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Contributes to safe and reliable potable water supply
In recent years water supply needs are increasing not only in urban areas but also in rural areas.
The reduction of operation costs and easy operation and maintenance are essential to cope with the demand for small-scale water treatment facilities.
The ‘T・O’ Model Upflow Slow Sand Filter was developed to suit small-scale water treatment.
This system enables a safe and reliable water supply.


The ‘T・O’ Model Upflow Slow Sand Filter incorporates slow sand filtration (bio-filtration) and the flow direction is lower to upper.

Recommended application

Small-scale water treatment plants in developing countries (capacity: up to 5,000m3/d)

Applied raw water quality

Maximum turbidity 50 NTU (more than 50 NTU requires pretreatment)


  1. High performance filtration
    • Filtration can continue for a long time since the turbidity is captured over the entire area of the filter bed.
    • Biological treatment is accomplished by microbes that propagate on the filter bed.
      *Filtration speed : 4-8m/day (depending on raw water quality)
  2. Safe and reliable treated water
    • Closed tank design prevents ingress of extraneous pollutants.
    • No flocculant addition allows water mineral content to remain unaffected.
  3. Easy operation and maintenance
    • Simple structure, no specialized technical knowledge required.
    • Cleaning is performed once or twice a year, and periodic cleaning of the filter bed such as exchanging the sand or scraping the filter surface is unnecessary.
  4. Low operating cost
    • Main mechanical equipment consists of the intake and distribution pumps only.
      →Low power consumption cost
    • No need for flocculant
      →Low chemical consumption
  5. Extensive supply record
    • More than 1,000 projects in Japan.

(In-house comparison)


For small-scale (less than 5,000m3/d) water supply

  • Low cost operation
  • Meets demand for safe and reliable water
  • Easy operation
  • Reinforces security


These technologies were developed by Okada Industry Co., Ltd., and both Okada Industry Co., Ltd. and Hitachi, Ltd. are cooperating for the purpose of promoting this technology.