Advances in Water Treatment and Enviromental Management

212 WATER TREATMENTTABLE 2Performance of Case B Stripping Towers During Commissioningwhich when compared with the actual value of 26.2 shows only a 26% mass transfer efficiencycompared with the value of 80% achieved in Case A.A number of measures were adopted in an attempt to improve the performance:i) Duplicate analyses confirmed that the problem was genuine and not created due toanalyticalii) In order to test whether poor distribution was the cause of the poor performance additionaldistributors were tried for air and water but no significant improvement in performancewas achieved—the removal of TCE increased by only 1% to 73.9%.OperationExamination of the subsequent operating results in Fig 9 shows that the removal efficiencyafter commissioning rose to 90.64% when six low points were discarded.From this data the operating K L a can be calculated to be 50.5, giving a mass transfer efficiencyof 51% which shows a considerable improvement over the 26% achieved during commissioning.It was thought that this performance improvement might have been due to the method ofoperation following commissioning. In order to follow demand, one well pump operatescontinuously whilst the second pump cuts in and out on demand but at all times the twotowers are in service. The effect is that both pumps operate typically for only 10 hours perday. The time of sampling was not selected to coincide with periods when two pumps wereoperating.The results have therefore been examined for three cases:i) Assuming 1 pump operating L m= 2682 kg mole/m 2 /h