RO Process Research Articles

Optimization of energy efficiency through comparative analysis of factors affecting the operation with energy recovery devices on SWRO desalination process

Recently, interest in the development of alternative water resources has been increasing rapidly due to environmental pollution and depletion of water resources. In particular, seawater desalination has been attracting the most attention as alternative water resources. As seawater desalination consumes a large amount of energy due to high operating pressure, many researches have been conducted to improve energy efficiency such as energy recovery device (ERD). Consequently, this study aims to compare the energy efficiency of RO process according to ERD of isobaric type which is applied in scientific control pilot plant process of each 100 ㎥/day scale based on actual RO product water. As a result, it was confirmed that efficiency, mixing rate, and permeate conductivity were different depending on the size of the apparatus even though the same principle of the ERD was applied. It is believed that this is caused by the difference in cross-sectional area of the contacted portion for pressure transfer inside the ERD. Therefore, further study is needed to confirm the optimum conditions what is applicable to the actual process considering the correlation with other factors as well as the factors obtained from the previous experiments.

Significant energy savings by optimising membrane design in the multi-stage reverse osmosis wastewater treatment process

The total energy consumption of the multi stage spiral wound RO process has continuously improved as a result of discovering the proper design parameters for each module that can save more energy besides keeping high removal of chlorophenol.

Two-stage Anaerobic Membrane Bioreactor (AnMBR) system to reduce UV absorbance in landfill leachates

Landfill leachate typically contains UV-quenching organics, which hinder disinfection at POTWs. This study tested a 2-stage submerged AnMBR for the degradation of UV-absorbing compounds in landfill leachate. Leachate was treated in a thermophilic reactor (55 ± 2 °C) followed by a mesophilic AnMBR (37 ± 1 °C), with HRTs of 25 ± 5 days and 40 ± 5 days respectively. Solids were not wasted, in order to promote biomass accumulation. COD, Organic carbon, and UV254 absorbance were monitored over 13 months of operation. Known UV-quenching compounds, including humic acids, fulvic acids and hydrophilic matter, were reduced by 55%. Molecular weight distribution analyses revealed that the thermophilic reactor hydrolyzed organic carbon >100 KDa into smaller fractions, which were removed in the AnMBR. The system consistently removed 50% of the total UV absorbance. This promising, new enhanced biological process may provide landfills with a feasible pretreatment alternative to expensive chemical oxidation or RO processes before discharging leachate into sewers.

Energy optimization of a multistage reverse osmosis process for seawater desalination

The water recovery, net specific energy consumption (SECnet) and osmotic pressure differential (OPD) are determined for a multistage reverse osmosis (MSRO) process relative to conventional and the recently advanced energy-efficient RO (EERO) processes. The MSRO process combines RO and nanofiltration (NF) stages in series, and blends permeate from the NF stages with the saltwater feed. This increases the water recovery and lowers the rejections required in the RO stages. The SECnet of the MSRO process to produce water containing ≤350ppm salt is evaluated at the thermodynamic limit for pump and energy-recovery-device efficiencies of 85% and 90%, respectively, which provides a basis of comparison relative to alternative processes. The MSRO process employing one RO and two NF stages in series achieves a 65% water recovery for a 35,000ppm seawater feed producing a product water with ≤350ppm salt at an OPD of 51.7bar and SECnet of 2.688kWh/m3, reductions of 35% and 8%, respectively, relative to conventional SSRO. For the same conditions, the MSRO process employing two RO and two NF stages in series requires an OPD of 68.0bar and SECnet of 2.22kWh/m3, reductions of 14% and 1.6%, respectively, relative to two-stage SSRO.

