NATIONAL ASSESSMENT OF PARTICLE REMOVAL BY FILTRATION   EE&T was chosen by the AWWA Research Foundation to conduct a comprehensive study of particle counting, Giardia, Cryptosporidium, microscopic particulates, turbidity, and indigenous aerobic bacterial endospores. The goals of the study were three fold - to develop a national database of particle count data, to determine the factors that affect finished water particle counts, and to determine if there is a relationship between particle count data and pathogen data. The approach used to meet these goals was to collect as much particle count data from as many water utilities as possible over the course of the three year study. EE&T designed and equipped a mobile pilot facility/laboratory with one grab sampling and three on-line particle counters, along with other standard water quality monitoring equipment. The trailer was sent to over one hundred surface water treatment plants around the country. At each plant monitors were connected to two filters and one raw water sample source, and one week's worth of data were collected. At the same time operations data, water quality information, continuous filtered turbidity, Giardia and Cryptosporidium analyses, microscopic particulate samples, and bacterial endospore samples were collected