Reverse Osmosis Literature Review

Search Terms[edit | edit source]

Google Scholar[edit | edit source]

"reverse osmosis" membrane
reverse osmosis "drinking water" international
reverse osmosis "international development" OR "developing countries"
drinking water treatment "reverse osmosis"

Reverse Osmosis[edit | edit source]

From Wikipedia: "Reverse osmosis (RO) is a water purification process that uses a partially permeable membrane to separate ions, unwanted molecules and larger particles from drinking water. In reverse osmosis, an applied pressure is used to overcome osmotic pressure, a colligative property that is driven by chemical potential differences of the solvent, a thermodynamic parameter."

Importance of Reverse Osmosis[edit | edit source]

RO is used to purify water by extracting particles of up to 0.0001 microns, the most powerful system for membrane purification. Completely removes dissolved salts in addition to everything said above. Using membrane technology can have many benefits such as:

Allows to remove most of the solids (inorganic or organic) dissolved in the water (up to 99%).
Removes suspended materials and microorganisms.
Performs the purification process in a single stage and continuously.
It is an extremely simple technology that does not require much maintenance and can be operated by non-specialized personnel.
The process is carried out without phase change, with the consequent energy saving.
It is modular and requires little space, which gives it exceptional versatility in terms of plant size: from 1 m3/day to 1,000,000 m3/day.
Treatment of municipal and industrial effluents for pollution control and/or recovery of valuable reusable compounds.

Literature[edit | edit source]

A Review on Reverse Osmosis and Nanofiltration Membranes for Water Purification[edit | edit source]

Yang, Zi, Yi Zhou, Zhiyuan Feng, Xiaobo Rui, Tong Zhang, and Zhien Zhang. 2019. "A Review on Reverse Osmosis and Nanofiltration Membranes for Water Purification" Polymers 11, no. 8: 1252. https://doi.org/10.3390/polym11081252

Abstract: "Sustainable and affordable supply of clean, safe, and adequate water is one of the most challenging issues facing the world. Membrane separation technology is one of the most cost-effective and widely applied technologies for water purification. Polymeric membranes such as cellulose-based (CA) membranes and thin-film composite (TFC) membranes have dominated the industry since 1980. Although further development of polymeric membranes for better performance is laborious, the research findings and sustained progress in inorganic membrane development have grown fast and solve some remaining problems. In addition to conventional ceramic metal oxide membranes, membranes prepared by graphene oxide (GO), carbon nanotubes (CNTs), and mixed matrix materials (MMMs) have attracted enormous attention due to their desirable properties such as tunable pore structure, excellent chemical, mechanical, and thermal tolerance, good salt rejection and/or high water permeability. This review provides insight into synthesis approaches and structural properties of recent reverse osmosis (RO) and nanofiltration (NF) membranes which are used to retain dissolved species such as heavy metals, electrolytes, and inorganic salts in various aqueous solutions. A specific focus has been placed on introducing and comparing water purification performance of different classes of polymeric and ceramic membranes in related water treatment industries. Furthermore, the development challenges and research opportunities of organic and inorganic membranes are discussed and the further perspectives are analyzed."

Comparison of different membranes in the improvement of water purification performance:
- Usage of inorganic and ceramic membranes
- Nanotechnology development for nanofiltration process
Desirable properties of developed membranes:
- Tunable pore structure
- Excellent mechanical and thermal tolerance
Challenges in the future for the application of RO technology

Nanoparticles in reverse osmosis membranes for desalination: A state of the art review[edit | edit source]

Haleema Saleem, Syed Javaid Zaidi,Nanoparticles in reverse osmosis membranes for desalination: A state of the art review,Desalination,Volume 475,2020,114171,ISSN 0011-9164, https://doi.org/10.1016/j.desal.2019.114171.

