On 25 February 2020, Thomas Wagner will defend his PhD thesis
The treatment and reuse of cooling tower water can substantially reduce the industrial fresh water footprint. This reuse requires desalination, but desalination is hampered by the presence of conditioning chemicals that are added to the cooling tower water, such as corrosion inhibitors and biocides. In this thesis, the applicability of constructed wetlands (CWs) as a pre-treatment step before cooling tower water desalination to remove these conditioning chemicals was assessed. CWs are man-made wetland systems that are built for the treatment of polluted water. In these CWs, various removal mechanisms, such as biodegradation, adsorption, plant uptake and photodegradation, function simultaneously to clean the water. The efficiency of these removal mechanisms for a set of target conditioning chemicals was assessed in lab-scale removal experiments and pilot-scale CWs. Commonly used corrosion inhibitor benzotriazole was removed by biodegradation and adsorption in lab-scale removal experiments. Biodegradation in lab-scale experiments was impeded by realistic concentrations of different biocides. Non-target screening showed that these biocides formed new products as a result of mutual interaction. The toxicity of cooling tower water containing these biocides was influenced by photodegradation. The treatment of synthetic cooling tower water in pilot-scale CWs showed that a combination of different CW types was able to remove many components that hinder cooling tower water desalination, but that the pre-treatment efficiency decreases with low temperatures. The outcomes of the lab-scale removal and pilot-scale constructed wetlands experiments are used to discuss the pathway towards full-scale constructed wetlands for cooling tower water treatment before its desalination.