Help with existing filter system


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Old 07-23-08, 09:10 AM
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Help with existing filter system

Professional lab water analysis 7/17/2008

Arsenic, Total <5 ug/L
E. coli <1 MPN/100mL
Chloride, Total 16 mg/L
Copper Total <0.05 mg/L
Iron Total 10 mg/L
Flouride <0.4 mg/L
Hardness by Calculation 20 mg/L
Manganese Total 0.57 mg/L
Sodium Total 12 mg/L
Nitrite-Nitrogen Total <0.2 mg/L
Nitrate-Nitrogen Total <2.0 mg/L
Lead Total <0.010 mg/L
pH electrometric 5.7
Total Coliform Colilert MPN <1 MPN/100ml

my comments:
This is a private well of 180ft drilled in 9/04. Water is clear when first drawn but will turn rusty if left to sit open or heated. Precipitated iron will settle but very slowly, takes longer than a week. We do not have a pool and do not water our lawn. There is a water filter system in place professionally installed that consists of a variable Stenner pump injecting a measured amount of bleach before an 80G pressure tank (Well Mate). This precipitates the iron. Then a filter tank of 2.0 cubic feet of Filter Ag with a backwashing filter head (Water Soft) to remove the precipitated iron. Then to a 2.5 cubic foot tank with a mixture of 2.0 cubic feet of activated carbon and 0.5 cubic feet of calcite to remove the residual Chlorine and to raise the pH. The level of residual chlorine is monitored by sampling the water after the Filter Ag tank and before the carbon/calcite tank, I typically maintain a residual of 1.0 mg/L.
We get a significant amount of precipitated iron that will bleed through the Filter Ag tank, especially at high flow rates. I do not like the fact that the Filter Ag tank backwashes with "dirty" water. I do not like the fact that the pH problem is not addressed before trying to precipitate the iron. I have added a draw off valve at the very bottom of the 80G pressure tank so that I can periodically remove any iron sludge that accumulates in the bottom of the tank. I do not have any confidence in the local person who designed and installed the system and would appreciate any suggestions you may have as to any additional equipment or changes to the system. Some specific questions/ideas that I have:

1. Could I fit a double Stenner head to the pump so that I can inject bleach as well as soda ash to raise the pH at the same time the iron is oxidized? Do those reactions work together?

2. Could I change the Filter Ag tank to a mixture of Filter Ag and calcite to correct the pH at the same time as the precipitated iron is being removed? Does calcite have any filtering properties? Could the filter tank be 100% calcite? Can I filter and correct the pH at the same time?

3. Is 2.0 cubic feet of filtering media sufficient to remove 10 mg/L of iron? Should that tank be bigger?

4. How much activated carbon is needed to remove a chlorine residual of 1.0 mg/L?

Dave
 
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Old 07-23-08, 06:20 PM
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Originally Posted by Dave-O View Post

my comments:
This is a private well of 180ft drilled in 9/04. Water is clear when first drawn but will turn rusty if left to sit open or heated.
This indicates ferrous iron turning to ferric iron.


Originally Posted by Dave-O View Post
Precipitated iron will settle but very slowly, takes longer than a week.
There is a water filter system in place professionally installed that consists of a variable Stenner pump injecting a measured amount of bleach before an 80G pressure tank (Well Mate).

More accurately, you have a retention tank. Pressure tanks have air bladders in them.

Originally Posted by Dave-O View Post
This precipitates the iron. Then a filter tank of 2.0 cubic feet of Filter Ag with a backwashing filter head (Water Soft) to remove the precipitated iron.
I suppose this is on a timer. If so, how often does it backwash?


Originally Posted by Dave-O View Post
Then to a 2.5 cubic foot tank with a mixture of 2.0 cubic feet of activated carbon and 0.5 cubic feet of calcite to remove the residual Chlorine and to raise the pH.
I never heard of a calcite / carbon mix. 0.5 cuft of calcite is not enough to raise pH from 5.7 to 7ish. Backwashing rates of those two media is different and the calcite make break the carbon up into fine particles taht, in turn, are backwashed out depleting the total.