Abstract: The development of thin-film nanocomposite (TFNC) membranes utilizing nanoparticles present remarkable opportunity in the desalination industry. This review offers a comprehensive and in-depth analysis of TFNC membranes for reverse osmosis (RO) desalination by focusing on different issues existing in the RO process. Recent researches on nanoparticle incorporated TFNC membranes for application in water purification have been critically analyzed. The widely tested nanoparticles in these researches include carbon-based (carbon nanotube, graphene-oxide), metal and metal oxides-based (silver, copper, titanium dioxide, zinc oxide, alumina and metal-organic frameworks), and other nano-sized fillers like silica, halloysite, zeolite and cellulose-nanocrystals based. These nanoparticles demonstrated pronounced effect in terms of water flux, salt rejection, chlorine resistance, and anti-fouling properties of TFNC membranes relative to the typical thin-film composite (TFC) membranes. Here, we also focus on the environmental impact, commercialization, and future scope of TFNC membranes. From the current review, it is evident that the nanomaterials possess exclusive properties, which can contribute to the advancement of high-tech nanocomposite membranes with improved capabilities for desalination. Despite all the developments, there still exist significant difficulties in the large-scale production of these membranes. Hence, additional studies in this field are required to produce TFNC membrane with increased performance for commercial application.

Review of recently developed TFNC RO membranes for desalination Improvement in the properties of TFNC membrane due to beneficial effect of nanoparticle Challenges associated with TFNC membranes and methods to overcome these Environmental impact of nanomaterials and their TFNC membranes Future prospects for advancement of TFNC membranes and their commercialization

Desalination Technologies for Developing Countries: A Review[edit | edit source]

Islam, M. S., Sultana, A., Saadat, A. H. M., Islam, M. S., Shammi, M., & Uddin, M. K. (2018). Desalination Technologies for Developing Countries: A Review. Journal of Scientific Research, 10(1), 77–97. https://doi.org/10.3329/jsr.v10i1.33179

Abstract: Fresh water is rapidly being exhausted due to natural and anthropogenic activities. The more and more interest is being paid to desalination of seawater and brackish water in order to provide fresh water. The suitability of these desalination technologies is based on several criteria including the level of feed water quality, source of energy, removal efficiency, energy requirement etc. In this paper, we presented a review of different desalination methods, a comparative study between different desalination methods, with emphasis on technologies and economics. The real problem in these technologies is the optimum economic design and evaluation of the combined plants in order to be economically viable for the developing countries. Distillation plants normally have higher energy requirements and unit capital cost than membrane plants and produces huge waste heat. Corrosion, scaling and fouling problems are more serious in thermal processes compare to the membrane processes. On the other hand, membrane processes required pretreatment of the feed water in order to remove particulates so that the membranes last longer. With the continuing advancement to reduce the total energy consumption and lower the cost of water production, membrane processes are becoming the technology of choice for desalination in developing countries.

Comparison of different desalination technologies.
Low energy requirements and brackish water treatment are most common in developing countries.
Unit capital cost and damage caused by corrosion or fouling are unusual in RO process.
Pre-treatment of intake water is required in RO.

Sustainable seawater reverse osmosis (SWRO) system design for rural areas of developing countries[edit | edit source]

van Asselt, J., & de Vos, I. W. (2021). Sustainable seawater reverse osmosis (SWRO) system design for rural areas of developing countries.

Solar-powered system, Kuwait
Drinking water system: intake, pre-., reverse osmosis, post-treatment (options within each stage)
- Physical membrane types pros and cons: plate/frame, tubular, spiral, hollow
- Pretreatment types pros and cons: sand, cartridge, micro, ultra, nano (lists pore sizes)
Debated: Open seawater vs. subsurface seawater intake

Engineering antifouling reverse osmosis membranes: a review[edit | edit source]

Zhao, S., Liao, Z., Fane, A., Li, J., Tang, C., Zheng, C., Lin, J., & Kong, L. (2021). Engineering antifouling reverse osmosis membranes: A review. Desalination, 499, 114857. https://doi.org/10.1016/j.desal.2020.114857

