From an asset management perspective there is an ongoing challenge to make strategic investment decisions which are based on maintaining asset serviceability, effluent quality requirements and providing for growth. Additionally, individual performance of treatment stages and changes in sewage flows and loads have to be considered to achieve an optimised outcome. Typically, large scale capital projects are required to address the many challenges that face a WWTP. However, significant cost savings can be made if smaller optimisation projects are pursued to maximise the capacity of existing infrastructure and therefore defer high cost capital upgrades. To achieve this end, SA Water started a formal process to review the capacity of each process element of the Bolivar WWTP and found several opportunities to optimise current process performance. Based on these outcomes a future strategy document was developed that enables the next major plant upgrade to be deferred by 8–10 years. This paper summarises SA Water's approach to develop such a documentation to allow a strategic asset management, optimise its capital expenditure and achieve significant cost savings. It also highlights some of the projects that were identified during this process to improve the current treatment plant performance.

Many decisions in the water industry, particularly related to large infrastructure projects, involve numerous discrete alternatives and criteria and are often characterised by uncertain consequences, complex interactions, and the participation of multiple stakeholders with conflicting interests. Multi-criteria decision analysis (MCDA) is a methodology that can be used to aid decision making when discrete alternatives are involved, as it facilitates stakeholder participation and collaborative decision making and does not require the assignment of monetary values to environmental or social criteria. This paper demonstrates the application of MCDA to a real case study in the water industry in South Australia. The case study involved undertaking an analysis of options for ensuring sufficient supply of treated wastewater to an expanded horticultural irrigation scheme. Participants from the water utility, United Water, and the water authority, SA Water, were involved in the decision analysis process through two workshops. Eleven options were assessed using fourteen criteria. The ranking of options utilised a reliability approach which took into account the participants preferences (i.e. criteria weights) and the uncertainty in the values assigned to the criteria.

Techniques to decrease the rate of chlorine dioxide (ClO2) decay in a treated water from Whitfield, Australia were investigated. Biofiltration, microfiltration (MF) and ultrafiltration (UF) were considered as possible means of removing organic compounds which react with the ClO2. Membrane filtration removed more organic material than biofiltration, but biofiltration led to greater ClO2 durations and lower biological regrowth potentials than MF or UF. The results indicated that biofiltration was able to preferentially remove the fast reacting component of organic material that led to rapid ClO2 decay and also lowered the biological regrowth potential of the water.