Calibrating Chlorine wall decay coefficients of water distribution systems based on hybrid PSO

Mathematical models of water distribution systems serve as tools to represent the real systems for many different purposes. Calibration is the process of fine tuning the model parameters so that the real system is well-represented. Chlorine wall decay coefficients vary between pipes and must be determined indirectly from field measured concentration data. A general calibration model under multi-mode for identifying these parameters is formulated, based on the simple first-order reaction of chlorine and the Lagrange time-based approach of dynamic water quality model. Multi-mode model was analyzed to collect more node residual chlorine for calibration. A hybrid piratical swarm optimization, combined with GA algorithms, was proposed to solve the calibration model that is coupled with hydraulic and water quality simulation models using EPANET2 Toolkits. The new methodology is then applied to a hypothetical network. Case study showed that the chlorine wall decay coefficients calibrated by the hybrid PSO algorithm gave perfect matching between actual and computed node residual chlorine values.