Improving a values

Later only the evaluation has been improved. A value close to that of eq. (3.60 a) was found (99). 

We previously identified a ratio of L/S equal to 1 as a threshold between potentially poor and good performance. This value clearly does not meet the criterion for acceptable performance, irrespective of the number of stages used. An increase of L/S to 2 (i.e., using twice the amoimt of water contained in the sludge as rinse) brings an immediate improvement. A value of 3, finally, either exceeds or falls just short of 99% recovery. 

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