S ometimes things are not what they seem. Take the performance of filtration plants, for example. You would think that how well these plants control turbidity would depend mostly on tangible variables such as source water quality, plant age, and the type of coagulant used.However, the authors found that this is not necessarily so. They studied 75 filtration plants in Pennsylvania to assess their readiness to meet the turbidity treatment technique requirements of the Interim Enhanced Surface Water Treatment Rule.Eight key water quality, design, and operation variables-coagulant type, population served, ownership, source type, plant type, plant age, type of filter media, and filtration rate-were evaluated to determine their effect on filtered water turbidity. These variables were then compared with the annual 95th percentile of finished water turbidity levels.The results showed no significant correlation between filtered water turbidity and any of the variables studied. Many plants were able to achieve low turbidity in spite of such limitations as small system size, high source water turbidity, or plant age. Intangible variables such as operator skill and awareness and a commitment to achieve low turbidity appeared to be just as important to plant performance as the tangible ones.Awareness of the importance of filter plant performance and optimization are extremely important to water quality in Pennsylvania-as well as any place drinking water is produced. The results of this study can help increase water suppliers' knowledge of the factors that influence filtration plant performance and concentrate on those items that appear to have the greatest effect on their particular plant.-LPS

By identifying weaknesses and optimizing treatment, Pennsylvania has greatly improved performance at its surface water plants. Pennsylvania's Department of Environmental Protection (DEP) initiated a statewide filter plant performance evaluation (FPPE) program for safe drinking water and completed 506 FPPEs at 290 surface water treatment plants. Only 39 percent of the plants were rated “acceptable” for performance at the program's inception in 1988, but by 1996 the percentage had increased to 91 percent—demonstrating that assistance to these systems could lead to successful improvements and decreased risks from waterborne protozoa. The percentage of positive Cryptosporidium (presumptive) samples of the finished water dropped from 35 percent in 1990 to <5 percent in 1996. Positive Cryptosporidium samples have remained below 5 percent in the last five years. The 90th percentile of particle count data showed a postfiltration count of 50/mL in the 3‐ to 18‐μm size range as the threshold for acceptable performance. Because optimized performance is a goal of the FPPE program, the concentrations of 3‐ to 18‐μm particles should remain below 10/mL to minimize breakthrough of pathogenic protozoa. The DEP considers turbidity of <0.1 ntu from each filter as a more optimum level of filter plant performance.

The Champlain Water District's Peter L. Jacob Filtration Facility in Northwestern Vermont treats low‐turbidity raw water from Lake Champlain's Shelburne Bay with the goal of producing consistent high‐quality finished water. From 1980 to 1989, the facility consisted of two deep‐bed, dual‐media filters and one converted deep‐bed, multimedia filter, preceded by flocculation basins operated in the direct filtration mode. In 1991, a phased three‐year facility upgrade was completed, that made modifications to the flocculation basins and additions to the filtration and disinfection barriers. This article discusses the means by which the facility was evaluated. The district invited an independent third‐party assessor to review the treatment facility in 1994. This paper discusses in detail the self‐assessment process, the recommendations that were issued, and the actions which resulted from the assessment.

This article discusses compliance to the Stage 1 Disinfectants/Disinfection Byproducts (D/DBP) Rule and the proposed provisions of the Stage 2 D/DBP Rule. The Stage 1 D/DBP Rule focuses on low‐cost steps to optimize treatment, thus lowering DBPs. US Environmental Protection Agency's guidance says the most cost‐effective approach to controlling DBPs may involve the removal of precursors that eventually lead to byproduct formation such as total organic carbon (TOC). This article discusses TOC removal, benefits of TOC removal, and a three‐part plan to help you gather the right data and determine if your treatment plant meets the regulations.

Since 1988, the Pennsylvania Department of Environmental Protection has conducted detailed evaluations of the state's surface water treatment plants. The ongoing program, called Filter Plant Performance Evaluation, is a method of determining the effectiveness of a water treatment plant in removing pathogens and pathogen‐sized particles from the incoming raw water. The evaluation process combines an onsite survey of filter plant operations and general physical conditions. Although the FPPE program evaluations capture a ‘snapshot’ of filter plant performance, they also entail a review of turbidity monitoring records to gain a long‐term picture. This article discusses this program, typical questions asked during filter plant performance evaluations, common problems in treatment, and evaluation tools of the future.