Integration of Mathematical Median Ranked Set Sample and Decision Making AHP Tools to Enhance Decentralized Wastewater Treatment System

Abstract

Environmental issues, including wastewater treatment plant sitting, usually have various aspects of criteria and involve many stakeholders from various backgrounds and levels. It is characterized as multi-criteria decision-making problem that requires extensive environmental, financial, social, operational and technical evaluations. Furthermore, the various background of involved stakeholders and conflict of interests among them complicate the decision-making process. The Median Ranked Set sample (MRSS) and Analytic Hierarchy Process (AHP) were integrated in this research to improve the decision-making process. MRSS was used to enhance the weighting process, to minimize inconsistency, uncertainty as well as conflict of interest during the stakeholder’s preferences determination, while AHP was used to determine the final priorities of the evaluation criteria. The stakeholders were divided into four groups in which four experts are in each to form 4-by-4 matrix. The results show that the environmental criteria got the highest importance followed by social and economic criteria, respectively. Furthermore, the most important criteria are outflow emissions (importance weight = 0.27) followed by public acceptance (importance weight = 0.22). Furthermore, the best decentralized option for wastewater treatment in rural area is based on cluster level and by using the activated sludge as a wastewater treatment technology with suitability index equals to 4.26 and 4.22, respectively. While, the modified septic tank is best treatment option (with suitability index = 3.85) for wastewater treatment on household level. The introduced integrated model may offer a promising tool to improve the decision-making process and will help the environmental planners in term of uncertainty reduction and subjectivity of human judgments.