Abstract: "Over the past decades, water scarcity and security have significantly stimulated the advances of reverse osmosis (RO) technology, which dominates the global desalination market. However, deterioration of membrane separation performance caused by inevitable fouling, including organic fouling, inorganic fouling, colloidal fouling and biofouling, calls for improved RO membranes with more durable antifouling properties. In this review, we analyze the correlations between membrane properties (e.g. surface chemistry, morphology, hydrophilicity, and charge) to antifouling performance. We evaluate the three key strategies for engineering fouling resistant thin film composite RO membranes, namely: (1) substrate modification before interfacial polymerization, (2) incorporating (hydrophilic/biocidal/antifouling) additives into the selective layer during interfacial polymerization, and (3) post (surface) modification after interfacial polymerization. Finally, we offer some insights and future outlooks on the strategies for engineering next generation of high performance RO membranes with durable fouling resistance. This review provides a comprehensive, state-of-the-art assessment of the previous efforts and strategies as well as future research directions for engineering antifouling RO membranes."

Different membranes pros and cons
Membranes get fouled: organic, inorganic, bio (most problematic), and colloidal
Factors for reverse osmosis fouling: feed water, operating conditions, and membrane properties
- Improve by being hydrophilic, neg. charge, smooth

Reverse osmosis technology for water treatment: State of the art review[edit | edit source]

Lilian Malaeb, George M. Ayoub, Reverse osmosis technology for water treatment: State of the art review, Desalination,Volume 267, Issue 1,2011,Pages 1-8,ISSN0011-9164,https://doi.org/10.1016/j.desal.2010.09.001

Abstract: This paper presents a review of recent advances in reverse osmosis technology as related to the major issues of concern in this rapidly growing desalination method. These issues include membrane fouling studies and control techniques, membrane characterization methods as well as applications to different water types and constituents present in the feed water. A summary of the major advances in RO performance and mechanism modeling is also presented and available transport models are introduced. Moreover, the two important issues of RO brine discharge and energy costs and recovery methods are discussed. Finally, future research trends and needs relevant to RO are highlighted.

Research areas include brine discharge, fouling and removal of specific compounds.
Modeling is important for better membrane characterization and for plant reliability.
Existing cost assessment methodologies are not sufficiently accurate.
Developing less energy-intensive systems is a main concern.
Using new membrane materials is also a subject of future research.

Reverse osmosis membrane fabrication and modification technologies and future trends: a review[edit | edit source]

Hailemariam, R. H., Woo, Y. C., Damtie, M. M., Kim, B. C., Park, K.-D., & Choi, J.-S. (2020). Reverse osmosis membrane fabrication and modification technologies and future trends: A review. Advances in Colloid and Interface Science, 276, 102100. https://doi.org/10.1016/j.cis.2019.102100

Abstract: "Reverse osmosis (RO) is the most widely used technology in water treatment and desalination technologies for potable water production. Since its invention, RO has undergone significant developments in terms of material science, process, system optimization, methods of membrane synthesis, and modifications. Among various materials used for the synthesis of an RO membrane, the polyamide thin-film composite (PA-TFC) is by far the most common, owing to its excellent water permeability high salt rejection, and stability. However, a tradeoff between membrane permeability and salt rejection and membrane fouling has been a major hindrance for the effective application of this membrane. Thus, a broad investigation has been carried out to address these problems, and among which co-solvent interfacial polymerization (CAIP) and the surface modification of substrates and active layers of RO membrane have been the most effective approaches for controlling and improving the surface properties of the PA-TFC membrane. In this review paper, the problems associated with the RO membrane processes and strategies has been discussed and addressed in detail. Furthermore, as the focus of this review, the major advancements in the strategies used for enhancement of RO membrane performance through CAIP, and surface modifications were scrutinized and summarized."

