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]

You have few options on this water. The fluoride concentration is too high making the water unsafe to drink.

You need to use a RO system to reduce the fluoride to a safe level. The RO system will also reduce the pH of the water.

Hydrogen sulfide is very difficult to remove. Hydrogen sulfide is usually removed with aeration and the aerated water is then chlorinated to oxidize any residuals. The amount of chlorine required to oxidize 1 ppm of H2S to sulfate is 8.32 ppm. This is not easily done in a residential application. Please provide information on the hydrogen sulfide concentration.

 

[ccbailey]

Thank you bimr,

I don't know the hydrogen sulphide concentration - where can a guy get a test kit (I'm in Canada, so a source up here is even better)?

I have heard of locals pumping water from their well into 300 gallon atmospheric tanks in their basement and adding 0.5 ppm of chlorine. The tanks are vented to the outside of the house, and then they pump the water into a pressure tank and through a carbon filter. I don't believe they are physically pumping air through the water - it is just a passive system. Is this a typical aeration setup? I have also heard that aeration introduces other problems. I suspect aerobic bacteria, but I don't know????

I am an engineer by training, but water and chemistry are not my specialty. I am hoping someone can explain some of the concepts to me (or direct me to some good resources). What causes high pH in water? What is it that the RO unit will remove that reduces the pH? I have heard that the higher the pH, the harder it is to remove H2S. Is there a simple explanation for this?

Is there such a thing as whole house RO units? Are they high maintenance? Do they cost an arm and a leg?

Thank you,
Chris

 

[cub3bead]

He you go...

At the higher pH the S is present as sulfide (S--) rather than HS- or H2S. If you acidify shift the equiulibrium back to HS- and H2S and with aeratation you can get rid of the H2S rather easily but your neighbors and the local airboard may not appreciate your efforts unless you scrub the H2S from vented gases. H2S scrubbers by the way use bleach and cuastic to obtain an elevated pH and oxidize the H2S.

Most residentail RO units are small point of use but you should be able to find whole house ones. The high F and alkalinity of your water are the biggest concerns with RO scaling. At 75% recovery you would be over 1,000% saturated for CaF2 so you will need an antiscalant. CaCO3 is a problem that can be addressed with acid or an antiscalant.

The RO unit rejects the bicarbonate and carbonate but passes the CO2, if it is present and it should not be at your pH, but would be if the water is acidified. Normally what happens is the ratio of CO2 : HCO3 changes across the membrane resulting in a pH drop to 4.5 - 5.4 range.

Now to an alternative solution. If you only use this water for services other than drinking water you might get by. This would mean you would need a bottled water supply for drinking, cooking, etc.

Ashai makes a F specific ion exchange resin but it is rather expensive.

A most interesting water.

 

[ccbailey]

Thank you,

In all of my reading, and asking local professionals, no one can explain why there is no chlorine residual on my hot water and there is a chlorine residual >10 ppm on the cold (measured at the tap). I have been monitoring for months, so these aren't bad readings. At present, I am adding chlorine just in front of the pressure tank. From the pressure tank, the water goes to a retention tank. From the rentention tank, the water goes to the carbon filter. I am by-passing the carbon filter because the chlorine residuals are too high and will spend the medium too quickly. From there, the water either goes into the cold water supply or into the hot water tank. If I reduce the chlorine, I can bring the residuals down on the cold water, but the hot water begins to smell.

Any thoughts are appreciated. I wonder if it has something to do with the high pH. Is there an easy way to bring down the pH in a home water system?

Thank you,
Chris

 

[bimr]

Hydrogen sulfide is an unusual water parameter in that it is feebly ionized. At low pH's hydrogen sulfide is present as a gas. At high, pH's the hydrogen sulfide, changes to an alkaline sulfide. So you can air strip H2S at low pH, but not at high pH.

http://www.freedrinkingwater.com/water-education2/78-hydrogen-sulfide.htm

Sulfide determinations must be done in the filed as shipped samples will allow the H2S to oxidize in route to the laboratory.

If you spray the water into your retention tank, you may be able to air strip the H2S with the spray nozzle.

