A Guide to Understanding Water Treatment

What is Water Treatment?

Water treatment is the process of enhancing the quality of water to make it safe, clean, and suitable for a specific purpose. Common applications include producing drinking water, supplying water for industrial operations, supporting recreational uses, and restoring natural ecosystems by replenishing rivers, lakes, and other environmental water sources.

Why is Water Treatment Important?

Clean water is a basic necessity for humans. While the human population grows, the demand for water grows as well. Since water is a finite resource, used water must be treated to continuously serve end-uses. This is where the importance of water treatment systems comes in.

Water treatment helps in removing contaminants and hazardous substances from the water, making it clean and safe to drink and be used for other purposes. Unfortunately, almost 2 billion people in the world use either untreated drinking water or get water from unsafe or contaminated sources. Having systems in place to improve water quality helps intervene in these situations and prevent unsafe water-caused incidents, such as water-borne diseases and fatalities.

On the other hand, water treatment is also helpful in ensuring that water gets reintroduced back to nature’s cycle. One of the end-uses of this process is to safely return water to environmental sources like rivers, lakes, and oceans. Of course, water treatment facilities must ensure that water is free from harmful substances before doing so to avoid contamination and other environmentally disastrous issues such as water pollution.

The United States Environmental Protection Agency (EPA) sets forth guidelines for organizations for protecting the environment and human health. One of the violations that an EPA report helps keep in check regarding an organization’s compliance with environmental safety is the illegal discharge of pollutants that could end up in bodies of water. An example of this is dumping untreated and contaminated wastewater directly into the sewer system, which is a violation of the Clean Water Act.

What are the 5 Steps of Water Treatment?

According to the Centers for Disease Control and Prevention (CDC), public water systems typically use five core steps to make water suitable for human use. Each of the following steps plays a unique role, building on the previous one to deliver water that meets health and safety standards:

Water Treatment Process | Source: Centers for Disease Control and Prevention (CDC)

1. Coagulation

Coagulation is the first treatment step where positively charged chemicals, such as aluminum sulfate or ferric chloride, are added to the water. These chemicals neutralize the negative charges on suspended particles like clay, silt, and organic matter. Once their charges are balanced, particles can bond together instead of repelling each other. For professionals, this step is about achieving the right chemical dose and pH balance to optimize particle destabilization. A well-controlled coagulation stage reduces the downstream load on flocculation and filtration systems.

2. Flocculation

Following coagulation, the water goes through flocculation, a process of gentle mixing that encourages particles to gather into larger aggregates called flocs. Mechanical paddles or hydraulic mixers are often used, and polymers may be introduced to strengthen the flocs. The mixing speed is carefully controlled. If it’s too aggressive and flocs shear apart or become too weak, they won’t form effectively. For operators, flocculation is about finding the balance where flocs are large, stable, and ready to settle during sedimentation.

3. Sedimentation

Sedimentation allows the formed flocs to slowly sink to the bottom while cleaner water stays on top. It’s a simple but very effective way to separate the solids before the water moves on to the filters. By removing most of the heavy particles at this stage, the system makes filtration easier and more efficient.

4. Filtration

After sedimentation, the water passes through filtration systems that remove remaining suspended particles and microorganisms. Traditional filters use layers of sand, gravel, and sometimes activated carbon, but modern facilities may also employ pressure filters, dual-media filters, or membrane technologies like ultrafiltration. Each filtration method has its strengths: granular media filters excel at particle removal, while activated carbon improves taste and odor. For operators, regular backwashing and filter maintenance are essential to prevent clogging and ensure consistent water quality.

5. Disinfection

The water needs to be disinfected to make sure harmful microbes are gone. The most common method is adding a small, safe amount of chlorine or other disinfectants, which kill bacteria and viruses. However, alternative methods like using chloramines, ozone, or UV light can also be done, depending on system design and regulatory requirements.  The choice of disinfectant involves balancing effectiveness, cost, and byproduct control. This last step not only makes the water safe at the plant but also keeps it clean as it travels through pipes to homes, schools, and businesses. Without disinfection, the water could pick up germs along the way.

Different Types and Uses

Generally, water treatment systems differ in serving specific end-uses. The 3 most common types are the following:

Household Water Treatment

Household water treatment refers to systems designed to improve the safety, taste, and quality of water used in homes. These solutions vary depending on the source of water, the types of contaminants present, and the specific needs of the household. According to the National Sanitation Foundation (NSF), there are two main categories of home water treatment systems:

• Whole-House or Point-of-Entry (POE) systems – These systems are installed where water enters the home, ensuring that all water used indoors is treated. Examples include municipal treatment add-ons, pressurized storage tanks, ultraviolet (UV) microbiological systems, and water softeners. POE systems are especially useful for addressing issues like hard water, bacterial contamination, or high levels of iron that can affect plumbing and appliances throughout the home.

• Point-of-Use (POU) systems – These systems treat water at the place where it is consumed. Common examples include water filter pitchers, faucet-mounted filters, under-sink filters, and Reverse Osmosis (RO) units. POU systems are ideal for targeting drinking and cooking water, providing a final barrier against impurities such as lead, chlorine, or sediment.

Industrial Water Treatment

This process refers to the treatment that is performed pre- and post-industrial use. Since businesses from various industries use water differently, water treatment processes can be done before or after performing business activities to serve the intended use of water.

For example, water treatment in the Food and Beverage sector under the Hospitality industry is crucial for ingredient water used in processing food. On the other hand, manufacturing plants in the Automotive industry need to reuse or dispose of wastewater, and water treatment can help in that process.

To manage biological hazards like Legionella in these complex systems, many facilities rely on Legionella risk assessment training to ensure safe, compliant operations.

Wastewater Treatment

This refers to any used or polluted form of water, generated after different types of uses and applications. Its sources include rainwater runoff and human activities. Wastewater treatment is key to removing any contaminants and improving the quality of wastewater and turn it into an effluent that can be safe to return to the water cycle.