Iron removal in small community system 3

[edwards1800]

Current iron level is .6 ppm, manganese is .06 ppm. Peak demand is 50 gpm. What is the best (most affordable, low maintenance, simple operation) way to remove the to get it less than .3?

 

[GarySCWSVI]

A Manganese Greensand iron filter. Batch regenerated with Potassium Permanganate.

Gary Schreiber, CWS VI
The Purolite Co.

 

[edwards1800]

Can a water softener remove iron?

 

[semo]

I agree with Gary that Manganese Greensand Pressure Filter is the way to go; but, I'd use continuous regeneration with Permanganate.

You can use an ion exchange (softener) type of system to remove iron; but, it will be more maintenance. In addition, you don't list your existing hardness. Softening will probably require some mixing/bypassing which will reduce the iron reduction capabilities.

I've worked on both types of systems and given the information you have provided would select a pressure filtration system.

 

[bimr]

Would agree with the previous posters. You can use a greensand pressure filter or a water softener.

The water softener will be less economical if you have have elevated hardness levels.

 

[edwards1800]

The hardness is about 175 mg/L.

I have heard "horror stories" of stripping media from mis-feeding permanganate, so I thought (mistakenly?) that a softener would be easier to use. Your advice helps alot.

What options are available with greensand that make the permanganate addition easiest?

Up front, does an iron filter cost less than a softener?

 

[GarySCWSVI]

A Water Softener should handle the Fe & Mn unless some of it is insoluble precipitated form. Without going into great detail, both should be about the same cost to buy. The softener may cost more in the way of operating (buying salt) cost. If you want softened water then that would be the way to go. Your original posting just talked about Fe and Mn removal. In that case the Greensand method is the lowest cost, low maintenance and simple operation.

The easiest is the KMNO4 batch method I originally suggested. May we ask is this a municipal, commercial/industrial or a single home residential application?

Gary Schreiber, CWS VI
The Purolite Co.

 

[edwards1800]

Municipal. Thanks.

 

[sbush]

The best way to acheive your goal of <0.3 mg/L iron at 50 gpm is to use a pressure vessel filled with 24" of silica sand and a 6" anthracite cap.

Inject chlorine ahead of the filter(s)in a dosage sufficient to carry a residual of free chlorine after the filter(s).

Backwash the filter(s) whenever the pressure loss exeeds 25 psid or sooner if necessary.

If you have at least 238 gpm (15 gpm/sf loading rate) available for backwash, then a single 54" diameter by 60" side shell vessel should be adequate. If you only have the 50 gpm available for backwash from the well, then use five 24" diameter by 60" side shell vessels in parallel. Backwash each filter sequentially for 10 minutes each.

Manganese Greensand has a typical life of 5 - 7 years where as silica sand will last indefinitely in your application. Greensand media is fragile and cannot be operated in excess of 12 psid max. Greensand requires potassium permanganate feed, in addition to chlorine for disinfection residual, where as silica sand only requires chlorine. Manganese Greensand costs 8 times more than silica sand and costs more to operate.

Water softeners should not be used for iron removal. Ten States Standards and most health departments and regulatory agencies specifically exclude ion exchange softeners from consideration for iron removal. Ion exchange resin manufacturers typically require the feedwater to be virtually free of iron for warranty purposes. Using an ion exchange softener for iron removal would require that the total flow be passed through the treatment system without any bypass blending. This would result in very low hardness water in the distribution system that could result in problems with lead and copper leaching as well as corrosion of piping.

In addition, you should consult with your local regulatory agency for further advice and/or seek professioal assistance from a registered professional engineer with municipal water experience.

S. Bush

http://www.water-eg.com