Using decision support systems and life cycle assessment approach for selecting wastewater treament system

Wastewater treatment systems are designed and used to minimize adverse impacts of the wastewater on the environment before discharging. Various treatment options for wastewater treatment have been developed and each of them has different performance characteristics (e.g. material and land usage, energy consumption) and environmental effects (e.g. greenhouse gas emission, water and soil emission) on construction, operation or maintenance phases. Assessing environmental impacts of wastewater treatment systems, all effects occurring on these phases should be taken into account. Treatment alternatives for wastewaters from agglomerations of more than 2000 PE are determined in EU Urban Waste Water Treatment Directive. However, the effluents of wastewater treatment plants which are discharged to sensitive areas from agglomerations of less than 2000 PE must receive "appropriate treatment". Appropriate treatment depends on the quality objectives of the receiving waters as well as the relevant provisions of the member states. Therefore, a decision support tool which can assess not only effluent quality, also all environmental effects occurring on construction, operation or maintenance phases of the treatment alternatives to help stakeholders is needed. In this study, wastewater treatment options, such as vegetated land treatment, constructed wetlands, rotating biological contactor, conventional activated sludge treatment, membrane bioreactor, extended aeration and stabilization pond by which effluents are discharged to sensitive and less sensitive areas are evaluated by the life cycle assessment (LCA) approach. For this purpose, data related to energy usage, land requirement, raw material consumption, and released emissions from the life phases were collected with an inventory study and the environmental impacts were assessed by using SimaPro 7.1 LCA software. Because scale of the LCA results is global, an excel-based decision support tool that includes the LCA result is developed in order to meet local demands. Weight factors can be assigned on the LCA results according to local conditions by using Analytical Hierarchy Process and the most environmentally appropriate treatment option can be selected.