Model Development for Residual Chlorine

Abstract

The research is to develop a mathematical model for the decay of residual chlorine at the nodes and compare with results from Epanet 2.0. All the influencing parameters of initial chlorine Ccl(init(o)), bulk decay (Kb), wall decay (KW) and travel time (t), were well represented and the equation is developed applying the differential form of the first order chlorine decay model, describing reactions occurring in the bulk fluid and at the pipe wall, which was transformed in to chlorine concentration-based integral expression Ccl (t) =Ccl (o).e-kt ,  is the free chlorine (HOCL) concentration (mg/l) at time (t), which is also called the residual chlorine. is the chlorine concentration at time zero, which is the initial chlorine concentration in the entire water distribution systems. KW is the pipe wall decay coefficient of the particular water distribution pipe network directly affected by initial concentration. K is expressed in the study as the decay due to the quality of water, known as bulk decay coefficient (kb), per unit hour (t=1) at any particular node per hour. he developed mathematical model was a reflection of the reality in the study area Rcl (n)=Ccl (init). KW. е-Kb . The results of the model at nodes 31, 12, 13, 14, 18, 10, 17, 15, 20 and 21 are 0.18 mg/l, 0.19 mg/l, 0.19 mg/l, 0.19 mg/l, 0.19 mg/l, 0.19 mg/l, 0.20 mg/l, 0.19 mg/l, 0.20 mg/l, 0.19mg/l, respectively. Epanet 2.0 results for the same nodes were determine to be 0.17 mg/l, 0.21 mg/l, 0.22 mg/l, 0.20 mg/l, 0.21 mg/l, 0.21 mg/l, 0.25 mg/l, 0.24 mg/l, 0.20 mg/l, 0.20 mg/l, 0.18 mg/l. The correlation between the developed mathematical model residual chlorine results and Epanet 2.0 results gives moderate correlation of 0.561, signifying 60% pearson correlation and 0.01, 2-tailed significance level at 99%.