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Planners and decision-makers in the wastewater sector are often confronted with the problem of identifying adequate development strategies and most suitable finance schemes for decentralized wastewater infrastructure. This paper research has focused on providing an approach in support of such decision-making. It is based on basic principles that stand for an integrated perspective towards sustainable wastewater management. We operationalize these principles by means of a geographic information system (GIS)-based approach 'Assessment of Local Lowest-Cost Wastewater Solutions' – ALLOWS. The main product of ALLOWS is the identification of cost-effective local wastewater management solutions for any given demographic and physical context. By using universally available input data the tool allows decision-makers to compare different wastewater solutions for any given wastewater situation. This paper introduces the ALLOWS-GIS tool. Its application and functionality are illustrated by assessing different wastewater solutions for two neighboring communities in rural Jordan. [ABSTRACT FROM AUTHOR]

With the application of system dynamics, a dynamic nonlinear model reflecting the relationship between decentralised water use and reclaimed water supply and demand has been established. Through a system analysis, the model has been applied to a small residential district to predict and analyse the situation of future use of fresh water, demand and supply of re-used water, and treatment scale of reclaimed water. It is illustrated in this paper that wastewater decentralised treatment and re-use can decrease the consumption of fresh water without lowering the standard of living water for the district residents. On this basis, a rational scale and construction time of the decentralised sanitation and re-use system have been determined. Also, the paper predicts the influencing factors of the increasing water cost and changes in consumers' acceptability to re-use water in the decentralised sanitation and re-use system. [ABSTRACT FROM AUTHOR]

Current sanitation concepts of decentralised wastewater treatment and reuse raise the issue of monitoring and maintenance of such systems. To guarantee high quality of the recycled water, systems with high requirements concerning process technology are essential. With increasing numbers of decentralised treatment systems spread over far distances it will become more and more impossible and uneconomic to have expert personnel on site. Therefore, new visualisation and intelligent information systems are necessary. The paper describes the structure and 3D-demonstrations as a base for information visualisation. Up-to-date visualisation techniques, facilitating the cognition of context-adapted information, make it possible to maximise the amount of information presented to the user without overwhelming her or him. Concerning diagnosis and decision support systems in the domain of wastewater treatment, several interesting approaches are presented, estimating their applicability for decentralised wastewater treatment systems. The intelligent decision support system presented here consists of a combined ontology- and case-based reasoning system in addition to a process monitoring system. It is responsible for plausibility checks, error diagnosis, solution proposals, and optimisation suggestions. [ABSTRACT FROM AUTHOR]

Decentralised systems have the potential to provide a viable option for long term sustainable management of household wastewater. Yet, at present, such systems hold an uncertain status and are frequently omitted from consideration. Their potential can only be realised with improved approaches to their management, and improved methods to decision-making in planning of wastewater systems. The aim of this paper is to demonstrate the value of a novel framework to guide the planning of decentralised systems so that asset management and risk management are explicitly considered. The framework was developed through a detailed synthesis of literature and practice in the area of asset management of centralised water and wastewater systems, and risk management in the context of decentralised systems. Key aspects of the framework are attention to socio-economic risks as well as engineering, public health and ecological risks, the central place of communication with multiple stakeholders and establishing a shared asset information system. A case study is used to demonstrate how the framework can guide a different approach and lead to different, more sustainable outcomes, by explicitly considering the needs and perspectives of homeowners, water authorities, relevant government agencies and society as a whole. [ABSTRACT FROM AUTHOR]

If technologies for decentralised sanitation and reuse (DESAR) and for natural stormwater management should at least partially replace existing systems, then intensive reconstruction work becomes essential. A conversion can only be realised successively over a long period due to high construction and financial expenses and requires new strategies. This paper presents the development and practical implementation of a mathematical tool to find an optimised strategy for the realisation of alternative and more decentralised drainage and sanitation concepts in existing urban areas. The succession of construction measures (e.g. the implementation of decentralised greywater recycling) for the whole period of consideration is determined based upon a mathematical optimisation model on the condition that the favoured future state is known. The model describes the complex interdependencies of the urban water and nutrient cycle and enables the minimisation of both financial efforts and ecological impacts on the way toward the future state. The results of the implementation for a rural area in Germany show that the mathematical optimisation is an adequate instrument to support decision-making processes in finding strategies for the realisation of sustainable urban water management. [ABSTRACT FROM AUTHOR]

Mega cities with rapid growth are challenged by two main problems concerning water supply and sanitation. One is water scarcity because local demand exceeds local supply. The other is that the infrastructure for water supply and the collection and treatment of wastewater cannot keep up with the rapid growth of the mega cities. The transfer of conventional centralised water and wastewater systems from industrialised countries to mega cities does not seem appropriate, because of the rapid and almost unpredictable growth in mega cities on the one hand and the regional shortage of water which requires an economical use and reuse wherever possible on the other hand. The transition from centralised to semi-centralised supply and treatment systems (SESATS) may be one method of resolution to the grave discrepancy between the rapid growth of cities and the provision of supply and treatment infrastructure. One important aspect of planning semi-centralised wastewater collection and treatment infrastructure including intra-urban water reuse is the assessment of the optimal size. Therefore, factors and indicators, which have an effect on the scale of semi-centralised sanitation systems, have to be developed. Beside the introduction in SESATS some of these factors, criteria and indicators and their effects on the system's scale will be introduced in this paper. [ABSTRACT FROM AUTHOR]