The waste water and sewerage industry looks after the waste water water from a wide range of populations and industries by measuring it with liquid flowmeters to see how much is being produced for planning purposes and environmental impact assessments, and treating it to reduce its impact on the environment. With our crowded planet, this industry keeps civilisation going by stopping all of us drowning in excrement and toxins.
Flow measurement of liquids is essential part of all the processes involved from the inlet works where most of the general industrial waste water and domestic inflows are measured using open channel flowmeters. These are usually arranged to measure the flows from different areas separately using concrete venturi profiles, stilling chamber upstream where the water level is measured and the flow in that channel is deduced and integrated by the local transmitter for onwards process control. The level measurement for channel venturi flowmeters in a modern waste water treatment plant uses a number of technologies ranging from bubbler probes, capacitance probes, radar and laser sensors.
If the flow is excessive and beyond the capacity of the treatment works, the process flowmeter measurements then enable the storm storage to come into use until the peak is past and then the flow is fed back into the main flow for treatment via a storm pump arrangement controlled by storm flow pipeline meters. The the type of flow meter vary but electromagnetic flow meters types are common.
The various aerobic and anaerobic processes to separate the solids in the form of sludge from the supernatent liquor are pumped into other parts of the process and controlled by various types of monitor and pipeline liquid flowmeters, mainly electromagnetic and venturi flowmeters. For thicker sludge, coriolis mass flow meters are normally specified.
For industrial waste water treatment where process waste contains toxins or corrosive liquids are present, precise control is needed to enable these dangerous liquids and solids to be separated and treated to ensure they do not enter the food chain or to otherwise pollute the environment downstream. Liquid flow measurement naturally plays a prominent part in the process control and a number of different types are used, particularly, electromagnetic meters.