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 for TOC and turbidity removal, including changes in pH and coagulant dose, use of alternative coagulant chemicals, and changes in the order of chemical addition.

No abstract

Organic chemical compounds have infiltrated many groundwater sources. Since thousands of small water systems rely on groundwater sources for potable water, an economical means of controlling or treating supplies is essential. This article outlines alternatives for bringing such systems into compliance and compares the costs of each method.

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.

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.