How Does Water Treatment Work?


The water you drink from your kitchen tap may have generated from any of the water sources. The quality of water may vary from one community to another. And so will the treatment process. Water from the rivers, lakes, and streams will require more water treatment procedures compared to groundwater. That is because surface water contains a lot more solids and pollutants than groundwater. If you are considering treating your water, you need to look at the iron filter for well water.

In other water sources, you may find inorganic chemicals, by-products, organic particles, and other disinfectants in water sources. Therefore, when getting rid of these impurities, specialized treatment methods are employed.

Despite the many water treatments available, read on to understand the most common water treatment process and how it works.

Water Source

At the water source is where the process begins. It can be a stream, a river, or a freshwater lake. At this point, water has contaminants, pollutants, dissolved solids, and other impurities. Therefore, the first step is to remove these contaminants.

Coagulation and Flocculation

First, coagulants – a chemical with a positive charge are added into the water at the source. The positive charges neutralize the negative charge of these dissolved solids and grime. During this process, the particles join with both charges to build floc (a large particle). The process happens in a flocculation basin. The large particles then settle in a sedimentation basin allowing water to flow to the next stage. Although large particles are out of the water, small particles, germs, and chemicals are still present.


Sedimentation is the second phase of water treatment. At the sedimentation basin, large particles settle, hence the name sedimentation.


The third phase is an intense process. Now that large particles are no more, the water with small particles and bacteria passes through three filters. It passes through sand, gravel, and charcoal. In this process, dissolved solids such as dirt, bacteria, viruses, parasites, and chemicals are removed through the filters. As the name suggests, a sand filter contains fine sand that filters water. Through the sand filter, the quality of water clarity is improved. The sand filters are designed so the water flowing can exit from the bottom and flow in at the top or vice versa.

Although that is the case, each type of flow has its pros and cons. Nevertheless, the most common sand filter allows water to flow in at the bottom and flow out at the top for efficiency purposes. Water passing through the gravel, sand, and charcoal will have low turbidity around 3 NTU or less. Now the water’s clarity is good, but bacteria is still present.

How Much Bacteria in water Is Dangerous to People?

In 1892, an Escherichia coli outbreak tore through Hamburg. The epidemic originated from the Elbe River. The water was untreated and used by locals. Robert Koch analysed a sample from the river and found an alarming number of bacteria colonies present. To prevent disaster striking again, Koch recommended the CFU to kept less than 100/100ml. The figure is still in use today. See how an alternative water treatment technology Merus talks about CFU and Legionella.


Disinfection is the last phase of this process. In this step, one can add chlorine-based compounds to remove microorganisms, bacteria, germs, viruses, and parasites. Alternatively, UV lights or Use of Ozone can be applied.

Importance of Using Chlorine in Your Water

Once chlorine is added to water, the remaining chlorine present in water is less concentrated. Chlorine acts as a barrier between germs and water. It also reacts to any organic agent available in the water.

The reaction between chlorine-based compounds and organic agents can generate carcinogens and other harmful chemicals. Also, it protects water all through the distribution process.

Chlorine is a powerful chemical compound that kills germs, causing diseases. Additionally, chlorine remains even after disinfection to protect water from pathogens in the pipes. Although that is the case, chlorine levels are regulated, and every water point has a chlorine level allowed to flow into households.

Other methods to disinfect water can be the use of Ozone or ultraviolet radiation. In UV light, the light shines upon the water in the process, destroying bacteria present. It does not necessarily kill the bacteria, but it makes them harmless by fighting the DNA responsible for multiplication and disease-causing germs.

The only drawback in this process is, once the water leaves the treatment plant to the households, bacteria in contact with the water will get ingested and cause diseases. There is no protection past the treatment plant. Maybe, that is why it is not commonly used in drinking water treatment plants.

After filtration and disinfection are complete, water is now ready to be distributed to different households. Water entering your home is pressurized to a 40psi. A 40 psi is maintained to ensure water flowing to the houses is on a continuous flow even at elevated points. If otherwise, the water below 40 psi will flow back, resulting in contact with the infection.