flow measurement options in wastewater manhole

[swazimatt]

We are looking at discharging ww from a new development into an existing ww network. The council will be running some WW models and I suspect there may be very little peak flow capacity in the network, but quite likely some off-peak capacity in the network. In which case I would like to be able to measure the flow in the network at the pinch-point of the WSP model (I suspect this will be a 225 or 300mm dia pipe) and when the flow in the network drops below a certain flow rate we will start pumping ww into the network.

I would like to know the easiest way of measuring the flow in the existing network with the access being in a standard (live) WW manhole.

I would imagine the flows we would be measuring will be about 100 l/s and lower. This is approximately the capacity of a 300mm pipe

I suppose if we used an ultrasonic sensor to measure the depth of flow in the channel through the manhole we would be able to work out flow, not sure how accurate this would be with flowing liquid (i only have experience of these for measuring wetwell levels)

 

[TugboatEng]

You can use a height sensor to approximate the cross section area of the flow but you'll also need a velocity measurement. Some type of paddlewheel could possibly work well for this.

 

[swazimatt]

You can use a height sensor to approximate the cross section area of the flow but you'll also need a velocity measurement. Some type of paddlewheel could possibly work well for this.

I will have channel grade so will be able to use mannings to calculate flow rate

 

[TugboatEng]

You're talking wastewater. It's going to have very inconsistent properties. If the flow is more of a slurry one day that is going to cause it to stac up higher in the pipe. You need a velocity measurement.

 

[LittleInch]

A quick google says you need a flume.

Many people supply these e.g.

https://siris.co.uk/guide-to-effluent-flow-meters/

https://www.openchannelflow.com/blog/wastewater-flow-monitoring

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[bimr]

People working on sewer I/I here in the states use the Flo-Dar by Marsh McBirney which is an easy and accurate flow measurement:

Link to Marsh McBirney

 

[pierreick]

Hi,
May be suitable for your application? Check with vendors

https://www.mccrometer.com/wastewater

Pierre

 

[swazimatt]

Thanks all. I think Flo-dar is what i was hoping for and have found a local agent

 

[FacEngrPE]

Using the FloDar solved all of the problems we has with a parshall flume flow meter. There is a version that comes with a datalogger and power supply which is intended for the sort of survey you are planning.
The FloDar is flow velocity by dopler radar, and depth by Ultrasonic / echo.

A mag meter is better if your sewage is in a flooded pipe, but you describe open channel flow, which requires something else.