5.6. T-P (mg/l) and T-N (mg/l) measurements
In the water purification test, the T-P (total phosphorus)
and T-N (total nitrogen), which are the major elements
causing eutrophication, were also measured. For T-P measurement,
the Ascorbic Acid Method [6] was used. A
standard PO4 solution was prepared and a calibration curve
was derived through measuring the absorbance of the solution
at an 880-nm wavelength. The absorbance of the
sampled test water according to dates was measured to