Wang J.Z. and R.S. Summers (1996) Biodegradation Behavior of Ozonated
Natural Organic Matter in Sand Filters. Rev. Sci. Eau 9 (1) : 3-16.
[article in English]
Communication presented at the International Symposium Matière
Organique Biodégradable, École Polytechnique de Montréal,
Natural organic matter (NOM) in drinking water is a complex mixture of organic
compounds. Some of the compounds are not biodegradable, while others are quickly
biodegradable and a third group is more resistant to biodegradation. To have
a better understanding of the biofiltration process in drinking water treatment,
it is important to identify the elements of the quickly and slowly biodegradable
NOM and to characterize the biodegradation rate of each element. In this study,
an ozonated NOM solution was used as the substrate. The NOM was isolated from
a groundwater in Germany using ion-exchange resins. The ozone dose was 0.35
mg O3/mg DOC (dissolved organic carbon). Previously bioacclimated sand was
used as filter media and biomass source and was homogeneously distributed in
the filter prior to each run. The substrate removal was evaluated by DOC, biodegradable
DOC (BDOC), assimilable organic carbon (AOC), aldehyde and ketoacid analyses.
When expressed in terms of the empty bed contact time (EBCT), the results showed
that filter velocity in the range of 1.5 to 15 m/hr had no impact on substrate
removal. This implies that substrate utilization, not external mass transfer,
is the rate limiting step for substrate removal in drinking water biofilters.
In this study, compounds or NOM fractions are termed quickly biodegradable
if they are removed in the first three minutes of EBCT. 15% of the DOC was
removed by the biofilter within three minutes of EBCT and was termed the quickly
biodegradable fraction. The BDOC fraction of the ozonated solution was determined
to be 40 to 45% of the DOC. In terms of BDOC, about one third of the total
BDOC was quickly biodegradable. The AOC results show that about 90% of the
total AOC was utilized by Spirillum sp. NOX (AOC-NOX). Most of the AOC
was quickly biodegradable and was removed within one minute of EBCT. For aldehydes,
glyoxal and methyl glyoxal were removed to below the detection limit after
two minutes of EBCT. However, only 60% of formaldehyde removal was achieved
in the first two minutes of EBCT, and no additional removal was achieved with
increasing EBCT. Additionally, no significant removal of acetaldehyde was observed.
The results of ketoacids show that their utilization rates were very high.
More than 90% of glyoxylic acid and pyruvic acid were removed within one minute
Biological filtration, biodegradation, ozonation, natural organic matter
(NOM), biodegradable dissolved organic carbon (BDOC), assimilable organic carbon
Jack Z. Wang, Louisville Water Company, Louisville, KY 40202, USA