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Investigating the Role of Biofilms in Trihalomethane Formation in Water Distribution Systems with a Multicomponent Model
Citation:
Abokifa, A., J. Yang, C. Lo, AND P. Biswas. Investigating the Role of Biofilms in Trihalomethane Formation in Water Distribution Systems with a Multicomponent Model. WATER RESEARCH. Elsevier Science Ltd, New York, NY, 104(1):208-219, (2016). https://doi.org/10.1016/j.watres.2016.08.006
Impact/Purpose:
Publication of the research results on DBP formation modeling in a drinking water distribution system, especially in its dead ends and perimeters. Biofilms ubiquitously exist in the pipes of drinking water distribution systems (DWDSs). Their role in the formation and fate of halogenated disinfection by-products (DBPs) is largely unknown. Recent experimental studies revealed that the chlorination of the microbial biomass carbon associated with the biofilm contributes to the total DBPs budget with reaction mechanisms that are distinct from natural organic matter (NOM) precursors. In this study, we developed a mathematical reactive-transport model to simulate the simultaneous transport and interactions of multiple-species in the distribution network including disinfectants, organic compounds, biomass, and DBPs, to investigate the contribution of bacterial disinfection to DBPs formation. We compared the model simulation results to chlorine decay and microbial regrowth dynamics in an actual DWDS, and DBPs formation in a pilot-scale distribution system simulator, which verified the model’s capability of reproducing the measured concentrations under different hydrodynamic and temperature conditions. The contribution of bacterial species to the total DBPs production was found to have a significant dependence on the system hydraulics, and seasonal variables such as the influent concentration of organic compounds and water temperature. The transformation of non-microbial carbon into microbial carbon precursors by the biofilms showed a noticeable effect on altering DBPs formation kinetics under system conditions that promoted fast bacterial re-growth in the system, including elevated water temperature and high concentrations of microbial growth substrates. The fraction of DBPs formed from microbial carbon was found to reach a peak of 8% of the total produced THMs, which demonstrates the importance of integrating bacterial dynamics in DBPs formation models. The results highlighted the significance of considering a parallel route for DBPs formation represented by the mass transfer of NOM to the biofilm followed by biotransformation and then detachment of biomass precursors back to the bulk phase as an important alternative to the well-known DBP formation route from chlorination of NOM precursors
Description:
Biofilms ubiquitously exist in the pipes of drinking water distribution systems (DWDSs). Their role in the formation and fate of halogenated disinfection by-products (DBPs) is largely unknown. Recent experimental studies revealed that the chlorination of the microbial biomass carbon associated with the biofilm contributes to the total DBPs budget with reaction mechanisms that are distinct from natural organic matter (NOM) precursors. In this study, we developed a mathematical reactive-transport model to simulate the simultaneous transport and interactions of multiple-species in the distribution network including disinfectants, organic compounds, biomass, and DBPs, to investigate the contribution of bacterial disinfection to DBPs formation. We compared the model simulation results to chlorine decay and microbial regrowth dynamics in an actual DWDS, and DBPs formation in a pilot-scale distribution system simulator, which verified the model’s capability of reproducing the measured concentrations under different hydrodynamic and temperature conditions. The contribution of bacterial species to the total DBPs production was found to have a significant dependence on the system hydraulics, and seasonal variables such as the influent concentration of organic compounds and water temperature. The transformation of non-microbial carbon into microbial carbon precursors by the biofilms showed a noticeable effect on altering DBPs formation kinetics under system conditions that promoted fast bacterial re-growth in the system, including elevated water temperature and high concentrations of microbial growth substrates. The fraction of DBPs formed from microbial carbon was found to reach a peak of 8% of the total produced THMs, which demonstrates the importance of integrating bacterial dynamics in DBPs formation models. The results highlighted the significance of considering a parallel route for DBPs formation represented by the mass transfer of NOM to the biofilm followed by biotransformation and then detachment of biomass precursors back to the bulk phase as an important alternative to the well-known DBP formation route from chlorination of NOM precursors.
URLs/Downloads:
DOI: Investigating the Role of Biofilms in Trihalomethane Formation in Water Distribution Systems with a Multicomponent Model
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