Removing iron and manganese from water supplies

In the early days of water treatment, naturally occurring zeolites (glauconite greensand) were used to soften and remove the iron and manganese from water. The greensand media was not ideal as it was a slow process which required periodic regeneration with potassium permanganate. Also, it couldn’t be used in lower pH waters and had relatively low operating temperatures. Therefore, in the 70s, scientists and researchers in Japan began to look for ways to apply oxidising technology to a silica-sand substrate and came up with the Quantum DMI-65 media.

The DMI-65 media is granular in nature and acts as an oxidation catalyst in aqueous solutions (mainly groundwater), facilitating oxidation - precipitation - filtration. It has tight particle size distribution, low level of fines, wide pH range between 5.8 - 8.6 and a coating that won’t be abraded or diminished under normal operating conditions. The media can be used to facilitate the removal of iron and manganese from water when operated in the presence of an oxidant such as sodium hypochlorite or bleach (12.5% NaOCl). In essence, the oxidants and the media work together to oxidise a dissolved solid into a suspended solid that is then filtered out in the depth of the media bed. 

As alternate water supplies are now being considered to supply Australia’s water demands, interest in the DMI 65 iron and manganese removal process has grown. It has recently been used by Amiad Australia as the filter media for the removal of iron from bore water to provide suitable water quality for an irrigation system at a residential development in Western Australia. The system consisted of four by 900 mm diameter pressure media vessels configured with activated diaphragm valves and a sodium hypochlorite and caustic soda dosing system including a controller. It also includes a backwash pump assembly, pressure differential switch, a small pressure pump for the command water and a filter controller. After a few weeks of operation, water analysis of the filtrate showed ‘no detectable iron’ using the DMI 65 media.

In another case in George Municipal Water Works, South Africa, over 550 metric tonnes of DMI-65 was used to treat the highly coloured water which contained humic and fulvic acids - the raw water colour is approx 800 PtCo colour units. The iron removal at this site is reported to be very effective regardless of the pH. The highest residual iron found was 0.01 mg/L. Manganese removal is also very efficient. The highest remaining manganese found was 0.06 mg/L Mn, this is best removed at higher pH 8. The plant has been running since the beginning of January 2007 and reportedly continues to have good results.

DMI-65 is manufactured by Quantum Filtration Medium and is certified by the Water Quality Association to be manufactured to the water treatment standard NSF ANSI 61 for health effects and safety in drinking-water applications.