Because of population increase and frequent drought caused by global climate change, water reuse has become an important practice worldwide. Especially for indirect and direct potable reuse, very advanced water treatment technologies (e.g., a combination of reverse osmosis (RO) and advanced oxidation process (AOP)) have been installed. In these cases, however, wastewater tends to be “over-treated.” A more rational way for water reuse should be established with respect to cost and energy consumption. One strategy to overcome this problem is to utilize aquatic environment such as soil aquifer treatment (SAT). With utilizing the advantage of SAT, finding a good combination with appropriate wastewater and drinking water treatment processes is essential. To establish necessary and adequate treatment processes, it would be important to induce advanced risk management tools that have been developed to date both from chemical and microbiological aspects. In other word, the purpose of this research is to find how to decrease treatment efficiencies of wastewater and water treatments with accepting acceptable risk level.