An artificial waste water containing phenanthrene and Tween 80(x) was
treated in the horizontal-vertical flow macrophyte-based treatment sys
tem. The pilot plant consisted of a cascade of five steel tanks filled
with lava, each tank planted with Typha spp, and Scirpus lacustris. T
he overall removal of phenanthrene in water was about 99.9%. Adsorptio
n of phenanthrene was primarily observed in the upper lava layer. 1-Hy
droxy-2-naphthoic acid (HNA) as a bacterial metabolite of phenanthrene
was quantified. An MPN(most probable number)-method for the enumerati
on of phenanthrene-degrading bacteria was modified by staining degrada
tion products formed in the culture media with diazonium salts. The nu
mber of phenanthrene-degrading bacteria was highest in the first tank
of the cascade. The number of total bacteria remained nearly constant
within the cascade. The amount of bacteria in lava exceeded that in wa
ter by a factor of 10(3). The number of phenanthrene-degrading bacteri
a in lava samples in a phenanthrene-loaded tank was approximately 10(6
) g(-1), and 10(2) g(-1) in a non-loaded tank. Furthermore, tracer exp
eriments were conducted in 1993 and 1994. The mean residence time was
determined to be 1.18 days (1993) and 1.15 days (1994) in the first ta
nk, and 6.66 days (1993) and 6.4 days (1994) in the whole cascade. The
experimental values agreed approximately with the theoretical values
of 1.27 days and 6.54 days. The Peclet numbers agreed with those of th
e dispersion characteristic of the lava filling as a porous medium. (C
) 1997 Elsevier Science Ltd.