Iron & Mn Removal

[JeffNY]

I have a small non-community potable water system (5 gpm well yield for small demand)that requires iron and manganese removal (0.6 mg/l each, approximately).

System design already uses filtration, then chlorine injection to atmospheric tanks for contact time, then booster pumps to distribution. I'm wondering what is the most cost-effective treatment process to add to the system, considering the following options:

greensand filter

aeration (pumped air or aeration trays - though I've heard it can be slow?)

water softener

proprietary oxidizing filters

sequestration by polyphosphates

Are there other solutions I've not come across? I have raw water test data if there are parameters of concern for any of these treatment processes.

Thanks for any information.

 

[GarySCWSVI]

All of those you named are viable techniques. Which one would be best for you depends upon the analysis of the water to be treated and the use for the treated water. You can post the analysis here to get other responses or I would be happy to assist you if you send me the info. GSchreiber@puroliteusa.com

Gary Schreiber, CWS VI
The Purolite Co.

 

[bimr]

The greensand filter is probably the best option. If your hardness is above 120, then you should consider adding the water softener in series.

The aeration system is difficult to work in a small system and will not work with low pH.

Sequestration by polyphosphates will not do anything for you.

 

[jartgo]

I agree with bimr. Considering only the information you've provided, the raw water iron/manganese levels you've listed are low enough that I would not recommend the aeration. I assume these are your only constituents of concern, but as Gary mentioned, you should certainly compare your analysis with primary and secondary standards.

Having said that, I would continue to use filtration. However, I would suggest switching the location of your chlorine injection so that it's injected prior to the filters. Inject enough chlorine at that point so that your 2mg/L is available as residual after the filter. Chlorine injection will act as a particularly suitable oxidation process at these iron levels and will greatly increase the amount of iron removed in the filter. For that flow rate, I'd recommend a pressurized filter vessel at least 14 inches in diameter.