Disinfection by‐product concentrations in a transmission system can change in response to downstream treatment processes. Semimechanistic models that describe the formation of disinfection by‐products (DBPs) (including trihalomethanes and haloacetic acids) were developed for the Massachusetts Water Resources Authority, an unfiltered surface water system using chlorine. The model's parameters were hydroxide concentration, chlorine decay kinetics or chlorine reacted, ultraviolet light absorbance at 254 nm, and algae concentration. One of the challenges in estimating or predicting DBP concentrations is that treatment processes at various points in the transmission system have substantial effects on the factors that affect DBP formation and rates of DBP formation. This article describes the formation of total trihalomethanes and haloacetic acids in the Massachusetts Water Resources Authority system and takes into account three treatment processes within the system. Coefficients used in the model were based on monitoring data collected from October 1997 to July 1999 and were validated with monitoring data from August 1999 to January 2000.

In order to eliminate potential seasonal complaints from customers concerning algal blooms in the Wachusett Reservoir, the Massachusetts Water Resources Authority (MWRA) installed a FlowCAMμ, a breakthrough particle‐imaging and flow‐cytometry system that takes high‐resolution, full‐color digital images of every particle and cell in a fluid sample. These images, along with their corresponding data sets, are saved in an interactive scattergram or in the company's proprietary Microsoft Excel spreadsheet‐based system, Visual Spreadsheetμ, for instant display and analysis. The article discusses additional data collected for each particle and cell, how to use the FlowCAM, and its benefits and uses for other water quality issues.