sewer smell 2

[Romeosperson]

I have an area where we drop a force main sewer into a gravity sewer. The residents are not so happy with the smell, especially in the summer months. I've been out there a number of times and the smell isn't pleasant next to the manhole, but I don't think it is really that bad. I guess I spend too much time in the sewer!

They also complain that they get sewer gas coming up into their homes as well.

I'm convinced that the gas is due to either their p-traps drying, or the plumber failing to plumb the house correctly in the first place. One homeowner claims that the silver in his home is tarnished from the gases!

We've tried the baskets with deodorant and added enzymes to the forcemain upstream of the manhole. The homeowners have tried capping and uncapping vents, adding scrubbers, and pouring bleach down the drain (nice huh?).

When I get these calls, about the only thing I can do is explain that unfortunately sewer smells. These people know more about anaerobic and aerobic sewers now than the average citizen.

So, before things start to warm up again and the complaints start, I thought I'd ask if anyone here has tried anything for stinky sewers.

 

[CarlB]

A slightly different situation was discussed but you may get some ideas from:

http://www.eng-tips.com/viewthread.cfm?qid=53982

 

[Scott367]

I dont know why sewage from a force main would create any different smell than sewage traveling via gravity.

 

[rconner]

As I suspect you now probably know forcemains, particularly if long and slow flowing to allow some digestive action enroute, can be some substantial sewer gas generators. Unfortunately also, a forcemain discharge (from pressurized to totally unpressurized) in a populated area manhole/gravity sewer provides it would appear a most convenient opportunity for those sewer gases to finally escape (and come out of solution etc.)
If you have no better nor more contemporary reference you might want to get hold and read (at least as an aid to generate ideas/discussion) a copy of ASCE MOP #69, “Sulfide in Wastewater Collection and Treatment Systems” – I think quite a bit of copy is devoted to politically popular odor and odor abatement issues. Incidentally, there is a list of “important considerations…” for “Design of Systems” (new or existing, for odor abatement) that starts out, “1. Any gas or vapor that might be toxic (such as H2S) should not be disguised.”…

 

[MissouriPE]

We had this problem in one area and found that semi-frequent flushing reduces the complaints, but we are hoping to more permanently fix the problem with a new lift station that will actually take that forcemain out of service. Not sure if that helps, but thought I would toss it out.

 

[IFRs]

Have you tried turning off the water where it comes in your house, then opening all the spigots everywhere (inside, outside, kitchen, bathrooms, laundry) and let all the water tun out, then close everything and open up the main.

 

[Romeosperson]

I looks like we are putting a new line in this year, but really this will only move the problem. Good news is that the new manhole we are dumping into has a signifantly higher volume of flow running through it, so it will be self flushing. Right now it is going into a very low volume line in front of expensive homes. I'm hoping that the additional flows will dilute the flows from the forcemain. Not to mention the distance to homes is increased, and the lay of the land should allow for more air flow.

Scott - the force main only pumps intermittently, so flows sit in a closed environment, leading to an anaerobic condition.

Missouri - thanks. We've been flushing as well. But due to poor plumbing in the houses (my opinion) the home owners claim that this pushes the gases up the service lines. Go figure, I can't win.

IFR's I'm not sure how draining the water lines would help with this situation other than perhaps aiding in flushing.

Thanks for the suggestions. Pretty much sounds like the other research I've done. I'm going to look into Hydrogen Peroxide as an option in another location, I think that might work over there.

 

[mytu]

It looks like you are pumping waste water from a septic tank before completing the anaerobic process. That is the smell producer. You can't blame the plumbing for the smell produced by the waste water. Try to have ventilation at the tank from you are pumping, an ventilation at the manhole where you discharge. Ventilations 4" and at less 4 mt above ground.

 

[dicksewerrat]

I thought adding a source of O2, peroxide, would help. also not letting the effluent fall will help. The falling and splashing allows the H2S to escape from the liquid.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[Civil3]

Typically, sewer smell is incresed at drop manholes. That is, where there is an significant elevation change between the inlet and outlet. This can be reduced by making sure that the vertical pipe on the inlet extends nearly to the bottom. This should reduce the spraying/splashing. Also making sure the top frame and grate is properly mortared. Often times the leak test is performed on the structure and everything looks great, but then the frame and grate is just slapped on which allows extra gas and smell. Finally is the structure located in the roadway or grass area. I have seen residents with green thumbs plant shrubs and flowers strategically around a structre to hide it visually and also make the area smell better.

 

[FiltrationEngineer]

I live in South Florida, and sewers here stink. It is becuase the wastewater goes septic very quickly with warm water / weather.

The best way to prevent septic odors is to prevent septic conditions. So to eliminate the odors you can try something like:

1. Don't let the water sit in the sewer very long, which means adjusting the level in the lift stations upstream of the problem area to pump more often (at lower levels), so the water doesn't have time to sit around and go septic.

2. Add something to the water to keep it from stinking. Hydrogen Peroxide or a product called odorphos are in common use here. I would at least let the WWTP know about chemical addition since it will affect their plant. Again, look upstream for the best place for chemical addition.

By the way, I agree with your statment about odors coming into houses is because of poor plumbing. Probably the same contractor took the same shortcuts for the housing development. Have you suggested to the homeowners that they pursue the plumbing problem and possibly get the installing contractor to fix it? I would also agree with the homeowner's silver being tarnished by the small amount of H2S.