Why Chlorine Dosage Isn’t Fixed in Wastewater Treatment: The Impact of Ammonia on Disinfection

In wastewater treatment, disinfection is a key step to ensure treated water is safe for the environment or reuse. Chlorine is one of the most common disinfectants used, but here’s something worth noting—it’s not always about adding a fixed amount of chlorine. One of the big factors that changes how much chlorine we need is the presence of ammonia in the water.

Ammonia is often found in wastewater, and when chlorine is added, it reacts with the ammonia to form chloramines. Now, while chloramines can disinfect, they’re not as effective as free chlorine. This means that as ammonia levels increase, more chlorine is needed to first deal with the ammonia before enough free chlorine is available to properly disinfect the water. So, in wastewater treatment plants with high ammonia, the chlorine dosage needs to be adjusted upward to make sure the water is truly disinfected.

This is why operators need to keep an eye on ammonia levels and adjust chlorine dosing regularly. Automated systems can help by monitoring these levels in real time, ensuring the right amount of chlorine is used without wasting chemicals. The goal is always to make sure the water is treated effectively while keeping things efficient and cost-effective.

In short, chlorine dosage in wastewater treatment isn’t a one-size-fits-all approach. It changes with the water’s chemistry, and adjusting it properly is essential for safe and reliable water treatment.

Ahmed Khaled

Water & Wastewater Treatment Specialist | CMRP