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However, the pH remained stable at 12 just for 20 minutes. It was necessary to calibrate the pH probe again, to clean the apparatus and to review the calculations in order to determine the reason for the abnormal pH behavior. Other reasons for this behavior included the fact that since the lime was poured into the narrow column in a powder-form, it resulted in the clogging and pressurizing of the column. Subsequent flushing (using higher flow rates to force the lime to unclog) caused loss of lime. More importantly, during this period of time, data was not recorded since the lime feeder had to be overturned manually to get the solidified, stuck-up lime to dissolve.
Figure 1. pH vs time
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