Waste Water Flow Metering

[fjvillegasjr]

Working on a Nutraceutical Facility that was previously existing, but with new owners, comes new rules.

Our scope is to modify the existing infrastructure to comply with current environmental code regulations.
A reviewer is requiring a flow meter for the existing plumbing system.
Due to branched out system, the 'waste water' that needs to be metered comes from multiple different branches, all to an exterior line running adjacent to the building which then is connected to a manhole.
The flow is intermittent as many all or no fixtures are being used to clean equipment & utensils which is where the waste derives from.

Based on the existing plumbing system and operation, we have concluded that the only way to accurately monitor the flow would be the following:
Add a pump/lift station following all non-domestic waste lines. Once tank meets certain level, pump activates and pumps through meter.
This provides a much more consistent flow and enables accurate readings for a flow meter. This has been discussed with many flow meter companies and seems to be the only route.

Ideally, I would like to prevent adding a pump station.

Any tips, advice, or alternative ideas are welcome.

Thanks and stay safe during the Q!

One More Designs

 

[bimr]

Most municipalities require a Parshall flume in a manhole to measure the discharge flow. If the flow is so low that this option will not work, you may be able to monitor the flow with a water meter on the inlet side, or use the approach that you posted.

 

[fel3]

How accurate do you need to be? Could you use a cutthroat flume instead of a Parshall flume?

============
"Is it the only lesson of history that mankind is unteachable?"
--Winston S. Churchill

 

[ashtree]

How much flow are we talking about?

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

 

[MartinLe]

Flow meters need to be submerged to function. You can build a lowered section of pipe, with the top below the lowest water level downstream, and install a flow meter there (with a shaft and manhole for maintenance.

Check with a vendor if any contaminants in the wastewater can damage the flowmeter (I was thinking MID but maybe a strap on ultrasonic flowmeter would be better anyway), make sure to include valves up- and downstream for service etc.

 

[fjvillegasjr]

Where were all you guys in April? lol
As of now, we have designed a AV flow provided with a flow dam.
According to the company and the minimum requirements of the meter, it should work.
If anyone wants additional information, feel free to reach out to me.
Thanks for the replies.

One More Designs

 

[bimr]

What is an "AV flow provided with a flow dam"?

 

[undertan1995]

I'm doing something similar. Very little flow. So little that even a parshall flume wouldn't be able to give an accurate reading. The minimum size of a parshall flume in a sanitary application is 3", due to solids flowing through the system. I was recommended to use an extra large 60 degree trapezoidal flume, which could measure flows down to roughly 0.5 gpm with no blockage of solids. I know this is much after the fact

 

[bimr]

There is no universal or best way to meter small flows. The best one can do is to install something that the local AHJ will accept.