Pharmaceutical depletion from nutrient solution
Fig. 1shows the removal efficiencies of the selected pharma-ceuticals from nutrient solutions enriched at a concentration of
0.5 mg L
1
. Nearly all of the caffeine, naproxen and diclofenac were
eliminated from solution, whereas carbamazepine and clofibric
acid showed relatively low removal efficiencies at 54e64% and 41e
73%, respectively. Furthermore, nearly half or more of all of the
selected pharmaceuticals were rapidly removed from solution
during the initial 7 d period. In particular, more than 80% of the
total mass of caffeine, naproxen and diclofenac was eliminated
within thefirst 3 d.
A linear correlation between the removal efficiencies of the
tested pharmaceuticals (except caffeine) and exposure time was
observed. Moreover, this elimination process followedfirst-order
kinetics. Details on thefitted first-order rate equations and the
volumetric decay rate constantkvare presented inFig. 1. The values
of the volumetric decay rate constant (d
1
) were obtained by using
linear regression of ln (Ce/C0) versus exposure time, and were
0.0228, 0.1901, 0.1224, 0.0648 and 0.4026 d
1
for carbamazepine,
naproxen, diclofenac, clofibric acid and caffeine, respectively