Optimization of chlorine consumption in water distribution networks by using the new ant colony optimization (ACOR) algorithm

Abstract

Chlorination by maintaining the injected chlorine concentration in the range between the minimum and maximum is among the most inexpensive and common disinfection methods in water distribution networks. The minimum concentration of residual chlorine must be observed to control the microbial quality of water. Besides, the maximum chlorine concentration must be observed to control problems related to water smell and taste and to prevent the production of toxic byproducts. This research has developed a model by combining the EPANET model and the ACO_R optimization algorithm to optimize the chlorine injection program during the operation period. According to the results, the ACOR algorithm could be used to derive a suitable program for chlorine injection in the water distribution network such that the permissible constraints of chlorine are observed in the consumption nodes of the network and the consumption of chlorine is reduced to the least level in the network. The developed model was applied to determine an optimal chlorine injection program in a classical example (the Branford network), which was also of interest to some previous researchers. Using the optimal injection program obtained by the model, the chlorine concentration was set at an acceptable network level between the permissible range of 0.2–0.8 g/l. This output was more favorable than the response of other methods in terms of the total residual chlorine concentration, which was 5.8% and 4.7% lower in this method than the methods based on PSO and genetic algorithms, respectively. Moreover, a better convergence speed was obtained in this algorithm, and the number of calculation times of the objective function was 49.5 and 64.4 less than the methods based on PSO and genetic algorithms, respectively. Therefore, the ACO_R algorithm can be used to derive the chlorine injection program to both comply with the permissible constraints of chlorine and reduce chlorine consumption to the minimum level.