Odor in your sewer system isn’t just a nuisance that needs to be treated. It’s a sign that destructive forces are sitting in your pipes, silently wreaking physical damage.

This problem doesn’t happen overnight. It starts with the film of bacteria that forms on every inch of the sewer pipe, each time wastewater makes its way through the system. Also referred to as the “slime layer,” this biofilm is primarily responsible for the creation of hydrogen sulfide (H2S), which produces the awful smell and corrodes pipes.


After our scientists and engineers studied the complex biological reactions going on in the biofilm, we figured out a way to disrupt this process to produce healthy bacterial reactions – instead of the kind that will bust open a pipe and cause a sanitary sewer overflow (SSO).

When Biofilm Goes Bad

Biofilms are communities of bacteria and other microorganisms that can be found attached to surfaces in many places: In soil, in our homes (such as in our showers), and even in our bodies. Many have positive effects.

They are often overlooked in the 800,000 miles of sewer pipe in the U.S. Pipes can contain biofilm “cities” that include complex polymers called extracellular polymeric substances (EPS), such as sugars and proteins. The microorganisms will interact within the biofilm and form a resistance to challenges in their environment.  Once they are protected, some of these microbes (let’s call them the “bad bacteria”) will start to consume the nutrients in wastewater (mostly sulfate), and release hydrogen sulfide as a byproduct.

The three main negative effects of hydrogen sulfide can be traced directly to this bacterial reaction. The gas is largely responsible for the toxic air in the pipes that can sicken workers and residents; corrosion of pipes; and the brutal odor that usually gets the most attention.



For example, hydrogen sulfide-based corrosion was blamed for the catastrophic failure of 4.5 miles of sewer pipe in Plymouth, Mass., several years ago. The collapse caused millions of gallons of contaminated wastewater to flow into town, including thousands into its harbor. The town had to pay approximately $48 million in repairs.





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Sewer Pipes as a Huge Bioreactor

Bad bacteria are not the only microbes present in the biofilm.  If conditions are right, the downstream effects of biofilms can actually be very positive for a sewer system and wastewater treatment overall. The key is to understand both the positive and negative bacterial reactions that take place in the pipes.

For example, bacteria from the soil often find their way into the sewer system – in the wastewater stream itself, and through inflow and infiltration of ground water into the sewer pipes. In sufficient quantity, they can begin to break down organic material, dissolve solids, and start to consume different forms of harmful nutrients – the very thing that the wastewater treatment plant is designed to do. 

Unfortunately, the good bacteria rarely become dominant in the collection system. In most cases, the bad bacteria massively outnumber the good, and hydrogen sulfide production is likely to continue unabated. This is why many sewer pipes emit a foul and dangerous odor and start to corrode.

Usually, wastewater departments only treat the odor itself, masking it or dosing it with chemicals. Not only can that potentially cause more challenges for the treatment plant, it’s totally inadequate. If there was a chemical spill in a manufacturing plant that caused a foul smell, would it be satisfactory if workers sprayed a chemical that suppressed the odor but left the spilled material there, potentially causing a safety and structural hazard?

Of course not. The better way would be to discover how the spill happened in the first place — and figure out the best way to stop it from ever happening again.

So how could we approach the sewer odor problem in a similar way?


Remember, when you’ve got bad odors in the collection system, it’s because the bad bacteria are out-competing the good bacteria. Thus, the only way to eliminate the source of odors is to create an environment where the good beats the bad. You can do this simply by consistently adding enough good bacteria – so you can start to produce far more positive biological reactions, and eliminate the negative ones.

If hydrogen sulfide comes from the biofilm, and you can change that biofilm so that it’s no longer capable of producing H2S in the first place, you’ve just eliminated the problem where it starts – no chemicals, scrubbers, or complicated equipment needed.

The Science

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The Solution

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3 Facts about FOG

The Link Between Odor and Corrosion