Raw Water generally contains soluble iron in the form of ferrous bicarbonate and insoluble as ferric hydroxide. Water containing ferrous bicarbonate is clear when drawn from a tube well. But as soon as it comes in contact with air develops a whitish haze which on longer standing turns yellowish and then forms yellowish to radish-brown deposits of hydrated ferric oxide, some of this deposit sticks to the side of the container and the rest sinks to the bottom.
Oxidation of I.R. FILTER : AERATION CHAMBER
Ferrous bicarbonate is usually accomplished by dissolved oxygen introduced into the water by aeration as per following reaction :
From the above reaction it appears that 1ppm of dissolved oxygen oxides 7ppm of ferrous iron as Fe. As solubility of oxygen from air dissolved in water at 60 F is 10ppm, theoretically water saturated with dissolved air contains enough oxygen toxidise 70ppm, of ferrous iron.
Water directly from tube well is first passed into the aeration chamber packed with manganese base catalyst. Before entering into the Aeration Chamber air is injected with water from an Air Compressor. Here according to the above reaction iron is oxidized into ferric form. Water is then passed through the Iron Removal Filter packed with Catalyst Filtering Media. Here the residual ferrous iron is oxidized into ferric and entire precipitated ferric hydroxide is filtered out.
The precipitated and entrapped ferric hydroxide is then removed from bed during back washing.