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ETP Odour Control: How We Eliminated Rotten Egg Smell in 24 Hours
Updated: 7 hours ago
Overview
A strong rotten-egg smell from an ETP collection tank often points to hydrogen sulphide formation under low-oxygen conditions. In this case, stagnant wastewater, poor oxygen levels and old sludge had created conditions for H₂S and other odour-causing compounds to form. Instead of covering the smell with fragrance, we focused on ETP odour control at the source. An oxidation-based treatment was applied directly to the wastewater, and the rotten-egg smell was no longer reported within 24 hours. This blog explains what caused the odour, how we investigated it, and what operators should check when dealing with recurring hydrogen sulphide smell ETP problems.
Table of Contents
The smell was obvious before anyone reached the collection tank.
A strong rotten-egg odour had started spreading around the ETP, and workers were noticing it throughout the day. The collection tank had become the main source.
This was not something that could be fixed by spraying fragrance around the area. We needed proper ETP odour control at the point where the smell was forming.
Within 24 hours of starting treatment, the rotten-egg smell was no longer present around the tank. Here is what we checked and why the treatment worked.
Why Does My ETP Smell Like Rotten Eggs?
When operators ask why my ETP smells like rotten eggs, hydrogen sulphide, or H₂S, is one of the first compounds to investigate.
H₂S can form when bacteria break down organic matter under low-oxygen conditions.
Collection tanks are especially prone to this because wastewater may remain there for hours before moving to the next treatment stage.
Old sludge at the bottom, poor mixing and stagnant areas can make the problem worse.
This type of anaerobic wastewater smell is common in industrial plants handling wastewater with a high organic load.
The Collection Tank Was the Main Odour Source
The first part of our collection tank odour treatment was finding out what had changed inside the tank.
The wastewater was sitting for long periods, oxygen levels were poor and old sludge had built up near the bottom.
These conditions can allow odour causing compounds wastewater plants often struggle with to form and escape into the air.
The strong hydrogen sulphide smell ETP operators where reporting was a warning that the tank had become septic.
For proper septic odour treatment, covering the smell would not have dealt with the compounds producing it.
Why H₂S Needed Immediate Attention
A foul smell in ETP is more than an unpleasant nuisance.
Hydrogen sulphide can be hazardous, so operators should use a suitable gas meter when H₂S is suspected. Smell alone should never be used to judge whether an area is safe.
This is especially important because people can lose the ability to smell hydrogen sulphide at higher concentrations.
Good H2S control wastewater practice starts with measuring the gas, limiting exposure and finding the wastewater conditions that are allowing it to form.
How We Approached Wastewater Odour Removal
We first checked the tank rather than treating the air around it.
The treatment steps were straightforward:
identify the collection tank as the main source;
check H₂S and low-oxygen conditions;
inspect sludge and stagnant areas;
dose an oxidising additive according to the treatment plan;
monitor the smell and tank conditions during the next 24 hours.
This gave us a direct form of wastewater odour removal rather than simply hiding the industrial effluent smell with perfume.
Why We Used an Oxidising Additive
For this application, we used NutriServe Rapid Oxidizer ETP.
It is a water-soluble powder intended for industrial ETPs with high-odour wastewater, including collection and equalisation tanks. It reacts with odour-causing compounds and organic matter in the wastewater. Amalgam Biotech also states that it can support reduction of COD and BOD and leaves no residue after reaction.
This type of treatment suited the problem because we wanted the treatment to act in the wastewater rather than cover the smell in the surrounding air.
No new treatment tank or major equipment change was required.
What Happened During the First 24 Hours?
Once dosing began, the smell did not disappear at the same instant.
During the first few hours, the strong rotten-egg odour started becoming weaker. As treatment continued, H₂S levels and the noticeable smell continued to fall.
By the end of the 24-hour period, the rotten-egg smell around the collection tank was no longer being reported.
Amalgam’s documented collection-tank case follows the same pattern: dosing began after low oxygen and old sludge were identified, the smell reduced during the following hours and was reported gone within 20–24 hours.
The result relates to that plant and those operating conditions. Other ETPs may require a different dose or treatment period.
How to Control Industrial Wastewater Odour Before It Returns
Knowing how to control industrial wastewater odour also means stopping the conditions that caused it.
Check how long wastewater stays inside the collection tank. Remove old sludge where required and look for dead zones where wastewater is hardly moving.
Regular H₂S checks are useful when the plant has a history of odour complaints.
If you are asking how to remove odour from wastewater tank areas, always begin with the source. An oxidiser may deal with certain odour compounds, but poor tank operation should also be corrected.
Why Does Treated Wastewater Smell Bad?
Operators sometimes ask why does treated wastewater smell bad even after the main ETP process has finished.
Odours can form later if treated water remains stagnant, still contains biodegradable material or enters a tank with sludge deposits.
This means industrial wastewater odour control should cover collection tanks, treatment stages and treated-water storage areas where odour can develop.
What Is the Best Treatment for Hydrogen Sulphide Smell?
The best treatment for hydrogen sulphide smell depends on why the sulphide is forming.
Low oxygen, stagnant wastewater and sludge should be corrected where possible. Where chemical oxidation is suitable, NutriServe Rapid Oxidizer ETP can be considered for collection tanks and other high-odour ETP streams.
The dose should be selected from the wastewater conditions rather than copied from another plant.
Conclusion
Good ETP odour control begins inside the wastewater tank, not in the air around it.
In this case, the rotten-egg smell was linked with septic conditions in the collection tank.
Once the source was found and oxidation-based collection tank odour treatment began, the smell fell during the same day and was gone within 24 hours.
For recurring hydrogen sulphide smell ETP problems, operators should check H₂S, oxygen, sludge and wastewater holding time before deciding on treatment.
Fixing the cause gives wastewater odour removal a much better chance of lasting.
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Eliminate Rotten Egg Odour Before It Disrupts Your Plant
Persistent rotten egg smell from collection or equalisation tanks can signal an H₂S problem that affects workers, nearby communities, and plant operations. The right wastewater treatment solution can rapidly control odour at the source while supporting more stable ETP performance.
