Identification and Modelling of Chlorine Decay Mechanisms in Reclaimed Water Containing Ammonia

Joana Costa, Elsa Mesquita, Filipa Ferreira, Maria João Rosa and Rui M. C. Viegas
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Joana Costa: Water Quality and Treatment Laboratory, Urban Water Unit, Hydraulics and Environment Department, LNEC—National Laboratory for Civil Engineering, 1700-066 Lisbon, Portugal
Elsa Mesquita: Water Quality and Treatment Laboratory, Urban Water Unit, Hydraulics and Environment Department, LNEC—National Laboratory for Civil Engineering, 1700-066 Lisbon, Portugal
Filipa Ferreira: CERIS, Instituto Superior Técnico, University of Lisbon, Av. Rovisco Pais 1, 1049-001 Lisbon, Portugal
Maria João Rosa: Water Quality and Treatment Laboratory, Urban Water Unit, Hydraulics and Environment Department, LNEC—National Laboratory for Civil Engineering, 1700-066 Lisbon, Portugal
Rui M. C. Viegas: Water Quality and Treatment Laboratory, Urban Water Unit, Hydraulics and Environment Department, LNEC—National Laboratory for Civil Engineering, 1700-066 Lisbon, Portugal

Sustainability, 2021, vol. 13, issue 24, 1-13

Abstract: Keeping an effective disinfectant residual concentration in reclaimed water is still a challenge, due to its high levels of ammonia and organic matter when compared with those in drinking water. This research proposes the integration of the reaction schemes of monochloramine auto-decomposition with an empirical kinetic mechanism accounting for reactive chlorine species decay in the presence of organic matter, for which three mechanisms were hypothesized and tested. A parallel second order mechanism, where monochloramine reacts both with fast and slow organic matter reactive fractions, was identified as the most suitable. The model, comprising two rate constants and two fictive concentrations of organic matter as parameters, was further successfully calibrated with real reclaimed waters with two initial free chlorine doses of 8.01 × 10 − 5 M (≈5 mg/L) and 2.67 × 10 − 4 M (≈20 mg/L). The proposed model is believed to support future studies aiming to predict and manage chlorine decay in reclaimed water distribution systems.

Keywords: reclaimed water distribution systems; urban water reuse; disinfection; chlorine decay; monochloramine; organic matter (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2021
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