On-going nitrification in chloraminated drinking water distribution system (DWDS) is conditioned by hydraulics and disinfection strategies |
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Authors: | Yi Shi Akintunde Babatunde Bettina Bockelmann-Evans Qijie Li Liang Zhang |
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Affiliation: | National Engineering Laboratory for Cereal Fermentation Technology, Jiangnan University, Wuxi 214122, China;Discipline of Civil Engineering, Cardiff University School of Engineering, The Parade, Cardiff, CF24 3AA, UK;Discipline of Civil Engineering, Cardiff University School of Engineering, The Parade, Cardiff, CF24 3AA, UK;School of Civil Engineering, University of Leeds, Leeds, LS2, 9JT, UK;Discipline of Civil Engineering, Cardiff University School of Engineering, The Parade, Cardiff, CF24 3AA, UK;National Engineering Laboratory for Cereal Fermentation Technology, Jiangnan University, Wuxi 214122, China |
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Abstract: | Within the drinking water distribution system (DWDS) using chloramine as disinfectant, nitrification caused by nitrifying bacteria is increasingly becoming a concern as it poses a great challenge for maintaining water quality. To investigate efficient control strategies, operational conditions including hydraulic regimes and disinfectant scenarios were controlled within a flow cell experimental facility. Two test phases were conducted to investigate the effects on the extent of nitrification of three flow rates (Q = 2, 6, and 10 L/min) and four disinfection scenarios (total Cl2=1 mg/L, Cl2/NH3-N=3:1; total Cl2=1 mg/L, Cl2/NH3-N=5:1; total Cl2=5 mg/L, Cl2/NH3-N=3:1; and total Cl2=5 mg/L, Cl2/NH3-N=5:1). Physico-chemical parameters and nitrification indicators were monitored during the tests. The characteristics of biofilm extracellular polymetric substance (EPS) were evaluated after the experiment. The main results from the study indicate that nitrification is affected by hydraulic conditions and the process tends to be severe when the fluid flow transforms from laminar to turbulent (23002/NH3-N mass ratio were found to inhibit nitrification to some extend when the system was running at turbulent condition (Q = 10 L/min, Re = 5535). EPS extracted from biofilm that was established at the flow rate of 6 L/min had greater carbohydrate/protein ratio. Furthermore, several nitrification indicators were evaluated for their prediction efficiency and the results suggest that the change of nitrite, together with total organic carbon (TOC) and turbidity can indicate nitrification potential efficiently. |
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Keywords: | Corresponding author. Nitrification Drinking water distribution system (DWDS) Biofilm Hydraulics Disinfection |
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