Experimental study on seeded precipitation assisted reverse osmosis for industrial wastewater reuse

Industrial wastewater reuse and zero liquid discharge (ZLD) has been a growing trend due to increasing water scarcity and tightening environmental regulations. In China, ZLD is becoming mandatory for all coal chemical plants newly built in water scarcity areas. As a promising technology to achieve high water recovery and reduce operation cost, the seeded precipitation assisted RO process was proposed for coal chemical wastewater reuse and the initial feasibility was evaluated in this study. A 100l/h laboratory system comprising a RO unit and an ambient temperature crystallizer (ATC) was designed, fabricated and tested with real wastewater from a coal chemical plant. This paper presents the detailed design of the laboratory system and major testing results on the pretreatment, the membrane process as well as the seeded precipitation happening in the ATC. Overall the seeded precipitation assisted RO process was proved to be feasible and promising for coal chemical wastewater reuse and future onsite pilot study was also suggested.

A novel TFC forward osmosis (FO) membrane supported by polyimide (PI) microporous nanofiber membrane

A novel interfacial polymerization (IP) procedure on polyimide (PI) microporous nanofiber membrane support with mean pore size 1.27μm was reported. Using m-phenylenediamine (MPD) as aqueous phase monomer, trimesoyl chloride (TMC) as organic phase monomer, ethanol as aqueous phase co-solvent, thin-film composite (TFC) forward osmosis (FO) membrane was fabricated by two IP procedures. The first IP procedure with the unconventional order (ie, the membrane was immersed in the TMC organic phase first, then in the co-solvent ethanol-water MPD aqueous phase) was used to diminish the pore size of PI microporous nanofiber membrane support for the formation of the polyamide layer. The secondary IP procedure was employed to form the relatively dense polyamide layer with conventional order (ie, the membrane was immersed in the co-solvent ethanol-water MPD aqueous phase first, then in the TMC organic phase). The experimental results showed that higher ethanol concentration led to the relatively higher pure water permeability in RO process and osmotic water flux in FO process, whereas NaCl rejection in RO process decreased and reverse salt flux increased. The specific salt flux (Js/Jv) of TFC FO PI nanofiber membrane (PIN-2-4) could be as low as 0.095g/L in FO mode. These results could be attributed to influence of the addition of ethanol into aqueous phase on the surface morphology, hydrophilicity and polyamide layer structure.

Synthesis and characterization of polyamide membrane forthe separation of acetic acid from water using RO process

The main challenge in many applications of acetic acid is acid dehydration and its recovery from wastewater streams. Therefore, the performance of polyamide thin film composite is evaluated to separate acetic acid from water. To reach this goal, the formation of polyamide layer on polysulfone support membrane was investigated via interfacial polymerization (IP) of meta-phenylenediamine (MPD) in water with trimesoyl chloride (TMC) in hexane. Also, the effect of synthesis conditions, such as concentration of monomers and curing temperature on separation of acetic acid from water were investigated by reverse osmosis process. Moreover, the separation mechanism was discussed. The solute permeation was carried out under applied pressure of 5 bar at 25oC. Surface properties of TFC membrane were characterized by ATR-FTIR, SEM and AFM. The performance test indicated that 3.5 wt% of MPD, 0.35 wt% of TMC and curing temperature of 75oC are the optimum conditions. Moreover, the permeate flux was 4.3 L/(m^2 h) and acetic acid rejection was about 43% at these conditions.

Osmotically assisted reverse osmosis for high salinity brine treatment

This work evaluates a novel osmotically assisted reverse osmosis (OARO) process for dewatering high salinity brines using readily available membranes and equipment. While traditional reverse osmosis processes are limited to treating brines with osmotic pressures below the membrane burst pressure, in OARO, the osmotic pressure difference across a membrane is reduced with a permeate side saline sweep. A series of OARO stages can be used to sequentially reduce the concentration of the feed until a traditional RO process can obtain fully desalinated water. This paper develops an OARO model to identify feasible operating conditions for this process and to estimate the water recovery and energy consumption across a range of brine feed concentrations. For a feed of 100–140g/L sodium chloride, we estimate that the OARO process is capable of a 35–50% water recovery with an energy consumption of 6–19kWh per m3 of product water. The results suggest that an OARO dewatering process improves upon the recovery of reverse osmosis for high salinity brines and has a comparable or lower energy consumption than mechanical vapor compression.

