Wastewater Grit Pumping

[JohnWeal]

Good Morning,

We have a requirement to pump out grit from a sump which is 4.5m deep. The water level is controlled with a bottom water level of 0.6m and a top water level of 1.6m.

There are two pumps in the wetwell which operate on a duty / standby basis.

Adjacent to the wetwell is a 1m deep valve chamber where each of the pump discharge pipelines has a non-return valve and isolating knife gate valve before the two pipes join and distribute the grit-laden effluent to three screw classifiers.

I would like to say at this point that I have always used drywell grit pumps such as a Wemco C-cup impeller. But the Chief Engineer does not want to introduce additional civil engineering costs.

But the question is regarding the discharge pipeline non-return valves. To prevent the duty pump back-flowing through the standby pump it is usual to install a non-return valve.
Has anyone had any experience of the reliability of non-return valves for grit effluent duties in terms of seating reliability and erosion?

I would be grateful for any recommendations in terms of a company and valve specification.

Regards
John

 

[ashtree]

John,

A couple of questions.

What is the concentration of the solids?
What is the nature of the solids? Sand, gravel , leftovers from industrial process etc?
What is the flow rate?

You are correct in that you will need a non return. When you have used a Wemco in the past do you not put a non return in the line even if you are not doing duty/standby?


Regards
Ashtree
"Any water can be made potable if you filter it through enough money"