Aeration piping for raw wastewater lagoon

[itsleighton]

We are a contractor installing a large aeration system for a raw wastewater lagoon and the engineer is calling for a cement lined ductile iron pipe to carry the air from the blowers to the HDPE headers and laterals inside the lagoons. The pipe sizes are 14" to 10" to 6". My concern is the cement lining will come off the inside of the pipe in the air-only and wastewater plant environment and clog the diffusers and cause a problem with the end user (city).

Does anyone have experience with installing / designing a system like this and if so, what type of pipe did you spec / use? I am looking for something other than stainless as I believe stainless will prove to be way out of the budget to suggest as a feasible alternative. My goal is to save them money and give them a better product with a longer life.
Suggestions?

 

[dicksewerrat]

Why can't you use HDPE for the whole thing?

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[itsleighton]

According to my supplier HDPE is not UV Friendly and the client wants the piping to be above ground for maintenece on the connections to the laterals. Maybe a wrap of some sort on the HDPE? Anyone? TIA for any help.

 

[civilperson]

Coal tar epoxy lined ductile iron will work.

 

[semo]

We've typically used un-lined or epoxy lined DIP. If you can bury the header, HDPE would be better.

They shouldn't have much maintenance on the connections and you can bury it shallow so that the flowline is above the lagoon water level to prevent leakage.

 

[itsleighton]

Has anyone had any experience with HDPE above ground on a permanent application? I the level of the water is such that an underground application simply will not work.

I want to find a solution that is not MORE expensive than the cement lined DI (Original design) The city simply has no more money. I could credit any amount back and offer them something else in the plant on their wishlist.

 

[civilperson]

Cheapest might be CPVC, UV resistant formulation.

 

[gerhardl]

Summary: You will probably have to take into consideration the possibillity for sulphuric achids and agressive gases in small amounts, hence corrosive resistent and low pressure, abovegound and UV resistent.

The rest is then a more commercial question:

Any suppliers near the location whith availability of UV-resistent plastic material, where transport and mounting costs are competitive?

GRP and/or UV resistent other plastic materials and/or cover ought not to be a problem not to be overcome. What is the lifetime requirement?

Call different suppliers, get a cost and life estimate and present total installment cost and present this and cost/lifetime factors for the different material solutions and let your customer choose.

 

[waterexpert]

Thin-walled low-grade stainless often saves on installation and maintenance costs so as to be cost competitive for above-water pipework. It's quite extensively used in the UK, teamed with uPVC for the permanently submerged sections.

Regards
Seán

http://www.wastewatertreatmentplantdesign.co.uk

 

[Ipiranga]

I´m interest to have a pdf format for crane technical paper # 410 to make calculations at air piping for aeration devices used at wastewater treatment plant: Somebody could help me to get it?

 

[bimr]

PVC pipe is probably the least expensive.

 

[rconner]

While certainly not purporting to be a foremost expert in this field nor knowing if the following is applicable to your specific application, I believe for major wastewater plants in the USA it is most common to see either unlined ductile iron and/or stainless steel piping employed off the blowers of aeration systems. With regard specifically to iron piping, I suspect however a wide variety of joints, coatings, and linings have been installed in accordance with what specifiers at one time or another have required and/or contractors etc. have installed for various air applications.
It should be noted however that some air piping applications reportedly often involve quite elevated temperature service, apparently due to at least some quasi-adiabatic effect that is most pronounced nearer the blowers. This in my opinion in particular should be very carefully considered in the design and specifying process for pipe, joints, gaskets, and perhaps also any coatings and linings one thinks is applicable.
I believe push-on and/or push-on gasketed restrained joint ductile iron piping, and gasket material also acceptable for the maximum temperatures actually involved are in general satisfactory choices for air piping. Bolted mechanical joint (MJ) seals, which are typically much more labor-intensive and labor reliant than push-on, and also any joints/gaskets e.g. with rubber gaskets other than those mentioned used beyond their temperature ratings, may be most adversely affected by imperfect installation and/or what goes along with high temperatures and/or fluctuating heating and cooling cycles. For these reasons the use of mechanical joints should probably be avoided (at least where they can be), e.g. use modern, available push-on joints at least in at least straight runs of air piping. EPDM gaskets are often used for air piping, although extremely high temperatures and/or a history of past system problems may make special fluoroelastomer (FE) gasket material the best choice for some applications [see e.g. the guidance at

http://www.dipra.org/pdf/gasketsForDIP.pdf

etc.] FE is the highest temperature and also most chemical resistant common gasket material available, although I believe FE gaskets also have the highest cost.
Incidentally, with temperatures for air piping I have seen sometimes seen specified approaching 300 degrees F. or so, I suspect some specifiers (at least those who are aware of real limits and behaviors) are not real comfortable with many aspects of most plastic pipe at that temperature.

 

[bimr]

rconner,

I took the original question as what type of pipe is acceptable "inside the lagoon".

It is common to have a stainless steel drop pipe entering the lagoon. From the drop pipe (under the water now), it is common to use PVC pipe.

 

[rconner]

Understood.