The submitted diploma thesis by Rachel O'Shea addresses a highly relevant and complex topic within the field of environmental engineering and circular economy: the removal and recovery of ammonia from industrial nickel-plating wastewater.
The experimental part was conducted in Germany, specifically at the ZEA facility of LOBBE Umweltservice GmbH & Co. KG, utilizing a pilot plant engineered by Graforce GmbH as part of the HydroNet research project.
I would like to emphasize that, although the practical and experimental parts of the thesis were carried out in Germany, the student regularly consulted with me regarding her approach, methodology, and results.
From a scientific and engineering perspective, Rachel addressed a major research gap by testing a pilot-scale system on real, highly concentrated industrial wastewater containing heavy metals, rather than just conducting simple laboratory tests
The methodology is solid, consisting of ten experimental trials that progressed from initial setups to optimized conditions.  The main goals were to lower the effluent ammonium concentration below 1,000 mg/L  and to recover a 10–25 wt% ammonium hydroxide product . Although she did not fully reach these strict targets in the given timeframe—achieving 1,700 mg/L and 8.08 wt%—her engineering analysis was excellent. She correctly identified the strong link between stripping and condensation efficiencies, and used kinetic extrapolation and mass balances to prove that the targets are technically possible with adjusted settings.
In addition, the thesis includes a thorough economic analysis demonstrating that scaling up this process is both profitable and feasible under real-world industrial conditions.
Formally, the diploma thesis is very well-written, with a comprehensive literature review and rigorous data evaluation.
The student demonstrated exceptional ability in conducting independent and comprehensive engineering research in a real-world setting, successfully bridging the gap between laboratory research and industrial applications.
Therefore, I strongly recommend this diploma thesis for defense and propose the overall grade of A (Excellent).

This thesis is of a high academic standard. I would like to commend the structured organization of the extensively cited literature review section, which provides a very detailed treatment of the subject matter not only from a theoretical perspective but also from the perspective of pilot-plant testing of the unit. The results and conclusions of the thesis are presented clearly and critically and provide clear conclusions regarding a potential upgrade to an operational scale. Topics for thesis defence:

1. 1. As part of this thesis, hypotheses were formulated that the thesis aimed to test. Particularly regarding the first two hypotheses—which concerned the final ammonia concentration in the effluent and the concentration of the ammonium hydroxide product—it is not entirely clear on what basis these hypotheses were established. Why was this particular final ammonia concentration at the outlet of the pilot plant chosen, and what was the basis for the hypothesis used to determine the concentration range of the ammonium hydroxide product?