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Channings Wood Top Security Prison, Exeter, England
Prison Effluent is not Typical
David Gerrard
Did you know that the effluent that flow into sewage treatment plants from many of our prisons is not typical?
This certainly puzzled me when I got a call to visit the site and recommend a suitable flowmeter, as the normal flowmeter called a "V-notch weir" constantly blocks up.
When sewage enters a treatment plant, coarse screens normally take out the solids leaving a brown fluid which is easily measured -- however prison effluent is different. Due to the fact that many prisoners sometimes remain in their cells and refuse to eat their meals, food gets flushed down the toilet. The result is that much fat, vegetables, meat and other waste food products finish up in the sewer and get through the screens. They then block the weir plates which must remain clean for successful measurement.
The answer was to use "ChannelMag", a flowmeter which has no blocking or restriction to the flow of effluent in the channels. ChannelMag is an electromagnetic flowmeter which measures the velocity of liquid over its surface. With the addition of a level transducer and defined width of channel, the flow volume can easily be computed in a single transmitter.
