Microscopic Evaluation Technique for Water Filtration Plant Performance

The purpose of this procedure is to evaluate the performance of public water supply filtration systems. A minimum of 300 gallons of both raw and finished water should be collected. The evaluation is based on the filtration plants ability to remove Giardia sized and larger particles. In addition to the MET evaluation, the evaluator should also consider the operational conditions of the plant, physical condition of the plant/ raw water, and effluent quality of the finished water.

Each analysis culminates in a filtration performance rating which reflects the overall effluent quality. The rating is always accompanied by an explanation which details the justification of the assessment. Filtration Plants with Excellent and Good ratings are reported as "Acceptable Filtration Performance". Filter which are rated Questionable or Poor are reported as "Unacceptable Filtration Performance".

The amounts of each of several specific groups of particulate matter and microorganisms are recorded. These groups include: small particulate debris, large particulate debris, cellular plant debris, diatoms, and other algae, protozoa, insects and crustaceans, nematodes, and rotifers. Also, pollen grains, Giardia, and other parasitic protozoa should be noted.