liquid reagent feeding

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feeding using metering pumps

Metering pumps normally used in water treatment applications are positive displacement reciprocating pumps where output is adjusted by adjusting the cubic capacity or the speed (operating rate). This adjustment can be carried out manually or automatically (variable speed motor or servomotor). In the latter case, reagent injection can be controlled by a parameter, for instance, the flow rate of the water to be treated, or even by two parameters such as flow rate and pH. Extremely variable output (a few cm3·h–1 to a few m3·h–1) pumps are available on the market with accuracy levels of up to 1/1,000th of full scale output.

These pumps can be piston or diaphragm pumps, hydraulically or mechanically controlled. They can be identified by their output, operating pressure and precision; the materials used to construct the metering pump must be compatible with the liquid pumped by the dispenser concerned. When several of these pumps are likely to be mechanically interlinked in a multiplex configuration, they must provide the proportional output of several liquids.