Venting Interceptor Sewers

[MarshfieldTimC]

I am looking for information on the proper venting of an interceptor (sanitary) sewer. I have an existing sewer that includes 24" to 36" ID concrete pipe, 6500 LF long and only carries wastewater that is discharged from a lift station (no other connections, no laterals, etc.). There is a vent on the manhole where the 20" force main discharges into this interceptor sewer, and another at the manhole where this interceptor discharges to our main WWTP interceptor. These vents appear to be allowing air to enter the manhole/pipeline ('inhaling'). The pipe and manholes of this 6500 LF interceptor sewer are severely corroded and will need rehabilitation and/or replacement soon. I believe that proper venting will not resolve or prevent the corrosion, but I would like to know what I should be doing regarding venting, and minimizing the H2S corrosion potential if possible.
Thanks in advance!

 

[bimr]

If the sewer outlet is submerged and there are few ventilated house connections, some special provision for ventilation may be necessary. A ventilating shaft with a cross-sectional area at least one-half that of the sewer and tall enough to extend above nearby roofs may be considered.

 

[rconner]

While not professing specific expertise in this subject, I think there are many potential issues that are associated with venting or ventilation (if that is what is being referred to) of sewer pipelines. While there are probably many other references, you will find many of these issues discussed to some detail in ASCE MOP's No. 37, 60, and 69.

 

[dicksewerrat]

The bacteria that produce the H2S is anerobic, I believe. Venting should not add to or reduce the corrosion. What it will due is remind everyone that there is a sewer nearby. And the H2S is coming out of solution at the outfalls. If you can make the flow transition more smoothly from pressure side to gravity side there will be less H2S coming out.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[cvg]

adding oxygen by venting, blowers or even by injecting peroxide may help to prevent it from going anerobic, therefor reducing the odor causing bacteria. This is a common problem problem with force mains and interceptors because of the long reaches without any oxygen and has been discussed on the forum many times.