What is a Drinking Water Plant (DWP)?

A Drinking Water Plant (DWP) is a water treatment facility designed to purify raw water from natural or municipal sources and make it safe for human consumption. The main objective of a DWP is to remove physical, chemical, and biological contaminants so that the treated water meets national and international drinking water quality standards.

A typical Drinking Water Plant (DWP) treats water collected from rivers, lakes, groundwater, or reservoirs using a series of scientifically controlled processes. These processes may include screening, coagulation and flocculation, sedimentation, filtration, and disinfection. Advanced DWPs may also use technologies such as Reverse Osmosis (RO), UV disinfection, ozone treatment, activated carbon filtration, and mineral balancing to enhance water quality.

DWPs play a vital role in protecting public health by eliminating harmful pathogens, suspended solids, heavy metals, unpleasant taste, odor, and toxic chemicals. They are widely used in municipal water supply systems, residential complexes, commercial buildings, hospitals, food industries, and bottled water production units.

Drinking Water Treatment Plant Process

1. Source Water Intake and Screening

Raw water is drawn from surface water sources (rivers, lakes, reservoirs) or groundwater sources (tube wells and boreholes). At the intake point, coarse and fine screens remove large floating materials such as plastics, leaves, wood, and stones. This step protects downstream equipment from damage and blockage.

2. Aeration (Pre-Treatment)

Aeration introduces air into the raw water to remove dissolved gases such as carbon dioxide and hydrogen sulfide. It also oxidizes iron and manganese, making them easier to remove later. Aeration improves water taste and reduces odor-related issues.

3. Coagulation

In coagulation, chemicals like alum, ferric chloride, or poly-aluminum chloride (PAC) are rapidly mixed with water. These chemicals neutralize the electrical charges of fine suspended particles and colloids that cannot settle naturally.

4. Flocculation

After coagulation, water flows slowly through flocculation tanks where gentle mixing allows destabilized particles to collide and form larger, heavier particles called flocs. Proper floc formation is critical for effective removal of turbidity and organic matter.

5. Sedimentation (Clarification)

The water enters sedimentation basins where flocs settle at the bottom due to gravity. The settled material, known as sludge, is periodically removed and treated separately. This stage can remove up to 90% of suspended solids.

6. Filtration

Clarified water is passed through multi-layer filters composed of sand, gravel, anthracite, or activated carbon. Filtration removes remaining fine particles, protozoa, bacteria, and organic compounds, significantly improving water clarity and safety.

7. Disinfection

Disinfection is a critical step in water treatment aimed at eliminating pathogenic microorganisms. Common methods include chlorination, which is valuable because it provides residual protection throughout the water distribution system. Another method is Ultraviolet (UV) treatment, which is highly effective against a wide range of bacteria and viruses. Finally, ozonation utilizes a strong oxidant that not only disinfects but also helps to improve the water's taste and odor. Often, a combination of these methods is employed to ensure complete and robust microbial safety.

8. pH Adjustment and Mineral Balancing

Treated water may require pH correction using lime or soda ash to prevent corrosion in pipelines. In some plants, essential minerals such as calcium and magnesium are adjusted to improve taste and stability.

9. Storage and Distribution

Final treated water is stored in clear water reservoirs or elevated tanks before being distributed through pipelines. Continuous monitoring ensures water quality remains safe throughout the distribution network.