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.

A 10‐gpm pilot plant was operated for four to five weeks at each of four US water treatment plants to evaluate the effectiveness of a magnetic ion exchange (MIEX) process for the removal of disinfection by‐product precursors. Variables examined were resin concentration, contact time, and regeneration frequency. Influent and effluent samples were taken on a regular basis and analyzed for ultraviolet (UV) absorbance at 254 nm, dissolved organic carbon (DOC), and bromide. Samples of the raw water and the MIEX‐treated water were also subjected to hydrophobic/hydrophilic fractionation, molecular size characterization, and chlorination under uniform formation conditions to determine the trihalomethane (THM) and haloacetic acid (HAA) formation potential before and after MIEX treatment. Results indicated that the resin removed substantial amounts of DOC and UV‐absorbing materials, except in one of the waters that had a high concentration of total dissolved solids and a low specific UV absorbance. The MIEX resin also removed bromide to some degree, depending on the presence of other competing anions in the raw water. Overall THM and HAA formation was decreased substantially as a result of MIEX treatment.

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This article chronicles advances in the filtration of public drinking water supplies from the late 1800s to today and discusses the future of filtration. Topics covered include: granular media's evolution over the years; pretreatment practices consisting of coagulation, mixing and clarification; current availability of filters and membranes; and, future advances in filtration.

Despite strenuous efforts to prevent them, waterborne disease outbreaks continue to occur from time to time in countries that have the knowledge and capability to prevent them. This article presents the concept that multiple adverse events or changes can often be associated with waterborne disease outbreaks. The information in this article is designed to encourage water treatment plant operators, water quality supervisors, and plant managers to maintain vigilance at all times so circumstances that might lead to a treatment failure and a disease outbreak can be avoided. The authors discuss the importance of water treatment plant personnel being alert at all times and remaining watchful for changes in source water quality, changes in treated water quality, or both to help minimize the likelihood of future waterborne disease outbreaks.