An insight of disinfection by-product (DBP) formation by alternative disinfectants for swimming pool disinfection under tropical conditions.
Sodium hypochlorite (NaClO) is the most commonly used disinfectant in pool treatment system. Outdoor pools usually suffer from the strong sunlight irradiation which degrades the free chlorine rapidly. In addition, more pools start to adopt the recirculation of swimming pool water, which intensifies the disinfection by-product (DBP) accumulation issue. Given these potential drawbacks of using NaClO in the tropical environment, two alternative organic-based disinfectants, trichloroisocyanuric acid (TCCA, C3Cl3N3O3) and bromochlorodimethylhydantoin (BCDMH, C5H6BrClN2O2), were investigated and compared to NaClO in terms of their self-degradation and the formation of DBPs, including trihalomethanes (THMs) and haloacetic acids (HAAs), under simulated tropical climate conditions. The result reveals that halogen stabilizer, TCCA, had the advantages of slower free chlorine degradation and lower DBP concentration compared to NaClO, which makes it a good alternative disinfectant. BCDMH was not recommended mainly due to the highly reactive disinfecting ingredient, hypobromous acid (HBrO), which fails to sustain the continuous disinfection requirement. Total disinfectant dosage was the main factor that affects residual chlorine/bromine and THM/HAA formation regardless of different disinfectant dosing methods, e.g. shock dosing (one-time spiking) in the beginning, and continuous dosing during the whole experimental period. Two-stage second-order-kinetic-based models demonstrate a good correlation between the measured and predicted data for chlorine decay (R(2) ≥ 0.95), THM (R(2) ≥ 0.99) and HAA (R(2) ≥ 0.83) formation. Higher temperature was found to enhance the DBP formation due to the temperature dependence of reaction rates. Thus, temperature control of pools, especially for those preferring higher temperatures (e.g. hydrotherapy and spa), should take both bather comfort and DBP formation potential into consideration. It is also observed that chlorine competition existed between different precursors from natural organic matters (NOM) in filling water and body fluid analogue (BFA). Among the composition of BFA, uric acid, citric acid and hippuric acid were found to be the main precursors for HAA formation.
Interdisciplinary Graduate School, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore; Residues and Resource Reclamation Centre (R3C), Nanyang Environment and Water Research Institute, Nanyang Technological University, 1 Cleantech Loop, CleanTech One, Singapore 637141, Singapore.
Linyan
L
Yang
Environmental Analytical Chemistry, Center for Applied Geoscience (ZAG), Eberhard Karls University Tuebingen, 72076 Tuebingen, Germany.
Christina
C
Schmalz
Division of Environmental and Water Resources, School of Civil and Environmental Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore.
Jin
J
Zhou
Environmental Analytical Chemistry, Center for Applied Geoscience (ZAG), Eberhard Karls University Tuebingen, 72076 Tuebingen, Germany.
Christian
C
Zwiener
Residues and Resource Reclamation Centre (R3C), Nanyang Environment and Water Research Institute, Nanyang Technological University, 1 Cleantech Loop, CleanTech One, Singapore 637141, Singapore; Division of Environmental and Water Resources, School of Civil and Environmental Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore. Electronic address: wcchang@ntu.edu.sg.
Victor W-C
VW
Chang
Residues and Resource Reclamation Centre (R3C), Nanyang Environment and Water Research Institute, Nanyang Technological University, 1 Cleantech Loop, CleanTech One, Singapore 637141, Singapore.
Liya
L
Ge
School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore.
Man Pun
MP
Wan
D002713:Chlorine; D004202:Disinfectants; D004203:Disinfection; D013551:Swimming Pools; D022882:Trihalomethanes; D018508:Water Purification
D004202:Disinfectants; D022882:Trihalomethanes; D002713:Chlorine
Bromochlorodimethylhydantoin; Disinfection by-products; Dosing methods; Swimming pools; Trichloroisocyanuric acid