Life cycle activity-based costing methodology for wastewater treatment using membrane system

Abstract

Currently, the world is experiencing water crisis of declining clean water supply due to many factors such as human population growth, climate change and pollution. Membrane technology is known as a sustainable solution in preventing water pollution by treating wastewater effluent especially from the textile factory. Many researches on membrane performance and life cycle assessments have been carried out, but study on the economic aspect of membrane system using a detailed cost estimation method is limited. This study aimed to develop a life cycle costing (LCC) methodology for estimating the total cost of membrane system for wastewater treatment in small-scale textile factory using the activity-based costing (ABC) method. The outcome of this study may help in estimating the total cost at any membrane life cycle and determine the LCC of the membrane system. It can also serve as an economic justification and used as a decision-making aid as it reveals the monetary as well as other beneficial information of the product. The ABC method was used to compute overhead costs based on resource and activity cost drivers. Next, the total cost of the membrane system was calculated by adding overhead cost with direct material and labour costs. Three case studies were used to demonstrate the capability of the developed methodology in estimating the LCC and acting as a decision-making aid. The validation process was carried out by comparing results from the developed methodology with Fabrycky’s parametric cost model and Kumar’s parametric cost model. To produce accurate cost results, the cost error of the developed model should be less than 10%. Based on the results from case study 1, the cost of fabricating the hollow fiber membrane module (HFMM) was found to be lower (RM241.10 per unit HFMM) compared to the cost for membrane application (RM1,561.94). Results from case study 2 revealed that the cost of operation and chemical cleaning for the submerged membrane bioreactor (SMBR) was cheaper than the series HFMM although both options have the same operation time and total filtering cycle. Lastly, case study 3 showed that the combination of Polyvinyl Chloride, N-Methyl-2-Pyrrolidone and Ethylene Glycol had the cheapest material cost hence indirectly reducing the total cost of the membrane system. Apart from that, the ABC analysis also revealed an area of improvement that is useful for overall cost reduction. In conclusion, a methodology to estimate the LCC of membrane system throughout its lifespan using ABC method was successfully developed. This method is able to produce accurate result, avoid cost distortion and make cost estimation process easier compared to the traditional technique. Hence, it helps membrane user in estimating the total cost of the membrane system throughout its life cycle and monitoring the high-cost activities as well as high consumable resources to avoid increase in total cost. Subsequently, this method encourages the use of membrane as a sustainable system in the water and wastewater industries.