What is the concentration of biodegradable organic matter in septic tanks?

The article will discuss the concentration of biodegradable organic matter in septic tanks and will also include elucidations to aspects such as 

  • What are septic tanks?
  • Are these good for the environment?
  • What is the best septic tank for your house?
  • What should and should not go in septic tanks?
  • What is the comparison between septic tanks and sewer systems?

What is the concentration of organic matter in septic tanks?

The concentration of organic matter in septic tanks is about 200-250 ppm. In another expression, it is claimed that the concentration of organic matter in septic tanks is about 50-70%. Therefore, it can be assumed that the majority concentration of septic matter is organic material. 

Septic tanks are structures made from materials such as plastics, concrete, or cement. The basic purpose of the septic tanks is to clean and work on the wastewater partially so that it can then be directed to ground, aquatic, and marine water sources and reservoirs. 

Are septic tanks good for the environment?

Usually, there is a positive relationship between septic tanks and the environment because of the purpose that septic tanks are built for. 

Septic tanks are built to act as partial wastewater treatment plants. Have you ever wondered what happens to the greywater and blackwater that leaves your home? It may enter either in septic tanks or sewer systems. 

Wastewater from houses enters the septic tanks wherein the solid resides (identified as sludge) settles down while the fluid part is discharged to the drainfield for further treatment. 

Therefore, the purpose of septic tanks is in line with the environmental interest because it means that when septic tanks are there, there will not be a direct exposure of wastewater into natural habitats such as groundwater, marine and aquatic ecosystems. 

If there are no septic tanks, then there can be negative effects or repercussions such as groundwater pollution and degradative effects on aquatic and marine life and ecosystems. 

Also, the negative effects may reciprocate and develop at various levels of food chains and thus, many species may be affected by the principle of bioaccumulation and biomagnification. 

What is the negative side of septic systems?

It has been explained that septic tanks come along with many benefits and advantages to the environment. However, there are certain precautions that we need to be careful about because otherwise, there can be negative repercussions. 

It needs to be ensured that there is no leakage in the septic tanks because otherwise, there will be no benefit of septic tank installation at all. 

The choice of material is another factor that needs to be well assessed and scrutinised. The choice must be made in a way that the utility is maxed and the environmental effect is also kept at the minimum. 

Therefore, it can be said that the negative aspects of septic tanks come mostly from subjective cases. From an objective point of view, septic tanks are built to help and alleviate environmental issues. 

What should and should not go in septic tanks? (7 things that should not go in septic tanks) 

Septic tanks are considered more sensitive than sewer systems. Also, it is a burgeoning matter that septic tanks can not be repaired or rectified that easily because it will require a lot of labour. 

As per what can go, here is a list of some materials that will give you a fair idea of what can go in septic tanks: 

  • Biodegradable household products 
  • Chemical free or chemical limited products
  • Perished foodstuff
  • Septic tanks compatible toilet rolls 

However, you need to be careful with the following material as it can disrupt the septic tank system that will eventually result in a replacement, which will be bad for both your pocket and the environment. 

  • Cigarette butts 
  • Harsh chemicals 
  • Medicines such as antibiotics 
  • Bleach 
  • Acid rich cleaners 
  • Weed killers and insecticides
  • Kitchen towels and nappies 

What is the best septic tank for your house?

The answer will vary based on subjective situations or questions. Generally, there are three main types of septic tanks. These include: 

  • Concrete septic tanks 
  • Fibreglass septic tanks 
  • Plastic septic tanks

While deciding the best septic tanks, you need to ask question such as

  • What is the size of home?
  • How many people live in the house as it will relate directly with the waste produced

If the waste produced is greater then concrete septic tanks are the best choice as they are durable and resistant to more handling of waste. 

If the waste produced is less then, fibreglass septic tank may be a better choice. Some studies argue that precast septic tanks are the best choice in most cases as these cater to the majority of needs. 

Are septic tanks better than sewer systems?

It has been stated above that the functions of septic tanks and sewer systems are almost the same; to treat wastewater (grey and black) and make sure that the polluted water does not damage ecosystems and natural reservoirs. 

However, the curiosity still remains about which is better: septic tanks or sewer systems. Well, the answer is neither black nor white; rather it is in the shades of grey. 

  • What this means is that the verdicts have to be decided on subjective bases because if there is a large community with many houses, then the sewer system is a better option because it is the collective treatment. The example is analogous to public transport vs individual cars. In the latter case, there is more consumption of resources which is rather unnecessary. 
  • However, if there is a subjective case of a small locality with a limited number of houses, then perhaps septic tanks can be a more befitting option.
  • In terms of maintenance and repairs, the sewer systems take the win because their maintenance is managed by the authority whereas septic systems are the responsibility of individuals which most of them do not abide by.
  • The environmental budget in the case of septic tanks will be greater because septic tanks are made from non-biodegradable materials that may take a big toll on non-renewable resources such as plastics. However, the raw materials for sewer systems ought to be less given the context that these are community-wide programs. 
  • Regardless of all, the basic point is that both the septic tanks and the sewer systems are rightly functional and there are no malfunctions like leaks et cetera because then there will be more bad than good. 


It is concluded that the concentration of organic matter in septic tanks is about 200-250 ppm. In another expression, it is claimed that the concentration of organic matter in septic tanks is about 50-70%. Therefore, it can be assumed that the majority concentration of septic matter is organic material. 

Other than that, the article built an edifice of what septic tanks are and what is their relationship with nature and the environment. A comparison with sewer systems was also drawn that led to the final conclusions. 


  • Maw, M. M., Boontanon, N., Fujii, S., & Boontanon, S. K. (2022). Rapid and efficient removal of organic matter from sewage sludge for extraction of microplastics. Science of The Total Environment, 853, 158642.
  • Precast concrete septic tanks. Retrieved from: https://sheaconcrete.com/septic-tanks
  • Types of septic systems. US EPA. Retrieved from: https://www.epa.gov/septic/types-septic-systems
  • Wood, Gareth. (March 2021). What should not go in a septic tank? Retrieved from: https://www.omdi.co.uk/news/what-should-not-go-in-a-septic-tank/

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