This study applies the fuzzy analytic hierarchy process (FAHP) to determine overall importance of various criteria and sub-criteria required for selection of domestic wastewater treatment system. Moreover, it also uses the fuzzy Technique for Order Preference by Similarity to Ideal Situation (TOPSIS) to figure out the rankings of different STP. The results of this study will assist customers in effectively managing and using STPs, contributing to the alleviation of water issues in society.