HelioPure: A Multi-Stage Photocatalytic-Ion Exchange-Adsorptive System for Decentralized Surface Water Treatment

Over 2.2 billion people globally lack safely managed drinking water while per- and polyfluoroalkyl substances (PFAS) contaminate the supplies of more than 180 million Americans, resisting all conventional treatment. This paper presents HelioPure, a floating, solar-powered multi-stage purification system integrating immobilized anatase TiO2 photocatalysis, strong-base anion exchange resin, granular activated carbon (GAC) adsorption, and fine filtration, designed and constructed independently from commercially available components at approximately $165 without laboratory facilities. We hypothesized that this integrated system would achieve significantly greater reductions in turbidity, total dissolved solids (TDS), and PFAS than a GAC-and-filtration-only control under natural winter sunlight in Waxhaw, NC. Across three independent field trials, the full system achieved mean turbidity reduction of 78.4% ± 2.1% and TDS reduction of 50.1% ± 1.9%, outperforming the GAC-only control by 15–22% (p < 0.05, two-sample t-test; Cohen’s d = 5.5 and 4.3 respectively). Integration of the anion exchange stage reduced PFAS from 59.12 ± 3.54 ppt to 9.04 ± 1.67 ppt, an 84.8% ± 2.0% mean removal (p < 0.001; d = 14.9). pH remained stable within potable limits. Conservative cost modeling suggests treated water production at $0.001–0.005 per liter under assumed operational parameters. These results demonstrate that integrated solar-driven photocatalysis and ion exchange separation can address both conventional contamination and emerging PFAS in real untreated surface water using accessible materials, without laboratory resources or grid infrastructure. The system targets off-grid deployment in resource-limited settings, motivated by water insecurity in Tirunelveli, Tamil Nadu, India.