Oxidation of H2S by chlorine is more rapid and complete at low pH's than at high pH's.

You are correct in being concerned regarding bacterial contamination of the water when it is left exposed to the atmosphere.

There is no chlorine in your hot water because the reactions of chlorine with water (hydrolysis and ionization) increase with temperature. The chlorine is being converted to the cl- ion.

 

[ccbailey]

If teeth absorb fluoride from tooth paste, is it also fair to say that fluoride is absorbed through the skin when bathing? Or is this a bad analogy. If it is correct, perhaps a whole house RO is the only good alternative?

It is my understanding that almost all of my sulphide exists as the HS- ion because of the high pH. Does the HS- ion have a rotten egg smell, or is it the minute amounts of H2S gas that is dissolved in the water that has a smell?

Can someone specify the chemical reactions (or point me to a resource) that indicates how chlorine oxidizes H2S? I am also interested in the reaction that oxidize the HS- ion (does this reaction resist)?

Chris

 

[quark]

You can give a try with activated alumina for fluorides. This is a cheaper option.

 

[bimr]

Teeth do not absorb fluoride from toothpaste. There has never been a double blind study that proved fluoride had any benefits. Ask your self the question, would the teeth retain any benefit if mud (or anything else) was smeared on the teeth and washed off.

Fluoride is not absorbed through the skin, only orally.

Only H2S, not HS has the smell, but the odor is so strong that you are able to detect minute quanitities.

Oxidation reaction:

H2S + 4CL2 > S + H2SO4 + 8HCl

Note that the acids produced by the oxidation reaction will neutralize alkalinity, slightly lowerly the pH of the water.

However Quark is correct, you should also investigate fluoride specific treatment as well. You can get a cartidrige filter or a whole house filter for fluoride.

Rereading your post a question comes to mind. Is this a new well?

Also, have you talked to the well driller regarding the water quality? There may be another option such as a deeper well. And what are the other well water users in your vicinty doing for treatment of this water.

 

[mmenarry]

I wouldn't see aeration as causing a huge problem in terms of promoting aerobic bacteria, the BOD of well-water should be pretty low (no food for microorganism to lunch on).

Sparging the water would aerate to a certain extent, and should strip some of the H2S out, but sparging from a pipe would be an unusual (although damn cheap) method of aeration.

A more effective method of aeration would be to install a break tank, with a small blower & diffuser. Costlier than sparging, but you'd only need a relatively small blower (figure $100-$200), diffuser ($15-$30) and a tank (100-200 gals, preferably a tall one rather than a narrow one). I have never seen it done on a small scale, admittedly - but it is certainly possible.

Chlorinate afterwards (aeration will "blow" the Cl out of the water in a short timescale). What you're doing at present is only masking the smell of sulphide with the smell of chlorine, by the looks of things (10mg/l of Cl stinks like crazy, but I guess that's your problem at the moment)

As I said, I have never seen this done in small scale, but is certainly a cheaper "try" than RO, and should be relatively easy to retro-fit to your current setup. Diffuse aeration would also have the benefit of being quieter than sparging.

If it works well, you could sell similar systems to your neighbours ;o)

M.

 

[ccbailey]

Assuming the chlorine oxidizes all available H2S before the fluid gets to the hot water tank, is it possible that some of the HS through the addition of heat is converting back to H2S and giving a smell?

It is not a new well. I don't know many of the neighbors, but the ones I do know, have high fluoride problems too.

Based on what I could find on the internet, it seems that there is a big difference between Calcium Fluoride, and the stuff they add to the city water supply in terms of toxicity.

Chris

 

[bimr]

Oxidation of hydrogen sulfide by chlorine should be complete within 10 minutes. You need to be adding 8.3 mg/l of chlorine for each mg/l of sulfide. At the pH (8.6) that you have, approximately 40% of the sulfides will be oxidized to sulfate (SO4) and 60% of the sulfides will be oxidized to water and sulfur.

The sulfur should show up as finely divided black particles in the water.

Is it possible that you are not adding enough sulfur to complete the oxidation?

Is it possible that what you smell is sulfur?

