H2S removal using polyphosphates

[linus2003]

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.

 

[GarySCWSVI]

Never did that or even gave it a minute's thought. I don't believe it would work. Secondly, polyphosphates would be a food source for some of the bacteria that cause those odors.

 

[semo]

Is H2S the only problems. We find this problem along with high iron and manganese levels. Aeration is what we use to strip most of it from the water.

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.

 

[GarySCWSVI]

semo,

I would be interested to know who those chemical companies are. I would like to look into that.

 

[semo]

I've seen more; but, I can only find one right now (Tramfloc). The company has a website at

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.

 

[GarySCWSVI]

Not a good website for the use of PO4 for "sequestering" H2S. It indicates only the corrosion protection of piping by PO4. That is acceptable. However, H2S is a corroder and with PO4 you will get corrosion protection, but, no effect on the odor caused by H2S. In addition, they claim that their products are "approved by NSF under Standard 60" for "reducing and eliminating scale and corrosion in piping". First, NSF approves nothing. They are a "Certifier" to their standards. Standard 60 "addresses the health effects implications of treatment chemicals and related impurities. Both the treatment chemical and the related impurities are considered contaminants for evaluation purposes. The two principal questions addressed are:

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.

 

[semo]

I agree GarySCWSVI, having NSF approval means nothing except for the health effects.

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.

 

[linus2003]

The argument I have heard in terms of using polyphosphates for H2S odor is:
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

 

[semo]

I can see those arguments if the H2S culpret is SRB (Sulfate Reducing Bacteria); however, if it is dissolved gases as I interpreted in your first thread, it doesn't hold water.

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.

 

[GarySCWSVI]

Semo's suggestions are good. There are any number of aeration/retention/filtration processes that are available which include that wich semo suggested.

I have applied some and have seen others. The &quot;when, why and how&quot; and &quot;how much&quot; 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 &quot;when&quot;. The &quot;how and why&quot; 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 &quot;how&quot; 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 &quot;how&quot;. Another potential H2S as a gas is concerned would be filtration by Catalytic Carbon.