Estimation of chloramine decay in drinking water distribution systems. (April 2022)

• Record Type: Journal Article
• Authors: Curling, Emily A.; McKie, Michael J.; Meteer, Laura; Saunders, Blair; Andrews, Susan A.; Andrews, Robert C.
• Is Part Of: Journal of water process engineering. Volume 46(2022)
• Publication Date: 2022-04
• Subjects: CI cast‑iron -- Cl2(final) final chlorine concentration (mg/L) -- Cl2(initial) initial chlorine concentration (mg/L) -- DI deionized -- kb first-order bulk water decay rate (h−1) -- kf mass transfer coefficient (m/h) -- kobs first-order observed decay rate (h−1) -- kw surface reaction rate (m/h) -- NR not reported -- PSR pipe section reactor; Chloramine decay -- Drinking water distribution -- Secondary disinfection -- Pipe section reactor -- Drinking water; Water-supply engineering -- Periodicals; Saline water conversion -- Periodicals; Seawater -- Distillation -- Periodicals; Sanitary engineering -- Periodicals; Sewage -- Purification -- Periodicals; 627
• DOI: 10.1016/j.jwpe.2022.102558
• Languages: English
• ISSNs: 2214-7144

Abstract

Abstract: When compared to free chlorine, chloramines represent an established secondary disinfectant that may be utilized to reduce disinfection by-product formation and improve residual stability. Maintaining an acceptable residual in distribution systems however may be challenging due to potential high maintenance costs associated with uni-directional flushing and swabbing. This study was designed to identify the primary sources of chloramine demand for a distribution system receiving surface and groundwater. Decay in the bulk water was quantified using a bottle point method. Bench-scale pipe section reactors (PSRs) were utilized to evaluate decay associated with cast‑iron and polyvinyl chloride (PVC) pipe sections that had been harvested from a distribution system, as well as to allow comparisons with new pipe material. Bulk water decay was compared to that observed in PSRs at flow rates of 0.03 m/s and 0.09 m/s, representative of distribution system conditions. Pipe material type and associated surface conditions were identified as the most critical factors influencing decay. Observed first-order decay rates for harvested cast‑iron pipe with an established microbial community and metal/silicate scale were significantly higher than those for PVC. In contrast, first-order decay rates for harvested PVC were comparable to new pipe, with water velocity exerting a negligible impact. Overall, these results reinforce the importance of determining the primary sources of chloramine decay in distribution systems. Graphical abstract: Unlabelled Image Highlights: Chloramine decay was evaluated through batch and pipe section reactor (PSR) trials. Pipe material was the greatest contributor to chloramine decay. Cast‑iron (CI) decay was 20–160 x that for polyvinyl chloride. Decay rates for CI with surface deposits were 5.5 x times those without.