Design principles for pretreatment of Reverse osmosis equipment

1. The raw water has oil and grease

a. The oil and grease in the water should be removed before the raw water enters the reverse osmosis equipment, which may cause the chemical degradation of the aromatic polyamide active layer of the reverse osmosis equipment membrane during the application process and cause the degradation of the membrane performance. The biological filter method is usually used. and many more.

b. When the content of oil and grease in the feedwater is above 0.1PPM, processes such as oil-water separation, chemical coagulation, activated carbon adsorption filtration or ultrafiltration membrane separation should be selected according to the specific conditions to remove them.

2. The raw water has insoluble inorganic salts

a. Ion exchange (softening)

It is often used in the case of low hardness content of raw water. At present, this process is most used in the pretreatment system of small reverse osmosis equipment and the reverse osmosis purified water preparation system for drinking water purification.

b. Metering and adding scale inhibitor

The process has strong applicability to raw water and field conditions, easy to realize automatic control, and reliable operation of the device. Therefore, it is widely used in large-scale reverse osmosis equipment and systems with high content of insoluble inorganic matter in raw water.

3. The raw water has high dissolved silicon

When the site conditions permit, the temperature of the feed water is adjusted to about 28-35°C through the heat exchanger installed in the system to improve the solubility of silicic acid compounds in the water and combine it with the process design to control the water recovery rate of the system. Ensure that no silica gel scale is formed during the operation of the reverse osmosis equipment. This is a method often used in engineering.

4. The raw water has metal oxides

A pre-oxidation process for the raw water is set in the pretreatment system, and then iron, manganese ions and their compounds in the raw water are removed through processes such as coagulation, sedimentation and sand filtration or manganese sand filtration.

5. The raw water has natural organic matter

a. In the pretreatment system, a combined treatment process of lime pre-softening, coagulation and clarification is set, and then processed through the process of multi-media filtration and fine sand filtration to remove the adsorbed natural humus organic matter in the raw water. This process is widely used in large-scale reverse osmosis pretreatment systems for the desalination and purification of surface water and circulating water.

b. Set up the activated carbon adsorption filtration process in the pretreatment system to remove the remaining organic matter in the raw water. This process is often used in small and medium-sized reverse osmosis pretreatments, especially in pure water production and drinking water purification systems.

d. In the pretreatment system, the nanofiltration membrane separation equipment is used as the pretreatment equipment of the reverse osmosis equipment, which can remove organic matter with a molecular weight of more than 200, microorganisms, viruses, and heat sources. It is widely used in secondary seawater desalination systems, ultrapure water preparation systems using surface water as the water source, and drinking water purification systems.

6. The raw water has particles and colloids

a. Set up a lime pre-softening process in the pretreatment system, and add a small amount of sodium aluminate to the clarifier to increase the clarification effect.

b. Before the pretreatment process links such as multi-media filtration or fine sand filtration, add coagulant/coagulant aid, sedimentation, clarification and other pretreatment combined processes.

7. The raw water has bacteria and microorganisms

a. Add permitted non-oxidizing chemical fungicides to the reverse osmosis water supply system intermittently, and add an ultraviolet disinfection process to the reverse osmosis pretreatment system.

b. Optimize the structural design of the reverse osmosis device. For example, when designing the piping of the reverse osmosis equipment, try to reduce the dead angle of the water flow; and when designing the system connection pipeline, try to reduce the high-low state of partial water accumulation in some pipelines during shutdown. High-form design and connection; add drain valves in the lower section of appropriate pipelines.

More inquiries related to Reverse osmosis equipment please contact:

Mob& Wechat& WhatsApp: (+86)13544774483

Email: sales010@water-sy.com

We will provide high-quality, all-round comprehensive professional services for project consulting, system design, manufacturing, installation and commissioning, personnel training, etc