Development of a multi-function software decision support tool for the promotion of the safe reuse of treated urban wastewater

Decision-making in environmental projects can be complex principally due to the inherent existence of trade-offs between socio-political, environmental and economic factors. This is why the MEDAWARE project which is an EU MEDA Water project (ME8/AIDCO/2001/0515/59341-P033) has focused its aims on the development of a software tool able to apply a scoring system for existing wastewater facilities based on the potential safe reuse of the final effluent. The scope of this work is to present the multi-criteria analysis user friendly software that has been developed. The tool is able to guide the responsible authorities to the most efficient solutions in terms of health and safety for the agricultural reuse of the produced effluent as well as to help them undertake actions that can be sustainable. The input data for the specific model are quite simple and can be easily collected (e.g. data concerning the population served by the facility, the possibilities for agricultural reuse of the water in the area, specific requirements or preferences on cultural, economical, technological or social issues), while the outcome is the ranking of the alternative scenarios and the suggestion of specific processes and treatment systems.

Environmental management is essentially a conflicting analysis characterized by technical, socio-economic, environmental and political value judgments. Therefore, in an environmental planning process it is very difficult to reach straightforward and unambiguous solutions. This implies that such a multi-related planning process will always be characterized by the adoption of compromising solutions. The most general principle of municipal water system design is that there are no general principles. All appropriate technologies are context specific (that is part of what makes them appropriate) and municipal water reuse is extremely context specific as well. The design process is complicated because of the great number of alternatives that can be generated and evaluated against criteria such as cost, safety, environmental constrains, technical and social factors. Many factors need to be considered to predict future wastewater facility flows and loadings in a manner that will ensure a cost-effective and sustainable design. This paper presents a systematic design methodology for urban wastewater treatment plants that combines a decision process with the information gathered in a relational database. It is important to underline that the objective of this work has not been the development of a highly sophisticated model for the design of wastewater treatment systems that can be used only by qualified engineers, but the development of a multi-criteria analysis user friendly software that can guide the responsible authorities to the most efficient solutions. The tool developed carries out a systematic evaluation of the different alternative designs with respect to a set of criteria. The first step of the design methodology is to define objectives. The following step is to select the alternatives to solve each issue and the criteria against which the design alternatives will be evaluated. These criteria are specific to each decision. Once the alternatives and criteria are selected, the evaluation of alternatives can be carried out. The output of the system is, then, a list of treatment methods (consisting of several unit processes), satisfying the objectives of effluent quality previously set. This list of treatment methods can be ranked by cost. The alternative that meets the quality objectives while at the same time is less costly will be the one recommended by the system. However the final decision will be taken by the process designer. Acknowledgments The authors gratefully acknowledge the financial support for the implementation of this study provided by the Euro-Mediterranean partnership (Project number ME8/AIDCO/2001/0515/59341P033) and more specifically by its Regional Program for Local Water Management. Authors also thank Mr. Raul Pérez for his collaboration in the development of the software tool.