I recently did a reagent plant trial and worked with a pretty nice flotation reagent metering pumps. The pump is supplied by http://www.pmps.co.za
This portable reagent supply unit is a mechanical diaphragm metering pump. As see on http://www.pmps.co.za/obl-mechanical-diaphragm-dosing-pump
They even had “Water Driven Pumps”
Other pumps I never worked with include http://www.awe-ltd.co.uk/products/dosing_pumps_electronic.html and http://www.lutzjescoamerica.com/index.php?id=1645