The United Nations Sustainable Development Goals (SDG) emphasize the task of organizations to implement sustainability and especially environmental issues. So far, scholars have focused on private sector and manufacturing organizations as they are regarded as the main polluters. However, despite their positive influence to a circular economy, public service organizations such as wastewater treatment plants (WWTPs) have negative environmental impacts as well. WWTPs shoulder the important task of mitigating environmental impacts caused by organizations and households at the end-of-pipe. We question whether WWTPs are mainly guided by their core mission of wastewater treatment or have an environmental thinking beyond this core activity and, thus, pursue a holistic environmental sustainability management approach. We investigate WWTPs’ experienced sources for pressure regarding environmental thinking and management in a multiple case study with three exemplary WWTPs by means of conducting semi-standardized interviews, analyzing homepages as well as reports, and attending internal meetings. Results indicate that WWTPs focus on the operational environmental performance of wastewater treatment, either regulated by laws, contributing to financial savings, or increasing customer satisfaction. However, WWTPs are highly reliant on the incoming wastewater streams on which they have little influence. To achieve the SDG, we conclude that it is important to gear up environmental sustainability thinking beyond reducing wastewater contamination in WWTPs as an end-of-pipe solution. To do so, WWTPs have to take responsibility beyond their core business and stakeholders have to rethink their prevailing wastewater discharging behavior at the pollution source. Rethinking habits and practices by all actors along the entire water cycle can contribute more to sustainable societies than taking a passive bystander role that attributes all responsibility towards WWTPs that continuously have to implement costly and elaborate upgrades.