Reverse osmosis steps
Four steps in reverse osmosis plant: pre-treat for compatibility, pumping/pressure (overcome osmotic pressure), membrane separation, and post-treat
Issues of reverse osmosis (+their solutions): membrane deterioration via fouling (smooth membrane, small neg. charge, high hydrophilicity), permeability/salt rejection, chlorination, boron extraction (run multiple times w/ pH balance), brine waste

The challenges of reverse osmosis desalination: solutions in Jordan[edit | edit source]

Maureen Walschot, Patricia Luis & Michel Liégeois (2020) The challenges of reverse osmosis desalination: solutions in Jordan, Water International, 45:2, 112-124, DOI: 10.1080/02508060.2020.1721191

Abstract: Desalinating water through reverse osmosis is becoming more economically affordable. Identifying the challenges in adopting desalination technology may help countries address water security concerns. In this article, we examine these challenges and present some of the solutions implemented in the Kingdom of Jordan, such as the creation of a cooperative water project to reduce financial investment and transportation costs and the coupling of renewable energy to desalination technology. Reverse osmosis desalination can play a role in promoting regional cooperation.

Financial challenges:
- Type of feed water (seawater or brackish)
- Energy source depending of the local availability and the cost of an energy source
- Plant size (most high and medium-income countries can afford large-scale desalination technology)
Environmental challenges and political concerns:
- Brine disposal to water bodies as the sea or open spaces
- CO2 emissions of, at least, 20%
- Energy consumption for its operation

Reverse Osmosis Water Purification by Cycling Action[edit | edit source]

Ravi V.K., Sushmitha V., Kumar M.V.P.., and Thomas A. (2017). Reverse Osmosis Water Purification by Cycling Action.International Journal of Latest Engineering Research and Applications, 2(5), 54-59.

Abstract: "Pure water is very much essential to survive, but now a days the water is getting contaminated due to Industrialisation which leads to many water-releated diseases. Reverse Osmosis(RO) Water Purification by Cycling Action meets the needs of people without requiring any electrical energy. RO is a physical process that uses the osmosis phenomenon, that is, the osmotic pressure difference between the salt water and the pure water to remove the salts from water. Water will pass through the membrane, when the applied pressure is higher than the osmotic pressure, while salt is retained. As a result, a low salt concentration permeate stream is obtained and a concentrated brine remains at the feed side. A typical RO system consists of four major subsystem: pre-treatment system, high-pressure pump, membrane module and post treatment system. In operation by pedaling the cycle, man power is converted into mechanical energy which is further converted into hydraulic energy in RO pump."

Human powered (electricity free) reverse osmosis
Five stages: heavy sediment removal, finer filters for sediment, taste/colour/odour, 0.0001 micron removal, and taste/colour/odour again
- "4 Stage = Sediment + Pre-Carbon + RO Membrane + Post-Carbon"
Lists advantages (compact, portable) and disadvantages (slow, requires lots of water)
- Collect water, cycle, and clean when home

Field evaluation of a community scale solar powered water purification technology: A case study of a remote Mexican community application[edit | edit source]

Elasaad, H., Bilton, A., Kelley, L., Duayhe, O., & Dubowsky, S. (2015). Field evaluation of a community scale solar powered water purification technology: A case study of a remote Mexican community application. Desalination, 375, 71–80. https://doi.org/10.1016/j.desal.2015.08.001

Abstract: "Lack of clean water in small remote communities in the developing world is a major health problem. Water purification and desalination systems powered by solar energy, such as photovoltaic powered reverse osmosis systems (PVRO), are potential solutions to the clean water problems in these small communities. PVRO systems have been proposed for various locations. However, small PVRO systems with production on the order of 1 m3/day for remote communities present some unique technical, cost and operational problems. This paper reports on a project in which a PVRO system is designed, fabricated and deployed in remote village in the Yucatan Peninsula of Mexico. The community residents are indigenous people who are subsistence farmers and beekeepers. Technical and economic models used to configure the system for the community are presented. A plan is developed in cooperation with the community aimed at making the system self-sustaining in the long term. Methods and materials are developed to permit the community members to operate and maintain the system themselves. The results provide insights for the design and deployment of small community-scale PVRO systems in remote communities."

