COMPONENTS

GENERAL INFORMATION

Depleting supplies of fresh water, ground water contamination and the rising cost of water have compelled industries to increasingly turn to the desalination of brackish/sea water as well as water recovered from treated industrial effluent and secondary treated municipal sewage.

All these recycled water systems use reverse osmosis (RO) system for removal of dissolved solids.

The presence of finely divided particles in feed water to an RO system can cause serious problems as they are too small to be retained by conventional pretreatment systems they find their way to the RO membrane. The function of an RO membrane is to concentrate dissolved solids on one side of the membrane and allow water molecules to permeate through the other side. Suspended, colloidal particles are larger than dissolved solids and are also rejected by the membrane.

These fine undissolved suspended particles tend to settle on the surface and, in the process, foul the membrane. The net result is an increase in feed pressure, reduced flow and high conductivity of permeate. Spiral wound and hollow fine fibre membranes are the most vulnerable and once fouled, cleaning of the element is often difficult.

Filter paper colouration after the SDI test:

i) Slightly yellow The possible problem could be presence of iron and/or organics in feed water. Check the source.

ii) Reddish brown Positive indication of presence of iron in feed water. Take corrective steps for removal of iron.

iii) Gray Indicates presence of carbon fines. Check the carbon filter, remove carbon fines.

iv) Particles present on Check the cartridge filter and the filter elements. the filter paper

v) Dark Black If the colour dissolves in the acid, it indicates the presence of manganese in the water.