It is well known that Japan has successfully dealt with severe water pollution that was caused during its rapid economic growth. The lessons learned by Japan, the technological developments that emerged and the policy measures Japan devised to cope with its pollution are shared widely with Asian countries that now face severe water pollution associated with economic growth. However, this information has been basically qualitative in nature. In this paper we discuss the potential of using patent data and perform analyses to substantiate the insights such data can yield in order to provide more quantitative information on historical trends in the development of essential technologies in this field. Specifically, we demonstrate an approach using patent data to verify the historical development of wastewater and sewage sludge treatment technologies over the past 50 years in Japan. We examined relevant patent data from 1961 onward and addressed technological development trends in relation to societal changes and the implementation of governmental policies during that period. As an example of the substantiating analysis, we applied principal component analysis and text mining to review the trends in a systematic manner. We demonstrate that the emergence of such developments can be closely associated with societal background factors such as the adoption of relevant governmental policies. We argue that this kind of patent data analysis, coupled with other essential data, can yield clues to the evolution of relevant technologies in the past, leading to useful implications for environmental management of economically developing nations.