight decrease in dye removal.     

正渗透策略和化学清洗海水淡化反渗透膜

为解决海水淡化过程中反渗透膜的污染问题，研究了基于正渗透策略的反渗透产水、模拟反渗透浓水、模拟海水不同的组合清洗和清洗时间对膜通量和截留率的影响。针对不可逆污染，研究了不同化学清洗药剂、浸泡时间、浓度对膜通量和截留率的影响。结果表明，正渗透策略清洗方式中，淡水/模拟反渗透浓水的组合清洗方式效果最佳，其归一化通量从9.48 L/(m²·h·MPa)提升至13.6 L/(m²·h·MPa)，截留率从80.59%提升至92.80%。此外，经质量分数为2%的柠檬酸溶液浸泡2 h后，再使用质量分数为1%的乙二胺四乙酸四钠盐和0.3%的三聚磷酸钠溶液浸泡1.5 h，其归一化通量从9.48 L/(m²·h·MPa)提升至14.3 L/(m²·h·MPa)，截留率从80.59%提升至96.27%。从SEM和AFM图可以看出，正渗透清洗策略并未对膜表面选择层造成损坏，且可以清洗膜表面的有机污染物和无机污染物，因此，应用这种方法对污染的反渗透膜进行清洗，可延长化学清洗周期，减少化学清洗剂用量，具有一定的工业应用前景。     

Hybrid systems in seawater desalination—practical design aspects, present status and development perspectives

Ever since seawater desalination has been applied on an industrial scale, and particular in the countries of the Arabian Gulf, the application of desalination processes in dual-purpose facilities—water and power—as a hybrid configuration has been discussed in many feasibility investigations and also planning concepts. It is above all the combination of reverse osmosis with thermal processes that has found increasing interest with the aim of ensuring, as economically as possible, uniform water supplies under the specific, greatly varying load conditions in the Gulf countries. Such design concepts for hybrid configurations encompass straightforward structures with a low degree of coupling between membrane and thermal desalination processes, but range up to very complex configurations with strong interconnections on both the water side and thermally, as well as with several desalination processes connected in series or in parallel. Classical hybrid concepts in which the permeate from an RO desalination component is mixed with distillate from thermal desalination have already been implemented in Saudi Arabian dual-purpose plants, like Jeddah and Yanbu-Medina. Although hybrid systems of greater complexity have been addressed in many design studies and publications, up to now none has been brought to fruition. Coming into consideration asthe design basis for determining the capacity shares of the various desalination processes operated in a hybrid configuration are: arrangement of thermal cycle of the power plant component; water/power ratio of the dual-purpose seawater desalination and power plant; provision of undiminished water production of the desalination plant as electricity generation varies; provision of a specified drinking water quality with regard to composition and salt content; combination of all these aspects. Also gaining in importance are concerns of environmental pollution and sustainable development when selecting seawater desalination and power plant configurations, as well as their optimization when considering desalination and electricity generation as a whole. In the practical design of hybrid membrane and thermal systems, aspects come to light, though, that restrict linking of the two systems and joint utilization of facilities, as conceived in studies and conceptual design investigations. This applies both for common utilization of intakes and the use of heated up cooling water from thermal processes as a feed stream for the RO part of the desalination process. Additionally, requirements of drinking water composition, particularly chloride content, TDS and compliance with a specific residual content of boron, influence specifically the design of the membrane process part and its share in the total desalination capacity. Such practical aspects have greatly influenced the design and configuration of the Fujairah hybrid plant for which, from a total desalination capacity of 100 MIGD (454,600 m³/d), the share of 37.5 MIGD (170,500 m³/d) makes its seawater RO plant the biggest currently being constructed anywhere in the world. From the findings of the engineering of this plant and the idea that, by increasing interconnection between the two processes on the water side, it is possible to advance a hybrid configuration of this type with regard to cost optimization in the membrane installation, but also by joint utilization of the intake equipment, perspectives result for applied research efforts over the near and long terms, for example: long-term behavior of membranes at elevated temperatures; tendency for biofouling in membrane process with common utilization of cooling water and brine; influences of such interconnections on the overall availability of the facility. But also for the operation and maintenance organization of such large facilities, consequences can be foreseen for the future development of hybrid plants, particularly for operation management and organisation of the interplay of the different power plant and desalination systems, monitoring of SWRO membrane replacement and cleaning, as well as controlling water quality.     

海水淡化反渗透复合膜元件的制备

论述了海水淡化膜元件制作过程中，支撑底膜的孔结构、水相及有机相单体的种类、浓度，界面聚合的时间、热处理温度以及产业化生产过程中各个工艺条件的控制对海水淡化反渗透复合膜性能和均匀性的影响；介绍了膜元件卷制的工艺对元件性能的影响以及国产海水淡化反渗透复合膜元件在实际工程中的应用情况及与进口膜元件的性能对比。     

Removal of boron from seawater by selective ion exchange resins

Reverse osmosis (RO) desalination process is an efficient and reliable membrane technology for the production of drinking water from seawater. However, some serious limitations had recently been discovered during the field practice. Boron problem is one of them. According to the WHO regulations, the boron concentration should be lower than 0.5 mg/L in drinking water. It is still difficult to reduce boron level to 0.5 mg/L or lower with the conventional reverse osmosis desalination plants equipped with commercially available RO membranes. Therefore, more efficient separation technologies are needed for boron removal.In this study, the performance of the boron-selective ion exchange resins containing N-methyl glucamine groups, as Diaion CRB 02 and Dowex XUS 43594.00, have been tested for boron removal from model seawater. The kinetic performances of these resins were compared. The kinetic data obtained were evaluated using Lagergren pseudo-first-order and second-order models. Also, the process kinetics were predicted by using diffusion models. In addition, column-mode tests have been carried out for boron removal from model seawater.     

