In this paper we explore the trend of professionalization, with a focus on autonomization, in the Swiss wastewater sector. The aim is to evaluate the performance of water utilities in terms of legitimacy, efficiency and effectiveness in the context of autonomization. We apply these criteria in an analytical framework to relate governance to the performance of water utilities. We argue that autonomization under public law may be a valuable means to create a business-oriented water utility but that it remains important to address the tradeoffs between legitimacy, efficiency and effectiveness. The empirical component of this paper draws from a case-study analysis of the wastewater utility in Zurich, Switzerland, which has undergone autonomization but remains under public law. We find that this organization under public law is a case-in-point for illustrating that it is possible to have good business management in a municipal enterprise without needing to involve private actors or reorganize a utility under private law. We find that while the autonomization of the wastewater utility enabled it to have increased efficiency and effectiveness, there are tradeoffs with regards to legitimacy indicators as the decoupling of management from political decisionmaking leads to less direct democratic influence.