ABSTRACT
Natural
Organic Matter (NOM) is a mixture of aromatic and aliphatic organic compounds
of natural origin in any type of aquatic system. Human activities impact the
constituents of NOM, from its production to its fate, particularly in the treatment
of domestic waste waters. In this work, the impact of microorganisms isolated
from a Waste Water Treatment Plant (WWTP) was investigated to determine the
fate of NOM fractions in raw sewage, using fluorescence spectroscopy. Wastewater
samples were taken at three different times from a WWTP, and incubated for 4
days under two treatments: 1) “raw sewage”, and 2) “spiked”, i.e., the same raw sewage, spiked with
bacteria previously isolated from the WWTP. The incubated waters were analyzed
by fluorescence spectroscopy, digitally resolved into NOM components: humic-
and fulvic-like, and two types of protein-like, i.e., tryptophan- and tyrosine-like, using a Parallel Factor
Analysis routine (PARAFAC). The results demonstrate that the “spiked” samples
showed the largest changes with incubation time. The signals of the tryptophan-
and tyrosine-like components decreased, suggesting a net microbial digestion of
proteinaceous material. In contrast, the fulvic-like signals, and to some
extent, the humic-like signals increased, suggesting the production of the
associated molecular materials during the incubation period. This study
provides direct evidence of human impact on the make-up of NOM: the cultures
of microbes found at a WWTP consume the proteinaceous material, whereas
humic-like and fulvic-like materials are produced.