[PS: I love Halifax]
Posted on 06/30/2009 7:33:17 AM PDT by Daffynition
The Halifax water commission has ordered two $5,000 ozone generators in an effort to solve the persistent sewage gas odour problem in parts of the city's downtown.
The smell of raw sewage has permeated the waterfront area around the Halifax casino since a nearby sewage treatment plant failed and flooded in mid-January.
The main goal is to mitigate the stench, said James Campbell, spokesman for Halifax Water.
"For the businesses and the residents, that's what we want to do," he told CBC News on Monday.
The decision to buy the ozone generators comes after a 20-year-old model was lowered down a manhole on Cogswell Street 10 days ago and hydrogen sulfide gas readings dropped "significantly."
"The results were quite successful," Campbell said. "And that was with a smaller unit. We're hoping with a larger unit that we're going to get in the next week and half we'll have even better results."
Campbell said the machine produces ozone, which essentially oxidizes the hydrogen sulfide molecules and turns it into a water-based compound, thereby eliminating the odour and the gas. Ozone chases odour away
The machine that convinced the municipality that ozone could solve the sewer gas problem belongs to Greg Murray, owner of Clean Air & Water Centre in Halifax. Murray said he was able to convince Ted Tam, the general manager of Halifax Harbour Solutions, to give his product a try.
Before the ozone generator was lowered into a catch basin, Murray said, hydrogen sulfide gas readings were around 150 parts per million.
"One minute after that machine was in place they were down to 60, and they would have kept going down if they left it longer. But one minute was all it took," Murray said.
The small, gold-coloured aluminum machine is more than 20 years old. It was once used as a smoke eater in a cigarette-smoking room at the Nova Scotia Rehabilitation Centre, part of the QEII Health Sciences Centre.
Simpson Environmental of Burlington, Ont., is supplying the two Model SF 5000 ozone generators.
"I would think it's going to make a huge difference. The ones we're bringing down are very potent machines, and they'll maintain ozone levels at quite a distance. If we're at the right place at the right time, we're going to get pretty close to zero residual odour down there," Murray said.
"Where the ozone is, the odour is going to be pretty much gone. We've been doing this for 25 years now and we've had a lot of good experience." Deodorant blocks, carbon filters
Municipal officials have tried a number of methods to eliminate the stench of sewage.
Earlier this month, they installed carbon filters and large deodorant blocks at two locations in the catch basin by the Halifax casino. The filter traps the gas, while the block masks the smell.
Officials expect the failed sewage treatment plant will be back in operation by next spring.
[PS: I love Halifax]
Gambling stinks.
parsy, who you can bet doesn’t gamble
What "water-based" (does he mean "water soluble"?) compound? H2SO4?
Ozone reacts immediately with hydrogen sulfide (H2S). But ozone generators are typically expensive. 2 $5,000.00 units probably produce no more than 30 - 40 grams per day (on oxygen). They could have bought 2 of mine for only $2,500.00 per unit. I love capitalism.
I'm sure it does. Ozone is a strong oxidizer. Am I correct about the product of the reaction?
SO2 or SO3- depending on the conditions. Both are very soluble. SO3- reacts with water to make H2SO4. Usually, the acid is very dilute and is subsequently neutralized by CO3- or CO2.
I’m in the business myself of using ozone as a means of eliminating odors.
Ozone IS very effective at oxidizing airborne contaminates... but it can also be lethal.
See... Ozone is simply O3... we breathe O2.
but our lungs cannot absorb 03. Long term exposure to high levels can result in asphyxiation. (sp?)
There is also the issue of free radicals.
O3 is very unstable, and converts back to O2 by shedding one of it’s oxygen atoms. It is that free radical of oxygen that seeks to bond with something else that “oxidizes” the odor source. Free radicals of any sort are considered a risk for triggering cancerous mutations. (so I’ve heard)
Ozone exposure is damaging to the inside linings of the nose and lungs, just as it is damaging to the bacteria cells that it eliminates. It is very much like using chlorine to sanitize pool water, only it is applied to volumes of air. Interestingly enough, ozone also has applications in purifying water.
Experience has taught me that while ozone IS quite effective, it is NOT a cure-all. It CANNOT physically remove the SOURCE of airborne contaminates such as feces or mold. It does have a limited capability to penetrate porous surfaces and oxidize small particles, but in the long term, it will do just as much damage to soft surfaces such as wiring (soft rubbers) in the process.