Evaluation of the suitability of groundwater quality for reverse osmosis desalination

In this study the suitability of brackish ground water quality for reverse osmosis (RO) desalination is evaluated. The results of initial laboratory and field analysis of 41 production wells were used to determine the hydrochemical properties of groundwater for both the Dammam limestone aquifer and the clastic Kuwait Group aquifer in the southwestern part of the State of Kuwait. The core samples of these wells were collected and analyzed in order to determine the hydrogeological properties of the same aquifers in the Umm Gudair area. Hydrochemical data of these aquifers were analyzed to help describe relations between hydrochemically distinct bodies of water and elucidate links between hydrochemical data and hydrogeological parameters. During this study, the Expanded Durov diagram was simplified and linked with the Sulin classification method in order to give more interpretation values. The results show that the aquifer materials influence the quality of ground water in each aquifer. The Kuwait Group aquifer water is characterized by ClMg and ClCa genetic water types with an average TDS of 4008 mg/l and belongs to the chloride water type. The Dammam limestone aquifer water characterized by the NaSO₄ and ClMg genetic type with an average TDS of 3480 mg/l belongs to the sulphate type. Both aquifers contain suitable water for RO desalination since they have a high concentration of chloride and monovalent ions, which reduces the requirements of antiscalant additives.     

Sustainable fuel cell integrated membrane desalination systems

According to the United Nations, between two and seven billion people will face water shortages by the year 2050. Further, it is estimated that the amount of water available per person will shrink by a third during the next two decades. Inadequate supply of good-quality water coupled with higher water demand due to rapid population growth and industrialisation in developing countries are among the major reasons for the worsening water situation. Current shortages of potable water around the world and looming water scarcity especially in the developing countries is the driving force behind the implementation of membrane technologies for seawater and brackish water desalination. Typical energy consumption in seawater reverse osmosis (RO) plants operating at 40–45% product water recovery and with energy recovery from the high pressure reject stream currently is about 3–4 kWh/m³. The near-term goal of the industry is to reduce energy consumption to less than 2 kWh/m³ by using a combination of energy efficient RO pumps, more efficient energy recovery devices, high performance low energy RO membranes, hybrid membrane systems, advanced pretreatment technologies and alternate energy integrated membrane systems. The beneficial aspects of using alternate energy systems such as on-site distributed fuel cell systems integrated with membrane desalination units in remote locations are discussed.     

Desalting of subsurface water using spiral-wound reverse osmosis (RO) system: technical and economic assessment

Subsurface water rise is a major problem in Kuwait. The impact of this problem is manifested in surface water ponds, cracks in buildings, flooded basements and damaged roads. Dewatering this water of moderate salinity is necessary. Being in an arid area with very limited water resources, treatment and recycling of the subsurface water could be very important to a country like Kuwait. For this purpose, a pilot study was carried out by KISR to desalinate the subsurface water using the reverse osmosis (RO) technique. The main aim of this study is to assess the viability and economic feasibility of using RO technology. This paper outlines the results of over 8000 operating hours performance data of an RO plant utilizing spiral-wound membranes (SW) used to desalinate subsurface water with TDS of about 11,000 mg/1 and an economic feasibility evaluation. Results indicate that the (SW) RO system is a viable technique to desalinate this type of water. The improvements in TDS, COD and BOD were 99%, 96% and 42%, respectively. The economic feasibility evaluation indicates that the unit cost of desalting subsurface water by RO is 0.235 KD/m³ (0.776 US$/m³), which is considered to be economically feasible for a small-scale plant.     

Tolerance of the rotifer Brachionus plicatilis to ozone and total oxidative residuals

Live prey items, such as the rotifer Brachionus plicatilis, are an essential component of many marine larval production systems. However, in intensive larval rearing systems live food items are also a potential source of pathogens which could adversely affect survival of the larvae. Consequently, it would be advantageous to reduce or eliminate potential pathogens associated with rotifers and their culture water prior to feeding. Ozone is a strong oxidizing agent which can be utilized as a disinfectant. Ozone is utilized extensively by commercial operators for disinfection and treatment of culture water, but there is limited data on tolerance of rotifers to ozone, residual oxidants associated with using ozone in seawater and the efficacy of an ozone wash. This study sought to evaluate the effects of exposing rotifers to ozone and/or residual oxidants associated with the use of ozone in seawater. Under the described conditions, the rotifer was found to be sensitive to ozonated seawater, both as total residual oxidants (TRO) consisting of ozone, chloramines and bromamines and residual oxidants (RO) excluding ozone. A “no observable effect concentration” (NOEC) of 0.22 mg/L TRO was determined for maximum survival of the rotifers. High levels of ozone (≥ 1.63 mg/L) were found to inactivate rotifer eggs. Based on published values of the inactivation of bacterial and viral pathogens, a NOEC of 0.22 mg/L TRO would appear to be sufficient to inactivate a variety of surficial potential pathogens. Consequently, the utilization of an ozone bath is suitable for the surficial disinfection of rotifers prior to feeding and hence may help reduce the vertical transmission of potential pathogens. Although RO did not appear as toxic as TRO, rotifers were sensitive to RO remaining in seawater after the dissipation of ozone. A NOEC of 0.3 mg/L for a 1 min exposure or 0.5 mg/L for a 5 or 10 min exposure time was observed for RO. Due to potential adverse effects of RO, it is recommended that RO be neutralized if ozone‐treated water is to be used to culture rotifers.