OK to pipe clearwell overflow to plant influent?
OK to pipe clearwell overflow to plant influent?
(OP)
I have a situation where the design engineer provided a clearwell overflow box on the side of the clearwell at ground level (the clearwell is below grade), but the owner wants to pipe it somewhere rather than have the water just flow out on the ground. Can I pipe this to the influent raw water wet well? The overflows should be rare, and if they do happen, the dilution of the chlorinated water by the raw water would be great.





RE: OK to pipe clearwell overflow to plant influent?
If you pipe the clearwell drain anywhere, I would think you would want (need) an air gap to where ever it drains, and probably a backflow preventer in the drain line as a secondary precaution.
Also, might be a good idea to have a visual if the well is overflowing, you know, so the operator knows something is up / not right. That becomes the problem when you pipe these kind of overflows. You might have the worst case scenario where transducer fails, SCADA fails, altitude valve fails, whatever fails, and no one realizes it until they see water flowing on the ground....
RE: OK to pipe clearwell overflow to plant influent?
Is this a filter plant? If so, where does the backwash water go?
Steve
RE: OK to pipe clearwell overflow to plant influent?
RE: OK to pipe clearwell overflow to plant influent?
RE: OK to pipe clearwell overflow to plant influent?
However, if the operator insists, it should not be a problem. I don't see any problem letting the water overflow back to the raw water wetwell, as long as you have an air grap.
You should install an air gap at the clearwell, so that the water will not siphon out of the clearwell.
RE: OK to pipe clearwell overflow to plant influent?
If you are treating surface water, I don't know why it couldn't be piped back to the headworks, except as alex mentioned, you don't want a cross connection.
A check valve also will more than likely not serve as a backflow prevention device. The DNR/DEQ will probably want an air gap or some other sort of device. A PRV valve will probably not work due to gravity situation.
Many states allow backwash water to be returned to the headworks provided it is at a reduced rate.
Note that depending on what you are treating, doing this will dilute your source water causing chemical feed dosages to be wrong. Don't know what kind of problems (if any) that may cause in your situation.
RE: OK to pipe clearwell overflow to plant influent?