Photovoltaic reverse osmosis system for drinking water
Issues with system: cost of shipping parts, language differences for training, hands-on training needed, water source quality
Physical parts in reverse osmosis system (solar panel, membrane, filters, pump, testing, electronics, batteries, UV lamps) and diagram of process shown
Cost: $10,000 USD to start and $1,342 USD annually

Purification of Contaminated Water with Reverse Osmosis: Effective Solution of Providing Clean Water for Human Needs in Developing Countries[edit | edit source]

Wimalawansa, S. J. (2013). Purification of Contaminated Water with Reverse Osmosis: Effective Solution of Providing Clean Water for Human Needs in Developing Countries. International Journal of Emerging Technology and Advanced Engineering, 3(12).

Abstract: "Approximately 25% of the world's population has no access to clean and safe drinking water. Even though freshwater is available in most parts of the world, many of these water sources contaminated by natural means or through human activity. In addition to human consumption, industries need clean water for product development and machinery operation. With the population boom and industry expansion, the demand for potable water is ever increasing, and freshwater supplies are being contaminated and scarce. In addition to human migrations, water contamination in modern farming societies is predominantly attributable to anthropogenic causes, such as the overutilization of subsidized agrochemicals―artificial chemical fertilizers, pesticides, fungicides, and herbicides. The use of such artificial chemicals continue to contaminate many of the precious water resources worldwide. In addition, other areas where the groundwater contaminated with fluorides, arsenic, and radioactive material occur naturally in the soil. Although the human body is able to detoxify and excrete toxic chemicals, once the inherent natural capacity exceeded, the liver or kidneys, or both organs may fail. Following continual consumption of polluted water, when the conditions are unfavourable and the body's thresholds are exceeded, depending on the type of pollutants and toxin, liver, cardiac, brain, or renal failure may occur. Thus, clean and safe water provided at an affordable price is not only increasingly recognized, but also a human right and exceedingly important. Most of the household filters and methods used for water purification remove only the particulate matter. The traditional methods, including domestic water filters and even some of the newer methods such as ultra-filtration, do not remove most of the heavy metals or toxic chemicals from water than can harm humans. The latter is achieved with the use of reverse osmosis technology and ion exchange methods. Properly designed reverse osmosis methods remove more than 95% of all potential toxic contaminants in a one-step process. This review explains the reverse osmosis method in simple terms and summarizes the usefulness of this technology in specific situations in developing countries."

Spiral-wound membrane shape + nanometer pore size for reverse osmosis
Why RO > other filtering methods
Physical parts in reverse osmosis system and process (including different options for each step)
% recovery depends: water temp, pore size, inconsistent/consistent pressure, membrane area
- Lowered contaminant removal via fouling (backwashing helps).

DIY[edit | edit source]

DIY Maple Sap Reverse Osmosis (RO) Unit[edit | edit source]

rsook74. DIY Maple Sap Reverse Osmosis (RO) Unit. Instructables. https://www.instructables.com/DIY-Maple-Sap-Reverse-Osmosis-RO-Unit/

Physical parts needed

DIY Reverse Osmosis For Home Drinking Water by Isopure Water[edit | edit source]

Isopure Water. DIY Reverse Osmosis System for Home Drinking Water by Isopure Water. (2020, December 12). Isopure Water. https://www.isopurewater.com/blogs/news/diy-reverse-osmosis-system

Cost: max $150 for parts + annual filters
Physical parts needed

Build Your Own Reverse Osmosis System for Maple Syrup[edit | edit source]

Michelle. (2019, January 8). Build your own Reverse Osmosis system for maple syrup. Souly Rested.https://soulyrested.com/2019/01/08/build-your-own-reverse-osmosis-system-for-maple-syrup/

Cost: roughly $300-$350
Physical parts needed

How to Make an RO Water Filter at Home[edit | edit source]

Derek. (2017, June 20). How to Make a Reverse Osmosis Water Filter at Home. best-ro-system.com. https://www.best-ro-system.com/make-your-own-water-filter/

Physical parts needed

Development and Filtration Performance of Polylactic Acid Meltblowns[edit | edit source]

