The main symptoms of the malfunction can be categorized into three types: decreased water production, decreased desalination rate, and increased pressure drop. These malfunctions will be discussed in detail below.
1. Low water production
If the system experiences low water production, the general principle for determining the cause is:
If the first segment has a problem, there will be deposits of particulate pollutants; if the last segment has a problem, there will be scaling; if all segments have problems, there will be blockage.
Low water production failures are often accompanied by normal, high or low desalination rates. Different combinations can lead to different causes of the failure.
low water production and normal desalination rate are microbial contamination or adsorption of organic matter.
Low permeate flow rate and low desalination rate are the most common system failures, and the possible causes are:
- Colloidal clogging
- Metal oxide clogging
- Scale buildup
Low water production and high desalination rate can be caused by membrane compaction or organic fouling.
2. Decreased desalination rate
Reasons for low desalination rate and normal water production:
- Sealing ring leakage
- Telescope phenomenon
- Membrane surface wear
- Back pressure of produced water
Reasons for low desalination rate and high water production :
- Membrane oxidation;
- leakage.
3. High voltage drop
The pressure difference between the feed water and the concentrate, also known as pressure drop, is a very high resistance along the water flow direction of the membrane element. The permeate center tube of a small-diameter membrane element will bear this force, while for an 8-inch membrane element, this force will be borne and transmitted by the fiberglass shell of the adjacent element.
The location and extent of the increased voltage drop can provide information for identifying the cause of the fault. Therefore, the voltage drop of each segment and the total voltage drop should be monitored. The following are some common causes:
- Security filter short-circuited
- Colloidal contamination
- Pump impeller wear
- Scale buildup
- The seal is damaged
