OPTIMAL SCHEDULING OF BOOSTER DISINFECTION IN WATER DISTRIBUTION-SYSTEMS

Booster disinfection is the addition of disinfectant at locations dist ributed throughout a water distribution system. Such a strategy can re duce the mass of disinfectant required to maintain a detectable residu al at points of consumption in the distribution system, which may lead to reduced formation of disinfectant byproducts in particular trihalo methanes. Here an optimization model is formulated for the dynamic sch edule of disinfectant injections; this schedule minimizes the total do se required to satisfy residual constraints over an infinite-time hori zon. This infinite-time problem is reduced to a solvable finite-time o ptimal scheduling model by assuming periodicity of mass injections and network hydraulics. Furthermore, this model is linear since the princ iple of linear superposition is shown to apply to disinfectant concent rations resulting from multiple disinfectant injections over time. A m atrix generator code was developed to interface with the EPANET networ k water quality model. This code automatically generates the Linear pr ogramming formulation of the optimal scheduling model, which is then s olved using the simplex algorithm. Results from application of the mod el suggest that booster disinfection can reduce the amount of disinfec tant required to satisfy concentration constraints, when compared to c onventional disinfection only at the source. The optimal booster sched ule reduced the average disinfectant concentration within the distribu tion system and, in some cases, the variability of these concentration s. The number of booster stations, booster location, and distribution system hydraulics were shown to affect the optimal schedule.