Reasons and solutions for the decrease in water production of reverse osmosis pure water equipment

Author: Hongjie Water

Reverse osmosis pure water equipment is an important device used in water treatment systems. After long-term use, due to various factors, it may cause a decrease in the water production of membrane components, which cannot meet production requirements. In order to solve this problem, Hongjie Water leads the team to understand the reasons for the decrease in water production of membrane components and how to solve it.

Reverse osmosis pure water equipment failures usually occur in the following ways: ① when the working pressure and conductivity are normal, the water production decreases; ② After standardization, the desalination rate decreases and the conductivity of the produced water in the reverse osmosis system increases; ③ After standardization, the water production decreases, and it is usually necessary to increase the operating pressure to maintain the rated water production, that is, the working pressure increases.

1、 After standardization, the water production decreases.

After standardization of the RO system, the water output has decreased, and the reasons can be identified based on the following three situations:

(1) The first stage of the RO system reduces water production and results in the deposition of particulate pollutants;

(2) The final stage of the RO system has reduced water production, resulting in scaling pollution;

(3) The water output of each section of the RO system has decreased, resulting in pollution and blockage.

2、 One of the most common system failures is a decrease in water output after standardization. Possible reasons are:

(1) The reduction of membrane components is carried out according to the designed number of membrane components;

(2) The reverse osmosis membrane operates at low pressure, i.e. at the design reference pressure (possibly with a throttle valve);

(3) If it is found that the membrane component is compressed, that is, the reverse osmosis membrane operates significantly above the reference pressure, and the membrane component will be compressed, so the membrane component must be replaced;

(4) Reduce the operating temperature to 25 degrees according to the design temperature;

(5) Running at a higher recovery rate will increase the TDS of the average incoming/concentrated water, thus increasing the osmotic pressure. When operating at a recovery rate of over 75%, the concentrated water volume will decrease, resulting in an increase in the concentration ratio of water in the membrane module, leading to a serious decrease in the inlet water quality. In severe cases, salt scale will precipitate on the membrane surface, and water must be produced at the designed recovery rate;

(6) The membrane is contaminated. Metal or dirt adheres to the membrane surface, causing blockage of the reverse osmosis membrane (most importantly);

(7) During operation, the reverse osmotic pressure pressure difference rises, the pretreatment operation management is improved, the reverse osmosis water quality is improved, and the reverse osmosis components are cleaned with drugs;

(8) When oil is mixed in, be careful not to let it enter the feedwater, as it may contaminate the reverse osmosis membrane;

(9) Ensure regular replacement of the filter element in the filter. If not replaced for a long time, the filter element will be blocked, which will affect the reverse osmosis water inlet;

(10) The increase of inlet water conductivity will increase the osmotic pressure that must be overcome when the produced water passes through the membrane.

3、 Solution for increasing conductivity

(1) Firstly, ensure that the valve opens correctly and the ratio of pure water to concentrated water is correct;

(2) Is the conductivity of the incoming water higher, that is, is the conductivity of the incoming water higher than before (such as the Humen saltwater tide, where the conductivity rises to 1000 μ s \ cm)；

(3) Whether the reverse osmosis membrane is contaminated, such as inorganic scaling CaSO4, MgSO4, BaSO4, organic matter pollution, metal oxide pollution, etc.;

(4) Is the reverse osmosis membrane in contact with strong oxidizing agents (such as Cl2) and degraded by strong oxidizing agents. Any contact with oxidizing substances can damage the membrane components;

(5) Damage or leakage of the O-ring can cause a rapid increase in the conductivity of the reverse osmosis effluent;

(6) The reverse osmosis membrane comes into contact with strong oxidizing substances such as Cl2 and O3, and is oxidized and degraded by strong oxidizing substances.

4、 Reasons and solutions for the decrease in water production

(1) Whether the RO reverse osmosis membrane is contaminated or blocked;

(2) The conductivity of the inlet water increases;

(3) If it is found that the membrane component is compressed, that is, the reverse osmosis membrane operates significantly above the reference pressure, and the membrane component will be compressed, so the membrane component must be replaced;

(4) Does the working pressure reach the rated working pressure of the reverse osmosis membrane. The rated working pressure can be determined based on the type of reverse osmosis membrane, and an appropriate increase in inlet pressure can increase water production;

(5) The raw water contains a certain concentration of suspended solids and dissolved substances;

(6) The rated water production of the reverse osmosis membrane is designed at 25 ℃ due to the influence of water temperature. For every 1 ℃ decrease in temperature, the water production decreases by 2-3%.

Warm reminder from Hongjie Water: The above factors gradually reduce the water production of the reverse osmosis membrane, increase the salt permeability, and decrease the quality of pure water. If the reverse osmosis membrane is damaged, it should be replaced in a timely manner, otherwise it not only affects the water production but also deteriorates the water quality.