Method for processing filter backwash fluid for reuse as cleaning fluid

A method of industrially cleaning objects, wherein said objects are cleaned in a cleaning process with the aid of a cleaning liquid and wherein at least a portion of the used cleaning liquid comprising impurities washed from said objects is pumped through filter means having an inlet side and an outlet side, thereby retaining impurities at said filter means, and then returned into said cleaning process, said method also comprising the steps of:

• (a) backflushing said filter means with said cleaning liquid thereby obtaining a contaminated backwashing liquid consisting of cleaning liquid and impurities previously retained by the filter means;
• (b) forming a volume from at least a portion of said contaminated backwashing liquid;
• (c) allowing said volume to stand for a first time period thereby allowing at least some of said impurities to settle within said volume;
• (d) applying a positive pressure to said volume during a second time period while said volume is allowed to stand, said second time period being at the most as long as said first time period, thereby increasing the sedimentation rate of said impurities;
• (e) performing a pressure-tight separation of a lower portion of said volume containing settled impurities from an upper portion of said volume after said first time period has elapsed;
• (f) removing one of said portions of said volume from the other of said portions thereby recovering at least a major portion of the cleaning liquid used for backflushing said filter means;
• and
• (g) returning said recovered cleaning liquid portion into said cleaning process.