This article summarizes tracer studies performed at 32 water treatment plants in Washington State ranging from 5 to 5,400 gpm, with contact basins from 200 gal to 1.5 mil gal. Multiple tracer studies were performed at each plant. The goal of the tracer studies was to determine the baffling efficiency (BE) of each basin by determining T10/T, where T10 is the time at which 10% of a tracer is measured at the outlet of a basin, and T is the hydraulic residence time. The tracer studies indicated that most facilities historically used BE values higher than what the tracer studies indicated for calculating compliance with disinfection regulations. The majority of the basins were rectangular, baffled basins. The tracer studies indicated that standard design parameters, such as length‐to‐width ratio, were not as accurate in predicting basin performance compared with calculating baffled channel cross‐sectional velocity. This effect was pronounced where cross‐sectional flow velocity was below the Reynolds laminar flow threshold. For circular, baffled basins, a relationship between cross‐sectional velocity and BE was also evident. The study also identified issues with plants having parallel, chlorine contact basins where uneven flow splitting between basins created an overall system BE less than the BE of individual basins.
This improved monitoring protocol, with its simple experimental design and four methods of analysis, allows for a more complete picture of corrosion processes and inferences about scale buildup.
The effect of orthophosphate addition (1 mg/L as P) on copper and lead–tin solder corrosion was monitored using an experimental coupon exposure apparatus with measurement by standing water metals analysis, gravimetric analysis, direct galvanic current metering, and potentiodynamic scan analysis. Orthophosphate addition appeared to have a significant effect on lead–tin solder corrosion although the results of each analysis differed in magnitude. The effect of orthophosphate addition on copper corrosion was less clear with gravimetric analysis showing a significant effect, whereas metals release analysis showed only a slight effect.
Key Takeaways
For its rainwater collection system to pass muster as a potable water source, Seattle's Bullitt Center adhered to strict design and building standards.
Meticulous planning, design, and performance testing of the Bullitt Center's water collection and treatment process provide a blueprint for future self‐contained potable water systems in buildings.
The Bullitt Center is a paragon of sustainability, demonstrating triple‐bottom‐line benefits for its tenants, the community, and the environment.
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