H2S in hot water even with chlorination system 1

[ccbailey]

I have H2S in my water, excessive levels of Fluoride, and it has a high pH (>8.5). There is a chlorination system (Hypochlor 12) and carbon filter installed. When I add sufficient chlorine such that the hot water no longer smells, the residual chlorine on the cold water side is >10 ppm. I am told this is too high to direct through the carbon filter because it will spend the medium too quickly. It is also too high to drink, so I've fixed one problem and created another.

I am curious if anyone has any recommendations; preferably something that would solve the high fluoride, chlorine, and high pH? I do intend to get professional help, but it was professionals that supplied the current system, and I wouldn't be on this forum if it was doing everything I had hoped it would do!

I recently had a water test completed on my well water(with no chlorine added):

pH = 8.6
Conductivity = 651 uS/cm
Na = 148.6 mg/L
K = 0.34 mg/L
Ca = 2.88 mg/L
Mg = 0.49 mg/L
Total Hardness (CaCO3) = 9.2 mg/L
Fe = 0 mg/L
Total Alkalinity (CaCO3) = 273.8 mg/L
Carbonate = 302.7 mg/L
Hydroxide = 0 mg/L
Chloride = 3.2 mg/L
Flouride = 6.5 mg/L
Nitrite = 0 mg/L
Nitrate = 0 mg/L
Sulfate = 44 mg/L
TDS = 370.29 mg/L

The magnesium rod has been removed from the water tank. I have been advised in other forums to turn up the temperature of the water tank to kill the SRB's, but this is not a workable solution with young kids in the house (and the one night I tried it, the odor was absolutely horrible for the next couple days.)

 

[bimr]

I am somewhat puzzled by the direction that this posting is taking and reread the beginning to see if I missed something. Lets go back to the beginning.

I see that you mentioned SRB's in the beginning. I assume that you mean sulfate reducing bacteria. Well, SRB's are generally present only in sewage, not drinking water. The reason for this is that there are nutrients in sewage that will support the growth of sulfate reducing bacteria that can oxidize the sulfate ion.

In drinking water, there are generally zero nutrients, and zero bacteria. That is why there are no SRB's in drinking water. In addition, you are chlorinating at high dosages that will obviously preclude the growth of any organisms in the water.

Sometimes in dead end water mains, black water from ferrous sulfide may be encountered where bacterial action has resulted in reducing some of the sulfate content to sulfide. In such cases, the black water usually comes out in shots. For instance, when a hydrant is opened, there is a shot of black water for a few moments and then the water will run clean. The remedy for this is chlorination with a slight residual maintained thereafter. This situation is probably different than what you are experiencing.

Going back to hydrogen sulfide in your water. What makes you think that you have SRB's instead of naturally occurring hydrogen sulfide in your well water?

Yes, you can have hydrogen sulfide in well water. Most sulfur waters are ground waters. Most sulfur waters have sulfur concentrations less than 10 mg/l and the majority of the waters have sulfur less than 5 mg/l.

You need to determine the amount of hydrogen sulfide in your raw water. This has to be done in the field as shipped samples undergo sufficient oxidation during transport to vitiate the results.

Here is an inexpensive test kit that you can use to test for sulfide:

http://www.lamotte.com/pages/domwat/testkits.html

Regarding oxidation of sulfide by chlorine, this reaction will be complete within 10 minutes. So if you have a 10-minute retention tank, you can be assured that the oxidation reaction is complete.

The amount of chlorine required to oxidize 1 mg/l of H2S to sulfate is 8.32 mg/l. It should be immediately obvious to you that if you have 2 mg/l of H2S present, that you then need to add 16.64 mg/l of chlorine to oxidize the H2S. But since you do not know how much H2S is actually present, you also do not know how much chlorine to add, do you?

In summary:

1. It is very, very, very, very unlikely that you have SRB's in your drinking water system, especially since you are chlorinating.

2. Go get yourself a test kit and measure the amount of hydrogen sulfide present in the raw water.

Only then will you know what you are facing.

 

[ccbailey]

Stephenw22, thank you for the retention tank idea!

Bimr, I latched onto the SRB idea, because it was something that might explain why there is no chlorine residual on the hot water (and smell). Your prior posts explain that the temperature promotes ionization and hydrolosis. Does this imply that the pool test kits I use to test for Chlorine are not testing for the Cl- ion?

Documentation from the prior owner indicates the H2S is 4 ppm.

The advice I am receiving from the local treatment experts appears to be incorrect. Do you have any suggestions on how I might go about getting rid of the smell, and maintaining water that has a healthy level of chlorine. Once I get the chlorine levels down, I am plan on installing a point of use RO system.

Is it easy to raise the pH of the water without introducing other complications? It sounds like the high pH of my water is the primary reason I am not stripping the smell and having to use such high concentrations of chlorine.

 

[kenvlach]

Another approach to removing the H₂S is Fe⁺² addition to form FeS precipitate which is fairly dense, black & filterable.* Do to the raw water, before any chlorination.
Note that H₂S is present due to lack of Fe⁺² and dissolved oxygen in the source.

