Fig. 4 shows the comparison of the TP effluent concentration
between batch and continuous flow modes for the 4-day hydraulic
retention time. For both planted and unplanted beds, there was
significant enhancement (p < 0.05) in TP removal in batch flow
operation (69.6% for planted beds; 39.1% for unplanted beds) as
compared to continuous flow operation (46.8% for planted beds;
25.5% for unplanted beds). In addition, in both batch and continuous
modes, planted beds showed significantly better TP removal
efficiencies (p < 0.001) than that in unplanted beds. However, for
the test series of 2-day HRT, and in comparing the batch operation
and continuous operation, the statistical results showed significant
differences only for the planted bed.