Biodigester Septic Tank

Biodigester Septic Tank

A biodigester septic tank is a waste and sewerage management and treatment system.  It can be of great use in both residential and commercial buildings.  Unlike the normal septic tanks, the solid and liquid wastes are treated so that they can be used in other ways. A biodigester septic tank is a one-time waste control and management solution.

How it works.

The biodigester septic tank is based on biodegrading processes.  This is the breaking down of organic waste matter into carbon dioxide, methane and water. The bacteria in the tank feed on the organic wastewater and the dark water as they come in. As a result, they become water and gas. The effluent takes about 2 weeks to decompose.

The methane gas is what most people call Biogas. It can be harnessed and used for cooking. However, the gas production is in small quantity except for large biodigesters. As a result, it is released to the atmosphere as the collection is impossible.  After the water treatment is complete, it leaves through the outlet for recycling or left to soak into the soil. The water is very rich in nitrogen therefore great for irrigation purposes. In addition, the water can be used for other things like flushing the toilets.

However, water is not safe for human or animal consumption. It is also not okay for household hold. This will require further treatment.

The septic tank uses the displacement principle. The amount of wastewater flushed into the system displaces the equivalent volume from the biodigester tank to the soak drain.

Advantages of Biodigester septic Tank


Installing a biodigester septic tank is cheaper than constructing the old septic tank. You only have to excavate a hole and drainage trenches if water will not be recycled. In addition, it saves money on emptying which is now not necessary. Currently, a septic tank cost around 100,000 Kshs to install.

Better Environment

A biodigester septic tank changes the environment in so many ways. It produces no foul smell. The water soaks into the surrounding soil, thereby increasing the amount of underground water. As a result, soil fertility raises and crop production improves. In addition, there is no wastewater discharge in the streets making it cleaner and most importantly safe.

Structure and Design

The biodigester septic tank is built from reinforced concrete. For this reason, it is much stronger compared to other materials plastic and brick septic tanks. Secondly, the tank already has enzymes. In addition to that, a biodigester septic tank is small and circular in shape. As a result, it can hold pressure and stress without cracking therefore very reliable.

In addition to this, the biodigester septic tank takes up relatively small space and produces no foul smell. It is eco-friendly.  The increasing demand for biodigester septic tanks has created job opportunities for many people, directly and indirectly.

A biodigester septic tank has full approval and recommendation from the National Environment Management Authority and the Ministry of Water and Irrigation. It also has 5 years post installation warranty which covers faults from the manufacturer.

Types of Biodigester Septic Tank

The difference in the biodigester tanks is based on the size. The 3 types are:

Standard biodigester

A standard biodigester tank is the smallest tank available. It has the capacity to manage waste for 20 users. As a result, it is most preferable for use at a residential home.

Jumbo Biodigester

It is of moderate size and has the capacity to hold waste from 100 people. For this reason, it is ideal for hotels, mid-size properties, apartments and small gated communities.

Jambo Deluxe Biodigester

This is the biggest tank in the market. It can hold up to 400 users. It is suitable for big establishments, shopping malls, big hotels, hospitals, schools and estates.

Despite the above, custom biodigester tanks can be created depending on user requirements.

Biodigester septic tank structure

The tank structural design is well thought out so as to ensure effectiveness and durability. Most design implies the power of gravity.

The biodigester septic system has three parts:

  • Grease interceptor
  • Biodigester tank
  • Soakage drain.
Grease Interceptor

On getting into the system, the wastewater is divided into grey water and black water. Blackwater is sewage that has come into contact with faecal matter. On the other hand, grey water is sewage from kitchen sink and bathrooms.

Greywater has a lot of oils, fats, grease and detergents. As a result, it is chemically unstable. For this reason, it passes over the biodigester tank and goes through the grease interceptor to remove the oils. This is because the oils can be harmful to the environment. After this, the oil-free water goes to the soak pit.

Biodigester Tank

On the other hand, black water is directed into the biodigester tank. The already present anaerobic bacteria feed on the faecal waste in order to rid it of the pathogens and treat the black water. The solid waste matter settles at the bottom of the biodigester tank through sedimentation. They decompose to water and gas as a result of biological activities.

The soakage drain is a tank where treated water collects and percolates into the ground.

Biodigester septic tanks provide the best sanitation system solutions. They are easy to manage and maintain with no extra cost.

It is important to note that disposing non-degradable waste materials into the system is not a good practice. Some of these materials include cigarette butts, sanitary pads, and condoms among others. If they disposed into the system, the system will block or fill up. In addition, some cleaning detergents like phenyl are not appropriate for use. This is because they can harm the bacteria in the tank making it less effective. Replace them with the recommended cleaning detergents. Other liquids like paint and solvents can also harm the bacteria. Do not flush them down.

Comments (12)

  1. Albert mugabe
    Apr 20, 2020 at 8:20 pm

    Thanks for this useful information. I would further want to understand how the grease interceptor operates.

      Apr 07, 2021 at 4:22 am

      Thanks this is helpful

  2. George Mucee
    Aug 23, 2020 at 10:58 am

    I need a quote for a domestic biodigestor in Juja High Point urgently

  3. Dinah kataka
    Nov 27, 2020 at 6:03 am

    Well explained however I would like to know if a biodigester is appropriate for a very large population like in an institution with a population of 3000 people.

  4. Victor
    Nov 28, 2020 at 11:49 pm

    Thank you for this, I want to be getting new post

  5. Prisca.
    Dec 19, 2020 at 3:56 pm

    Thanks for this. Please can I know the total cost(construction plus materials) for a jambo deluxe biodigester.

  6. Aliu Musiliu
    Jan 06, 2021 at 10:01 am

    Will like to know more about the construction

  7. Jared Onyango
    Feb 12, 2021 at 1:09 am

    How dose the grease interceptor operate. Otherwise thanks

  8. Derick Agaba
    Mar 16, 2021 at 10:55 am

    Thanks for the information however can you provide images and diagrams for study purposes and more understanding

  9. David
    Apr 08, 2021 at 12:00 am

    Thanks. Very educative. I would like to know the sizes of the different bio-digester septic tanks

  10. Henry
    Apr 09, 2021 at 4:05 pm

    Thanks for having got knowledge about biodigeste system I do have a clue on how it works I would like to get more knowledge on how to build it

  11. Godfrey Were
    Apr 11, 2021 at 6:01 am

    What is the cost of the standard biodigester?

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