Decentralised systems - definition and drivers in the current context.

This paper explores the current context for decentralised approaches in the provision of urban water services. It examines the recent history of decentralised systems' implementation in Australia and identifies its drivers. The drivers included addressing capacity constraints of centralised systems, mitigating the environmental impact of urban development, and increasing the resilience of urban water systems to episodic droughts and the projected impacts of climate change. The concepts of integrated urban water management and water sensitive urban design were prevalent in many of the innovative approaches used for the provision of decentralised urban water services. However, there remains a degree of confusion among water professionals in the terminology adopted for on-site and decentralised systems. Based on a literature review, consultation with water industry professionals and examination of decentralised urban developments in Australia, this paper has developed a generalised definition of decentralised systems for adoption across the water sector. The definition encompasses the various development scales in which decentralised systems are implemented, and reflects the new functions and characteristics inherent to those systems.

Impediments and constraints in the uptake of water sensitive urban design measures in greenfield and infill developments.

Water sensitive urban developments are designed with integrated urban water management concepts and water sensitive urban design measures. The initiatives that may be included are the substitution of imported drinking water with alternative sources using a fit-for-purpose approach and structural and non-structural measures for the source control of stormwater. A water sensitive approach to urban development can help in achieving sustainability objectives by minimising disturbance to ecological and hydrological processes, and also relieve stress on conventional water systems. Water sensitive urban developments remain novel in comparison with conventional approaches, so the understanding and knowledge of the systems in regards to their planning; design; implementation; operation and maintenance; health impacts and environmental impacts is still developing and thus the mainstream uptake of these approaches faces many challenges. A study has been conducted to understand these challenges through a detailed literature review, investigating a large number of local greenfield and infill developments, and conducting extensive consultation with water professionals. This research has identified the social, economic, political, institutional and technological challenges faced in implementing water sensitive urban design in greenfield and infill developments. The research found in particular that there is the need for long-term monitoring studies of water sensitive urban developments. This monitoring is important to validate the performance of novel approaches implemented and improve associated guidelines, standards, and regulatory and governance frameworks, which can lead to mainstream acceptance of water sensitive urban development approaches. The dissemination of this research will help generate awareness among water professionals, water utilities, developers, planners and regulators of the research challenges to be addressed in order to achieve more mainstream acceptance of water sensitive approaches to urban development. This study is based on existing water sensitive urban developments in Australia, however, the methodology adopted in investigating impediments to the uptake of these developments can be applied globally. It is hoped that insights from this study will benefit water professionals in other countries where there is also a move towards water sensitive urban development.

Vulnerability of water services in Pacific Island Countries: combining methodologies and judgment.

Water services in Pacific Island Countries are particularly vulnerable due to a range of circumstances such as the scale of operation, remoteness of location, financial constraints, cultural complexity and the ability to access technical and other capacity by their administrations. Additionally, the authors argue that comparative assessment of water needs for differing locations is fraught with difficulty because of the combination of systemic complexity, diversity of situations and lack of suitable, consistent and objective data. In these challenging situations, a method for assessment of the vulnerability of water services has been developed on the basis of knowledge and experiences of water professionals, elicited using a structured group interaction known as a Delphi survey. The Delphi survey has been undertaken with a range of stakeholders including panels of experts, funding agencies and local decision makers. Through the Delphi process, key factors contributing to vulnerability have been identified and the output has been used to develop an index methodology. Such an index methodology, similar to the Climate Vulnerability Index, has a number of dimensions, variables and appropriate weights expressed within a set of equations. Given quantification of variables, this method can be used to assess the relative vulnerability of water services in Pacific Island Countries. The method used to develop this index could also be applied to other contexts where appropriate.

Biofouling potential and material reactivity in a simulated water distribution network supplied with stormwater recycled via managed aquifer recharge.

The injection of stormwater into aquifers for storage and recovery during high water demand periods is a promising technology for augmenting conventional water reserves. Limited information exists regarding the potential impact of aquifer treated stormwater in distribution system infrastructure. This study describes a one year pilot distribution pipe network trial to determine the biofouling potential for cement, copper and polyvinyl chloride pipe materials exposed to stormwater stored in a limestone aquifer compared to an identical drinking water rig. Median alkalinity (123 mg/L) and colour (12 HU) in stormwater was significantly higher than in drinking water (82 mg/L and 1 HU) and pipe discolouration was more evident for stormwater samples. X-ray Diffraction and Fluorescence analyses confirmed this was driven by the presence of iron rich amorphous compounds in more thickly deposited sediments also consistent with significantly higher median levels of iron (∼0.56 mg/L) in stormwater compared to drinking water (∼0.17 mg/L). Water type did not influence biofilm development as determined by microbial density but faecal indicators were significantly higher for polyvinyl chloride and cement exposed to stormwater. Treatment to remove iron through aeration and filtration would reduce the potential for sediment accumulation. Operational and verification monitoring parameters to manage scaling, corrosion, colour, turbidity and microbial growth in recycled stormwater distribution networks are discussed.