Removing organic micro-pollutants (OMPs) can enable wastewater reuse to alleviate pressure on fresh water sources. This research aims on the prediction of OMP removal efficiencies by ozonation and biofiltration based on experimental data sets and/or modelling. Comparison of experimental data on average OMP removal of three different studies from literature, in combination with new data obtained from an ozonation pilot plant treating the effluent of a wastewater treatment plant, shows that average removal efficiencies at specific ozon dosage in all experiments are in the same range. Removal of individual OMPs were predicted using the equation Lee and von Gunten (2016). The modelled OMP removal efficiency is compared with data obtained from a measuring campaign at the ozonation pilot plant. The model accurately predicted observed removal efficiency, with an average deviation of 6.9% point. Predictability of specific OMP removal efficiencies from existing data sets would change current practice: ozonation pilot trials at each wastewater treatment plant with effluent OMP requirements.

Climate change and urbanization put increasing stress on urban water management (UWM). Prolonged periods of drought in densely populated areas threaten the quantity and quality of freshwater sources. Closing the water cycle by wastewater reuse can alleviate pressure on these freshwater sources. However, a closed water system requires a different institutional environment. A comprehensive and specific institutional analysis framework can provide guidance to stakeholders in the regional water system. A literature review has concluded that academia has not yet provided such framework (van Es, 2017a). This research proposes an institutional analysis framework by combining two widely used frameworks in institutional analysis: the four-layer model of Williamson (1998) and the Institutional Analysis and Development (IAD) framework of Ostrom (2011). The aim of the institutional analysis framework is twofold: 1) to find the critical issues that can be expected in closing the regional water cycle and 2) to provide recommendations on coordination of the action situations in which the critical issues are addressed. The framework is applied to the case of closing the water cycle in the service area of water authority Delfland in the western part of the Netherlands. This research shows that the proposed institutional analysis framework is highly useful in finding and coordinating crucial issues in closing the water cycle. An empirical operation of the four-layer model of Williamson (1998) provided a deep and structured understanding of the expected issues by relevant stakeholders. It also provided insight into the attitude and main drivers of stakeholders on a closed water cycle. The IAD framework of Ostrom (2011) helped to specify the most critical action situations. Further research can contribute to the field of institutional analysis by conducting more case studies with the proposed Williamson-Ostrom framework and execute the case study in a theoretical way instead of an empirical way.