Potentials of biological oxidation processes for the treatment of spent sulfidic caustics containing thiols.
This research focused on the biological treatment of sulfidic spent caustics from refineries, which contain mainly hydrogen sulfide, methanethiol (MT) and ethanethiol (ET). Also various organic compounds can be present such as BTEX. Biological oxidation of 2.5 mM MT in batch experiments occurred after MT was first auto-oxidized into dimethyldisulfide (DMDS) whereafter oxidation into sulfate was completed in 350 h. DMDS as sole substrate was completely oxidized within 40 h. Therefore, DMDS formation seems to play an important role in detoxification of MT. Biological oxidation of ET and buthanethiol was not successful in batch experiments. Complete oxidation of MT and ET was observed in flow-through reactor experiments. Simultaneous oxidation of sulfide and MT was achieved when treating a synthetic spent caustic, containing 10 mM sulfide and 2.5 mM MT, in a bubble column reactor with carrier material at a hydraulic retention time of 6 h. Addition of 7.5 mM phenol, a common pollutant of spent caustics, did not adversely affect the biological oxidation process and phenol was completely removed from the effluent. Finally, three different spent caustics solutions from refineries were successfully treated.
Sipma
Jan
J
Sub-Department of Environmental Technology, Wageningen University, Bomenweg 2, P.O.Box 8129, 6700 EV Wageningen, The Netherlands.
Svitelskaya
Anna
A
van der Mark
Bart
B
Pol
Look W Hulshoff
LW
Lettinga
Gatze
G
Buisman
Cees J N
CJ
Janssen
Albert J H
AJ
D001673:Biodegradation, Environmental; D018533:Biomass; D019149:Bioreactors; D002424:Caustics / Q000302:isolation & purification* / Q000378:metabolism*; D007220:Industrial Waste; D010084:Oxidation-Reduction; D013438:Sulfhydryl Compounds / Q000302:isolation & purification* / Q000378:metabolism*; D014872:Water Movements
D002424:Caustics; D007220:Industrial Waste; D013438:Sulfhydryl Compounds; C005231:methylmercaptan; C007638:ethanethiol