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Failure analysis of reverse osmosis equipment

Dec 10, 2019

Reverse osmosis equipment will inevitably have such problems in the long-term operation, and some of these problems are caused by improper operation of the user. This article provides a summary analysis of equipment failures caused by improper operation.

1. Improper operation of reverse osmosis equipment causes damage to membrane performance

1. The residual gas in the reverse osmosis equipment runs under high pressure, and the formation of the air hammer will damage the membrane.

There are often two situations: A. After the equipment is emptied, when the gas is re-run, the gas is quickly boosted when it is not exhausted. The remaining air should be drained at a pressure of 2 to 4 bar, and then gradually boosted. B. When the joint between the pretreatment equipment and the high pressure pump is not well sealed or leaks (especially the microfilter and the pipeline behind it), when the pretreatment water supply is not sufficient, such as microfiltration, the seal is not sealed. A good place sucks in some air due to the vacuum. The microfilter should be cleaned or replaced to ensure that the tubing is not leaking. In short, the flow should be gradually increased without bubbles in the flow meter, and the bubbles should be gradually reduced during operation to check the cause.

2. The method of shutting down the reverse osmosis device is incorrect.

A. The quick step-down at shutdown is not completely flushed. Since the concentration of the inorganic salt on the concentrated water side of the membrane is higher than that of the raw water, it is easy to foul and contaminate the membrane. B. Rinse with pretreated water with chemical reagents. Water containing chemical reagents may cause membrane fouling during equipment outages.

When the reverse osmosis water treatment equipment is ready to shut down, it should stop adding chemical reagents and gradually reduce the pressure to about 3 bar and rinse with pretreated water for 10 minutes until the TDS of the concentrated water is close to the TDS of the raw water.

3, the reverse disinfection and maintenance of reverse osmosis equipment leads to microbial contamination

This is a common problem in the use of composite polyamide membranes. Because the polyamide membrane is poor in residual chlorine resistance, the disinfectant is not properly added during use, and the user's attention to the prevention of microorganisms is insufficient, which is likely to cause microbial contamination. Many manufacturers produce pure water microbes exceeding the standard, which is caused by poor disinfection and maintenance.

The main performance is: when the factory is out, the RO equipment is not maintained with disinfectant; after the equipment is installed, the whole pipeline and pretreatment equipment are not disinfected; the intermittent operation does not take disinfection and maintenance measures; there is no regular disinfection of the pretreatment equipment and reverse osmosis equipment. The maintenance fluid has failed or the concentration is not enough.

4. The residual chlorine in the reverse osmosis equipment is poorly monitored.

If the pump with NaHSO3 fails or the chemical fails, or if the activated carbon is saturated, the membrane will be damaged by residual chlorine.