Reverse osmosis (RO) water treatment equipment operates based on the following principle: Two containers, one containing a dilute solution (such as fresh water) and the other containing a concentrated solution (such as seawater or brine), are separated by a semi-permeable membrane. The solvent in the dilute solution naturally passes through the semi-permeable membrane towards the concentrated solution, causing the liquid level on the concentrated solution side to be higher than that of the dilute solution, creating a pressure difference. This pressure difference is known as osmotic pressure, which is determined by the type and concentration of the concentrated solution and temperature, regardless of the properties of the semi-permeable membrane. When a pressure greater than the osmotic pressure is applied on the concentrated solution side, the solvent in the concentrated solution flows in the opposite direction to the original osmosis process. This process is called reverse osmosis.
Pre-treatment
Pre-treatment typically consists of quartz sand filtration, activated carbon filtration, and precision filtration. Its main purpose is to remove harmful substances in the raw water, such as sediment, rust, colloidal matter, suspended solids, pigments, odors, organic substances, and reduce ammonia residue values and pesticide contamination. If the raw water has a high content of calcium and magnesium ions, a water softening device is also required to protect the reverse osmosis membrane from damage by large particles and extend its service life.
Reverse Osmosis Equipment
Reverse osmosis equipment is a water treatment system organized around a reverse osmosis membrane. A complete reverse osmosis system consists of pre-treatment, reverse osmosis main unit (membrane filtration), post-treatment, and system cleaning sections.
The post-treatment section further treats the purified water produced by the reverse osmosis main unit. If it is used in industrial processes requiring ultrapure water, it can be connected to ion exchange or electrodeionization (EDI) equipment. If it is used in domestic drinking water processes, it is often followed by disinfection devices such as ultraviolet sterilization lamps or ozone generators, making the water safe for direct consumption.
Mechanical Filters
Mechanical filters are used to reduce water turbidity and can serve as pre-treatment devices or standalone filtration units for applications with less stringent water quality requirements. The principle of mechanical filters relies on one or more filtering media to remove suspended solids, organic matter, colloidal particles, microorganisms, chlorine, odor, and some heavy metal ions from water under a certain pressure, achieving water purification. The filter media commonly used include quartz sand, anthracite coal particles, porous ceramics, and manganese sand. Generally, when the raw water turbidity exceeds 5 NTU and the suspended solids content is above 300 mg/L, quartz sand is selected as the filter media. When the iron and manganese content in the water exceeds 0.3 mg/L, manganese sand can be used to effectively remove excessive iron and manganese ions. The choice of mechanical filters depends on the actual conditions. They are also known as pressure filters and are important components of pretreatment for producing purified water. They can be made of steel with rubber lining or stainless steel. Depending on the filtering media used, they can be categorized as multimedia filters, activated carbon filters, manganese sand filters. They can be used individually or in combination as required. Their functions include the removal of suspended matter, mechanical impurities, and organic substances, thereby improving water clarity.
Activated Carbon Filters
Activated carbon filters are cylindrical steel containers equipped with upper and lower water distribution devices, along with corresponding pipelines, valves, and instruments. Activated carbon granules are filled into the container to form the activated carbon filter. During operation, the water to be treated enters from the upper part of the filter and passes through the activated carbon bed from top to bottom. Through the adsorption capability of activated carbon, harmful substances in the water, such as organic matter, colloids, microorganisms, oils, residual chlorine, and odors, are adsorbed onto the surface of the activated carbon and removed.