(S) The global transition to a carbon-neutral economy increasingly relies on alternatives such as hydrogen as a clean energy carrier. However, hydrogen production through electrolysis requires ultrapure water, which places additional stress on freshwater resources that are already under pressure due to population growth, urbanisation, and climate change. Over 2.7 billion people are affected by water scarcity yearly and this poses major challenges to human health, socio-economic development, and environmental stability.
Desalination of seawater is a promising solution to produce the required water. However, water desalination also produces a high-salinity byproduct called brine. Consequently, traditional discharge methods threaten marine ecosystems with brine disposal. New desalination approaches such as Zero Liquid Discharge (ZLD) and Minimal Liquid Discharge (MLD) technologies offer a potential to mitigate environmental harms with brine by reducing or even eliminating the liquid waste. However, these systems require a lot of technologies placed in series with energy demand which makes the new approach expensive. This leads to concerns about the economic feasibility of MLD and ZLD technologies. (C) Most studies evaluating MLD and ZLD systems rely on Techno-Economic Analysis (TEA). TEA methods focus on capital expenditures (CAPEX) and operational expenditures (OPEX). The downside of TEA is that it often fails to capture broader societal and environmental externalities such as marine degradation from brine discharge or benefits of freshwater recovery in water-stressed regions. Furthermore, the choice between ZLD and MLD is also very complicated. ZLD achieves higher recovery rates than MLD and single water desalinations but at the same its technological complexity and high energy consumption make it a difficult application. In contrast, MLD systems offer lower recovery rates but may present a more cost-effective and feasible solution. Despite this, the literature lacks a more societal and environmental application such as a Cost-Benefit Analysis (CBA) to assess whether the broader societal value of MLD systems justifies their higher costs. This absence represents a significant knowledge gap in the literature and policy evaluation. (Q) To address this knowledge gap, the following research question is formulated which focuses on Nanofiltration (NF) and Multi-Effect Distillation (MED) as the core technologies for MLD, in order to keep the research feasible within the 21-week timeframe of this study: "What are the societal costs and benefits of Minimal Liquid Discharge (MLD) technologies, with a focus on Nanofiltration (NF) and Multi-Effect Distillation (MED), for hydrogen production?" (A) This thesis applies a CBA framework to assess the economic and societal viability of two MLD configurations. The first MLD is a stand-alone MED system and the second MLD a hybrid NF-MED system. The research uses a mixed-methods approach by combining a structured literature review with expert interviews to identify and validate cost elements, operational parameters, and environmental impacts. All cost elements of the CBA including CAPEX, OPEX, and environmental externalities were monetised, so the Net Present Value (NPV) of the two MLDs can be calculated. The CBA demonstrates that while both systems carry significant upfront and operational costs, the standalone MED and the hybrid NF-MED result in positive NPVs. The hybrid NF-MED MLD results in higher water recovery at reduced steam cost per unit of ultrapure water because of the opportunity to operate at higher temperatures. The COSEM Master Thesis Minimal Liquid Discharge for Hydrogen Production results show that wider benefits, such as protecting ecosystems and saving freshwater, can make up for the high upfront costs. Especially if certain conditions are met such as access to green electricity or free waste heat. However, this is dependent on which individuals have standing in the CBA and how they value the wider benefits. The study also shows that using only a TEA gives an incomplete picture, because it leaves out these important environmental and social benefits. (R) This research recommends the adoption of CBA as a complementary tool to TEA in evaluating MLD systems, especially in sustainability sectors like hydrogen production. Policymakers should consider regulatory frameworks that internalise the environmental impact of brine discharge, making MLD systems financially more competitive. For project developers and investors, the hybrid NF-MED system represents a promising solution between conventional water desalination brine discharge and the more expensive ZLD. Further research should focus on scaling the pilot project with additional pre- and posttreatment, and exploring the integration of entirely renewable energy sources and alternative waste heat to further reduce OPEX.