Liu, Y., Cheng, B. and Cheng, G., 2010. Development and filtration performance of polylactic acid meltblowns. Textile research journal, 80(9), pp.771-779. https://doi.org/10.1177/0040517509348332

Polylactic acid (PLA) is a biodegradable material that can be used to make meltblowns (MBs, which are fabrics made by the meltblowing method) using direct melt spun. PLA MBs were successfully produced in a 20 cm laboratory meltblown line. The relationships between the processing parameters and the filtration performance of PLA MBs were explored in this study. The key parameters regarding the filtration performance of PLA MBs, including the PLA chip drying process, the melt temperature, the hot air temperature, and the width of the air gap, were thoroughly investigated using scanning electronic microscopy, filtration efficiency, and breathability tests. It was found that the processing parameters were significant to the structure, thus the filtration performance of PLA MBs. PLA turned out to be a favorable material for meltblowing. The preferred spinning temperature was 220°C for optimal web quality. The diameter of PLA MB fibers became larger with the increase of hot air temperature. With the increase of air gap width, the diameter of PLA MB fibers went up, whereas the crimp level went down. This information may be useful for the future development of a commercialized production line of PLA MBs.

basic schematics of MB system and spinning die; could base on recyclebot and winding system

Fabricating RO Membranes[edit | edit source]

The production is divided into the following process stages:

Mechanical conditioning of the pulp: The pulp is fibrillated by different types of crushers, such as hammer mills and disc refiners, where the successive arrangement of both types of crushers ensures optimal dissolution.
Chemical pretreatment: The fibrillated cellulose is treated with acetic acid with moderate agitation at 25°C to 50°C for approximately 1 h, resulting in continuous evaporation and condensation of the acetic acid in the spaces between the fiber particles. In addition to this acetic acid steam pretreatment, there is also a fine pulp state pretreatment. In this process, the cellulose is introduced in large quantities of water or diluted acetic acid and is vigorously stirred. Subsequent process steps, such as pressing or centrifugation, constantly increase the concentration of cellulose in the pulp.
Cellulose Acetylation: In the commercial production of cellulose acetates, the acetic acid process or the methylene chloride process is often used for acetylation. In acetic acid processes, the pretreated cellulose mass is reacted in an acetylation mixture of acetic acid solvent with excess acetic anhydride, which serves as esterification agent, and with sulfuric acid as catalyst under vigorous mechanical mixing. In the methylene chloride process, methylene chloride is used in the acetylation mixture as a solvent instead of acetic acid. Since low boiling methylene chloride can be easily removed by distillation, process control is achieved even with highly viscous solutions. Even at low temperatures, it can dissolve cellulose triacetate very well. A small amount of sulfuric acid can be used as a catalyst, but often perchloric acid as well.
Partial Hydrolysis: To obtain the desired secondary cellulose acetate types, cellulose triacetate is obtained by hydrolysis. For this purpose, the triacetate solution is typically heated to 60-80°C in the presence of an acid catalyst (usually sulfuric acid) by adding water while stirring and heating. Hydrolysis is controlled by the concentration of sulfuric acid, the amount of water and the temperature in such a way that the desired molecular degradation is achieved. The hydrolysis process is then stopped by adding basic salts that neutralize the acid catalyst.
Cellulose acetate precipitation: When precipitating cellulose acetate from the reaction solution using dilute acetic acid, it is important to obtain uniform and easily washable cellulose acetate flakes. Before precipitation, any methylene chloride present must be completely removed by distillation. Acetic acid is then recovered.
Washing and drying: By means of intensive washing, which is usually carried out against the current, the acetic acid must be removed from the flakes down to the smallest traces, otherwise damage ("charring") will occur during the drying process. After pressing the washing liquid, the flakes are dried in a conveyor dryer through which hot air flows to a residual moisture content of approx. 2-5%. For the further production of very high-quality, thermally stable, brightly colored and color-stable thermoplastic molding compounds, the cellulose acetate flakes are also bleached and stabilized in additional process steps before final drying.
Flake Mixing: Before transporting the cellulose acetate flakes to a collection container from where they are transported to the appropriate processing plants, the flakes are mixed in a precisely controlled manner. This is to compensate for deviations of the cellulose acetates from different production batches.^[1]

