Iron in Water
High concentrations of iron are predominantly an aesthetic concern since ferrous salts are unstable under the pH conditions prevailing in drinking water and precipitate as insoluble ferric hydroxide, which settles out as a rust-coloured silt.
The concentration of dissolved iron in water is dependent on the pH, redox potential, turbidity, suspended matter, the concentration of aluminium and the occurrence of several heavy metals, notably manganese. The natural cycling of iron may also result in the coprecipitation of trace metals such as arsenic, copper, cadmium and lead.
Iron in water supplies is most conveniently removed by applying conventional water treatment processes of coagulation with lime or alum, followed by settlement and filtration. Iron can also be removed from water using an oxidising process which will convert the iron into an insoluble hydroxide or hydrated oxide, removable by filtration.
Iron Removal Treatment
1.) The water can be aerated by devices such as fountains, cascades or mechanical aeration;
2.) The addition of lime to the water will raise the pH and facilitate the oxidation of iron by air in the water, followed by settlement of the iron oxide
3.) The water can also be chemically oxidised by dosing with chlorine, hydrogen peroxide, ozone or other strong oxidants. On an industrial scale chlorine is commonly used as the chemical oxidant.
Post-treatment, high levels of residual chlorine should be avoided since this may interfere with the quality of the water.
Removal of iron can be achieved on a household scale by cascading the water through the air and allowing the iron oxide particles to settle. On an industrial scale the process usually needs to be more closely controlled and monitored because the consequences of incomplete treatment may be severe.
NBB ***For the optimisation of treatment processes it is important to determine both the total and dissolved iron species and their relative concentrations.
Excessive ingestion of iron may result in haemochromatosis, wherein tissue damage occurs as a consequence of iron accumulation. Haemochromatosis generally results from prolonged consumption of acid foodstuffs cooked in kitchenware made of iron.
Poisoning is rare since excessively high concentrations of iron do not occur naturally in water. The extreme unpalatability of such water would probably prevent consumption. Further, iron in the distribution system promotes proliferation of iron-oxidising bacteria which oxidise ferrous iron to ferric iron, and manifest as slimy coatings in plumbing when the iron concentration of the water in the distribution system approaches 0.3 mg/R.
Effects are predominantly aesthetic, such as the staining of enamelled surfaces of baths, hand basins and lavatory cisterns/bowls and laundry. Iron causes discolouration of water supplies when present at low concentrations in association with aluminium. Iron that settles out in distribution systems gradually reduces the flow rate of water. The only associated health effects are those that could arise from the presence of microbial deposits on internal surfaces of plumbing
It is imperative that you filter your water to a quality that you can rely on and in a way that when municipal systems fail you will still be safe. A water conditioner loaded with Green Sand or Birm sand is usually supplied to rectify this problem.