Floc Characterisation at Full Scale: The Case of Humic Waters
This paper describes part of a larger scale investigation designed to characterise humic flocs and focuses on those found in the flocculators at full scale. Following a section dealing with the basic parameterisation, the paper provides insight into the techniques which were employed. Insight is provided into some limitations of image analysis when attempting to measure floc size. It is shown that floc sizes measured in a sample stream withdrawn from a stirred vessel bares little resemblance to those measured in situ. From a survey carried at ten WTWs, it was apparent that the greatest influence on floc size and density was the presence of polymer. There was evidence that the presence of high alkalinity induced properties comparable with polymer addition. Little correspondence existed between floc sizes at full scale and those found in a laboratory scale mixer at identical values of velocity gradient. It was evident that DAF plants performed satisfactorily whatever the size of the incoming floc.
KeywordsFiltration Turbidity Settling Alkalinity Flocculation
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