Comparing the Cost-Effectiveness of Conventional Activated Sludge Wastewater Treatment Systems and Stabilization Ponds (Case Study: Refineries of Kermanshah, Islamabad West and Gilangharb)

Background & Objectives: The economic feasibility of wastewater treatment plants requires applying some methods with ability to assess the cost-effectiveness of their systems. This study aimed to determine and compare the cost-effectiveness of two types of wastewater treatment systems which are used in Kermanshah province. Materials & Methods: This is a descriptive-analytical study in which the information on the wastewater treatment plants were collected from water and wastewater companies and wastewater treatment plants operators, and the data were analyzed statistically using the SPSS software program. All costs, efficiency of treatment processes, and their cost-effectiveness index was calculated for existing systems and they were compared in terms of this ratio. Results: The results showed that, in activated sludge and natural systems, the average total efficiency, which is the result of mean removal of total suspended solids, biochemical oxygen demand and chemical oxygen demand, were respectively 76.37±18.19 and 61.69±19.02. Also the results showed that the difference between the efficiencies of two systems was significant. The cost-effectiveness of activated sludge and natural systems were respectively obtained as 0.23 and 0.58. Conclusions: According to the results, we can say that, despite the lower efficiency, natural systems are better than activated sludge systems and have better cost-effectiveness for wastewater treatment. These results indicates the natural systems is more successful in term of cost-effectiveness, and the most important factor in this success can be attributed to lower required investments and lower maintenance costs, compared to activated sludge systems.