"Suitability of treated wastewater as feedwater for green hydrogen electrolysisimpurity screening, treatment requirements, and technoeconomic comparison."
Abstract
Green hydrogen production demands high-purity water, which makes water procurement and treatment a Huang constraint in arid climates. Stoichiometrically, there is a consumption of approximately 9 L (9 kg) of water per 1 kg of H₂ produced [1]. In actual application, this can be expected to be significantly higher (12-15 L/kg-H₂) after consideration of purification requirements. Treated wastewater can potentially fully or partially substitute fresh supplies. However, salts, chloride, hardness, silica, organic materials, and trace metals can cause problems of scaling, fouling, and corrosion [2]. Projects thus commonly aim for very low conductivity/resistivity and low TOC, with a common basis for requirements matching laboratory ultrapure-water standards based on ASTM/ISO or at least equivalent manufacturer recommendations [3]. The present work screens a number of treated wastewater candidates against key parameters, namely conductivity/TDS, chloride, hardness, silica, iron/manganese, turbidity, and TOC/COD, against their respective treatability toward electrolyzer-grade water. Measurements are translated into both a pass/fail regime and weighted compatibility scores based on the prevailing mechanisms that include scale formation, media and membrane fouling, corrosion risk, and organic breakthrough [4]. The train compositions for minimumcompliance treatment are established for each source: pretreatment (screening + MF/UF), desalting (RO/NF), and polishing (EDI or ion exchange), with GAC/AOP when organics control is restrictive. A techno-economic analysis calculates CAPEX and OPEX, specific energy consumption (kWh/m³ product water), recovery ratio, concentrate production rate, and transmutes water treatment cost to a hydrogen cost increment (Δ$/kg H₂) [5]. Challenges include chloride removal, silicon/hardness removal, and TOC. Sensitivity analysis assesses the credibility of electricity prices, the recoveries of RO technologies, and membrane life to determine source rankings using electricity price, RO, and membrane life [6,7].