CCWI2017: F98 'Two-Point Constraint Control of Water Quality in Distribution Networks'

Providing potable drinking water, with sufficient free residual chlorine to prevent microbial regrowth and contaminant by-product formation, is of utmost importance for municipal authorities. This work aims towards water quality control as it transports through water distribution networks. Presence of excessive chlorine (used as disinfectant worldwide) in water causes the generation of carcinogenic disinfectant by-products such as Tri-halo methane (THMs). On the other hand, lower chlorine levels in water results in microbial contamination. Hence, this leads to a two-point constraint control problem of maintaining free residual chlorine levels under the upper and lower bounds, by suitably optimizing the disinfectant dosage at booster stations. However, transport delay and complex interrelations present amongst the nodes in large water distribution network, makes it difficult to design a global feedback control system. Therefore, in this work we have proposed to decentralize the system by clustering demand nodes of the network based on concentration sensitivity matrix analysis. Further, input-output pairs for decentralized controllers were mapped with the knowledge of interactions between manipulating and control variables using partial correlation analysis. We also considered the results of partial correlation analysis to generate communication links which will be implemented for higher level co-ordinated decentralized control to account for dynamic, non-negligible interactions as disturbances to local control units. The proposed three step clustering-mapping strategy and mathematical formulation for two point control by optimized dosage is successfully verified for the steady state case on a prototype distribution example network.