There is a lot of relevant advice above. One point I would like to add about the coagulant and/or flocculant dosing is to check the mixing energy and how well the reagent stream is mixed in to the entire inflowing water body. I have seen a single small diameter pipe dropping reagent at one point into a water stream that is 1meter or more wide.  That will not work effectively. It is better to add the coagulant/flocculant to the water stream using a perforated spreader bar for distribution across the entire flow width and it is important that there is a hydraulic jump, drop, baffles or some other form of hydraulic or mechanical mixing at that point to make sure the reagent is mixed throughout the water body. Treatment works in India are normally well enough designed hydraulically, if they follow the CPHEEOO manual. If you have enough kinetic and/or potential energy at the dosing point you can create turbulent mixing energy by adding baffles. If not a mechanical mixer may be required.

Published March 7, 2017 07:46 by Ian Rushton, Project Manager at Royal HaskoningDHV