effects of high ph (>10) on sanitary sewer piping and WWTP processes 2

[jenr]

I am interested in hearing about any experience or knowledge that anyone has with the effects of wastewater with a pH >10 on sanitary sewer collection system piping and waste water treatment plant processes. Additionally, is concrete piping used for most sanitary sewer collection systems?

Any information will be greatly appreciated. Thanks!

 

[stanier]

The high pH would indicate low sulphur levels and their may be some solids build up on the pipe walls.

Concrete pipes are rarely used in Australia for other than very large diameter sewer mains. Traditionally cement lined ductile iron hjas been used. More modern systems are using solvent welded ABS (

http://www.eurapipe.com.au)

or butt fusion welded PE. These systems over come the problem of ingress of water through the rubber ring joint. In time the RRJ loses the inherent resilience and this allows the roots to penetrate.

Other materials used are FRP or GRP for large mains. However some FRP materilas have low strain tolerance and thus require more care in embedment techniques or wider trenches. There is still some concrete pipe used however this requires plastic lining where hydrogen sulphide exists and causes corrosion. Concrete pipe is only available in short lengths compared to the more modern thermoplastics. Hence trenches are generally kept open for longer.

 

[SanEnr1]

I would be concerned about the quantity of such wastewater discharges. I know that my local law and many others prohibit the discharge of such concentrated wastes into the public sanitary sewer system. Obviously a concentrated discharge of a high pH wastewater would have adverse effects on the biological systems as well as physical equipment at a WWTP that is not designed to handle the discharge.

As far as sanitary sewer piping, I see PVC as the predominant material for small (less than 24” diameter) gravity sanitary sewers. PVC is resistant to corrosion and is available in enough classes to handle most loads.

 

ITs all relative to the flow of this high pH water. If there is a lot of it in relation to wastewater then it will serve as a disinfectant and kill most everything in the plant. If there isn't much of in in relation to the flow of wastewater, then the plant will most likely welcome it to provide a buffer and improve settling provided amonia release is not too bad.

Hope this helped.