As the saying goes, any RO plant is only as good as the pre treatment feeding it.
When installing a Reverse Osmosis plant it is important that a full survey is completed of the feed water quality and the operating conditions of the proposed plant. In installing a Reverse Osmosis plant four key factors should focussed on to establish good RO performance.
Feed Water Temperature
The permeate flow, (treated water flow) from an RO plant can vary widely depending on the temperature of the feed water being treated. In some areas the feed water temperature during winter months can drop to as low as 5 degrees. It is important that RO plants are designed and specified correctly to perform adequately during temperature variations.
A background level of free chlorine is dosed into the feed water by the municipal water company. However free chlorine will damage RO membranes. Any good RO system must have a FILTERMAT AC activated carbon filter, to remove free chlorine.
Iron in the feed water will also damage and block RO membranes. Iron is not very often a problem in municipal feed water supplied, but many RO plants are installed to treat bore hole water supplied which can be quite high in iron. It is important that the iron content is analysed before the RO is installed and if necessary a FILTERMAT FE unit is installed to act as a catalyst and remove the iron.
Feed Water Hardness
It is very important that feed water hardness is reduced to less than 4 parts per million on the feed to any RO unit. If this is not the case the RO membranes will very quickly become fouled and recovery rates will be reduced. Almost without exception RO plants should have the water fed to them via duplex meter controlled water softeners.
In some areas where the feed water is of a “surface” nature organic levels in the feed water can be quite high. If not treated this organic matter will also foul the RO membranes. This problem should be established or discounted before the RO unit is installed. Organic contamination can be removed with a FILTERMAT AC or a FILTERMAT OS, depending on the application and the level of organics.
As can be seen from the above, adequate pre treatment of the RO feed water is very important for efficient trouble free operation.
In an effort to reduce costs many RO units are installed without the facility to CIP clean the membranes. This can be a false economy as very often users end up replacing RO membranes where a CIP clean would have recovered the original membranes. A CIP rig is also a very useful tool where a good bacteria performance is required from the RO unit. The CIP rig can also be used to disinfect the RO membranes and manifold. Effective maintenance and monitoring.
Quite clearly from all of this there is no substitute to the potential user in receiving good qualified advice in considering all of the options.