Nanotechnology offers promising solutions for the control of waterborne pathogens by enhancing disinfection treatments using specialized nanomaterials. This study explores whether coffee waste-based nanostructures (CNs) enhance water solar disinfection (SODIS) against Cryptosporidium parvum, a waterborne protozoan parasite that resists conventional treatments and is classified by the WHO as a reference pathogen. Coffee waste was carbonized at 600 °C for an hour, and CNs were obtained via pyrolysis and hydrogen peroxide treatment, followed by dialysis membrane removal. CNs were characterized by particle size and zeta potential. Quartz tubes containing several CNs concentrations (0.1, 0.4, 0.9, and 1.4 mg/mL) in distilled water were spiked with 2×10⁶ oocysts/mL of C. parvum and exposed to simulated solar radiation (40 W/m², 290–400 nm) at 40 °C under polyethylene terephthalate cover. Oocyst viability was assessed at 2, 4, and 6 hours through hsp70 mRNA quantification using reverse transcription qPCR with previous induction at 42 °C. After 6 hours, oocyst inactivation rates were 0.87±0.01, 1.71±0.06, 2.55±0.08, and 1.96±0.02 log reductions (LR) at CNs concentrations of 0.1, 0.4, 0.9, and 1.4 mg/mL, respectively, significantly higher than those observed in distilled water without CNs (0.60±0.09 LR). These findings highlight the improvement of the C. parvum inactivation by SODIS by using CNs, achieving ≥2 LR at a concentration of 0.9 mg/mL. The optimization of water treatment technologies could provide sustainable alternatives to conventional methods, addressing the challenges posed by resilient protozoan pathogens and contributing to better public health. At the same time, reusing coffee waste in a circular economy reduces environmental impact while promoting innovation.

Acknowledgments. This project was funded by the Autonomous Government of Galicia (grant ED431C 2021/26) and the European Union's Horizon 2020 research and innovation programme (grant 820718). S.D. was granted by a Doctoral Fellowship of the National Operational Programme Research and Innovation 2014-2020 (grant CCI2014IT16M2OP005).