Treatment of Simulated Oily Wastewater by Ultrafiltration and Nanofiltration Processes

A study in the treatment and reuse of oily wastewater generated from the process of fuel oil treatment of gas turbine power plant was performed. The feasibility of using hollow fiber ultrafiltration (UF) membrane and nanofiltration (NF) membrane type polyamide thin-film composite in a pilot plant was investigated. Three different variables: pressure (0.5, 1, 1.5 and 2 bars), oil content (10, 20, 30 and 40 ppm), and temperature (15, 20, 30 and 40 ᵒC) were employed in the UF process while TDS was kept constant at 150 ppm. Four different variables: pressure (2, 3, 4 and 5 bar), oil content (2.5, 5, 7.5 and 10 ppm), total dissolved solids (TDS) (100, 200,300 and 400 ppm), and temperature (15, 20, 30 and 40 ᵒC) were manipulated with the help of statistical method of Taguchi in the RO process. Analysis of variable (ANOVA) and optimum condition was investigated. The study shows that pressure has the greatest impact on the flux of UF process, while temperature and pressure have similar contribution on flux of NF process. The temperature seems to have the greatest effect on TDS rejection. It was noticed that more than 96% oil removal can be achieved with flux of 624 L/m2.hr by UF process and that the fouling mechanism of UF process follows the cake/gel layer filtration model. It was observed that 100% removal of oil content can be achieved along with 79% for the TDS rejection and flux of 65 L/m2.hr by NF process. The result shows fouling in NF process follows the cake filtration model. It was concluded that the observed values are within ±5% of that the predicted which reflects a strong representative model. The treated wastewater has the characteristics that it can be reused in the process to reduce the operating cost.

Carbonate scale reduction in reverse osmosis membrane by CO2 in wastewater reclamation

Reverse osmosis technology is being used on large scale for treatment of ground water, brackish water, wastewater and sea water. The most challenging issue in RO process is carbonate scaling which is directly linked with the efficiency and economy. Considering the natural phenomena of carbonate scaling different adaptations have been made to control scaling on the surface of RO membrane including acid dosage and antiscalant addition. As carbonate scaling is directly related with pH level of feed water, present study describes an experimental approach to reduce scaling on RO membrane by lowering the feed water pH by purging CO2. In this comparative study four different conditions including control process (without any scale inhibitor), with dosage of antiscalant, with purging of CO2 and with co addition of antiscalant and CO2 in a feed stream line; it was established that CO2 is a better appliance to reduce carbonate scaling on the membrane surface by reduce pH of feed stream. It was also observed that CO2 and antiscalant mutually function better for scale control.

Characterization of distillery wastewater – An approach to retrofit existing effluent treatment plant operation with phycoremediation

Raw distillery wastewater (RSW) has the characteristics such as pH 4.0–4.6; chemical oxygen demand 85,000–110,000 ppm; total dissolved solids 85,000–110,000 ppm and biological oxygen demand 25,000–35,000 ppm. Anaerobic digestion is the widely used treatment process in distillery to reduce the pollution load by 65–70%. Further, the pollution load is treated by RO process. The operation of RO process becomes difficult due to high influent load. This research work suggests the positioning of an additional biotreatment step, called phycoremediation to retrofit into the existing effluent treatment plant (ETP). The wastewater from the nearby distillery is collected at the various treatment stages of ETP such as before and after anaerobic digestion, settling lagoons and RO process. The physico-chemical, thermal and spectroscopic characteristics of wastewater are studied and the analysis is made based on the stage-wise characterization. It is inferred from the analysis that the phycoremediation step needs to be retrofitted into the existing ETP after anaerobic digestion. Anaerobically digested distillery wastewater treatment with Oscillatoria sp. resulted further reduction in chemical oxygen demand up to 55%, which reduce the influent load to the reverse osmosis plant.

