Preliminary Results on the Ozonation and Biodegradability of
Anionic Surface Agents of Municipal Wastewaters
F.J. Beltrán, J.F García, P. Alvarez, L.A. Fernández(1)
Chemical Engineering and Energetic Deparment. Extremadura
University, Badajoz Spain.
1 – Ozone Research Center, Cuba.
Commercial surface agents or surfactants constitute an important
fraction of organic content of municipal wastewater. They are
harmful for aquatic life and specially undesirable as far as the
reuse of treated wastewater is concerned. Presently, anionic
surfactants form the group of surface agents of highest
application due to their biodegradable character. Thus, among
this group one can highlight both the alkyl benzene sulphonates,
like ABS and LAS the latter characterized by their linear chain.
In spite of their high biodegradability, these compounds are not
completely removed in wastewater treatment plants because of the
high hydraulic residence time they need. In this work the chemical
oxidation of ozone as alternative to degrade sodium sulphate
dodecylbenzene (possibly the most representative anionic detergent
of the ABS group) is studied. Best conditions achieved correspond
to pH 11 in distilled water (after 30 min 82 % conversion of
surfactant is obtained with 100 mg/L of ozone dose). In wastewater
however conversion has a significant decrease (only 27.5 %) at the
same conditions likely due to the competitive effects of other
substances for ozone and hydroxyl radicals generated. On the
other hand, the influence of preozonation on the biological
oxidation of the surfactant in conventional activated sludge
system has also been studied. Best results in this case are
reached after 4 weeks and with 100 mg/L of ozone dose. At these
conditions and starting with 1500 mg/L VSS in prepared wastewater
(300 mg/L COD) batch mode after 12 hours biological oxidation
performance of surfactants increased about 35.7 % with respect to
the non ozonated treatment.
Source: 2nd International Symposium on Ozone Applications
Havana, Cuba – Mach 24-26, 1997.