Reverse osmosis (RO) is a water treatment method that gets rid of dissolved solids with the use of spiral-wound membranes. RO also removes alkalinity, hardness, shade, turbidity, and some bacteria apart from solids. An RO system has three streams:
- Feed stream: Water is pumped to the membrane.
- Permeate stream: Clean water is collected.
- Reject stream: Concentrated waste water is discarded.
The system makes use of a semi-permeable membrane that enables water to pass by when contaminants are flushed away. The purified water is known as permeate and the waste is known as reject water. By applying pressure greater than osmotic pressure, water moves from high to low concentration which increases purification. RO can treat various water sources like brackish, well, surface, sea, and wastewater. RO is a secure and environment friendly option since it requires few or no chemicals.
The primary element of the RO unit is its semi-permeable membrane. The membranes are chosen based on the water properties to be purified. There are plenty of membrane options to be had for distinctive applications. Often, acid and anti-scalant dosing is done prior to the RO unit. Acid dosing is followed to decrease the pH which is a good way to inhibit carbonate and bicarbonate scaling. The RO machine produces top quality water by casting off 99.8% of the dissolved solids. RO systems are extensively used in industries, households and companies for obtaining pure water.
Some coastal regions facing water scarcity rely on the desalination process using RO systems to convert saline water to fresh water by removing dissolved solids and minerals. The reverse osmosis process is applied to several industrial wastewaters to obtain the stringent discharge standards proposed by the authority. Other than that, the RO system is proposed as an advanced treatment method for wastewater if the treated water is intended to be reused.
The main part of an RO system is its semi-permeable membrane which is chosen based on the water to be purified. There are many membrane options for different uses. Before water enters the RO unit, acid and anti-scalant are often added. Acid lowers the pH to prevent scaling. The RO system removes 99.8% of dissolved solids which produces high-quality water. It is used in industries, homes, and businesses for pure water. Coastal areas with water shortages use RO for desalination which turns salty water into fresh water. RO also treats industrial wastewater to meet strict discharge standards and is used for advanced wastewater treatment when the water will be reused. Here you know what is a reverse osmosis system? Now continue reading to know more about it.
How Osmosis is Different from Reverse Osmosis?
Osmosis is water moving through a semipermeable membrane from lower to higher concentrations. Reverse osmosis is water moving through a semipermeable membrane from higher to lower concentrations with help of external pressure created by a high pressure pump. RO units can recover up to 75 to 85 percent of all the water entering the system while closed circuit reverse osmosis can recover 91 – 98 percentage of water entering to the system.
What is Closed Circuit Reverse Osmosis?
Closed Circuit Reverse Osmosis is a special technology developed by Desalitec which is now a part of DuPont Water along with Alantech as the system integrator. In a regular RO system, the reject water is full of contaminants and must be properly disposed of to protect the environment. CCRO improves on this by boosting water recovery to over 91% and cutting energy use by 35%.
Unlike conventional RO which wastes the reject water and needs three to four stages to reach 85% recovery, CCRO eliminates reject water by recirculating it with the feed water in a closed loop. This process reduces waste and increases freshwater recovery without lowering water quality.
What is Multistage Reverse Osmosis?
Multistage Reverse Osmosis units are used to enhance the quantity of purified water (permeate) produced. In those systems, the reject water from the first degree is used as the feed for the next ranges and the permeate from all degrees is gathered in a single tank. A multistage RO system can achieve up to 85% recovery depending on the water type and the number of stages. In comparison, a single-stage system only recovers about 50% of the water.
Applications of Reverse Osmosis
The applications of reverse osmosis are as follows.
Desalination:
Sea water may be handled with reverse osmosis to get fresh water. Coastal areas with water shortages frequently use this method to get rid of dissolved solids and other contaminants from sea water.
Drinking water purification:
Common sources of consuming water encompass groundwater, rainwater, and surface water. RO systems are extensively utilized in houses and workplaces to cast off chlorine, heavy metals like lead and arsenic and other dissolved solids which make water safer and improve its taste and look. Groundwater can contain metals like iron and manganese thus prefiltration will be needed before RO treatment.
Industrial applications:
Industries like food and beverages, pharmaceuticals, dairy, chemical manufacturing, automobile, and bottling need high-quality water. Even tiny impurities can affect product quality thus these industries extensively use RO for water purification.
Agriculture:
Water for agriculture may contain salts that harm crop growth. RO is used to remove these dissolved salts which help crops grow better.
Wastewater reclamation and reuse:
RO is used as an advanced treatment technology to reclaim and reuse water for irrigation, industrial purposes, and more.
Benefits
The benefits of RO are as follows.
- Rejection of all kinds of impurities such as physical, chemical and biological contaminations.
- Highest purity of water compared to any other membrane-based treatment system.
- Lower chemical consumption and less changes in original water composition.
- The rejection of neutral organic molecules increases with their molecular weight. Those over 100 Daltons are highly rejected. The type of membrane material greatly affects this.
- Some solutes like phenol and benzene have negative rejection coefficients in cellulose acetate membranes.
Conclusion
Reverse Osmosis (RO) is a reliable method for reducing water contaminants and treating water effectively. After RO, further treatment like mixed bed deionization can improve water quality for demanding uses. Proper pretreatment and regular monitoring are essential to avoid expensive repairs and maintenance. With a good system design, a proper maintenance plan, and expert support, your RO system can provide high-purity water for many years.
You can contact Alantech for the best water treatment and wastewater treatment solutions at affordable prices. We have gained significant expertise in water treatment, wastewater treatment, bottle manufacturing, and filling technologies with 11 years of experience in bottling and water treatment. We serve the food and beverage, chemical, cosmetics, detergents, and pharmaceutical industries.
