Introducing ...


The term ‘Johkasou”, literally means “purification tank” in Japanese. Johkasou is a standard wastewater treatment system used all over Japan. The system is made for buildings that are off the municipal sewer system.

The unit is a fibre-reinforced plastic tank and contains five functional chambers (sedimentation, anaerobic, aeration, sedimentation and disinfection) in a tank. Such an anaerobic and aerobic combined biological process with high efficiency has been commonly employed as an onsite wastewater treatment system for over 30 years in Japan

Treatment Process

  1. The first compartment is a SEDIMENTATION chamber where raw wastewater settles into distinct sludge and scum layers under anaerobic conditions. The relatively clear effluent flows through twin baffles into the next chamber.
  2. This second chamber is the largest in the unit, providing retention time for the slow process of ANAEROBIC biodegradation. In contrast to a standard septic tank, the anaerobic treatment process in the Johkasou is enhanced with the use of filter media. Retained in the bottom half of the chamber, these media are designed to provide a large surface area optimised for biofilm development. The result is a biologically rich activated sludge blanket through which organic matter in wastewater is decomposed faster and more efficiently.From this unit,water is baffled again as it flows into a third chamber.
  3. The third chamber is the site of AEROBIC treatment. Air, supplied by a linear compressor, travels through a perforated piping system called a diffuser and escapes into a column of smaller propylene media. These contact media are also designed for optimal biofilm formation. They provide a surface for aerobic microorganisms to attach and grow.The action of the air constantly circulates the media in the top two-thirds of the chamber, creating a fluidised bed with sufficient air.Aerobic bacteria thrive in this rich, oxygenated environment, resulting in a high degree of treatment. The organic matter in the wastewater is further broken-down into simpler products due to the progressive decomposition.In this case,the organic matter is converted to new cells,carbon dioxide and water.The new cells are then precipitated together resulting in sludge which is suspended in the treated water.
  1. The fourth chamber ,which is the site for the second sedimentation,allows for settlement of sludge resulting from the aeration process.The settled sludge is then recirculated  to the head of the system through an air-lift pump (powered by the compressor). The recirculation process also allows a specific amount of treated water into the head of the system for denitrification and flow equalisation.
  2. Finally, the treated water is disinfected as it flows past a tablet chlorinator, before being discharged to a storm sewer, a nearby body of water or recycled for irrigation.

Treatment performance

The fact that treated effluent empties directly into Japan’s public water bodies without resulting in contamination is a testimony to the high degree of treatment achieved by Johkasou technology.

The system achieves the following levels of standards:

BOD (Biochemical Oxygen Demand) Equal or Less than 20mg/L

T-N (Total Nitrogen): Equal or Less than 20mg/L
SS (Suspended Solid) Equal or Less than 20mg/L
COD (Chemical Oxygen Demand) Equal or Less than 30mg/L

Installation, Maintenance, & Warranty

  • Delivery takes 14 – 17 weeks from order
  • Installation takes 2 – 3 weeks
  • We offer maintenance service throughout the product’s lifecycle,
  • We give a 10 year warranty on effluent quality so property owners can have peace of mind. Warranty subject to maintenance agreement with Usafi Comfort.