What Is Water Potabilization (WTP)?
Water potabilization turns raw water into safe drinking water through coagulation, sedimentation, filtration and disinfection at a treatment plant.
Water potabilization is the set of physical and chemical processes that turn raw water (from a river, reservoir or well) into drinking water that is safe for human consumption. The facility where this happens is called a Water Treatment Plant (WTP; in Spanish ETA, Estación de Tratamiento de Agua), and its classic treatment train includes four main stages: coagulation-flocculation, sedimentation, filtration and disinfection.
The stages of a WTP
Each stage removes a type of contaminant and prepares the water for the next:
- Coagulation-flocculation: a coagulant is dosed (typically aluminum sulfate or ferric chloride) to neutralize the charge of colloidal particles; with gentle mixing, those particles clump into larger flocs.
- Sedimentation (clarification): the water passes to settling basins where the flocs, heavier than water, fall to the bottom by gravity and are removed as sludge.
- Filtration: the clarified water passes through beds of sand, anthracite or multimedia that trap the remaining fine particles.
- Disinfection: the microbiological load is eliminated, usually with chlorine (which also leaves a protective residual in the network), or with ozone or UV light as alternatives.
Reference parameters
| Parameter | Indicative value for drinking water |
|---|---|
| Turbidity | < 1 NTU (recommended, per WHO guidance) |
| Free residual chlorine in network | 0.2–2.0 mg/L |
| pH | 6.5–8.5 |
| Fecal coliforms | Absent in 100 mL |
The exact values that apply in Paraguay depend on current regulations; for the design and operation of a WTP, the applicable drinking-water quality standards must be verified with the relevant authority.
Why storage matters
A WTP does not work without tanks. Storage serves several functions: raw-water reservoirs buffer the variation in the source flow; treated-water tanks (clearwells) provide the contact time needed for chlorine disinfection to be effective; and distribution reservoirs absorb peak network demand and maintain pressure.
For drinking water, the tank's interior coating is critical: it must be inert, add no taste or contaminants and resist corrosion. Bolted steel tanks with a glass-fused-to-steel (GFS) coating per ISO 28765, or stainless steel tanks, are common choices for their chemical inertness and long service life; the structural design of the tank follows the AWWA D103 standard.
Where it fits in Tech Tank projects
Tech Tank supplies turnkey drinking water (WTP) solutions, integrating storage with the rest of the treatment train. The conceptual basis of the storage equipment is in what a bolted steel tank is, and to calculate the reserve volume see how to size a water storage tank. We also offer glass-fused-to-steel tanks and stainless steel tanks suitable for potable water.
If you are designing a water treatment plant or need treated-water reservoirs, contact us to size the storage to your flow and network.
Frequently Asked Questions
What does WTP mean?
WTP stands for Water Treatment Plant, the facility that potabilizes raw water. It is different from a WWTP (Wastewater Treatment Plant), which treats sewage or effluent before discharge or reuse.
What are the basic stages of potabilization?
The four classic stages are coagulation-flocculation, sedimentation, filtration and disinfection. Depending on raw-water quality, steps such as aeration, softening or activated-carbon adsorption may be added.
Why is chlorine used?
Chlorine kills bacteria and viruses and leaves a residual that protects the water as it travels through the distribution network. That residual chlorine is the main barrier against recontamination between the plant and the user.
Which tank is best for drinking water?
Inert coatings that do not alter the water are preferred. Glass-fused-to-steel (GFS) tanks per ISO 28765 and stainless steel tanks are frequent choices for their chemical inertness, hygiene and durability, with structure per AWWA D103.
How much residual chlorine should stay in the network?
As a general reference, a free residual chlorine on the order of 0.2 to 2.0 mg/L is maintained in the distribution network. The exact required value must be verified against the applicable drinking-water quality regulations.