Fundamentals of Membranes for Water Treatment[edit | edit source]

Sagle, A. and Freeman, B., 2004. Fundamentals of membranes for water treatment. The future of desalination in Texas, 2(363), p.137. https://texaswater.tamu.edu/readings/desal/membranetechnology.pdf

Good intro to the tech
Commercial cellulose acetate (CA) membranes used for reverse osmosis have a degree of acetylation of about 2.7

Tubular Membranes[edit | edit source]

Daicen Membrane-Systems Ltd. (n.d.). Tubular Type Module. Tubular type module. Retrieved September 22, 2021, from https://daicen.com/en/products/membrane/chube.html.

Treats human waste
Specs for membrane (# of tubes, inner diameter, area)

PCI Membranes Filtration Group. (2021, August 25). C10 Series Tubular Membrane Modules. PCI Membranes. https://www.pcimembranes.com/products/c10-series-tubular-membrane-modules/

Data Sheet: Components of a tubular membrane (ex. O Ring)

A review of polymeric membranes and processes for potable water reuse[edit | edit source]

David M. Warsinger, Sudip Chakraborty, Emily W. Tow, Megan H. Plumlee, Christopher Bellona, Savvina Loutatidou, Leila Karimi, Anne M. Mikelonis, Andrea Achilli, Abbas Ghassemi, Lokesh P. Padhye, Shane A. Snyder, Stefano Curcio, Chad D. Vecitis, Hassan A. Arafat, John H. Lienhard. (2018). A review of polymeric membranes and processes for potable water reuse, Progress in Polymer Science, Volume 81, Pages 209-237, SSN 0079-6700. https://doi.org/10.1016/j.progpolymsci.2018.01.004.

Abstract: Conventional water resources in many regions are insufficient to meet the water needs of growing populations, thus reuse is gaining acceptance as a method of water supply augmentation. Recent advancements in membrane technology have allowed for the reclamation of municipal wastewater for the production of drinking water, i.e., potable reuse. Although public perception can be a challenge, potable reuse is often the least energy-intensive method of providing additional drinking water to water stressed regions. A variety of membranes have been developed that can remove water contaminants ranging from particles and pathogens to dissolved organic compounds and salts. Typically, potable reuse treatment plants use polymeric membranes for microfiltration or ultrafiltration in conjunction with reverse osmosis and, in some cases, nanofiltration. Membrane properties, including pore size, wettability, surface charge, roughness, thermal resistance, chemical stability, permeability, thickness and mechanical strength, vary between membranes and applications. Advancements in membrane technology including new membrane materials, coatings, and manufacturing methods, as well as emerging membrane processes such as membrane bioreactors, electrodialysis, and forward osmosis have been developed to improve selectivity, energy consumption, fouling resistance, and/or capital cost. The purpose of this review is to provide a comprehensive summary of the role of polymeric membranes and process components in the treatment of wastewater to potable water quality and to highlight recent advancements and needs in separation processes. Beyond membranes themselves, this review covers the background and history of potable reuse, and commonly used potable reuse process chains, pretreatment steps, and advanced oxidation processes. Key trends in membrane technology include novel configurations, materials, and fouling prevention techniques. Challenges still facing membrane-based potable reuse applications, including chemical and biological contaminant removal, membrane fouling, and public perception, are highlighted as areas in need of further research and development.

Pre-filters[edit | edit source]

A critical overview of household slow sand filters for water treatment[edit | edit source]

B.L.S. Freitas, U.C. Terin, N.M.N. Fava, P.M.F. Maciel, L.A.T. Garcia, R.C. Medeiros, M. Oliveira, P. Fernandez-Ibañez, J.A. Byrne, L.P. Sabogal-Paz,A critical overview of household slow sand filters for water treatment,Water Research,Volume 208,2022,117870,ISSN 0043-1354,https://doi.org/10.1016/j.watres.2021.117870.

