Septic Tanks in Sri Lanka

Septic tanks are a common wastewater treatment system in Sri Lanka, where public sewer systems are not always available. Septic tanks work by separating the solids from the wastewater, allowing the solids to decompose naturally and the wastewater to be discharged into the ground.

Types of septic tanks

There are two main types of septic tanks: precast concrete septic tanks and plastic septic tanks. Precast concrete septic tanks are more durable and have a longer lifespan, but they are also more expensive. Plastic septic tanks are less expensive, but they are not as durable and may need to be replaced more often.

Disadvantages of septic tanks

  • Prone to bacterial growth,regular inspection and maintenance are crucial.
  • Risk of overflow and environmental contamination if not properly sized or maintained.
  • Repairs or replacements can be challenging

Johkasou wastewater treatment systems

Johkasou wastewater treatment systems are a type of wastewater treatment system that is becoming increasingly popular in Sri Lanka. Johkasou systems are more compact and efficient than septic tanks, and they produce higher-quality effluent.

How Johkasou systems work

Johkasou systems use a combination of aeration and filtration to treat wastewater. The wastewater is first pumped into a chamber where it is aerated. This helps to break down the solids and promote the growth of beneficial bacteria. The wastewater is then filtered to remove any remaining solids and bacteria.

Advantages of Johkasou systems

Johkasou systems have a number of advantages over septic tanks, including:

  • They are more compact and efficient, so they require less space to install.
  • They produce higher-quality effluent, which can be reused for irrigation or other purposes.
  • They are less likely to overflow or cause environmental contamination.
  • They are easier to repair and replace than septic tanks.

Advantages of Johkasou Treatment Plant Over Conventional RC/ Septic Tank Treatment Plant

Space Requirement

Jonkasou treatment plants give a wide range of capacity selections for customers to install the treatment plant centralized or decentralized. As this is a prefabricated unit, it is moveable & can be replaced above ground or underground.
Compared to the conventional system Johkasou treatment plant requires less space.

High Treatment Performance

With 60 years of trusted Japanese technology, Johkasou comes with combined treatment of anaerobic and aerobic treatment which will reduce the generation of sludge. As this will be a compact system there will be no generation odor.


There will be diaphragm-type Air blowers which will generate a sound below 48Db.

Quick Installation

As there’s less amount of construction to be done within a short period of time the plant can be installed and commissioned for use.

Structural Material

Johkasou treatment plants are made of Fibre-reinforced plastic (FRP) which will not cause any deterioration or corrosion. These FRP tanks are structurally designed to absorb vibration and shock.

Expandable Capacity & Moveability

Even with a requirement of expanding the design capacity, Johkasou allows the customers to combine preferable units and expand the volume. Also, this prefabricated system can easily move to another place from the installed area according to the client’s future requirements. But ordinary, conventional plants cannot move or transfer to any place after the installation.

Operation & Maintenance Cost

Daiki Johkasou treatment plant doesn't require a permanent operator, it is a self-operating system.
Johkasou is a seal-type vessel. No chances of mosquito breeding.
As it’s only the Air blowers that are the only electrical consumption unit running cost is low.
Cleaning and desludging is easy.

Recovery from the damages

Compared to conventional systems, it is easy to clean the filter media and recover it. Even during a power failure the Johkasou system will not fail.


Johkasou system is less expensive compared to conventional systems as FRP tanks are compacted with all the necessities. Equipment & pumps used in the conventional system are very expensive therefore the initial cost is higher than Johkasou.


70 years of trusted usage in Japan Daiki Axis Japan, 60 years experience in Johkasou manufacturing & maintenance.

Septic tanks vs Johkasou wastewater treatment systems

The following table compares septic tanks and Daik Johkasou wastewater treatment systems:

Choosing the right wastewater treatment system depends on your individual needs. For those seeking a more efficient and environmentally friendly option, a Johkasou wastewater treatment system is the superior choice

Feature Septic tank Daiki Johkasou wastewater treatment system
Less efficient
Highly efficient
Effluent quality
Doesn’t meet CEA standards
Meets CEA standards
Risk of overflow
Risk of environmental contamination
Ease of repair and replacement
Cost of installation and maintenance
Power requirement
Suitable for all types of wastewater
High water table area
Unable to use
Able to use
All waste into one tank