Empirical equations describing the relationship between Ce and
Ci for both RP and SRP at different HRT’s are presented in Table 4.
Generally, the R2 values indicate a good fit of the equations. More
importantly, the reasonably high positive correlation between Ce
and Ci for both RP and SRP in most of the cases illustrate the fact
that effluent P concentration increased with corresponding
increase in influent P concentration. Other authors have reported
similar observation for P behaviour in sub-surface flow wetland
systems (Pant et al., 2001; Tang et al., 2008). Furthermore, Table 4
shows that the R2 values were mostly greater for RP than for SRP in
each HRT. It therefore follows that under the same HRT, effluent RP
concentrations were more dependent on influent concentrations.
The modified first-order removal model (Eq. (5), Section 2.3.3)
could estimate the actual k value since other parameters are
known. C* was set to zero based on common assumptions
(Tang et al., 2008).