decrease after the 3rd day of measurement. For the porous
concretes with 5 to 10 mm aggregate size, T-P for the porous
concrete with P/G of 30% decreased to 0.02 mg/l at the 7th
day recording (96% reduction); T-P for the porous concrete
with P/G of 40% dropped to 0.15 mg/l at the 11th day
recording (72% reduction) and T-P for the porous concrete
with P/G 50% went down to 0.178 mg/l at the 14th day
recording (66% reduction). However, the T-P increased
above the initial T-P of 0.53 mg/l starting at the 7th and
11th days of measurement. The reversion may be due to the
fact that (1) the capacity of removing microorganisms
attached to the porous concrete reached a limit within a
short period of time because the water was circulated within
the confined water purification channel or (2) the microorganisms
could not be activated anymore due to the lack of
dissolved oxygen depleted by fast growing bio-film facilitated
by abundant phosphate, a nutrient for the aquatic
microbes. The relationships among the P/G, aggregate size
and the T-P are displayed in Fig. 10. In general, the porous
concrete with 5 to 10 mm aggregate size showed 1.7 times
higher removal capacity than the one with 10 to 20 mm
aggregate size. As for the T-P removal capacity according to
P/G, the amount of phosphate removed by the porous