Originally Posted by Dave-O View Post
The level of residual chlorine is monitored by sampling the water after the Filter Ag tank and before the carbon/calcite tank, I typically maintain a residual of 1.0 mg/L.
That is a good residual amount of chlorine.

Originally Posted by Dave-O View Post
We get a significant amount of precipitated iron that will bleed through the Filter Ag tank, especially at high flow rates. I do not like the fact that the Filter Ag tank backwashes with "dirty" water.
Twin tank backwashing filters have the advantage of backwashing with treated water. Kinetico's Macrolite media (engineered ceramic) filters down to 3-5 microns. Fliter ag is between 20 - 30 microns.

Originally Posted by Dave-O View Post
I do not like the fact that the pH problem is not addressed before trying to precipitate the iron. I have added a draw off valve at the very bottom of the 80G pressure tank so that I can periodically remove any iron sludge that accumulates in the bottom of the tank.
Draining the tank is very important.

Originally Posted by Dave-O View Post
I do not have any confidence in the local person who designed and installed the system and would appreciate any suggestions you may have as to any additional equipment or changes to the system. Some specific questions/ideas that I have:

1. Could I fit a double Stenner head to the pump so that I can inject bleach as well as soda ash to raise the pH at the same time the iron is oxidized? Do those reactions work together?
Yes, < http://www.stenner.com/product.htm > you can cahnge to a double head. It is a good product.

Originally Posted by Dave-O View Post
2. Could I change the Filter Ag tank to a mixture of Filter Ag and calcite to correct the pH at the same time as the precipitated iron is being removed? Does calcite have any filtering properties? Could the filter tank be 100% calcite? Can I filter and correct the pH at the same time?
I have never done this but it makes more sense than than mixing carbon and calcite. pH below 6.0 will need a mix of calcite and MagOxide.
Originally Posted by Dave-O View Post
3. Is 2.0 cubic feet of filtering media sufficient to remove 10 mg/L of iron? Should that tank be bigger?
Yes, it should be if washed often enough and the media is fine enough. Again, twin tank systems have an advantage in preventing bleed through.

Originally Posted by Dave-O View Post
4. How much activated carbon is needed to remove a chlorine residual of 1.0 mg/L?
Not very much. I simple upflow (no backwashing valve) can do that effective as long as sediemt has already been cleared. 1.5 cuft might be a good start.

You have very challenging water and it can be fixed.

Andy Christensen, CWS-II
 
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Old 07-25-08, 09:17 AM
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Thanks for the reply the information helps a lot

I suppose this is on a timer. If so, how often does it backwash?

Yes it is my understanding that the WaterSoft filter head is just a re-badged Fleck 5600.


Twin tank backwashing filters have the advantage of backwashing with treated water. Kinetico's Macrolite media (engineered ceramic) filters down to 3-5 microns. Fliter ag is between 20 - 30 microns.

They sound interesting, unfortunately the closest dealer is 3 hours away. I'll keep it in mind as I consider my options.


I have never done this but it makes more sense than than mixing carbon and calcite. pH below 6.0 will need a mix of calcite and MagOxide.

What volume and mix ratio would be appropriate?


You have very challenging water and it can be fixed.

Do you have any experience with hydropneumatic set-ups, where the iron and manganese is oxidized by injecting air into the incoming water which is then maintained as a large bubble of air in the retention tank. The UT80 Well Mate tank I already have can be converted to this type of tank. Then I could inject soda ash prior to the retention tank to correct the pH, oxidize the iron and manganese in the hydropneumatic tank and then filter with the two tanks I already have. I have no idea whether the UT80 tank is big enough to allow for the complete oxidation. How quick are the soda ash and oxidizing reactions? Not as "clean" a system as the Kinetico because I would still be backwashing with dirty water.

Thanks again for the help.
Dave
 
 

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