The robustness of technical systems denotes their ability to function and perform to meet the set objectives even amidst changing environments and vulnerable operating conditions (Spiller et al., 2015). Robustness is the capacity of a treatment system to withstand a disturbance without entering a phase of unsatisfactory performance (Cuppens et al., 2012). For example, a robust water supply and sewerage infrastructure is the one that continues to function satisfactorily till the end of the design period amidst varying loads, influent characteristics and effluent quality standards. Interestingly, a resilient system is allowed to fail under extreme conditions, but the ability to recover quickly from stress and sustain the minimum functionality and service is referred to as adaptability or adaptive capacity. The time taken by the system to recover from a perturbation and regain its satisfactory performance plays a key role and is referred to as rapidity (Cuppens et al., 2012). Furthermore, the flexibility of a system denotes the ability of the infrastructure to cope with changing operational conditions in response to emerging circumstances by entailing changes in scale, functionality, structure and operational objectives (Spiller et al., 2015). Flexibility refers to the ability of UWI to meet the newer guidelines with minimal infrastructural changes. It facilitates the integration of unpredicted advances in technologies, such as easy retrofitting for resource recovery options or capacity expansion (Spiller et al., 2015). The advantages of decentralized systems with regard to resilience have been outlined in Table 2.