*A quickie metallurgical chemistry test for dissolved Fe⁺² is to bubble some H₂S through the solution. Also , note that Fe⁺² works better than many other sulfide-forming metals since it has negligible formation of other, soluble side species of types HMS⁺ or HMSO^-.

 

[bimr]

ccbailey,

If you will reread my post, you should see that you are not adding enough chlorine to completely oxidize the H2S.

The amount of chlorine required to oxidize 4 mg/l of sulfides, expressed as H2S is 8.32 X 4 = 33.28 mg/l. After the H2S is oxidized, you should find a chlorine residual of around 20-23 mg/l of chlorine, that you will then have to remove (probably with carbon).

Some other thoughts for you. Aeration is widely employed for reduction of the sulfide content of sulfur waters, but the reduction in water expecially in waters of rather high alkalinity, is usually only partial.

Hydrogen sulfide is very difficult to remove and changing the pH in a residential application is not easy to accomplish.



l

 

[bimr]

Correction to my last post:

The amount of chlorine required to oxidize 4 mg/l of sulfides, expressed as H2S is 8.32 X 4 = 33.28 mg/l. After 10 minutes, you should find that the H2S is oxidized and you have a chlorine residual of around 10 mg/l of chlorine.
The reaction is as follows:

H2S + 4Cl2 + 4H2O > H2SO4 + 8HCl

 

[ccbailey]

Are potassium permanganate systems with the Greensand filters a better alternative when you have high pH? I just learned that this is what a number of my neighbors have, and they are happy with their water. But, their wells are at a different depth than me, so I don't expect it is exactly the same water.

Chris

 

[bimr]

The pH is not going to have a large effect on greensand filters. Although, if you have a low pH due to carbon dioxide present, manganese may be stripped off the greensand and put back into solution.

Greensand filters are generally used for iron and manganese removal and can be used to remove up to 2-3 mg/L of hydrogen sulfide. Potassium permanganate is a rather expensive chemical, so that is the main reason that the greensand process is limited to applications with low amounts of iron.

The higher the concentration of hydrogen sulfide, the more frequently the greensand unit will need regeneration and backwashing.

http://resources.cas.psu.edu/WaterResources/pdfs/HydrogenSulfide.pdf

 

[ccbailey]

Thanks Bimr,

You have indicated that I need to inject about 20 ppm of chlorine, and I will have a residual of 10 ppm to remove all H2S. This seems to be consistent with my experiences. Is it easy for you to explain the math/chemistry in terms of how you generated this number (I have lost all chemistry skills). The reason I ask is because I am dealing with people that are telling me that the chlorine should be added at 4 ppm, with a residual of 0.5 ppm.

Will a carbon filter handle a residula of 10 ppm? I have been told that it will spend the media very quickly.

Thank you,
Chris

 

[bimr]

The reason for the difference is that your sources are only calculating the amount of chlorine to oxidize the hydrogen sulfide to sulfur, not the amount of chlorine to oxidize the hydrogen sulfide to sulfate.

Unfortunately, you cannot add just enough chlorine to only oxidize the hydrogen sulfide to sulfur since the oxidation reaction to sulfate occurs and can not be stopped. The oxidation to sulfate takes place to a great extent even when there is a deficiency of chlorine is added.

This reation shows the amount of chlorine (2 mg/l) to oxidize 1 mg/l of H2S to sulfur:
H2S + Cl2 > S + H2O

This reaction showss the amount of chlorine (8.32 mg/l) to oxidize 1 mg/l of H2S to sulfate:
H2S + 4Cl2 + 4H2O > H2SO4 + 8HCl

Here are links to a few pages from an old out of print textbook that may help.

http://home.earthlink.net/~bimrone/sitebuildercontent/sitebuilderpictures/0227_001.jpg

http://home.earthlink.net/~bimrone/sitebuildercontent/sitebuilderpictures/0226_001.jpg

If you enlarge the pages, you should be able to read them.

 

[ccbailey]

Thank you Bimr for the scanned information!

A company in my area is going to try a Centaur Carbon System on my water. I did a search through the archives, and I can not find this product mentioned. Based on Calgon's website, this is a carbon product designed specifically for H2S removal. Essentially he is going to remove my chlorine system and just have a carbon filter.

He tested my water at +5 ppm H2S (that is where his test kit topped out). However, based on his experiences in our area, he is quite confident it will work. I am skeptical, but he has promised to remove his equipment and replace my old equipment for free if it does not work (yes, I have it in writing). Basically, I have nothing to lose except the H2S from my water.

Does anyone have experience with the Centaur Carbon product? I am concerned how quickly the media will spend. I am also curious whether the removal of the H2S is negatively impacted by the high pH?

Thank you,
Chris

 

[ccbailey]

Thank you to everyone for the information - I learned a lot.

I thought I would give everyone an update. This centaur carbon system is amazing so far. We are not adding any chlorine. There is a passive system to suck air into the line before the pressure tank, and there is one to take it out after the retention tank (we left the 80 gallon retention tank plumbed in). Then the water passes through a Centaur Carbon System.

I can't smell H2S on either the hot or cold. I can taste something in the water (I think it is H2S). Hopefully we can get an RO system to work now. The guy that installed it is expecting we will get several years of the carbon before we need to rebed.....

Chris