Description

Process Description

Iron in rural groundwater supplies is a common problem: its concentration level ranges from 0 to 50 mg/l, while WHO recommended level is < 0.3 mg/l. The iron occurs naturally in the aquifer but levels in groundwater can be increased by dissolution of ferrous borehole and submersible pump components. Iron-bearing groundwater is often noticeably orange in colour, causing discoloration of laundry, and has an unpleasant taste, which is apparent in drinking and food preparation.
Iron dissolved in groundwater is in the reduced iron II form. This form is soluble and normally does not cause any problems by itself. Iron II is oxidised to iron III on contact with oxygen in the air or by the action of iron related bacteria. Iron III forms insoluble hydroxides in water. These are rusty red and cause staining and blockage of screens, pumps, pipes, reticulation systems etc. If the iron hydroxide deposits are produced by iron bacteria then they are also sticky and the problems of stain and blockage are many times worse. The presence of iron bacteria may be indicated by rusty slime inside the pipework, reduced water flow form the bore and unpleasant odour from water pumped from the bore, slimy deposits blocking main and lateral lines, severe staining on pavements and fixtures.

Birm® is an efficient and economical media for the reduction of dissolved iron and manganese compounds from raw water supplies. It may be used in either gravity fed or pressurized water treatment systems. If the removal of Manganese is also required, we recommend the use of Manganese Greensand, as Birm requires a pH of above 8.
Birm acts as an insoluble catalyst to enhance the reaction between dissolved oxygen (D.O.) and the iron compounds. In ground waters the dissolved iron is usually in the ferrous bicarbonate state due to the excess of free carbon dioxide and is not filterable. Birm, acting as a catalyst between the oxygen and the soluble iron compounds, enhances the oxidation reaction of iron and produces ferric hydroxide which makes the iron combine into sediment particles and may be easily filtered.
The physical characteristics of Birm provide an excellent filter media which is easily cleaned by backwashing to remove the precipitant. Birm is not consumed in the iron removal operation and therefore offers a tremendous economic advantage over many other iron removal methods.

Note: Negligible labour costs are involved because Birm does not require chemicals for regeneration, only periodic backwashing is required.

Contain no oil or hydrogen sulphide
Organic matter not to exceed 4-5 ppm
The Dissolved Oxygen content equal at least 15% of the Iron content
A pH of 6.8 or more and for Manganese removal a pH of 8 to 9.
If the water contains both Iron and Manganese the pH should be below 8.5, as the possible formation of colloidal iron may cause issue with filtration.
No Polyphosphates – Polyphosphates are known to coat Birm and reduce Birm’s ability to remove iron or manganese.
Free chlorine less than 0.5 ppm
Freeboard should be 50% minimum
Backwash Bed expansion 30-40%.
Service Flow rate: 3.5 to 5 gpm/ ft3