It would take bacterial action to convert the sulfate back into sulfide. That is very unlikely. The sulfur is not going to dissolve back into the water.

Calcium fluoride dissolves in water and there is no difference in terms of toxicity between natural background fluoride and the added calcium fluoride.

Hopefully, your neighbors are not drinking high fluoride water. Just because something is naturally occurring, it does not mean that it is not toxic.

http://www.fluoridealert.org/limeback.htm

http://www.fluoridealert.org/absurdity.htm

http://www.fluoridealert.org/health/epa/nrc/excerpts.html

 

[monaco8774]

Late starter on this one but you realise that despite numerous myths about what will kill SRB or H2S forming bacteria they are all based on information from 60s and 70s and are largely out of date. There are now hundreds of recognised forms of bacteria that can give you high H2S levels. These are anaerobic bacteria and will be living beneath slime and (possibly corrosion products) within your tank unless they are delivered in large numbers from your source. In either case your chlorine is not killing them, note also that there are many species that can live at pH above 9 which will be the dominant species in your case and also these forms are immune to temperature above 150 C. If the chlorine was contacting them for more than 30 minutes at 0.5ppm it would kill them so you need to clean up your system first before you can solve your problem.

Numerous chemical ways of doing this but I recommend draining the system and inspecting / cleaning it. Then you will be able to treat it at a reasonable low dosage of chlorine to keep it clean.

Note also that activated carbon will simply remove the chlorine and any organic carbon sources, all it will do for your bacteria is give them plenty of breeding surfaces.

When you look at your system think about the spots where bacteria might be breeding and start with those.

Good luck

 

[ccbailey]

Thank you,
- in the oil patch, SRB's survive at temperatures well in excess of the temperatures in hot water tanks. Is your ascertion that they are still producing H2S (even with a continuous chlorine feed >> 0.5 ppm), and this is what is consuming the chlorine in my hot water tank?

- someone suggested that my chlorine is so high that I have just replaced the smell of H2S with chlorine. Ironically, my water does not have a strong chlorine smell. It smells a bit like sulphur. I test the chlorine content using a test kit from a pool. Do the titration chemicals ever expire? I am wondering if perhaps my readings are inaccurate? The instructions for the test kit indicate that I am to add drops of the chemical to the water, and then compare it to the color scale provided. The kit is only good for 4 ppm chlorine. By the time I add the 2nd drop, the color is already a dark yellow and well past 4 ppm. This is what I have been calling >10 ppm. I recognize I should be diluting the water with distilled water in order to get an accurate reading past 4 ppm, but I have been lazy.

- has anyone ever read a scientific study that supports the claim that naturally occuring fluoride is absorbed through the skin? With all of the hysteria on the net, I am unable to sort out fact from fiction. Some websites suggest I should not even bath in my water. IF this is true, a point of use treatment for the fluoride is not going to work, and I will be forced to look at whole house solutions.

 

[monaco8774]

Sorry forgot an important point, chlorine works as a biocide by dissociating to hypochlorous acid, if your pH is alkaline it is completely innefective, belo pH of 6 it is 100% effective, i.e. 10ppm chlorine gives you 10ppm of killing power, at a pH of 8 its only 20% effective so your equivalent to 2ppm at 10ppm measured. Note that at 10 and above its completely useless.

As for the hysteria on the web about flourine, Flourine was originally put in drinking water to combat diseases such as cholera, before flourine this was a big killer post the use of flourine in drinking water the disease has practically disappeared. I have yet to hear of anyone dying of flourine poisening but I guess it is a powerfull oxidant so its not completely harmless. The reality is you take a slight risk to overcome a real killer.

 

[bimr]

ccbailey,

The primary drinking water standard in the US for fluoride is 4 mg/l. As a minimum, you should at least treat your drinking water such that the fluoride is below that level.

monaco8774 (Petroleum)

ccbailey is inquiring about the removal of naturally occurring H2S from groundwater, not something produced from anaeobic decomposition of the sulfate ion. ccbailey is also talking about potable drinking water so your comments regarding killing power of chlorine are somewhat off the mark.

