Definition And Guide To Choose The Best Reverse Osmosis System
- The process used in the system
- What is Reverse Osmosis?
- Basic Advantages of Reverse Osmosis system:
- Usage on large units
- Choosing the Best Reverse Osmosis System
- Types of water a Reverse Osmosis System Treats
- Advantages and Disadvantages of Reverse Osmosis System
- Industrial Applications of Reverse Osmosis Systems
Reverse Osmosis System consist of a water purification process originally developed for desalination of sea water.
The idea behind the process was to make sea water usable for daily life activities like drinking, washing, recycling and even producing energy.
This process has been very successful and it works efficiently in removing salt and other sea mineral from the sea water.
Water treatment plants and purification units have widely adopted the reverse osmosis process for cleaning and purifying the water.
According to International Association of Desalination, over 1300 water plants are successfully working on reverse osmosis technology.
The purified water is used for industrial purposes as well as for the production of potable water.
The process used in the system
The reverse osmosis process doesn’t only desalinate the water, but also removes other molecular impurities and contaminants from water.
To understand the reverse osmosis process, we must first take a look at the process of osmosis. Water has the tendency to move towards high concentration solute solutions.
Osmosis is the process in which two solutions, separated by a semi-permeable membrane and one is of high concentration solute tend to equalize themselves as the water moves from low concentration solution to the higher concentration solution hence balancing out the solvent-solute ratio.
What is Reverse Osmosis?
In reverse Osmosis, pressure is applied to keep water from moving towards the high concentration solution.
As the water is pushed toward the lower concentration solution and passed through a perforated membrane, the solute is extracted from the solution and only pure water is allowed to pass through the semi-permeable membrane.
This process is used to extract larger molecules from water such as salt, bacteria, ions and other molecular impurities.
The semi-permeable membrane used during the process has a tight structure and its diameter is 500,000 times less than the diameter of a human hair.
The membrane effectively blocks all kinds of molecular impurities, letting only water molecules to pass through. The Reverse Osmosis process has been tested to provide 99% pure water.
Basic Advantages of Reverse Osmosis system:
The Reverse Osmosis process is an economical and relatively simple water purification process.
The water produced from a reverse osmosis process can be easily used for drinking purposes without having the need for further purification treatment. There are several advantages of it:
- Removes water odors and the distinct salty taste.
- Improves appearance and texture of water.
- A convenient and economical process.
- Does not require high efficiency, energy units to operate.
- Easy to manage and clean the system components.
- Pollutants are flushed out and removed from the purification system.
- The production cost is low as compared to other filtration processes.
Usage on large units
As said earlier, this process is a widely used filtration process acquired by many of the water purification plants.
Huge industrial units have been designed to carry out the reverse osmosis process on a large scale.
All of these distinctive industrial units have some basic components that are used during the process.
Some of the essential components of a reverse osmosis system are discussed below, in order to get a better understanding of the whole process:
Raw Water Source:
This is the raw water supply of the RO system. Some systems use a large water tank for the storage of contaminated water and a pipe feed is used to draw water from these tanks.
It is important to always have enough water for the RO system as lack or shortage of water can damage the filtration pump.
Pre-filter water Treatment:
A pressure pump is used to provide external pressure to push water through the filtration system. At this stage, water is also pre-treated against contaminants such sand, dirt and other sediment minerals.
These are called sediment filters. Sometimes when water is suspected to be contaminated with gases, carbon filters are also used in the pre-treatment phase to protect the filter membranes.
Reverse Osmosis Unit:
Reverse osmosis unit is the fundamental element of the system. S
pecially designed Reverse Osmosis Membranes are used in this unit to filter the water and purify it from all kinds of bacterial impurities.
Two types of osmosis membranes are commonly used.
The Cellulose Tri-acetate(CTA) spiral wound membrane which is chlorine tolerant and would not be damaged by the presence of chlorine in water.
The TFM (Thin File Material) membrane is not chlorine tolerant and it requires carbon filters during the pre-treatment phase. With a steady intake of water, the Reverse Osmosis Unit can produce one million gallons of water in a day.
Post-Filters are used to remove any taste or odors that might be present in the water. Post filters are usually carbon filters and water is run through them after it leaves the Reverse Osmosis Unit.
Flow Restrictor and Drainage:
The Reverse Osmosis unit also has a drainage line to drain out all the impurities and contaminants from the system. The drain pipe and the purified water supply pipe, both are attached to the Reverse Osmosis unit, hence a flow restrictor is required to keep the purified water from going down the drain pipe.
A large storage tank is used to store the purified water. Usually, this tank can store up to 2.5 gallons of water. This water can be used for drinking purposes or any other daily usage.
Choosing the Best Reverse Osmosis System
All the industrial or domestic reverse osmosis systems are built on the same technology and they all have common basic components. It can be difficult to choose the best reverse osmosis system, but there are some points that must be kept in mind while judging a reverse osmosis system.
- Pressure Pump for water inlet.
- Temperature of the water.
- The material quality of filter membranes and their efficacy in removing the impurities.
Types of water a Reverse Osmosis System Treats
For a Reverse Osmosis system, the inlet water can come from three major sources. Tap water, ground water or Sea water. Tap water is the most common source for reverse osmosis systems.
