Water quality and purification processes have improved over time, while demand for drinkable water has increased. Today’s membrane treatment plants can be tailored to the overall composition of water to be processed, and the membrane treatment methods used can reduce more possible contaminants. Where the desired outcome is stable, clean water with an appreciable return on the investment, upgrading to a membrane water treatment system is backed by cutting edge industry science.
An important part of operating membrane systems is accurate data collection on a daily basis. The data will help predict normal maintenance schedules and will help determine the cause of any system upsets. Comprehensive data is very useful in determining when the membranes need to be chemically cleaned, or eventually replaced. It also alerts the operator to changes taking place such as fouling, leaking “O” rings etc.
Pretreatment Equipment - Theory of Operation
Some raw feed waters contain suspended particulate material. This material is commonly sand, iron oxides, clay or elemental sulfur.
Introduction of such materials into the membrane system can cause the development of excessive system differential pressure (dP), or even complete blockage of the brine channels with the resultant reduction of permeate flow. It can also cause physical damage to the membranes themselves. This usually results in a decrease of permeate quality and reduction of membrane life. Cartridge filtration is normally a simple and cost-effective way to reduce the amount of particulate matter reaching the membrane surface.
Recovery is the amount of water permeated per unit time - usually in gallons per minute (gpm) and expressed as a percentage of the raw water feed flow rate. The design recovery is calculated as follows:
Membrane filtration systems are helping water treatment providers simplify and automate their processes while significantly improving water quality. Replacing or augmenting conventional treatment with membrane processes helps avoid heavy use of chemical processes and methods and can provide a superior finished water quality.
It is important to check on the level of semi-colloidal suspended solids in the feedwater to RO systems. The level can be estimated (not measured absolutely) by the Silt Density Index or SDI test which measures the blocking rate of a 0.45 micron filter pad under controlled pressure conditions.