Life cycle assessment of sodium hypochlorite supply in an advanced ultrafiltration drinking water treatment plant: commercial purchase versus on-site electrolytic generation

Disinfection with chlorine-based reagents is an important stage in potable water treatment. Sodium hypochlorite (NaClO) is a widely used chlorine-based disinfectant. However, the supply route may affect overall environmental performance. Life cycle assessment (LCA) provides a structured framework to quantify these differences. This work aims to compile the life cycle inventory (LCI) of the case-study plant. The plant is a full-scale advanced ultrafiltration (UF) facility in Brazil. It also aims to compare two NaClO supply routes. Route 1 is commercial purchase; route 2 is on-site electrolytic generation. The foreground inventory came from the plant's executive design project. The functional unit was 1 m³ of treated drinking water. An attributional, operational scope was adopted, with a cradle-to-gate boundary for the inputs. The LCA was performed in openLCA 2.6.1. The BAFU 2025 v2 database supported the modelling. Impacts were assessed using the ReCiPe 2016 Midpoint (Hierarchist) method. The Brazilian electricity mix was accounted for in the energy-intensive chemical supply chain. This represents the site-specificity of the water treatment facility. Results are reported for global warming potential (GWP). In route 1, it reached about 2.49×10⁻² kg CO₂-eq per m³. NaClO production was the dominant hotspot, at about 61% of impacts. In route 2, on-site generation lowered it to about 1.80×10⁻² kg CO₂-eq per m³. This corresponds to a reduction of roughly 28%. In route 2, the burden shifted to electricity, at about 82% of the GWP. On-site generation thus reduces the disinfection carbon footprint. On the other hand, electricity consumption becomes the main contributor. This outcome is conditioned on the hydropower-dominated Brazilian grid. Both routes are electricity-intensive, so a carbon-intensive grid is expected to raise their burdens, which deserves further study. The net advantage could narrow or reverse.