Ultra filtration

Ultra filtration is a pressure-driven process used to purify water from emulsions, colloids and suspended substances which are not able to be separated gravimetric.

The contaminated water is pumped at a high speed parallell to the membrane surface. The contaminations are trapped by the membrane and are concentrated in a process tank. The tank is emptied when full and the membrane is cleaned when needed. The sludge that has been collected in the process tank is transported to a sludge plate where it is allowed to dry before it is sent to other plants for recycling.

The water continues its way through the purifying process.


  • An emulsion is a mix of two fluids that usually do not mix very easy, for example water and oils or grease. Mayonnaise is one example, the contaminations being sent to our plant is another.
  • Colloid is a greek word meaning glue. In our process, it means that one substance is finely divided into another substance, for example when salts and chemicals are dissolved in the water.
  • Suspended substances are substances such as fibres and particles in the water, large enough to easily be removed from the water by passing it through a filter.
  • Gravimetric separation is a way of separating oils. The water goes through a large tank which is constructed to make the sludge sink to the bottom of the tank and for the oils to rise. This way, the oils and the sludge can be separated from the water. What’s left in the water are substances that need to be separated by ultra filtration.