What Happens in Tertiary Treatment of Wastewater: A Technical Overview

In-Pipe Technology
May 2
3 min read

As municipalities and industrial clients strive to meet stricter environmental regulations and sustainability goals, understanding what happens in tertiary treatment of wastewater becomes increasingly important.

Tertiary treatment is the final, most advanced stage in the wastewater treatment process. It goes beyond removing solids and organic material—this phase targets the microscopic pollutants, nutrients, and pathogens that primary and secondary treatments often leave behind.

In this article, we’ll take a detailed look at what happens in tertiary treatment of wastewater, why it's critical for compliance and environmental protection, and how technologies like those from In-Pipe Technology support and enhance this essential step.

What Happens in Tertiary Treatment of Wastewater?

So, what happens in tertiary treatment of wastewater exactly? This stage is designed to polish effluent and prepare it for safe discharge into the environment—or for reuse. While primary treatment removes suspended solids and secondary treatment uses biological processes to break down organic matter, tertiary treatment eliminates the remaining contaminants that could still harm public health and ecosystems.

Here’s a breakdown of what happens in tertiary treatment of wastewater step-by-step:

1. Filtration: Removing Remaining Suspended Solids

The first part of what happens in tertiary treatment of wastewater often involves high-level filtration to remove any remaining fine particulates.

Sand filtration is commonly used in municipal plants to trap residual solids.
Membrane filtration (like microfiltration or ultrafiltration) is increasingly popular in advanced systems because of its ability to remove bacteria, viruses, and colloidal particles.

This stage ensures that effluent is clear, free from turbidity, and ready for further treatment.

2. Nutrient Removal: Targeting Nitrogen and Phosphorus

Another critical part of what happens in tertiary treatment of wastewater is the removal of nutrients, particularly nitrogen and phosphorus, which contribute to eutrophication in lakes, rivers, and coastal waters.

Biological nutrient removal (BNR): Specialized microbes convert ammonia to nitrate and then nitrogen gas, effectively removing nitrogen from the system.
Chemical precipitation: Chemicals like alum or ferric chloride bind with phosphorus, allowing it to be removed via sedimentation or filtration.

By focusing on nutrient reduction, tertiary treatment prevents harmful algal blooms and protects aquatic life.

3. Disinfection: Eliminating Pathogens

Disinfection is a vital step in what happens in tertiary treatment of wastewater, ensuring that the treated water is safe for discharge or reuse.

Ultraviolet (UV) light: Destroys DNA in bacteria and viruses without adding chemicals.
Ozonation: Powerful oxidant that removes pathogens and improves water taste and odor.
Chlorination: Still widely used, especially for municipal systems, but often followed by dechlorination to protect aquatic environments.

Disinfection is often the final step of what happens in tertiary treatment of wastewater, making it the safeguard for public and environmental health.

Why Understanding What Happens in Tertiary Treatment of Wastewater Matters

Knowing what happens in tertiary treatment of wastewater is essential for several reasons:

Regulatory Compliance: Tertiary treatment is often required to meet discharge permits such as those issued under the U.S. EPA’s National Pollutant Discharge Elimination System (NPDES).
Water Reuse: Treated effluent that undergoes tertiary treatment can be safely reused for irrigation, industrial processes, and even indirect potable reuse.
Environmental Stewardship: Proper tertiary treatment helps reduce pollution, preserve water quality, and protect ecosystems.

For municipalities, failing to understand what happens in tertiary treatment of wastewater can lead to non-compliance, costly fines, and public backlash.

How In-Pipe Technology Supports Tertiary Treatment

Now that we understand what happens in tertiary treatment of wastewater, it’s important to note how In-Pipe Technology can enhance this process even before the water reaches the tertiary stage.

Upstream Wastewater Optimization

In-Pipe Technology introduces specialized, non-pathogenic bacteria into the collection system—well upstream from the treatment plant. These microbes digest organic material, reduce nutrient loads, and promote healthier microbial communities within the system.

Benefits for Tertiary Treatment

By reducing biological oxygen demand (BOD), chemical oxygen demand (COD), and FOG (fats, oils, and grease) early in the process, In-Pipe’s solutions allow tertiary systems to operate more efficiently and with fewer chemical inputs.

Less sludge production
Improved filtration performance
Reduced energy consumption
Lower overall operating costs

So, when you ask what happens in tertiary treatment of wastewater, remember that it can be dramatically improved by upstream interventions like those from In-Pipe Technology.

Final Thoughts on What Happens in Tertiary Treatment of Wastewater

Understanding what happens in tertiary treatment of wastewater is crucial for operators, engineers, and decision-makers in municipal and industrial wastewater sectors. From filtration and nutrient removal to disinfection, each step ensures that treated water is safe for the environment and potential reuse.

With innovative partners like In-Pipe Technology, facilities can reduce the burden on their tertiary systems by optimizing wastewater treatment at the source. The result? More efficient operations, lower costs, and stronger environmental outcomes.

👉 Learn more about how In-Pipe supports wastewater utilities before, during, and after tertiary treatment by visiting www.in-pipe.com.