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Cold Region Bacteria for STP: How We Stabilised MLSS Without Changing the Existing Process
Overview
A winter STP does not always need a new tank, new equipment, or a different treatment process when MLSS starts falling. This article follows a different approach: looking at the bacterial population before making physical changes to the plant. It explains what happened when low temperatures affected the existing biomass and how cold-region bacteria for STPs can be used alongside an existing treatment setup. The article also covers the points operators should check before deciding that a process change is needed.
The proposal was simple: change the STP process because winter had started affecting MLSS.
We decided not to.
There was no new tank to install, no major equipment failure, and no sudden increase in the sewage load. The plant was running on the same process it had used before winter. The change was in the biology.
As the wastewater temperature fell, the microorganisms in the aeration tank became less active. MLSS became harder to keep at the required level, and the treatment results began to move with the temperature.
Instead of rebuilding the treatment process, we looked at the part of the plant that was being affected first: the bacteria.
Table of Contents
The Plant Had Not Changed. The Conditions Had.
This was the part that took some attention.
The STP was receiving wastewater as usual. The blowers were running. Aeration was being maintained. There was no obvious mechanical fault.
But the wastewater was colder.
Temperature has a direct effect on microbial activity. Bacteria that work well in warmer wastewater may become slower when temperatures fall. This can affect STP biological treatment, sludge growth, and the way organic matter is removed.
So, the same plant can give different results in January compared with June without any change to its basic design.
We Looked at MLSS Differently
MLSS is not simply a number that needs to be kept within a set range.
It tells us about the solids and microorganisms present in the aeration tank. If the microorganisms become less active, simply increasing the amount of sludge may not solve the problem.
We started looking at MLSS alongside:
Wastewater temperature
BOD and COD
Dissolved oxygen
Sludge settling
Sludge wasting
Organic load
This gave us a better picture of the change.
The issue was not that the plant suddenly needed a different treatment method. The existing biomass was dealing with a colder environment.
The Question We Asked Before Changing Anything
Instead of asking, “What should we change in the STP?”, we asked:
Can we give the existing biological stage bacteria that are better suited to the winter temperature?
That changed the direction of the work.
Cold-region bacteria for STP are selected for wastewater conditions where lower temperatures can reduce the activity of ordinary treatment bacteria.
Some cold-adapted bacteria are described as psychrophilic bacteria. Others are referred to as cold-active microorganisms. The important point is that their activity is suited to lower temperatures.
Keeping the Existing Treatment Process
This was the main reason for considering cold climate wastewater bacteria.
The plant already had its tanks, aeration system, and treatment stages in place. Changing the process would have meant more work, more cost, and a longer period of adjustment.
A bacterial culture can be introduced without rebuilding those parts of the plant.
Amalgam Biotech's Cold Region Bacteria for STP is intended for low-temperature wastewater treatment. The manufacturer lists activated sludge, extended aeration, SBR, MBBR and MBR plants among its applications.
That makes it worth considering when the main winter problem is reduced bacterial activity rather than a fault in the physical treatment system.
What Happens When the Temperature Falls?
The effect is gradual.
Lower temperatures can reduce microbial activity in cold weather. Organic matter may then take longer to break down. BOD removal can fall, sludge behaviour can change, and MLSS can become harder to maintain.
This is why biological treatment in winter needs closer observation.
It is also why adding a bacterial culture without checking the plant first is not a good idea. If the actual problem is poor aeration, excessive sludge wasting, or a sudden increase in organic load, bacteria alone will not fix it.
Where Low Temperature Bacteria Fit In
Low-temperature bacteria are meant for a specific job: biological activity when the temperature is working against the normal microbial population.
Amalgam Biotech's Cold Region Bacteria for STP contains microorganisms selected for cold conditions. The product information states that the bacteria can help with organic matter breakdown and BOD and COD reduction in low-temperature STPs.
For a plant where winter has slowed the biological stage, this gives operators another option before making changes to the treatment layout.
We Watched the Plant Before Calling It a Success
One mistake in wastewater treatment is judging a change from one test result.
We looked at the plant over time.
MLSS was checked regularly. BOD and COD were tracked. Sludge settling was watched. Wastewater temperature was recorded.
The purpose was not simply to push the MLSS number upwards. We wanted to see whether the biological stage was behaving more steadily under cold conditions.
That distinction matters.
MLSS stabilisation should mean a healthier and more consistent biological stage, not just a higher solids reading.
Best Bacteria for STP in Winter: What Should You Check?
There is no single best bacteria for STP in winter for every plant.
Before choosing a product, check:
Minimum and average wastewater temperature
Type of STP
Daily wastewater volume
BOD and COD load
Existing MLSS
Current sludge condition
Aeration levels
A culture made for warm wastewater may not be the right choice for a plant working through a cold winter.
For plants in colder regions, cold-region wastewater treatment products made for low temperatures are more relevant.
How to Maintain STP Efficiency During Winter
The answer to how to maintain STP efficiency during winter is not always a process change.
First, find out what changed.
If temperature has fallen and the biological stage has become less active, check the operating conditions and the bacterial population before altering the plant itself.
For plants where cold weather is affecting biological treatment, Cold Region Bacteria for STP from Amalgam Biotech can be considered alongside normal STP operation. It is intended for use in low-temperature conditions and can be used with several existing biological treatment systems.
The lesson from winter was quite straightforward: we did not need to change the plant. We needed to pay closer attention to what was happening inside it.
Frequently Asked Questions
1. What are cold region bacteria for STP?
Cold region bacteria for STP are microorganisms selected to remain active in lower wastewater temperatures. They can be used in biological treatment where winter temperatures reduce the activity of the normal bacterial population.
2. Can bacteria work at low temperatures in an STP?
Yes. Some microorganisms can remain active at low temperatures. These include certain psychrophilic bacteria and other cold-active microorganisms. The suitable culture depends on the wastewater temperature and the type of STP.
3. How do cold-active bacteria improve STP performance?
Cold-active bacteria can help break down organic matter when low temperatures slow the normal microbial population. This can help maintain BOD and COD removal and may help with MLSS stabilisation during winter.
4. How can we maintain STP efficiency during winter?
To maintain STP efficiency during winter, monitor wastewater temperature, MLSS, BOD, COD, dissolved oxygen, and sludge settling. If cold water is reducing bacterial activity, a bacterial culture made for low-temperature wastewater can be considered.
5. What is the best bacteria for STP in winter?
The best bacteria for STP in winter depends on the wastewater temperature, organic load, and treatment process. Plants working in cold regions should consider bacterial cultures intended for low-temperature conditions rather than using a culture selected only for warmer wastewater.
