This paper reports on field studies and model development aimed at understanding coliform fate and transport in the Quabbin Reservoir, an oligotrophic drinking water supply reservoir. An investigation of reservoir currents suggested the importance of wind driven phenomena, and that both lateral and vertical circulation patterns exist. In-situ experiments of coliform decay suggested dependence on light intensity and yielded an appropriate decay coefficient to be used in CE-QUAL-W2, a two-dimensional hydrodynamic and water quality model. Modeling confirmed the sensitivity of reservoir outlet concentration to vertical variability within the reservoir, meteorological conditions, and location of coliform source.
The removal of selected pharmaceuticals and personal care products, atrazine, and disinfection by-product precursors, was evaluated during a pilot-scale study conducted at the Bollman Water Treatment Plant in Concord, California, USA. Treatment alternatives included ozonation followed by biologically active filtration (BAF), and nanofiltration. Both technologies exhibited excellent broadspectrum removal of the spiked target contaminants. The ozone/BAF system in particular showed a high degree of effectiveness despite relatively low ozone doses corresponding to a low disinfection target (0.5-log Giardia reduction). The BAF system was observed to remove several contaminants that were relatively unreactive with ozone, demonstrating an important synergy between the ozone and BAF.
Natural organic matter (NOM) in water sources differs in terms of both character and concentration. Water treatment processes and the aesthetic quality of water may be influenced by NOM concentration and character. NOM is also related to nutrient cycling and availability and the general trophic state of an aquatic ecosystem. Quabbin Reservoir is the primary drinking water source for metropolitan Boston, Massachusetts. Measures of NOM present in samples collected from the watershed included, but were not limited to, total organic carbon (TOC), dissolved organic carbon (DOC), ultraviolet absorbance (UVA), and trihalomethane formation potential (THMFP). Samples were collected at the mouths of the 12 major Quabbin tributaries and from a horizontal transect of six sites within the reservoir. A variation was found in the relationships between measures of NOM from the reservoir and tributary samples. Regression analyses showed positive linear relationships between DOC and UVA, THMFP and TOC, and THMFP and UVA. Relationships between measures of NOM in the reservoir samples were weaker than those obtained for the tributary samples. These weaker relationships were attributed to the low concentrations and narrow ranges of measures of NOM in the reservoir and the overall complexity of the aquatic system.
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