FREEZING IN AN ULTRASONIC BATH AS A METHOD FOR THE DECONTAMINATION OFAQUEOUS EFFLUENTS

The freezing of aqueous solutions on cooled heat-conducting surfaces a t atmospheric pressure was investigated to assess the freeze process e fficiency. Taguchi orthogonal design techniques were employed to plan the experiments in view of the number of factors involved. Resultant q uality assessment of each variable was judged using analysis of varian ces to examine its effect on the efficiency of the freeze-thaw operati on. In this series of experiments, the results showed that five of the seven variables studied that have a positive significant effect on th e freeze decontamination efficiency are: lower cooling rate, higher in tensity of ultrasound, stainless steel cooling surface, presence of ai r in the solution, and starting freezing at a small supercooling. The ultrasonic intensity was, however, observed to be the most significant variable. The decontamination factor values obtained with best and wo rst suitable conditions are 16.9 and 1.9 respectively.