Iron Removal

Have you spotted reddish-brown stains on your clothes? Does your water smell of rotten eggs? Do your fixtures and sinks have rust stains? Are your pumps and pipes clogged with slime? If your answer is “Yes”, you likely have excessive iron content in your water. The recommended limit for iron in drinking water is 0.3 mg / l (ppm). And this recommendation is based on taste and form rather than any harmful health effects. However, a slight increase in concentration can cause water to turn a reddish-brown color. And managing the iron content in the water is very important due to this.

There are three types of iron present in well water. Ferrous iron, Ferric iron, and bacterial irons.

Ferrous iron, also known as clean water iron is found in the groundwater and is soluble in water. In the presence of oxygen in the well or in your home, it gets oxidized to insoluble or red iron. A quick way to test the presence of ferric iron is to pour a glass of cold clear water and keep it overnight in the presence of air. There will be reddish brown particles that will settle down in the bottom of the glass.

This is the method of converting soluble iron to insoluble iron. In this method, oxygen is introduced to the water to remove dissolved gases and to oxidize dissolved metals including iron, hydrogen sulfide, and volatile organic chemicals. After aeration, a sediment filter or any other screen filter could be used to entrap the solid impurities leaving the water clean and iron free.

Water softeners work on the principle of Ion exchange. There will be ion exchange resin beads inside the water softener tank. Ion exchange takes place when the hard water which contains calcium and magnesium goes through these resin beads. Water flows around the plastic beads covered by sodium ions and sodium swaps places with the calcium magnesium. Water coming out will be soft water containing sodium ions. This process can remove small amounts of ferrous iron from water. However, if there is any ferric iron present in the water, a sediment pre-filter will be necessary to prevent the water softener from becoming clogged with iron slugs.

Manganese Greensand is a strong oxidizing media. In this method, the ferrous irons are converted to ferric irons and then removed from the water. When water containing iron and manganese flows through this oxidizing media, they are oxidized out of the dissolved form and turned into solid

particulate matter. This ferric iron is then pulled out of the water and the clean soft water flows out of the filter. This media needs to be back-washed periodically with potassium permanganate powder. Potassium permanganate powder pumps out the collected insoluble iron down the drain and regenerates the greens and media. This will restore the oxidizing capacity of the greensand.

BIRM is an efficient and economical medium for the extraction of dissolved iron and manganese compounds from water. It can be used in gravity feed or pressurized water treatment systems. The advantage of BIRM over manganese greensand is that it doesn’t require a chemical oxidizing agent like potassium permanganate to remove the iron. But the pH of the water should be at a minimum of 6.8 and dissolved oxygen should be 15% of iron and manganese. Therefore, most systems utilizing BIRM will combine it with calcite which elevates the water’s pH, and enables the BIRM media to effectively oxidize the ferrous iron and remove it from the water.

Ferric iron also known as red water iron is insoluble iron. When water containing ferric iron is poured into a glass, it appears rusty or turns red or yellow. Ferric iron is abundant in shallow wells and surface water. This can create severe taste and appearance problems for users.

Filtration is the best way to remove insoluble ferric iron. It also removes sand, mica, dirt, or sediment if present in your well water. Most of the time, a cartridge filter works to remove ferric iron. Chemical-free backwash filter is the best filtration option if the levels of iron are high. Like softeners, backwash filters have service and backwash cycles. The difference is, the filters use a different media and no salt is required. They only use water to wash away particles that have accumulated in the drain.

If the well water contains both ferric and ferrous iron, the best solution is to first pass the water through a cartridge or backwash filter and then pass through a water softener. In this method the two types of iron are handled separately; the cartridge filter captures ferric iron and residue, and the softener captures soluble ferrous iron. An additional advantage of this method is that the hardness is removed by softening which results in clean, soft, and iron-free water in the home.

The following steps are involved in the physical removal of bacterial iron from wells.

• Remove and clean the pumping equipment.

• Brush the surface of the well with brushes.

• Once done a chemical treatment is required.

Chlorine

Chlorine is cheap and easy to use, but it does not always get rid of iron bacteria. You may need to use chlorine more than once. The concentration of chlorine and the extent to which the chlorine solution is in contact with bacteria are also important. Some people have used continuous chlorine injection in the well, but this is generally not recommended. Continuous chlorine injection will cover up other bacterial contaminants and cause destructive problems.

Shock Chlorination

Shock chlorination is the process of using a strong chlorine solution to disinfect a well or system. Chlorine concentration should not exceed 200 parts per million (ppm). Concentrations above 200 ppm reduce the effectiveness of the disinfectant. Before adding the chlorine solution, the well

should be pumped until it is clear or physically clean.