Express Drainage Solutions Kenya Ltd is also involved in the design, supply and Installation of Decentralized Waste Water Treatment Systems. The diagrams below indicate under normal circumstances how biomass, waste drainage water as well as fecal waste flow through Major DEWAT system and how the biogas plant and bio-digester tanks (Anaerobic Buffle Reactors) acts upon them. The first diagram indicates a general overview of the process while the second indicates the detailed view of the components of a Major DEWAT System.


The detailed view of the components of a Major DEWAT System.


Some institutions Express Drainage Solutions Kenya Ltd deals with do not have a wide range of biomass resources e.g. forest crops and residues, animal residues, agricultural crops and residues, municipal solid waste, sewage and Industrial residues and therefore may rely on just sewage as the main biomass.

For those institutions Express Drainage Solutions Kenya Ltd has dealt with, we advise them that it is rather uneconomical to install just the Anaerobic Buffle reactors alone for the production of recycled water without a biogas plant because the extra benefit of biogas is lost and the demand for energy in institutions is so high. On the other hand, the biogas quantity produced inside the Buffle Reactors alone is of no economical value because the quantities are small and have little pressure to have any impact on energy output of the system.

What are the sources of Biomass for the DEWAT system?


The main biomass resources which can be produced by any institution are;

  • Forest crops and residues.
  • Animal residues.
  • Agricultural crops and residues.
  • Municipal solid waste.
  • Sewage – mainly fecal matter from the institutions toilets.
  • Industrial residues.

What is the Role of the Bio-gas Plant Chambers?

  1. Inlet/mixing chamber/Tank – This the initial point of the digester where the biomass sources are put. At this point the inlet can be directly connected to sewer drainage system.
  2. Bio digester Tank. – This is the airtight chamber where the initial biological process (Anaerobic digestion) takes place leading to formation of methane gas. At this stage there are various gas processes as follows; Methane Average 60%, Carbon dioxide (co2) 35% and other gases less than 5%.
  3. Expansion chamber/Overflow Tank – This chamber acts as the pressure regulation mechanism, its designed such that the weight of the bio-slurry is used to control pressure within the dome and the piping system such that the biogas produced has enough pressure to be of economic value.

What is the role of the Anaerobic Buffle Reactor (ABR) chambers?

  • The first chamber (largest); bio-slurry arrives from the Biogas plant, the solids drop to the bottom of the tank and the catalysts, start doing their digestion.
  • The water overflows 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 overflows into the third chamber, it is almost 90% clean; final digestion takes place. When the water finally comes out from the fourth chamber it is 98% clean and free of pathogens. This water is now safe to be used for underground irrigation and flushing toilets. Its unfit for human or animal consumption, or for household cleaning without going through additional treatment vide gravel filters and chlorination.

The picture below illustrates a Major DEWAT system with the foreground showing the Anaerobic Buffle Reactors and the background showing Biogas biodigester plant;


The volume of the sludge reduces to a very minimal volume as you move to the fourth chamber where it is at bare minimum.

The Institutional DEWAT concept actualization process

Successful implementation is more than merely delivering biogas and recycled water to a point of use. There are long-term concerns regarding matching supplies and demands, planning adequately for increased demands, and identifying alternative supply sources if the biogas and recycled water supply are inadequate to meet demands

The step by step process to implementation Express Drainage Solutions Kenya Ltd follows involves;

  • Identification of Project Needs and Project Drivers.
  • Project Planning.
  • Identification and Characterization of the biogas and recycled Water Sources.
  • Residents’ involvement, information and education.
  • The intended use and infrastructure assessments
  • Environmental issues and approval
  • Economic and financial review
  • Project outline submission
  • Regulatory review and approval by county and state regulators
  • Project design
  • Budgeting and forecasting of costs.
  • The Permitting Process
  • Construction

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

+254 727 160738

+254 738 627632

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