Commercial Reverse Osmosis System Maintenance Manual

VI. Pressure drop increases after regular running

Pressure drop increases after regular running, and it causes the decrease in permeate flow or rejection rate.

Pressure drop refers to the pressure difference between feed water and rejected water. The upper limit of pressure drop is 3.5bar for each pressure vessel containing a number of membrane elements, or 1bar for each membrane element held in FRP casing. Excessive pressure drop will cause the telescoping phenomenon to occur in the membrane element and the FRP casing to be broken, thus resulting in the mechanical damage of membrane element. If the flow rate of feed water remains constant, the increase of pressure drop is caused generally by the contaminants or scaling substances contained in the flowing passage of feed water mesh. Once the flowing passage of feed water is blocked, the permeate flow will decrease as a result.

Following are the reasons frequently seen that causes the increase of pressure drop:

1. Microbial Fouling

Microbial contamination can usually cause obvious increase of pressure drop in all stages of RO system. Microbial contamination occurs mostly in those systems using surface water or reused waste water as raw water.

A. Solutions to Microbial Contamination

1) Dose germicide in feed water. Be sure to prevent the oxidant germicide from entering the membrane element so as to prevent the oxidation of membrane element.

2) Change to use the oxidation-resistant membrane element and dose germicide in the whole system (including RO system)

2. Scaling Contamination

Since the scaling that fouls the feedwater flow passage can usually cause the increase of pressure drop in the membrane elements of the last stage, it must be ensured that suitable measures be taken to control the scaling, that proper chemicals be used for cleaning the membrane element and that the recovery rate be kept at reasonable level.

More questions regarding the Commercial Reverse Osmosis System, please feel free to contact us:

Whatsapp/Wechat/Call me via +86 13544774483

Email: sales010@water-sy.com