Lost in optimisation of water distribution systems? A literature review of system operation
Environmental Modelling & Software
Optimisation of the operation of water distribution systems has been an active research field for almost half a century. It has focused mainly on optimal pump operation to minimise pumping costs and optimal water quality management to ensure that standards at customer nodes are met. This paper provides a systematic review by bringing together over two hundred publications from the past three decades, which are relevant to operational optimisation of water distribution systems, particularly
... al pump operation, valve control and system operation for water quality purposes of both urban drinking and regional multiquality water distribution systems. Uniquely, it also contains substantial and thorough information for over one hundred publications in a tabular form, which lists optimisation models inclusive of objectives, constraints, decision variables, solution methodologies used and other details. Research challenges in terms of simulation models, optimisation model formulation, selection of optimisation method and postprocessing needs have also been identified. control or pump operating costs were very similar. For the third model considering concentration deviations, nonetheless, the optimal solution had higher value of pump operating time/costs than for the first model. The explanation provided was that the objective function implemented in the third model (i.e. concentration deviations) does not force the algorithm to reduce pump operating time/costs further after all of the constraints are satisfied. Ostfeld and Salomons (2006) discovered that pumping costs are significantly reduced if water quality is absent from the optimisation model and conversely, that the best water quality outcome corresponds to the highest pump operating costs. This competing nature of tradeoff between water quality and operating costs was confirmed by Arai et al. (2013), and Kurek and Ostfeld (2014). Those models were improved by the incorporation of control valves to direct disinfectant laden-water where required (Kang and Lansey 2009; Kang and Lansey 2010) and by inclusion of uncertainties on demands, pipe roughness and chemical reactions of the disinfectant (Rico-Ramirez et al. 2007). Furthermore, a multiobjective approach was applied with additional objectives being the number of instances of not meeting quality requirements (Ewald et al. 2008; Kurek and Brdys 2006), the costs of tanks (Kurek and Ostfeld 2013), and the number of polluted nodes and operational interventions (OIs) as responses to WDS contamination (Alfonso et al. 2010). Water quality parameters (such as chlorine) were typically modelled as non-conservative using first order decay kinetics, except for Murphy et al. (2007) and Prasad and Walters (2006) , who used water age as a substitute for water quality. Optimisation methods used were mainly LP and mixed integer nonlinear programming (MINLP) (for example Arai et al. (2013), Biscos et al. (2003), Boccelli et al. (1998)) and metaheuristic algorithms (GA and others) linked with a network simulator EPANET (for example Alfonso et al. (2010), Dandy and Gibbs (2003)). Most recently in order to reduce computational effort, EPANET simulations were replaced by the ISM (Arai et al. 2013) and ANN (Wu et al. 2014b).