Abstract: Household, or point-of-use (POU), water treatments are effective alternatives to provide safe drinking water in locations isolated from a water treatment and distribution network. The household slow sand filter (HSSF) is amongst the most effective and promising POU alternatives available today. Since the development of the patented biosand filter in the early 1990s, the HSSF has undergone a number of modifications and adaptations to improve its performance, making it easier to operate and increase users' acceptability. Consequently, several HSSF models are currently available, including those with alternative designs and constant operation, in addition to the patented ones. In this scenario, the present paper aims to provide a comprehensive overview from the earliest to the most recent publications on the HSSF design, operational parameters, removal mechanisms, efficiency, and field experiences. Based on a critical discussion, this paper will contribute to expanding the knowledge of HSSF in the peer-reviewed literature.

Household slow sand filter is one of the most promising home scale treatments.
HSSF is efficient in improving drinking water quality in isolated communities.
Modification in the HSSF design and operation may encourage research.
There is a lack of literature on protozoa, cyanobacteria, and emerging pollutants.

Components[edit | edit source]

https://www.watertechonline.com/wastewater/article/15550715/understanding-reverse-osmosis-valve-functionality
- Valve descriptions
Sondhi, R., & Bhave, R. (2001). Role of backpulsing in fouling minimization in crossflow filtration with ceramic membranes. Journal of Membrane Science, 186(1), 41–52. https://doi.org/10.1016/S0376-7388(00)00663-3
- "These tubular membranes were 250 mm in length with internal diameter of 7 mm."
Centers for Disease Control and Prevention. (2020, August 4). Technical information on Home Water Treatment Technologies. Centers for Disease Control and Prevention. Retrieved October 1, 2021, from https://www.cdc.gov/healthywater/drinking/home-water-treatment/household_water_treatment.html.
- Pore size for ultra, micro, and nano filtration

What Contaminants do Reverse Osmosis Systems Remove?[edit | edit source]

Public water suppliers work hard to provide clean water for their customers. The problem is that there are many contaminants, especially those that cause taste and odor issues, which are simply not EPA regulated. These contaminants can easily penetrate aquifers, streams and rivers, bringing impurities straight to your water lines.

That's where Reverse Osmosis comes in. With a Reverse Osmosis filtration system, you can filter out impurities and produce outstanding drinking water for your home or business.

How Much Of A Contaminant Can A Reverse Osmosis System Remove?

Fluoride (85-92%)
Lead (95-98%)
Chlorine (98%)
Pesticides (up to 99%)
Nitrates (60-75%)
Sulfate (96-98%)
Calcium (94-98%)
Phosphate (96-98%)
Arsenic (92-96%)
Nickel (96-98%)
Mercury (95-98%)
Sodium (85-94%)
Barium (95-98%

There are generally four stages in the Reverse Osmosis Process[edit | edit source]

SEDIMENT FILTER: This pre-filter stage is designed to strain out sediment, silt, and dirt and is especially important as the sediment filter protects dirt from getting to the delicate RO membranes that can be damaged by sediment. Learn more about sediment filter.

CARBON FILTER: The carbon filter is designed to remove chlorine and other contaminants that affect the performance and life of the RO membrane as well as improve the taste and odor of your water.

REVERSE OSMOSIS MEMBRANE: The semipermeable RO membrane in your RO system is designed to allow water through, but filter out almost all additional contaminants.

POLISHING FILTER: In a four-stage RO System, a final post filter (carbon filter) will "polish" off the water to remove any remaining taste and odor in the water. This final filter ensures you'll have outstanding drinking water.

Some factors that may affect the performance of a Reverse Osmosis System[edit | edit source]

Incoming water pressure (most on municipal city tap water have 40-85 psi, but if water pressure is too low, RO system will not operate properly)
Water Temperature (i.e. cold water takes longer to filter to filter)
Type and number of total dissolved solids (TDS) in the tap water
The quality of the filters and membranes used in the RO System (see operating specifications for your system)

References[edit | edit source]