Question about chemical elimination of iron
asked 23 September 2015 asked by Redoxx (1140 points)
Bonjour, The answer is not straightforward and is subject to interpretation by local health authorities. If the chlorine is used as an oxidant and there is no organic matter in the raw water, this does not pose a problem. In the opposite case, especially with the risk of THM formation, your municipal authorities might say no. You mention breakpoint? Is this to treat ammonia? If so, treatment rates will likely be high and the municipal authorities will get involved. You could use oxidation via aeration with a high oxygen concentration, which often allows for biological removal of ammonia. The downstream chlorination rate would then be moderate.
In groundwater where there is reduced iron, it is not uncommon to also find ammonia (ammonium sulphide). Oxidation generates chloramines if the breakpoint is not exceeded and therefore the risk of an unpleasant “chlorine taste.” It is better to use only oxidization by air, possibly adding permanganate if there are traces of manganese.
Hello, Physicochemical deferrization using chlorine is approved, and there is normally no relationship to breakpoint chlorination. When we talk about breakpoint, it is essentially to treat ammonia. So if your raw water contains ammonia and you inject chlorine, you have to treat at the breakpoint to prevent by-products like chloramines, etc. This type of treatment is mostly used ‘as needed’ for contaminants because continuous treatment at breakpoint would likely be prohibited by the municipal authorities. So if your raw water does not contain ammonia, and little NOM, there is no reason deferrization using chlorine would be prohibited.