Least-squares optimization approaches are employed to select adequate manipulated variables, control objectives, measurements and control algorithms for chlorine residual feedback control design in booster disinfection systems. These methods allow for the selection of proper control structure and investigation of its limitations. Application on an example network shows that system residual controllability depends on the number of booster stations, disinfectant source type used, disinfectant injection updating rules and feedback control goals to be achieved at few sensed network locations.