Chemical treatment of an anionic surfactant wastewater: Electrospray-MS studies of intermediates and effect on aerobic biodegradability.
The effect of wet air oxidation on the aerobic biodegradability of a model wastewater containing 1000 mg L(-1) of linear alkylbenzene sulfonate (LAS) has been investigated. Semibatch oxidation experiments were performed temperature of 473 K, oxygen partial pressure of 1.3 MPa and residence times varying from 40 to 390 min, while continuous oxidation experiments were performed at a residence time of 120 min. Oxygen uptake tests were performed to assess the aerobic biodegradability of both the oxidised and the original LAS solutions using cultures that had been adapted to both LAS and oxidation intermediates. The concentration of total organic carbon, chemical oxygen demand and active detergent were followed throughout the wet oxidation and biodegradation experiments, while the main intermediates formed during wet oxidation were identified by means of Electrospray-MS and high performance liquid chromatography. It was found that LAS could be easily oxidised at 473 K to yield a group of molecules with short alkyl chains which do not behave as active detergents. Sulfonated aromatics are produced as intermediates which have had the alkyl chains shortened. The segments of alkyl chains broken off the intermediate compounds appear primarily as short chain organic acids. The original unoxidised 1000 mg L(-1) LAS solution was found to be readily biodegradable in the laboratory aerobic reactors operating at low organic loadings and substrate to microorganism concentration ratios. However, wet oxidation resulted in effluents that were less readily biodegradable than the original LAS with biodegradability decreasing with increasing degree of oxidation. These results suggest that, at the conditions under consideration, a combined chemical pre-oxidations and biological post-treatment process may be less effective in removing LAS than a single-stage biological or chemical process.
Mantzavinos
D
D
Department of Chemical Engineering, University of Leeds, UK.
Burrows
D M
DM
Willey
R
R
Lo Biundo
G
G
Zhang
S F
SF
Livingston
A G
AG
Metcalfe
I S
IS
D000332:Aerobiosis; D017738:Alkanesulfonic Acids / Q000737:chemistry; D000838:Anions / Q000737:chemistry* / Q000378:metabolism; D001673:Biodegradation, Environmental; D019149:Bioreactors; D003247:Conservation of Natural Resources; D006863:Hydrogen-Ion Concentration; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism; D021241:Spectrometry, Mass, Electrospray Ionization; D013501:Surface-Active Agents / Q000737:chemistry* / Q000378:metabolism; D013997:Time Factors; D018508:Water Purification / Q000379:methods*
D017738:Alkanesulfonic Acids; D000838:Anions; D013501:Surface-Active Agents; C030641:alkylbenzyl sulfonic acid; D010100:Oxygen