The Use of Coagulation in Water Treatment

A municipal water supply comes to the treatment plant with mineral particles like sand and clay and biological impurities like protozoa and viruses. Removing these substances requires a multi-step process that includes filtering, settling, and disinfecting. Coagulation is another step commonly employed by water treatment plants.

What Is Coagulation?

The plant adds a chemical coagulant to the untreated water in this treatment. These substances carry a slight positive charge and attract negatively charged impurities. In neutralizing the solution, the particles gather together into larger flocs that are heavy enough to settle out of the water. The water treatment plant can then remove the flocs from settling tanks or through a filtering step.

Impurities Removed by Coagulated Water

The coagulating process removes floating impurities that range from a few millimeters down to the microscopic level. However, the floccing speed depends on the size and weight of the captured substances. Flocs of fine sand will settle out of the coagulated water in about two minutes. Microscopic particles like bacteria and algae can take up to a week to drop to the bottom of a tank using this process.

Common Types of Coagulants

Aluminum sulfate and ferric sulfate are the most prevalent chemical coagulants in use today. These chemicals are affordable and readily available. Treatment plants can purchase them in block or powder forms depending on the configuration of their processes. Because these substances dissolve in water, they add ions to the supply. Generally, plants that use aluminum sulfate produce water with higher aluminum levels.

Recently, some water systems have used polymer chain molecules as coagulant chemicals. The chemical structure of these compounds creates a series of positively charged points that are more effective at trapping impurities. Chain molecules also produce larger flocs that are easier to remove from the treatment system.

How Water Coagulation Works with Other Water Treatment Methods

The spread of coagulating times means this technique must be used in conjunction with other treatments to produce potable water. The coagulating step is one of the first in the treatment process. It’s especially effective at removing larger particles from the water stream.

Coagulating may happen in a settling tank where the treatment plant periodically removes the flocs from the bottom. The treated water may also flow directly to a filtering step that will capture flocs.

Another advantage to incorporating a coagulating treatment is that flocs tend to gather other smaller particles. A large percentage of single-celled organisms bind to the flocs as they grow. This step won’t entirely remove organic impurities but will allow the plant to use less chlorine during disinfection treatments.

SCADA and Coagulants in Water Treatment

Many industries use System Control and Data Acquisition technology to monitor and run automatic processes. A SCADA system is well-suited to keeping track of a variety of water treatment methods. Sensors can report water pressure, flow volume, and water quality throughout the system.

In a coagulating treatment step, SCADA sensors can track the volume of coagulant chemicals in use and determine when to add more. They will notify employees about the current volume of flocs in a settling tank and alert them of the need for removal. In a well-designed system, managers can set the system to divert the flow automatically for tank or filter cleaning.

A Cloud-Based SCADA Partner

High Tide Technologies specializes in cloud-based SCADA solutions for the water industry. We help municipal water collection, distribution, and treatment systems improve their quality and efficiency. With a cloud-based solution, managers can access system data from any location on their mobile devices, leading to faster response times and fewer disruptions. Contact us to learn more about the benefits of a cloud-based SCADA system for your operation.