TP removal rates in T2 varied considerably, without any apparent
correlation to either seasonal temperature changes or influent
concentrations (Table 2). It was shown, however, to be affected by
the contact duration of the straw and wastewater between the
14th and 39th days (Fig. 2). The lowest rate of TP removal was
recorded when the contact time exceeded 90 day. In other relevant
tests, water hyacinth materials also posed a significant increase in
TP after being adsorbed with various types of wastewater (Table 3).
According to Howard-Williams (1985), several factors affect the
interactions between phosphorus in wastewater and various storage
compartments, such as vegetation, detritus, fauna, microorganisms
and benthic substrates like soil and gravel. Sakadevan and
Bavor (1998) reported that under field situations the removal of
phosphorus highly correlated with the contact time between effluent
and substrate and the infiltration capacity of the substrate for
the effluent. As there are a limited number of sorption sites on any
substrate surface, when those sites are saturated, the sorptive
material must be replaced or efficiency will significantly decrease
(Hylander and Simán, 2001). Results of present study are basically
in agreement with these statements.