OxyFile #486

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.