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The objectives for coagulation-based processes have changed significantly as a consequence of new goals for lower treated-water turbidity and criteria for total organic carbon (TOC) removal to meet requirements for enhanced coagulation. Although the application of coagulation for TOC removal has garnered considerable interest, the capability to maintain effective turbidity removal is a higher priority and cannot be compromised. This article describes evaluations for assessing this broader view of the coagulation process and underlines the necessity of identifying coagulant adjustments that not only remove TOC but also achieve effective particulate removal. Several basic coagulation adjustments are available for improving capability to meet goals forTOC and turbidity removal, including changes in pH and coagulant dose, use of alternative coagulant chemicals, and changes in the order of chemical addition.

The Safe Drinking Water Act and its Amendments (SDWAA) will pose a massive challenge for the drinking-water industry in the United States. As the SDWAA regulations reach implementation, increasing effort will be devoted to understanding the factors causing deterioration of water quality between treatment and consumption. A cooperative study involving the U.S. EPA, the University of Michigan, and the South Central Connecticut Regional Water Authority (RWA) demonstrated and validated the use of modeling techniques in the RWA distribution system. Models are used to predict the propagation of chlorine residual in one portion of the RWA system. It is found that residuals varied widely both spatially and temporally. Long residence times in storage tanks caused residual disinfection concentrations to be low or nonexistent during discharge cycles. It was found that system operation has a significant effect on the distribution and concentration of chlorine residuals in the system.

Water may undergo a number of changes in the distribution system, making the quality of the water at the customer's tap different from the quality of the water that leaves the treatment plant. Such changes in quality may be caused by chemical or biological variations or by a loss of system integrity. A computer-visualization technique, coupled with a dynamic water quality model for analyzing spatial and temporal water quality variations, was studied at two systems

This article briefly reviews an extensive field study by the US Environmental Protection Agency and the North Penn Water Authority, which resulted in the development of a series of models to investigate contaminant propagation in a water distribution system. The application of one such model to the exploration of contaminant movement in the distribution network of Cabool, Mo., is explained. An extension of this work to a large water utility - the South Central Connecticut Regional Water Authority - is also discussed.

Plant-scale comparison of direct filtration versus conventional treatment was mg/L. It was anticipated that modifying achieved bv a solit stream ooeration at a 340-ML/day (90-mgd) water treatment the treatment process to utilize direct plant in thestate of New York. filtration would reduce the amount of alum required by about two thirds. Direct filtration was also expected to lower chemical costs, reduce sludge production (with attendant savings from reduced sludge handling and disposal costs), and reduce the aluminum hydroxide content of alum sludge, thereby improving the dewatering and landfilling characteristics of sludge. The Erie County Water Authority provides filtered water to a population of over 400 000 in twelve towns and the city of Lackawanna in Erie County, N.Y. Some two thirds of the water is treated at the water authority’s Sturgeon Point filter plant, located in the town of Evans, about 50 km (30 mi) south of the city of Buffalo. Constructed in 1961 and subsequently expanded to its present 340ML/day (90-mgd) capacity, the Sturgeon Point plant withdraws low turbidity water from an intake in Lake Erie. Treatment facilities at the plant include four flash mixers, five flocculation-sedimentation basins, and ten reverse-graded mixed media filters approved to operate at filtration rates of up to 4 mm/s (6 gpm/sq ft). Sludge from the water treatment process is gravity-thickened, conditioned, dewatered by filter pressing, and landfilled. Recent studies have indicated that for such low turbidity raw waters as that available from Lake Erie, direct filtration is capable of producing high quality water at a lower cost than conventional treatment with sedimentation ahead of filtration, particularly when reversegraded (coarse-to-fine) mixed media are used in the filters. Direct filtration eliminates the need for sedimentation prior to filtration and reduces alum usage and sludge production. In April 1978 a full-scale study of direct filtration using one reverse-graded mixed media filter was conducted by Malcolm Pirnie, Inc., for the Niagara County Water District’s water treatment plant in Lockport, N.Y., to develop preliminary design data for plant expansion. The raw water quality at this plant was essentially the same as at the Sturgeon Point plant. The study results at this

The writers describe the development of a 5-yr master plan to implement a modern integrated total system automation of the City of Philadelphia's water treatment and distribution facilities including associated components. Analytical instrumentation and other devices located in the rivers, the treatment process, and distribution system provide information through communication links to process control computers. The data are analyzed by the master control computer which utilizes especially derived algorithms to determine adjustments of chemical feeds and process flows via supervisory control of the plant's equipment. This paper examines the multidisciplined approach taken to the problem, starting with the review of the treatment processes, continuing with strategies for improving treatment methods, the development of the five-level hierarchical control structure and the derivation of advanced control strategies for computer-based process control and management.