The unique micro porous structure of DMI makes it efficient in the removal of manganese, and iron, to almost undetectable levels. The media acts as an oxidation catalyst allowing immediate oxidation and filtration of the insoluble precipitates derived from the oxidation reaction. The catalytic surface contains manganese oxide, and to ensure that the oxidative layer is not compromised the media operates in the presence of chlorine (sodium hypochlorite - NaOCl), which removes electrons and is consumed in the process. DMI requires the continuous injection of 0.1 – 0.3 ppm of Sodium Hypochlorite to remain activated during operation and backwash. Another function of the chlorine is that it keeps the media free from bacterial or slime growth, and sterilizes the water for domestic use. No other chemicals are required. Sediment filters (5 micron) are built in line, post DMI filtration to capture any slippage of manganese or iron oxide that may occur, and prevents contamination of permeate water in the storage tank. The residual chlorine in the water simultaneously sterilizes and disinfects the water for downstream use.
To ensure the absolute effective removal of Mn and residual Fe:
- The pH of the water should be above 7 through caustic dosing.
- Chlorine is continually dosed and monitored regularly to ensure minimum levels of sodium hypochlorite are maintained (0.2 ppm). This will ensure that the oxidation and catalyst reaction at the media bed will be maintained.