Chlorine oxidation of H2S is effective anywhere between the pH of 3.2 to 10.1 units, which is well outside pH range of drinking water. Get yourself a copy of Water Treatment by Eskel Nordell if you have any doubts.

Regarding "hysteria on the web" regarding fluoride, fluoride has never been used for cholera prevention. The last outbreak in the US of cholera was in 1911, whereas fluoridation of water did not begin until the 1950's.

Here are some sources for poisoning and deaths from fluoride:

http://www.fluoride-journal.com/97-...soning from fluoridation of water systems USA

ccbailey, here is a good answer regarding absorption of fluoride through the skin:

http://answers.google.com/answers/threadview?id=37038

 

[bimr]

Here are some more options for you:

Hydrogen sulfide concentrations up to about 5 to 7 ppm can be removed using an oxidizing filter. These filters are similar to the units used for iron treatment . This filter contains sand with a manganese dioxide coating that changes hydrogen sulfide gas to tiny particles of sulfur that are trapped inside the filter. The sand filter must be backwashed regularly and treated with potassium permanganate to maintain the coating. Hydrogen sulfide concentrations exceeding 7 to 10 ppm can be removed by injecting an oxidizing chemical such as household bleach or potassium permanganate followed up by filtration. The oxidizing chemical should enter the water upstream from the storage or mixing tank to provide at least 30- 45 minutes of contact time between the chemical and water. The length of the holding time is a function of the chemical dosage, tank configuration, and water temperature. Sulfur particles can then be removed using a sediment filter and the excess chlorine can be removed by activated carbon filtration. When potassium permanganate is used a manganese greensand filter is recommended.

http://www.water-research.net/sulfate.htm#sources

 

[stephenw22]

I had a similar problem with my hot water system, and I took care of the problem with a strong chlorine shock. This is how I did it:

1. Drain the hot water heater
2. Fill hot water heater with a high concentration of chlorine. Depending on what you have around, there are several ways to do this. What I did was to remove my main sediment filter (upstream of the heater tank) and fill the housing with 12% chlorine solution (approx 1L). Then I filled the hot water tank from my main water line, and the chlorine was pushed into the tank.
3. Let it sit for a while (I let it sit overnight)
4. Drain the tank
5. Fill and drain the tank 1 more time just to flush out any chunks of stuff that might have loosened.

 

[ccbailey]

Thanks Stephen,

It seems there are two possiblities:
1) There is a colony of SRB's in the hot water tank and the H2S generated by them is consuming the chlorine.
2) The water chemistry is such that the heat of the water tank is consuming the chlorine and some of the HS ion which is present at these high pH's is being converted to H2S.

I am planning to shock chlorinate the tank to eliminate option #1. SRB's form a gellaceous coating, and I am told they will survive, but the chlorination should set them back for a bit. It should be noted that I have not found "slime" in any part of my water system yet, so this makes me think Option 2 is more practical (but I don't know if there is any science to my assumptions????)

I am talking to the people that installed the water system, and they think I don't have sufficient retention time for the chlorine to oxidize the H2S. They want me to spent $4500 on a 2nd tank, and an extra filter. I don't believe this will solve the problem because we have not noted that the problem is any worse under conditions of high or low water use. Once I fix the chlorine problem, they want another $1500 to $2000 for a point of source RO system. Does anyone know what an 80 gallon, fiberglass pressure vessel is worth or a filter to knock out any solids the chlorine knocks out? Any time I flush my tanks, I find almost no solids. I wonder if the small, cheap filters you get at any hardward store (without back wash), would suffice? Currently I have no complaints about sediments in the system, and I have no filter downstream of the retention tanks (and I am by-passing the carbon filter).

Chris

 

[stephenw22]

As a test, you could fill a big pot with water, cover it, and warm it up to around the same temp as your hot water heater. Let it sit for a few hours, and then go back and take the cover off and see what it smells like. A pressure cooker would be ideal, since it has a nice tight sealing surface. This would let you know if it's the water or the heater.

As far as a retention tank goes, you can find a cheap 60-gallon electric water heater, and just don't power it up.