[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: Odor Prevention at Lift Stations
Tammy Allen writes:
> In addition to concerns for sewer personnel exposed to accumulated
> gases, sewer gases left to accumulate in air-tight environments can
> create additional toxic gases and underground potential for explosion,
> stagnation, and dead space in lines. Aeration is a viable option to
> reduce odor. Many odors accumulate because of oxygen-deficient
> environments. The cost to retrofit old sewer systems (lines, stations,
> can be astronomical for a municipality.) Judy, I am still looking
> forward to your additional information on pump rates, etc. for odor
>>> Rudy Moehrbach <Rudy_Moehrbach@p2pays.org> 01/29 9:04 AM >>>
> Judy Mirro, Tammy Allen opened the subject a few days ago.
> a great deal of experience in that area and offered suggestions for
> dealing with the odor. I am interested in the problem but
> unfortunately I don't know one thing about it. I inquired why the
> odor must be allowed to get out and was told that the fumes
> presented a danger to maintenance personnel(I'm assuming that a
> lift station is not occupied). Obviously that is an important
> consideration, but that type of problem is dealt with safely in many
> other situations---OSHA addresses it in detail. My question was:
> "Let me ask some questions since I am not familiar with a waste
> water lift station. Are you pumping from one underground waste pipe
> to another under ground waste pipe at a higher elevation? Is
> venting to atmosphere necessary or is it "just there". Why is there
> a vent? Can everything just be sealed up? Can the atmospheric vent
> be changed to a closed vent, perhaps with a blower, that ends up in
> the upper pipe?" I'm looking for an opportunity to PREVENT
> POLLUTION. Prevent the fumes from polluting the air and causing a
> nuisance. Prevent the addition of chemicals to mask the odors that
> pollute the air. So, Judy, have you run into a sealed lift station?
> If not, and knowing the requirements, do you believe one can be
> designed to be sealed? Can existing ones easily be modified to be
Where do I begin? Prevent pollution by preventing the wastewater?
Obviously, with industry we do our best to help them reduce at the
source, but when it comes to domestic wastes in communities...
reduction is really limited. So you end up with wastewater and you
have to deal with its inherent problems. Odors being one of them.
Lift stations: Yes, typically located at a junction, a lift/pump
station pumps the waste stream upward into another part of the
collection system to hopefully flow freely toward the wastewater
treatment facility. Normally, a pump station has two parts: a dry
well (where the pumps are located) connected to a wet well (where
the sewage accumulates). Venting is necessary and required by
OSHA in both the wet well and the dry well. Both are considered a
Confined Space.. and entry into one means you follow the confined
space entry procedures your facility has established.
Sealed stations would be impractical and dangerous. Access
and maintenance in the "wet" well portion of the station is
necessary (and required by most state regulatory agency's), in
order to clean pump control mechanisms and insure the station is
running properly. (I'll get back to the maintenance of a pump
station a little later.) Since the wastewater is accumulating in the
wet well, you'll naturally have odors and need to vent them.
Explosion proof electrical systems are required in a wet well
situation because of the potential for such a hazard.
Gases can vary in a wet well. O2 difficiency, hydrogen sulfide,
methane, ammonia,... and again, the explosion potential can be
high. With proper pumping rates, some of this goes away. In
some situations, with the best pumping rates, the problems will
still be there and 'other' mechanisms are brought in to help out.
Hence the need for chemical addition or some sort of odor control
mechanism (such as biofilters).
Most of the time the odors leaving a pump station are not 'toxic' to
the public, but they are considered a nuisance. I suppose you
could tell the tax payers that they just need to live with the odors -
but I don't think you'll get far with that. ; ) Again, in order to reduce
what chemicals you'll use, first (reduce!) by optimizing pumping
rates. You really will need to get an engineer to sit down with your
pump station design plans and a years worth of actual flows, in
order to do this. Unfortunately, I can't give you an easy fix for this
problem over e-mail. I would need to see collection pipe sizes,
current daily pumping rates, pump capacities, wet well size, wet
well operating depths,... and talk to the neighbors to see when the
odors are at their worst and to the operator that maintenances the
station. That's why bringing in someone (engineer or not) would be
I am not saying that *all* pump stations require chemical or other
odor control methods. On the contrary, odor control at a pump
station is NOT a typical part of the operation. If anything, it is the
rare case. I can count on one hand the number of odor control
systems in place at pump stations here in VT.
A little more on pump station maintenance:
If pumps have failed, there will be only a certain amount of time
(depending upon the size of the wet well) before raw sewage will
reach ground level. Pollution prevention IS maintenancing the
pump station on a regular basis. A pump seal could blow and even
though the pump appears to operate properly while you are
standing in the dry well reading a pump hour meter, it may not
actually be pumping.. Unless you access the wet well, you may
not know until its to late.
And Yes, you do have alarms built into the system for just such a
reason, but how do you know your alarms are working unless you
test them regularly, tripping them on and testing the audio and
visual alarms. Another reason to access the wet well.
Tammy mentioned the high cost of replacing wastewater collection
system pipes. Re-lining, instead of replacing collection system
lines is a viable alternative for older systems. Quite cost effective,
I sure hope I've helped clarify some of your questions. I could just
keep rambling on here, but I won't. If you need more specific
answers, ask away.
Judy Mirro, Compliance Assistance Engineer
VT ANR/DEC/Environmental Assistance Division
Small Business Compliance Assistance Program
103 South Main St./Waterbury/VT/05671-0411
phone 802-241-3745 fax 802-241-3273