Economic analysis on environmentally sound brine disposal with RO and RO-hybrid processes

Economic analysis on environmentally sound brine disposal with RO and RO-hybrid processes

Geothermal water treatment. Membrane selection for the RO process

Geothermal water treatment. Membrane selection for the RO process

Application of multiple modified fouling index (MFI) measurements at full-scale SWRO plant

Recently, a modified fouling index (MFI) is published on ASTM, and thus, is expected to become a standard method for evaluating fouling potential, as a supplement to silt density index (SDI). Employing membranes with smaller pore size in MFI measurements has been continuously suggested in many previous studies. However, there was a lack of practical studies verifying the usefulness of MFI. In this study, the applicability of multiple MFIs (i.e., MFI0.45, MFI-UF100kDa and MFI-UF10kDa) were evaluated at a full-scale UF/RO seawater desalination plant located in the Middle East. For a year, MFIs were measured with RO feed water and the results were correlated with increments in differential pressure (DP) of RO process. Regression analysis was conducted in order to find out whether the fouling index could predict RO performance deterioration. The observed MFIs clearly showed correlation with DP variation, while SDI and water quality parameters (e.g. turbidity and UV254) exhibited relatively low accordance. Particularly, MFI-UF100kDa was the most sensitive, indicating that colloidal fouling is the main cause of fouling in SWRO desalination. The regression results were reconfirmed through specific events where feed water quality was severely changed due to red tide or ship movement at intake. These events provided unconventional feed water characteristics, but similar trend was observed that MFI-UF100kDa was most sensitive. The application of MFI in an actual plant provided valuable contribution for the further advancement of MFI measurements.

A study on optimal schedule of membrane cleaning and replacement for spiral-wound SWRO system

In this work, the optimal schedule of membrane cleaning and replacement of spiral-wound SWRO (seawater reverse osmosis) system was studied and analyzed under different feed conditions. Firstly, the spiral-wound RO process model described by differential and algebraic equations was established with the consideration of membrane fouling. Then the optimization problem was formulated to minimize the daily cost of the SWRO system, and a new method by which the optimization problem was transformed as an NLP problem was proposed to solve the problem effectively and quickly. The method was used for SWRO case study and was compared with the traditional method in the form of MINLP. Computing results demonstrate that the proposed method has the advantages of efficiency and stability. Moreover, it can get schedule of membrane cleaning and replacement with lower operational cost as well as give more detailed information of membrane channel. Lastly, influence of feed temperature and feed concentration of seawater was analyzed with the new method. Computing results show the stability of the new method and lead to new profiles of optimal operational variables and performance when feed temperature and salt concentration change, which are quite different from those in designed conditions.

Electrochemical Pretreatment as a Suggested Alternative, More Compatible with Environment and Sustainable Development in RO Desalination System

RO processes have more promising future perspectives. Nevertheless, there are some constraints that require certain efforts to be spent on research and development. First of all, pretreatment step must be optimized for minimum environmental impact by eliminating chemicals additives as can as possible. This review study focuses on RO technology and introduces electrocoagulation as a suggested alternative which can play an important role for many tasks in a manner more compatible with environmental and sustainable development, depending on clean and economic energy.

Zero Waste Membrane Technology for Whey Processing

Objectives: The study is currently significant insofar as it considers reprocessing of secondary resources represented by milk whey generated in bulk in the course of curd and cheese production. Methods: Zero waste method of whey reprocessing has been experimentally justified employing two stages of baromembrane technology: ultrafiltration at the first stage to recover macromolecular components followed by reverse osmosis concentration of lactose applying modern domestically produced membranes. Findings: The materials and methods for investigating the processes of ultrafiltration and reverse osmosis concentration of whey have been described. Proprietary solution has been suggested for whey ultrafiltration without its preliminary treatment using ceramic membranes of CUFE Type (ceramic ultrafiltration elements) (0.01). Optimum operating parameters for the processes of ultrafiltration and reverse osmosis concentration of whey have been experimentally established and verified in the workshop environment. A technological process for zero waste whey processing has been developed. The results of the experimental investigations have been discussed and the relevant conclusions have been made. Applications/Improvements: CUFE (0.01) ceramic membrane can be recommended as the most preferable technical solution for separating whey without any preliminary treatment during UF process. Recommendations are given for RO process conditions.

