The role of enzymes and bacteria in a septic tank

Category: Septic tank
23 Jan 2023

In situations where municipal sewer lines are not available, wastewater from homes is disposed of into a septic tank for treatment. The septic tank has microbes, especially bacteria, which break down and liquefy the organic waste. In most septic systems, wastewater is treated in two main phases. In phase one, the wastewater is introduced into the septic system where solids settle down to form the sludge and scum layers as the anaerobic bacteria digest the organic waste. In the second phase, effluent is passed into the drainfield area where it is treated further through physical and biological processes as it percolates in the soil.

What are enzymes?

Enzymes are a group of proteins that are secreted by bacteria. Enzymes are very specific on the kind of organic matter they break down. Unlike bacteria, enzymes are not living things. They neither grow nor reproduce. Enzymes are typically generated by bacteria and they serve as catalysts for anaerobic digestion. Enzymes can be thought of as knives that chop down the complex molecules into smaller pieces which are more palatable for the bacteria.  Enzymes, therefore, play a vital role in the septic tank by speeding up the degradation of organic waste by bacteria.

Types of enzymes found in septic systems

The following are some of the important enzymes in septic systems

Protease – breaks down protein-based waste like blood and fecal matter

Lipase – breaks down fats, greases, and oil

Amylase – breaks down starches like porridge, rice, pasta, etc.

Cellulase – breaks down cellulose e.g. from paper-based products

Urease – breaks down urea

Xylanase – breaks down any plant material like veggies.

Most of these enzymes are produced naturally by the bacteria. However, it is a good idea to use biological additives to increase the bacteria count. Bio-Sol’s upkeep products introduce billions of bacteria and enzymes like amylase, protease, cellulase, and lipase into the septic tank in order to break down the organic matter and help in the digestion process in the tank.

What are bacteria?

Bacteria are the most dominant and important microbes in a septic system. Other microbes include fungi, protozoa, rotifers, and nematodes. Bacteria are microorganisms, which means they are extremely small, but they are also living things and so they need some form of sustenance. They feed on organic matter. A bacterium is approximately 1/25,000 of an inch long. Because of their microscopic sizes, lots of them can grow in a small space. According to US Chemicals, it is possible to grow up to 50 billion bacteria in 1 cubic inch. Bacteria that need oxygen are referred to as aerobic while those that do not need oxygen are called anaerobic.

Bacteria are pH sensitive and they require the pH levels to be maintained between 6 and 7.5. This explains why some household products are not very good for the septic tank. Basically, any product that can cause a pH imbalance in the septic tank should not be allowed to go down the drain. When the conditions are favorable, bacteria can reproduce every 15-20 minutes. Unfortunately, the conditions in the septic tank are rarely that conducive, mainly due to the toxic substances that are used in the home. This often leads to the depletion of the bacteria population, a phenomenon that is responsible for the failure of many septic systems. Luckily, you can easily replenish the bacteria in the septic tank by adding billions of bacteria every month using Bio-Sol’s keepup product.


Types of bacteria found in the septic tank

There are four broad categories of bacteria with respect to septic systems. They are anaerobic, aerobic, facultative, and bacteria spores. Let’s look at each of these in more detail.

Anaerobic bacteria

Anaerobic bacteria thrive in environments with little or no oxygen and this is why they are found in conventional septic tanks. They utilize compounds like nitrates and sulfates for energy and this helps to reduce their metabolism. Even though they are smaller than aerobic bacteria, they are very specific and it’s harder for them to produce enzymes due to the reduced metabolism. They are very resilient and so they can survive even when their environment changes drastically. Anaerobic bacteria typically feed on organic waste and then convert them into gases and liquids which can be safely sent into the drainfield. The advantage of using anaerobic bacteria is that you will not need to have electromechanical equipment

Facultative bacteria

Facultative bacteria can flourish in both the presence and absence of oxygen. When oxygen is present, they survive by aerobic respiration. When oxygen is absent, these bacteria switch to fermentation. Facultative bacteria can, therefore, be said to have the ability to transform to either aerobic or anaerobic depending on the conditions in the environment. This transformation typically takes a couple of hours.

Aerobic bacteria

These are the kind of bacteria that require the presence of oxygen for them to flourish. Aerobic bacteria are very efficient in feeding on organic waste and can, therefore, be used to break down waste in advanced systems. Aerobic bacteria are however very sensitive to changes in the environment. They are also generally larger than the anaerobic bacteria. The metabolism rate of aerobes is significantly higher than that of anaerobes. Aerobic bacteria will, therefore, achieve treatment faster than anaerobic bacteria.

Bacteria spores

Bacteria endospores refer to a dormant structure that is produced by stressed bacteria cells. They develop a kind of shell that protects the cell from adverse environmental effects. Endospores can, therefore, withstand conditions that would easily kill any other bacterium For instance; they can withstand high pressure, high UV radiation, chemical destruction, etc. Even though this makes it easy for them to survive in the septic tank, they are not very useful when it comes to digestion of organic waste.

What are pathogenic bacteria? 

A pathogen is a microorganism that causes disease. Pathogenic bacteria, therefore, refer to any bacteria that can cause diseases to humans. The septic system relies on bacteria for breaking down organic waste in the septic tank. In an efficient septic system, the pathogenic bacteria are removed from the treated water before it is released back to the water cycle. A failed system might not properly remove the pathogenic bacteria and that causes groundwater contamination. According to the University of Newcastle, most people do not realize the danger that pathogenic bacteria from their septic systems pose to them. There are a plethora of waterborne diseases that are caused by pathogenic bacteria. Every septic system owner must, therefore, inspect their system every now and then to ensure it is working the way it is meant to. If you experience a blocked drain field, use shock treatment immediately to get it back to normal working condition.

The sludge layer

When wastewater from the house enters the septic system, the heavy solids in the wastewater settle at the bottom of the tank to form the sludge layer. Anaerobic bacteria help in the partial decomposition of the sludge. The sludge layer is usually made up of both biodegradable and non-biodegradable solids and so the bacteria cannot completely break it down. For this reason, septic tanks must be pumped frequently as per stipulated by your provincial laws.

Applying probiotics to septic systems

Every septic system eventually fails. It is not a question of if but a question of when. This imminent failure can be blamed on the toxic substances used in homes which eventually find their way into the septic tanks. Even though the septic tank has billions of naturally occurring bacteria, these bacteria need a pH level of around 7. The toxic substances from homes interfere with the pH levels of the septic tank and that results in the death of lots of the bacteria. As a direct consequence, organic waste is not digested as quickly as it should. Applying probiotics to septic systems is one of the ways of dealing with this problem.


There are thousands of septic tank additives on the market but not all of them achieve the same result. In fact, some of them will do the septic tank more harm than good. Some studies have shown that chemical additives can actually result in the failure of the septic system as well as groundwater contamination. This is why you should only stick to biological additives like the ones supplied by Bio-Sol. Biological additives are made from bacteria and carefully selected enzymes and they introduce billions of bacteria into the septic tank. They, therefore, help to rejuvenate the bacteria flora and can actually be used to clean a septic tank or unclog the drainfield. It is a good idea to add biological additives monthly just to ensure your septic tank is working as efficiently as possible.

About the author


CEO at Bio-Sol

Our goal is not only to offer you the best products on the market but also to educate and empower you with the insights you need for successful wastewater treatment.


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