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Venting foul gas from pressurized municipal sewer line....help!!

Venting foul gas from pressurized municipal sewer line....help!!

Venting foul gas from pressurized municipal sewer line....help!!

(OP)
The city wastewater management department has installed a pressurized sewer line near a piece of property I own. There's a manhole about a hundred feet away, and there's an automatic system in the manhole that vents the gas from raw sewage through the manhole cover. The gas drifts across my property whenever the wind is blowing from that direction, and the stench persists depending on the wind speed and other conditions. I've complained about the situation repeatedly, but they tell me the line won't work properly if the gas isn't vented, and I'll just have to live with it. I've put my plans for the property on hold because I don't want to put up with the smell of raw sewage.

Is there some way the gas can be vented that doesn't have such an adverse affect on nearby properties?

RE: Venting foul gas from pressurized municipal sewer line....help!!

Quote (Retiredat46

.....Is there some way the gas can be vented that doesn't have such an adverse affect on nearby properties?)


Yes ...
Nowadays , the ventilation concept is ; the sewer network is ventilated thru the house drains and vent pipe extending the roof. In past, ( at least AFAIK some municipality typical details )each line of sewer was ventilated separately through vent columns, connected to the first manhole of the line .
Ventilation columns are also required at manholes where having the discharge from pumping stations.

The vent columns typically 200 mm steel pipe with 180 degr. bend at the top with fly screen . The height typically 8-10 meters and connected to the manhole shaft 700-800 mm below the surface. 8 they were like lighting mast ) .

I will suggest you to ask them,

- to install vent pipe similar to the set up described above,
- change the manhole cover with air tight model,
- Improve the benching ( flow channel at the bottom of manhole, my guess is , sewage is at free fall from the pressure pipe ) benching channel should directly connect the inlet and outlet levels without free fall..



My opinion but based on past experience..






Not to know is bad;
not to wish to know is worse.

NIGERIAN PROVERB

RE: Venting foul gas from pressurized municipal sewer line....help!!

A pressurized sewer pipe is typically the discharge from a sewage lift station. Just like our water supply lines, there has to be a pressure release at the high points to keep things flowing correctly.

I think requesting the vent column is probably your best bet. Good luck, since some municipalities think they don't need to be concerned with what the public wants or needs.

RE: Venting foul gas from pressurized municipal sewer line....help!!

(OP)
Thanks for the replies. While I was looking for a picture of a vent stack as described I came across this article: https://archive.jsonline.com/watchdog/pi/38515444....

It's not very encouraging. I don't see the city paying for the installation or upkeep of a carbon filter installation.

The manhole is at the high point of the line about two miles from the lift station near the apartment complex it serves. I was told there's nothing in the manhole except the vent mechanism, so the sewage isn't exposed. I don't know how it works, but there's no visible electrical service or wiring around the manhole.

RE: Venting foul gas from pressurized municipal sewer line....help!!

Injecting kno4 or hydrogen peroxide into the force main at the pump station or the wet well is an option to treat the actual issue. The sewer is going anaerobic or anoxic in the force main. Odor control is expensive and often ineffective. Aeration in the wet wet might help.

RE: Venting foul gas from pressurized municipal sewer line....help!!

Quote (Retiredat46

....
The manhole is at the high point of the line about two miles from the lift station near the apartment complex it serves. I was told there's nothing in the manhole except the vent mechanism, so the sewage isn't exposed.)


You are not supplying a lot of information here.

I bet the manhole is drop type ( the sewage flows to outlet after free fall with aeration, literally the invert level of inlet pipe is not the same with outlet pipe.)

If the aeration of sewage water is avoided with Channel improvement at benching together with vent stack at suitable location should work.


Can you provide the detail of the manhole?




Not to know is bad;
not to wish to know is worse.

NIGERIAN PROVERB

RE: Venting foul gas from pressurized municipal sewer line....help!!

(OP)
I'm just going by what the supervisor of the wastewater department told me. The only thing I can see is a concrete square with a manhole in the center. I've never seen the inside. I was told that the vent valve opens when the amount of gas accumulating at the high point in the pipe starts to impede the flow. That sounded reasonable, so I didn't ask for further explanation.

The smell is intermittent at various times throughout the day and night, but it's always stinky near the manhole for a while around seven or eight in the morning. It seems like it would smell all the time if the sewage was exposed. It's either really bad or no smell at all near the manhole.

RE: Venting foul gas from pressurized municipal sewer line....help!!

The least expensive solution is to inject Calcium nitrate for Hydrogen Sulfide Control. See the link:

Calcium Nitrate

RE: Venting foul gas from pressurized municipal sewer line....help!!

I would imagine there are planning and environmental regulations they are in breach of. H2S (the rotten egg smell) is also noxious but easily dispersed
Down at this end of the world we generally install a biofilter (big footprint and prone to not working properly) or a carbonfilter Link
If sized properly these are not high maintenance - just replace the carbon every few years

RE: Venting foul gas from pressurized municipal sewer line....help!!

(OP)
That Green Dome is really interesting, but it doesn't show up on the https://www.xylem.com/en-us/ website. It might only be available in Australia. Xylem is buying Evoqua, and there's an Evoqua factory right here in town, so I'll ask about it there. Getting the city to buy something from a company with a local footprint might be easier.

Thanks for the suggestion.

I'm also going to contact the Georgia Environmental Protection Division to see if there are any regulations that apply to this situation or help they can offer. It just never occurred to me that the city would install something like this and then tell me I'd just have to put up with the stench of someone else's sewage.

RE: Venting foul gas from pressurized municipal sewer line....help!!

If you do enough complaining, eventually they will do something for you.

Wastewater sits in pumped force mains and goes anaerobic. It is common and inexpensive to inject calcium nitrate into the pump station to eliminate the odors.

RE: Venting foul gas from pressurized municipal sewer line....help!!

(OP)
The Green Dome isn't available in the US at this time, and I didn't find anything similar. The Georgia EPA offered no help at all.

I found a cost analysis for treatment with calcium nitrate for approximately 40,000 gallons a day with eight stations costing around three million dollars a year. It's difficult to get an accurate comparison for a single station serving seventy-five apartments, but it's assuredly going to be several tens of thousands of dollars a year. I can guarantee that's not going to happen since they tell me I'm the only one complaining. I rarely see anyone out in the yards of the other properties nearby. Even if they've noticed the odor, they probably haven't determined where it's coming from.

At least I now have a better understanding of the problem, and I can see it's not going to change anytime soon.

RE: Venting foul gas from pressurized municipal sewer line....help!!

Not sure how you have calculated the dosage, the dosage should be around 1 gallon per day for 40,000 gallons. Also believe that every pump station will require chemical addition.

https://www.webpages.uidaho.edu/ce432/WET-CaNO3-Fe...

An odor control package will probably cost approximately $100,000 for the equipment which will be approximately $300,000 installed.

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