Scalants removal from synthetic RO brine using natural zeolite

Membrane distillation (MD) is the thermally driven water separation process based on the vapor pressure difference across the membrane. In order to increase the water recovery of the conventional RO process, the additional MD-PRO pocess was suggested. In this study, the syntheric RO brine was used as a feed solution of the MD process. Due to the high salinity of the RO brine, the MD membrane could be fouled by the scalants. In order to mitigate the scaling on the MD membrane surface, the pre-treatment process using the column filled by natural zeolite was applied. The roughing filter was installed between the pre-treatment process and MD system in order to prevent possible particulate fouling by the debries of the natural zeolite. Moreover, in order to enhance the CEC of the natural zeolite, the NaCl soaking was conducted. The flux and electronic conductivity were monitored under given experimental conditions. And the membrane morphology and the chemical compositions were analyzed by using the SEM-EDX.

Recent developments in forward osmosis membrane bioreactors: a comprehensive review

Forward osmosis or osmotic membrane bioreactor (FOMBR) has attracted great attention for wastewater treatment and reuse since conceptually introduced as a process. It has been proposed to reduce the high energy consumption in the conventional MBR, has lower membrane fouling propensity, and produce higher quality water. Moreover, RO process can be used after FOMBR to reconcentrate the diluted DS to be used for FO again. Besides significant advantages, when compared to conventional MBRs; lower water flux, concentration polarization, and salt accumulation because of high retention of FO in the bioreactor still remains as major drawbacks and challenges of FOMBR systems that need to be solved. In the last few years, many advances in development of FOMBR are stated to overcome the drawbacks of the system. The researches focused on manufacturing of high performance FO membranes and orientation, utilizing various different draw solutions providing required osmotic pressure and minimum reverse salt flux, and recently hybrid systems to alleviate the salt accumulation in bioreactor. However, the main critical challenges of FOMBR have not been completely resolved yet. This paper reviews the design and applications of FOMBR process in wastewater treatment. Particular focus was given to reverse salt flux and effects of the system performance; recent developments in FOMBR applications from beginning till today are reported.

MO‐AB‐204‐03: Profile Development and IHE Process

You've experienced the frustration: vendor A's device claims to work with vendor B's device, but the practice doesn't match the promise. Getting devices working together is the hidden art that Radiology and Radiation Oncology staff have to master. To assist with that difficult process, the Integrating the Healthcare Enterprise (IHE) effort was established in 1998, with the coordination of the Radiological Society of North America.Integrating the Healthcare Enterprise (IHE) is a consortium of healthcare professionals and industry partners focused on improving the way computer systems interconnect and exchange information. This is done by coordinating the use of published standards like DICOM and HL7. Several clinical and operational IHE domains exist in the healthcare arena, including Radiology and Radiation Oncology. The ASTRO‐sponsored IHE Radiation Oncology (IHE‐RO) domain focuses on radiation oncology specific information exchange. This session will explore the IHE Radiology and IHE RO process for; IHE solicitation process for new profiles. Improving the way computer systems interconnect and exchange information in the healthcare enterprise Supporting interconnectivity descriptions and proof of adherence by vendors Testing and assuring the vendor solutions to connectivity problems. Including IHE profiles in RFPs for future software and hardware purchases. Learning Objectives: Understand IHE role in improving interoperability in health care. Understand process of profile development and implantation. Understand how vendors prove adherence to IHE RO profiles.S. Hadley, ASTRO Supported Activity