The diagram below indicates the physical layout of a Domestic Bio-digester System which Express Drainage Solutions Kenya Ltd can design, supply and install;

Physical Layout of a Double Chamber Biodigester Tank Drainage System

Physical Layout of a Double Chamber Biodigester Tank Drainage System

The diagram below illustrates how a Domestic Double chamber Bio-digester system works in order to digest waste, produce methane gas and give out clean water at the outlet.

Residential Bio-digester Drainage Tank System

Residential Bio-digester Drainage Tank System

Method of Action of the Residential Bio-digester Drainage System;

  • The first chamber is the larger of the two. Here sewage arrives from the toilets, the solids drop to the bottom of the tank and the catalyst found in the sewage start doing their job, eating away organic waste and decomposing pathogens.
  • When this chamber is filled, the water flows to the second chamber where more of the same happens, except this time most of the biological matter has been left in the first chamber. When the water flows into the second chamber, it is almost 90% clean and here, the final stage of digestion
  • The sanitation system works through a process called Bio-degradation. This process completely breaks down organic matter into gases and water. The gases produced are carbon dioxide, methane and nitrogen.
  • When the water finally comes out from the bio-digester and into the irrigation pipelines or the drainfield, it is 98% clean and free of disease causing micro organisms. However, the treated water should not be used for human or animal consumption, or for household cleaning without going through additional treatment.
  • It is a good idea to add a tablet of bio-digester catalyst to jump-start the process. Once the bio-digester catalyst colonizes the bio-digester tank, we recommend adding 1 bio-digester catalyst tablet every year to keep the digester fresh and hungry. However we now have a variety of Bio-digester tanks into which the bio-catalysts are attached to their walls even before they go into any use. On the other hand we have devised our own natural bio-digester tablets which are eco-friendly and can be used in the process. Note that the sludge reduces in volume to a very minimal amount as you move from chamber 1 to Chamber 2.
  • It takes just about 2 weeks for the breakdown of matter to be complete, ensuring that only water is discharged out of the tank. This is made possible by the action of the catalyst present in the tank. The catalysts are actually placed on the inside of the tank as it is being manufactured.
  • The treated water can then be taken to a soaking area or other place where it can be recycled for other uses. The carbon dioxide and the methane gas produced are simply released into the atmosphere while the nitrogen produced simply dissolves in the water. This nitrogen-rich water is great for watering gardens and irrigation.

Advantages of Domestic Bio-digester systems;

  • It digests organic solids in an ecological way;
  • It prevents human waste and untreated water from contaminating groundwater;
  • It offers an alternative to dumping sewage into rivers, lakes and fields in rural and semi-rural areas where there are no city sewage systems;
  • The effluent of water can be used as fertilizer for soil, to water plants, or for fish ponds;
  • It’s cleaner, more effective and easier to use than a septic tank because it doesn’t need to be cleaned or emptied and doesn’t create leakage problems;
  • It is odorless, as opposed to composting toilets and septic tanks;
  • It doesn’t require the work and energy involved in relocating composting toilets every year.
  • They have been fully approved and recommended by both NEMA (National Environmental Management Authority) and the Ministry of Water and Irrigation for dealing with commercial and domestic waste water in Kenya. The bio-digester has been in use in Kenya for over 17 years without any major issues.
  • The apparent madness of using fresh drinking water to flush the toilet or water the garden partly explains the appeal for using recycled water for these purposes taking into account that in populated cities and institutions scarcity of water during water rationing is a problem.
  • The recycled water contains higher levels of nutrients such as nitrogen, phosphorus and oxygen which may somewhat help fertilize garden and agricultural plants when used for irrigation. By using recycled water we can save on the space and cost of storm water capture and storage.
  • Recycling wastewater can decrease the discharge of effluents that may damage and pollute the ecosystems of the sensitive bodies of water in its environs.

Different Types of the Bio-digester Tanks in Kenya;

There are 3 different types of bio-digester septic tanks which Express Drainage Solutions Kenya Ltd can design, Supply and Install, based on size;

  • The Standard Bio-digester – This is the smallest size and it can handle between 18-21 people (continuous users). This is the best size for residential properties and small commercial establishments.
  • The Jumbo Bio-digester – The jumbo bio-digester can easily handle 100 people (continuous users) and is therefore ideal for mid-size establishments, apartment blocks, hotels, farms and small gated communities.
  • The Jumbo Deluxe Bio-digester – This is the biggest size available and it can handle up to 400 continuous users. This is great for much bigger establishments, estates, shopping malls, hotels, schools, hospitals and blocks of flats.
  • Apart from these 3 standard sizes, different sizes can be created based on the need and the size of the project. Custom designs can also be created for different clients.

Garden Chambers, 2nd Flr. Off Jeevangee Gardens, Mokhtar daddah Street

+254 727 160738

+254 738 627632

P.O.BOX 8620-00200, Nairobi, Kenya