The impurities and debris in the tap water can easily be removed with an RO system and furthermore, it also softens the water and removes any kind of taste or odors.
The water coming from these sources, after passing through RO system is categorized on the basis of Total Dissolved Solid (TDS) content of the water. The American Health Association has declared that the drinking water should be less than 1,000 PPM TDS.
The water with higher TDS content can be used for other industrial purposes like agriculture, mining, bottling etc.
Advantages and Disadvantages of Reverse Osmosis System
The biggest advantage of reverse osmosis system is that it can provide purified drinking water in a cost effective manner. However, there are several disadvantages to this system as well.
- The reverse osmosis system purifies water of all kinds of impurities, but during the purification process it also removes necessary minerals from the drinking water that are otherwise healthy.
- The drinking water produced from a reverse osmosis system is acidic in nature which is not good for health.
- The domestic reverse osmosis units do not have proper pressure pumps and thus can only retrieve 10-15% of the water and the rest of the water is drained out along with the impurities.
- The industrial units can recover 75% to 80% of the water passing through the system, but their level of TDS also increases.
Industrial Applications of Reverse Osmosis Systems
The Reverse Osmosis Purification process was invented in 1940’s and was initially used for desalination of sea water to make it usable for agriculture, industrial as well as domestic purposes. This process is widely used in industries because of its low cost of production.
The most common industries that have acquired Reverse Osmosis Process include:
Medicine and Pharmacy :
Reverse Osmosis is an a pproven process for treatment of water which is used in preparing medicines and other pharmaceutical needs.
Food and Water:
The food and water industry also uses the reverse osmosis process for production of clean water.
Electric Power Industry:
The water used for the production of energy and electricity is passed through the reverse osmosis units before feeding into the energy boilers.
Domestic Reverse Osmosis Systems:
Reverse Osmosis Systems that are designed for domestic purposes are more thorough and have higher quality filtration membranes to ensure high quality drinking water with the least level of TDS. Some of the more important features of domestic reverse osmosis systems are discussed below:
- They have multiple stages of filtration and post treatment processes to eliminate dissolved solids, chlorine, fluoride and other microorganisms from the treated water.
- In a post treatment phase, water is treated to balance its alkaline level as water produced from the reverse osmosis process is sometimes acidic in nature.
- The filter membranes can be replaced easily and are economical.
- The filter faucet can be easily connected to your dispenser units.
- It has automatic system, which shuts off the filtration process once the tank is full.
In conclusion, Reverse Osmosis systems are an approved technology for providing purified water. There are several reverse osmosis systems available in the market, but they all follow the similar process. If you are looking to buy or deploy a reverse osmosis system the key points to asses any systems are pressure, temperature, recovery, pre-treatment and post-treatment processes.
RO System terminology can be confusing at times, so if you’re stuck wondering what a certain term means, the following short list should give you a helping hand:
Reverse Osmosis Standards:
There are several organizations that check the standards of Reverse Osmosis systems and certify them according to their level of functionality. Manufacturers design and build their systems, according to these standards.
WQA is the source of information for water filtration industry to educate professionals and provide a testing lab for water filtration products. The products developer under WQA standards are certified and give an acknowledgement to public about the purity of water being used. The entire WQA certified reverse osmosis products are built on the following standard.
“NSF/ANSI 58 (02/29/2012): Reverse Osmosis Drinking Water Treatment Systems* is within WQA’s ANSI and SCC approved scope of accreditation”
NSF & FDA are public health and safety organizations and manufacturers design their products to conform with their standards.
This gives them market advantage as well as a satisfaction of building standard products. Several components of Reverse Osmosis systems are NSF certified like filter pipe fittings and polythene tubing. Manufacturers use these products to assemble their reverse osmosis systems.
JG or John Guest Fittings and Plumbing:
John Guest is the world known fittings and plumbing that provide standard fittings for Reverse Osmosis systems. They offer several fitting components like UV Light Replacement Parts, RO Faucets and Accessories, RO system installation accessories, Replacement Pumps etc.
VOCs are volatile organic compounds that contaminate water and may result into harmful effects on human health. These VOCs can be transferred to the human body when a person drinks the contaminated water. During reverse osmosis the osmotic membrane filters, micro-particles, including VOCs and ionic compounds to improve the quality of drinking water.
POU and POE systems
RO systems can be used in two different ways. It can be a POU or point of use system. Such a system is fitted right on the spot with the tap or water supply.
While the POE reverse osmosis systems work at the point of entry . It means such systems are placed where the main supply of water enters.
TFC and CTA membranes
TFC membranes are used in RO purification systems and are thin film composites used to purify water. Another type is CTA membranes or cellulose tri-acetate which is also used in these systems. Of these two, TFC is known to work much better as compared to the CTA membranes.
What is GAC?
Granular activated carbon filters are used as pre-filters in RO water purification systems that purifies the water and facilitates further purification processes.
Cross flow system
A Cross flow system used in the RO water purification system provides a double flow of of water in which the water flows through the membrane and gets purified as well as some water flow downside to take the impurities to the drain of the tank.
It makes the water completely safe and purified as the impurities are constantly washed away during the filtration process.