H2S removal using polyphosphates
H2S removal using polyphosphates
(OP)
Has any one used addition of polyphosphates as a means of removing H2S related odors in drinking water wells. Any input in regards to this will be appreciated. Thanks.
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H2S removal using polyphosphates
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RE: H2S removal using polyphosphates
RE: H2S removal using polyphosphates
Other methods include injection of chlorine or Potassium Permanganate.
I've never sequestered H2S; but, some chemical companies promote their poly/ortho/mixed phosphates as doing so.
RE: H2S removal using polyphosphates
I would be interested to know who those chemical companies are. I would like to look into that.
RE: H2S removal using polyphosphates
http://www.tramfloc.com/tf26.html
When I cross some others, I'll post them.
I've never used any of their products So I will not say if their products work or not. As you probably know, the literature for these types of products say a lot that sometimes isn't delivered. I know some has to do with the water characteristics; but, I think their lab results also show different things than in the real world.
RE: H2S removal using polyphosphates
Is the chemical safe at the maximum dose, and
Are impurities below the maximum acceptable levels?"
In other words it certifies that the chemical does not add "impurities" to the water. It does not "approve" that the chemical performs as claimed.
RE: H2S removal using polyphosphates
I've used; but, not been real supportive of sequestering agents. With really low Fe/Mn levels, they work ok (not great; but, ok); but, I've never found them to solve an Fe/Mn problem. They will keep them in suspension for some period of time; but, the metals eventually drop out if the water is not turned over in that time period.
In rural systems that I work with, the turn-over time is typically longer than the effective time of the phosphate.
I also feel system operators shouldn't believe everything in the chemical reps literature. There are still snake-oil companies out there. Don't get me wrong, there are some good companies with good products out there (for water and wastewater) and they have to shake off the images from the bad ones, which is a shame.
As I mentioned earlier, most of our H2S removal is done with aeration. It seems to do the better job.
RE: H2S removal using polyphosphates
H2S can be caused or aggravated by stagnant water and levels of chlorine residual dissipating. The argument is that the (1) polyphosphates reduce the chlorine demand by sequestering cations that exert cl demand, (2) polyphosphates protect CI pipe from corrosion fo free chlorine and (3) PolyPs helps clean out biofilm in system to reduce cl demand.
Now, does this argument hold water.
Also, Semo or Gary, can you tell me more about aeration, in terms of where, when and how you provide aeration to the system. And, have any of you successfully used the aeration and how much H2S levels were brought down. Thanks
RE: H2S removal using polyphosphates
Also in regard to those arguments, Do you have a problem with maintaining a Cl2 residual in the system? My thoughts are arguments 1 & 3 just means you use less chlorine (cheap cost); but, use PolyPs (higher cost) instead. I may be off base on this one; but, I've never seen free Cl2 by itself do damage to distribution mains either.
We utilize force draft tray aeration immediately after the well. There are numerous manufacturers of this equipment (U.S. Filter, Tonka, Layne-Christiansen, etc.). It does an excellent job of removing H2S (basically all) and also strips any CO2. This also increases the pH for a more friendly water. The H2S will form a weak acid in the water if left.
Following aeration, you will want to provide a detention tank sized with low downward velocities to help any released oxygen escape prior to pumping it into the mains. We typically treat for other constituants such as Fe/Mn so our settling basins do this; but, we have had surging problems with retrofits where air binding occurred in piping leading to a clarifier. This is typically solved using a (head tank) basin with low downflow rates (<0.5 ft/sec) where the air can escape. If no other treatment is necessary, this tank can also be sized for disinfection detention.
RE: H2S removal using polyphosphates
I have applied some and have seen others. The "when, why and how" and "how much" reduction is far too detailed to discuss here. I have seen H2S levels so low that they are not detected by testing with current testing methods but are detected by a sensitive nose. That is probably the closest I come to the "when". The "how and why" would depend upon the particular causer. Whether the causer be high sulfer content, H2S content or SRB/IRB content. The closest I can come to "how" is use aeration when caused by H2S as a gas. Use other conventions with high sulfur or SRB/IRB content. Where SRB/IRB is the causer, chlorination/retention/filtration is a "how". Another potential H2S as a gas is concerned would be filtration by Catalytic Carbon.