Following is the standard cleaning procedure and should be applied to any installation of Toray’s Pressurized UF/MF system. Please contact our technical support team for cleaning assistant of your UF/MF system.

Chemical cleaning is done for removing pollution accumulated in the membrane pores or clung on the membrane surface before the trans-membrane pressure rises up to 200 kPa.

The chemicals suitable for a kind of dirty materials and suitable for the membrane module should be chosen. Should the module be treated with wrong chemicals and/or under unsuitable conditions, not only pollutant would not be cleaned out but also the membrane module might be deteriorated. Please contact us if you need more detailed information.

Above diagram shows the flow for cleaning up simultaneously both outer surface and inside of hollow fiber membranes.

  • The flow can be changed case by case. Please contact us if you need the detailed information.
  • Open the chemical return valve of the membrane module and then open the chemical feed valve.
  • Run the chemical feed pump to start the circulation of chemical and then open the chemical permeate valve to have the chemical permeate through the membrane.
  • Circulate the chemical for a fixed time.
  • Stop the chemical feed pump.
  • Drain the chemical and rinse the cleaning line and the module thoroughly with product water.
  • Before the chemical cleaning operation is undertaken, make sure the right assembling steps are taken. Be careful for the chemicals not to get into the product water.
  • Please note that the cleaning time should be changed by the type of chemicals.

The standard conditions for chemical cleaning are indicate in the table below:

Pollutants Chemicals Maximum
Time (hr)
Inorganic substances Citric acid *1 3.0 wt% 1 - 3
Organic substances Sodium hypochlorite 3,000 mg/l
as chlorine
(10 ≤ pH ≤ 12)
1 - 3

*1: Besides citric acid, hydrochloric acid (with the maximum concentration of 1.0 mol/l), oxalic acid (with 1.0 wt%), sulfuric acid (with 0.05 mol/l) and nitric acid (with 0.1 mol/l) are acceptable.

  • The above are the standard conditions and may be changed by how membrane module is polluted actually.
  • The standard cleaning temperature is 20-30 degree C and circulation flow rate of chemical is 50 l/min for 8 inches module.