The filtration process is designed to remove all unwanted physical, biological, and chemical impurities while maintaining (or achieving, through re-mineralization) the desired composition. BlueTurtleWater should employ a multi-barrier filtration system.
| Filtration Stage | Method | Purpose | Typical Pore Size/Action |
| Pre-Filtration | Sand, Multi-media, Cartridge Filters | Removes large suspended solids, sediment, rust, and dirt. Protects downstream fine membranes. | 5 to 20 microns ($\mu m$) |
| Activated Carbon Filtration | Granular or Block Carbon | Adsorbs organic chemicals, chlorine, and other substances responsible for bad taste and odor. | Adsorption action |
| Microfiltration (Optional) | Fine Membrane Filters | Removes remaining finer particulates and large microorganisms like some bacteria and cysts. | 0.1 to 10 microns ($\mu m$) |
| Reverse Osmosis (RO) / Nanofiltration (NF) | Semi-permeable Membrane | The core purification step. Removes most dissolved inorganic solids (salts, minerals), heavy metals, viruses, and most organic molecules. RO is more aggressive, while NF retains some beneficial minerals. | < 0.0001 microns ($\mu m$) (RO) |
| Disinfection | Ultraviolet (UV) Sterilization and/or Ozonation | Kills or inactivates remaining bacteria, viruses, and other pathogens that may have passed through membranes. Ozonation leaves a residual disinfectant that quickly dissipates. | UV light, Oxidizing action |
| Post-Filtration & Re-mineralization | Cartridge Filter, Mineral Dosing System | A final polish filter and the step where specific minerals (like Calcium and Magnesium) are added back (or adjusted) to achieve the target composition and improve taste. | Final filter: 1 to 5 microns ($\mu m$) |