AWWA WQTC60713

Many communities are, unknowingly, practicing indirect, unintentional reuse by relying onwastewater effluent impacted sources for drinking water. An immediate concern identified withreclaimed water as a drinking water source are the potential health impacts associated with bulkeffluent organic matter (EfOM), measured as dissolved organic carbon (DOC), and trace organiccompounds. The characteristics of the DOC in recycled wastewater are less understood thanthose in traditional drinking water sources.The main goal of this investigation was to characterize the DOC in an existing wastewater reusesystem. Specifically, the investigation compared the concentrations of the three separate DOCfractions defined by size exclusion chromatography with on-line DOC detection (SEC-DOC), that included: high-molecular weight, polysaccharide or protein-like substances; humic-like substances; and,low molecular-weight acids.The wastewater reuse system investigated was a segment of the South Platte River near Denver,Colorado. The segment studied began at Chatfield Reservoir and continued downstream to thecity of Thornton, Colorado. In between Chatfield Reservoir and Thornton, the largest singlewastewater effluent (the Metro Wastewater Reclamation District Treatment Plant) discharges intothe South Platte River. Overall, this study segment is an example of indirect, unintentionalwastewater reuse, where samples from Chatfield Reservoir represent a water source unaffected bywastewater effluents and samples from the South Platte River at Thornton represent a watersource affected by wastewater effluents.The resultant concentrations of each DOC fraction were significantly greater in the South PlatteRiver at Thornton than in the Chatfield Reservoir. Between these two sampling points, the DOCconcentrations increased by 59%, 59% and 34% for proteins and polysaccharides, humicsubstances, and low-molecular weight acids, respectively. This DOC increase suggests thatdrinking water treatment must be modified or optimized for removing larger quantities of each ofthese DOC fractions when treating effluent-affected sources similar to the South Platte River atThornton, as opposed to sources unaffected by effluents. As examples, protein-like (nitrogenous)substances should be removed to avoid the formation of nitrogenous disinfection byproducts at aconcentration that would be health hazardous, and polysaccharide-like substances should beremoved before membrane treatment. In conclusion, the DOC in recycled wastewaters exhibitshigher concentrations of proteins and polysaccharides, humic substance, and low-molecularweight acids than waters unaffected by wastewater effluents. Other analytical techniquesincluding fluorescence excitation-emission matrices and DON measurements are discussed tofurther elucidate the SEC-DOC trends. Includes 23 references, tables, figures.

Product Details

Edition:

Vol. - No.

Published:

11/15/2004

Number of Pages:

20

File Size:

1 file