Water Treatment for "Green" Hydrogen Production in Alkaline Electrolyzers

This paper systematizes typical feedwater quality requirements for AWE systems and explains why the parameters of specific electrical resistance (resistivity) and electrical conductivity are interrelated quality-control indicators. The main technological solutions for producing demineralized water are reviewed, including mechanical filtration, activated carbon filtration, reverse osmosis (RO), and electrodeionization (EDI). Key operational risks are also discussed, such as channeling, increased pressure drop (ΔP), carryover of carbon fines, biofouling, and oxidative damage to RO membranes. As a practical example, an aggregated process scheme is presented for a water treatment line designed to produce demineralized (DM) water with a target quality of approximately 1 MΩ·cm or higher. Recommendations are provided for monitoring (conductivity/resistivity, SiO₂, TOC, Cl⁻, iron), filter backwash regimes, protection of RO membranes from chlorine, and reduction of factors that contribute to increased cell voltage during AWE operation.