John O'Connor

Drinking Water Process Performance Evaluations

Blog Post created by John O'Connor on Nov 29, 2011


Well-formed floc fully entrains bacteria and other micrometer-sized particles, facilitating sedimentation and filtration.


Evaluations of drinking water treatment process performance, particularly regarding the removal of particles of potential health significance, are of major importance for the protection of public health. However, some of these evaluations may be far from simple, rapid, or unambiguous.


The attached paper, written primarily for the drinking water quality scientist, addresses regulatory issues as it critiques and augments the methods currently used for assessing water treatment process efficiency.


Microscopic Observation: Or to paraphrase Yogi, ‘You can tell a lot by looking ...’


As alternatives (or supplements) to regulatory reliance on turbidity, coliform and heterotrophic plate count organisms, five non-standard parameters, based on the direct microscopic count, were used to evaluate treatment plant organism and particle removal performance. Reductions in the numbers of total bacterial cells, planktonic bacteria, particle-associated bacteria, total particles larger than 3 µm, and nematodes were observed over a calendar year (to observe seasonal temperature effects) at a water plant treating Missouri River water. Subsequent microscopic measures were made of algal cells and colonies and carbon fines.


Of special interest was the pronounced effect of low (winter) source water temperatures on the efficiency of bacterial and particle removals, particularly, by filtration.



We encourage your comments and observations, especially if you have had experience with microscopic methods of particle analysis.