How to treat water to remove iron and manganese

How to treat water to remove iron and manganese

Chlorination (Oxidation) Plus Filtration (5 ppm to 25 ppm of Iron)

Chemical oxidation followed by filtration is the accepted method of iron and manganese removal when concentrations are greater than 5 ppm. A number of strong oxidants have been used in this procedure; however, chlorine is generally used in household systems

A chlorine solution is injected with a chemical feed pump ahead of a sand filter. Soluble iron and manganese begin to precipitate almost immediately after contact with the chlorine solution. However, approximately 20 minutes of contact time is needed for the precipitate to form particles that can be filtered. Often the standard 42 gallon pressure tank used on many household systems will provide the needed contact time if water is forced through the tank. A simple T-connection from the pipeline to the pressure tank will not work, since much of the water bypasses the tank. Additional contact time can be provided by connecting another tank in series or using a plastic pipe coil.

This type of system will remove both soluble and suspended particles of insoluble iron and manganese from the source water. Backwashing the sand filter to remove precipitated iron and manganese is an important part of continued filtration. As with the greensand filter, the system flow rate should be checked to make sure it can provide the needed rates for backwashing. An additional advantage of using the chlorination system is its bactericidal effect. Iron and manganese bacteria along with other bacteria, are destroyed. Potential clogging problems in the sand filter are eliminated. Chlorination does produce trihalomethanes (THM) when organic matter is present in the water. THMs are considered to be carcinogenic (maximum contaminant level permissible in public water systems is 0.1 parts per million) and if necessary can be filtered out with an activated charcoal filter

The optimum rate of oxidation of iron and manganese by chlorination is at a pH of about 8.0 and 8.5, respectively. Soda ash injected with the chlorine will increase the pH to optimum levels. Adjusting the pH to alkaline levels also reduces the corrosiveness of the water in pipes and plumbing.