Limitations on Optimizing Location and Scheduling of Chlorine Boosters in Water Distribution Systems

Boosting chlorine concentrations at intermediate locations within water distribution systems is a common way to maintain a specified minimum level of disinfectant to control microbiological regrowth. At the same time, maximum levels of both chlorine and its disinfection by-products should not be exceeded. Various mathematical procedures are available to find optimal solutions for the locations and dosing schedules of these booster plants. The problem is that most formulations have assumed unrealistic linear kinetics for chlorine decay in bulk water and at pipe walls, resulting in unrealistic solutions. Recent research shows that accurate prediction of chlorine and by-product concentrations resulting from initial and booster dosing requires more complex kinetic representation, in which chlorine reacts with dissolved substances remaining after treatment and with biofilms adhering to pipe walls. Optimization then requires more general nonlinear solution techniques. In addition, minimization of the total costs involved, both operating and capital, is needed to match the decision-making processes of water utilities in this field.