Factors affecting filtered water turbidity

Approximately 8 million of Pennsylvania's 12 million residents receive water from 329 surface water treatment plants. This study evaluated the performance of a subset of these plants to determine whether they are prepared to meet the turbidity treatment technique requirements of the Enhanced Surface Water Treatment Rule. Using 75 filtration plants, the authors reviewed key water quality, design, and operational variables to determine their effect on filtered water turbidity. Except for plants that did not use a coagulant, served populations of < 3,300 people, or used streams for source water, there was no strong statistical correlation between any of the variables and filtered water turbidity. Many plants were able to consistently achieve low turbidity levels despite limitations such as small system size, plant age, or high source water turbidity. The results of this study show that intangible variables such as commitment to achieving low turbidity, operator skill level, and operator attention appear to be more important than tangible variables such as source water quality, ownership type, plant age, coagulant type, and other operational or design factors.