Exploring water quality variations and biofilm growth in a drinking water distribution system via a biofilm annular reactor series system and predictive modelling of residual chlorine

The hydraulic conditions vary significantly across different segments of the drinking water distribution system (DWDS), leading to distinct variations in water quality throughout the system. Understanding these changes in water quality and biofilm development over time is crucial for enhancing drinking water management efficiency. This study focused on replicating the hydraulic conditions found in transmission and distribution pipelines within a specific pipeline path of the DWDS in Singapore using a biofilm annular reactor series system (BARSS). The BARSS experiment revealed that the total residual chlorine (TRC) concentration in water was greatly influenced by both flow velocity and the amount of biofilm present. TRC decay occurred more rapidly at higher flow velocity and was influenced by bacterial growth under fast flow conditions. Furthermore, UV₂₅₄ levels in the water decreased with extended water age in the BARSS, due to the degradation of organic matters into smaller molecules. The study also found that higher TRC concentrations had a more pronounced inhibitory effect on biofilm formation and the proliferation of minor taxa. In the last part of the study, a predictive model for TRC concentration was developed using water quality parameters from preceding stages in the BARSS. This model demonstrated excellent prediction accuracy for TRC concentration, with a mean square error (MSE) of 0.0110 and R² of 0.9893.