Factors controlling the effectiveness of rechlor(am)ination to recover chloramine from nitrification

Karthik, N.B.; Krishna, K. S.; Sathasivan, Arumugam

doi:10.1016/j.scitotenv.2021.151322

Cited by 4 publications

(1 citation statement)

References 36 publications

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“…For the other DS and residential sample locations, temporal nitrate concentrations (Figure S25) changed in accordance with variations in temporal EP nitrate concentrations. Even though the average free ammonia concentration (Figure 3e) was greater than the recommended EP concentration (<0.10 mg‐N/L) at times (American Water Works Association, 2013), the extent of nitrification that occurred (i.e., only observed at the MRT during Pre‐FCC‐DP) was likely limited due to maintaining minimum disinfectant concentrations at measurable concentrations (≥0.5 mg‐Cl 2 /L) using booster chlorination (Karthik et al, 2022). Additionally, chlorine booster stations were operated to minimize free ammonia (“≈0.01 mg‐N/L” is stated in the CDWS standard operating procedure), which would further limit the extent of nitrification.…”

Section: Resultsmentioning

confidence: 99%

Evaluation of distribution system water quality during a free chlorine conversion

Alexander,

Woodruff,

Mistry

et al. 2024

AWWA Water Science

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Chloraminated drinking water systems commonly use free chlorine conversions (FCCs) to prevent or control nitrification, but unintended water quality changes may occur, including increased disinfection by‐product and metal concentrations. This study evaluated water quality in a chloraminated drinking water system and residential locations before, during, and after their annual, planned FCC. Water quality alternated between relatively consistent and variable periods when switching disinfectants. During the FCC, regulated four trihalomethane and five haloacetic acid concentrations increased by four and seven times, respectively, and exceeded corresponding maximum contaminant levels. Implications of disinfection by‐product sampling during an FCC were assessed, and an approach to account for increased FCC disinfection by‐product concentrations was proposed. For metals, the FCC had minor impacts on distribution system concentrations and did not appear to impact residential concentrations. Overall, observed variable water quality appeared primarily associated with switching disinfectants and depended on distribution system hydraulics.

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Section: Resultsmentioning

confidence: 99%