At DEOSAI, purification is not a single filter. It is a sequence of nine stages, each one removing a different kind of contaminant or adding back something the body needs. The water is produced under ISO 9001:2015 quality management and ISO 22000:2018 food-safety systems, and the brand is licensed by the Pakistan Standards and Quality Control Authority under licence CML/N-492/2025.
Here is each stage in order.
1. Chlorination
Chlorine is dosed into the incoming raw water to disinfect it and reduce the microbial load before filtration begins. Dosing is held at 0.5 ppm or less and checked at every plant start-up.
2. Sand Filter
Water passes through a sand bed that traps dirt, silt and suspended solids. This clears turbidity and protects the reverse-osmosis membrane further down the line.
3. Carbon Filter
Activated carbon adsorbs chlorine, organic compounds and volatile organic compounds. It removes the chlorine that would damage the membrane and improves taste and odour.
4. Cartridge Filter
A fine, replaceable cartridge captures the remaining fine particles and sediment, polishing the water immediately before reverse osmosis.
5. Reverse Osmosis
The heart of the system. A semi-permeable membrane forces out dissolved salts, heavy metals such as lead and arsenic, chemicals and any remaining microorganisms.
6. Remineralization
Calcium, magnesium and sodium bicarbonate are added back in measured amounts, restoring a clean, balanced taste and a healthy mineral profile.
7. UV Sterilization
Ultraviolet light inactivates any microorganism that survived earlier stages. It is a final safeguard that adds nothing to the water.
8. Ozonation
Ozone, a powerful oxidant, destroys any remaining bacteria and viruses and leaves no chemical residue. It is the disinfection method preferred by bottled-water producers.
9. Wash, Inspect & Fill
Every returned bottle is inspected and smelled, then washed and sterilised with hydrogen peroxide and hot water at 70 degrees Celsius. Bottles are filled and screened on a fluorescent line, and any that fail inspection are rejected.
Why the order matters
Each stage protects the next. Chlorination and the sand and carbon filters remove the chlorine, sediment and organic matter that would otherwise damage the reverse-osmosis membrane. Reverse osmosis does the heavy lifting on dissolved solids and heavy metals. Remineralization restores taste and balance, and UV and ozone provide a final, chemical-free safeguard before the water is sealed into an inspected, sterilised bottle.
You can watch the full process play out, stage by stage, on the Our Water page. Ready to get started? Request service for your home or office today.