Getting What You Paid For: DCWASA's Blue Plains Wastewater Treatment Plant's Improved Polymer Evaluation and Quality Control

The purpose of polymer evaluation is to fairly and impartially evaluate polymers provided by the manufacturers and obtain the best polymer at the lowest price. Our specific goals were:Encourage competitionDefine the polymer testedEliminate ‘luck’ in our evaluation so far as possibleEnsure the sludges tested had a somewhat higher secondary content than normalEnsure the sludge tested was the same for all andEnsure the idiosyncrasies of any particular centrifuge system impact all equallyWe invited six polymer manufacturers to participate, and three responded, to supply polymer for full scale evaluation by DCWASA personnel. The evaluation was to be double blind, and tested on two sludge blends, the normal 50/50 Primary/Secondary Blend One, and a 40/60 Primary/Secondary Blend Two which would be a ‘worst case’ sludge. The three polymers were each tested on three centrifuges. A spreadsheet automatically calculated the total cost (polymer, lime stabilization, recycle and hauling costs) per dry ton of sludge from this data. Some operational problems were encountered with blend one, but blend two went exceptionally smoothly. In the end, the performance of the polymers was deemed identical, and the bid was issued based upon price. Bid prices for dry polymer ranged from 1.42 to $1.60/lb of dry polymer delivered in bulk.