It is best to use ozone as a FINAL stage of cleanup... using it to take care of what conventional cleaning techniques cannot. REMOVE the source first, evacuate the air, and THEN shock with ozone.
From what little I can gather from this article, they are using ozone in a contained outdoor environment (sewer).
While they may be getting lower sulfer dioxide readings, they are most likely now getting much higher than normal ozone levels that should be considered dangerous to maintenance personnel.
I would recommend to them that they install an air evacuation system (like a large scale radon evacuation system), and TREAT THE AIR IN THE EVACUATION VENTS as it is being forced into the atmosphere.
This should do 3 things for them...
1. Make it safer (and more pleasant) in the source area
2. Eliminate the odor before it is released into the atmosphere where the ozone can dissipate safely
3. REDUCE the amount of ozone they need to fix the problem.
Of course... applicability of this is not based on 1st hand knowledge of the situation... just going by what I’m reading.
>>> They could have bought 2 of mine for only $2,500.00 per unit. I love capitalism.
How many milligrams per hour?
Corona discharge or UV based?
OK
Usually, the acid is very dilute
Not surprising ... the actual quantity of H2S in question is quite small
subsequently neutralized by CO3- or CO2.
What's the product of that reaction? I'm curious as to where the sulfur ends up.
Very interesting. The Halifax people are using a machine that is more than 20 years old. Do you think that this effect the results?
>>> Very interesting. The Halifax people are using a machine that is more than 20 years old. Do you think that this effect the results?
If it’s more than 20 years old, it is most likely electrical.
Spark based generators also produce nitrous oxides as a by-product. The grid or mesh that generates the ozone becomes calcified with dirt and carbon over time and must frequently be cleaned. Otherwise the ability to generate the ozone is significantly reduced to a point of zero with no maintenance. I have to regulary clean my ozone generators to keep them at peak performance... and when I expose them to environments with heavy levels of contaminates and humidity (like a sewer), maintenance requirements are drastically increased. Electrical based generators operate best in conditions of very low humidity. If humidity is too high, efficiency of the generator is reduced, the ozone itself cannot travel as well, and the generator plates quickly become contaminated.
The advantage of electrical over UV is that you can produce a lot more of it.
The advantage of UV light based generators is that you get a “Pure” form of ozone with less maintenance, but a lot less ozone for the buck.
In answer to your question, I would say that the age of the machine is not an issue as much as the size and quantity of plates, level and frequency of cleaning, and humidity/contaminate levels in the air that is being fed into the machine.
I guess in short, my point is that its not their equipment, but rather their application that sounds like it needs improvement.
In addition to my previous recommendation, if they could de-humidify the air in an evacuation vent before it is hit with ozone, it would reduce maintenance costs and increase efficiency.
Sounds as if the town fathers in Halifax need your expertise!
Since this is happening on the waterfront .... evacuating a lot of the humidity would probably be expensive. They are in the height of their tourist season. Sounds like their solution is temporary, but urgent.
>>> evacuating a lot of the humidity would probably be expensive.
Thanks... I would be glad to help them if I could.
Natural forms of de-humidification may be possible if we are talking about just treating the evacuated air. Example... venting the air lower into the ground may result in cooling which reduces the air’s ability to hold water. Metal grills located inside the vent could be “naturally” cooled and would serve as condensation surfaces. Then as the air is vented back out, it is hit with ozone before it is released.
>>> 20-year-old machine that once was deployed in a hospital smoking room.
The fact that this machine was previously used in a smoking room tells me something about it’s ozone output.
The output is probably much less than 2000 milligrams per hour. Ozone generators designed for indoor use during occupancy must maintain EPA “safe” levels of ozone at .05 parts per million or less.
In Ozone shock therapy, we get ozone to quite unsafe levels... 8-20 parts per million if at all possible... the more the better.
Normal atmospheric levels of ozone range from .01 to .03 parts per million. But ozone doesn’t really start doing it’s real magic until it exceeds 8 parts per million.
I like the smiley face.
The sulfur ends up as fully oxidized sulfates. Totally harmless stuff, providing the concentration is not too high (which it won’t be). As for the ultimate fate (locked in some lattice somewhere) I am not sure.
Dirt, IOW.
Thanks.
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