Disinfection Data Integrity in Washington State

Deem, Steve; Feagin, Nancy

doi:10.5942/jawwa.2016.108.0157

Cited by 3 publications

(4 citation statements)

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“…Typical drivers for accurate metering, including accounting (e.g., billing) or critical chemical pacing (e.g., ammonia for chloramination), may not apply to many reactors. A recent study of 33 systems in the state of Washington found that 58% did not directly measure flows for disinfection calculations (Deem & Feagin ); 85% of systems also did not calibrate or verify the peak hourly flow or the plant effluent flowmeter. A reactor in which influent flow exceeds effluent flow (i.e., volume accumulation in a reactor used for both storage and disinfection) could also produce V norm > 1.…”

Section: Resultsmentioning

confidence: 99%

“…These limitations may stem from incorrectly estimating reactor geometry (i.e., water level versus volume) or incorrectly estimating how water level changes over time. Deem and Feagin () found that 55% of systems did not verify contact chamber volume and that dimensions of contact chambers in five of 11 systems measured did not match the dimensions used for contact volumes. They also observed that half of systems using tanks or clearwells for disinfection contact did not record tank levels.…”

Section: Resultsmentioning

confidence: 99%

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Modeling Water Treatment Reactor Hydraulics Using Reactor Networks

2018

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Reactor hydraulics are integral to water treatment processes such as disinfection and chemical contaminant oxidation. This work uses reactor networksconceptual reactors arranged in parallel and series combinations-to simplify the accurate modeling of residence time in water treatment reactors. Reactor networks were selected for 14 clearwells, ozone contactors, clarifiers, and filters using tracer data sets from literature. For seven of 14 full-scale reactors, two parallel tanks-in-series reactors best balanced accuracy and simplicity. Reactor networks accurately represented tracer data using between two and eight fitting parameters, while segregated flow analysis required 32-164 inputs (two per tracer data point). The modeling work revealed that tracer data sets may have overestimated baffle factors by >10% in 10 of the 14 full-scale reactors, potentially as a result of inaccurate measurement of flow rate or volume. Applications of reactor networks include more accurate approaches to disinfection regulation and modeling the degradation of emerging contaminants.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Modeling Water Treatment Reactor Hydraulics Using Reactor Networks

2018

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“…In contrast, disinfection contact time and its design are likely the least understood part of disinfection, and the design of disinfection contact basins is usually performed using a limited number of resources. Furthermore, contact time can be the largest single source of error in determining pathogen inactivation (Deem & Feagin, ).…”

Section: Introductionmentioning

confidence: 99%

“…The work described in this article was prompted by the findings of an earlier study of disinfection data and practice by the Washington Department of Health (WDOH), which found that eight of the nine systems with a BE above 0.1 were using empirically derived values not verified by a tracer study (Deem & Feagin, ). This group included two utilities with unbaffled chlorine contact tanks that were using an unusually high BE of 0.3.…”

Section: Introductionmentioning

confidence: 99%

Baffling efficiency insights gained from tracer studies at 32 Washington treatment plants

et al. 2018

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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.

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