Biodegradability of linear alkylbenzene sulfonates subjected to wet air oxidation (original) (raw)
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Journal of Hazardous Materials, 2007
Wet air oxidation (WAO) and catalytic wet air oxidation (CWAO) were investigated as suitable precursors for the biological treatment of industrial wastewater containing sodium dodecylbenzene sulfonate (DBS). Two hours WAO semi-batch experiments were conducted at 15 bar of oxygen partial pressure (P O 2 ) and at 180, 200 and 220 • C. It was found that the highest temperature provides appreciable total organic carbon (TOC) and chemical oxygen demand (COD) abatement of about 42 and 47%, correspondingly. Based on the main identified intermediates (acetic acid and sulfobenzoic acid) a reaction pathway for DBS and a kinetic model in WAO were proposed. In the case of CWAO experiments, seventy-two hours tests were done in a fixed bed reactor in continuous trickle flow regime, using a commercial activated carbon (AC) as catalyst. The temperature and P O 2 were 140-160 • C and 2-9 bar, respectively. The influence of the operating conditions on the DBS oxidation, the occurrence of oxidative coupling reactions over the AC, and the catalytic activity (in terms of substrate removal) were established. The results show that the AC without any supported active metal behaves bi-functional as adsorbent and catalyst, giving TOC conversions up to 52% at 160 • C and 2 bar of P O 2 , which were comparable to those obtained in WAO experiments. Respirometric tests were completed before and after CWAO and to the main intermediates identified through the WAO and CWAO oxidation route. Then, the readily biodegradable COD (COD RB ) of the CWAO and WAO effluents were found. Taking into account these results it was possible to compare whether or not the CWAO or WAO effluents were suitable for a conventional activated sludge plant inoculated with non adapted culture.
Journal of Xenobiotics, 2011
Aerobic biodegradation of linear alkylbenzene sulfonate (LAS) by LAS-utilizing bacteria (LUB) in the presence of other sources of carbon (glucose and soluble starch) was examined. Biodegradation of LAS was monitored as primary degradation in terms of half-life (t½) of the surfactant. Biodegradation of LAS by the individual LUB was slower in the presence of Glucose. Biodegradation of the surfactant by the various consortia of LUB was slower in the presence of the carbon sources: t½ increased to 3 days. The rates of biodegradation by the consortia can be ranked as: four-membered (t½=9 days) > three-membered (t½=9 to 13 days) > two-membered consortia (t½=10 to 15 days). Generally, degradation in the presence of the carbon sources was faster with the consortia than the individual species. Degradation of the surfactant by the LUB was generally fastest in the absence of additional carbon sources. The possible role of additional carbon sources in pe...
Biodegradation of Coproducts of Commercial Linear Alkylbenzene Sulfonate
Environmental Science & Technology, 1997
Dialkyltetralin sulfonate (DATS) and single methyl-branched isomers of linear alkylbenzene sulfonate (iso-LAS) are coproducts that together can range from 1 to 10% of commercial LAS depending on the manufacturing process. Biodegradation studies using radiolabeled DATS and iso-LAS showed mineralization by indigenous microbial populations in laboratory simulations of aquatic and soil environments. Half-lives ranged from 2 to 20 days, which is rapid enough to suggest that accumulation would not occur in these environments. Upon exposure to laboratory activated sludge treatment, most model iso-LAS compounds showed greater than 98% parent compound removal, extensive mineralization (>50%), and 79-90% ultimate biodegradation (mineralization plus conversion to biomass). Activated sludge treatment of DATS and one of the iso-LAS isomers (methyl group attached to the benzylic carbon of the alkyl chain) resulted in >98% removal, 3-12% ultimate biodegradation and apparent formation of carboxylated biodegradation intermediates that accounted for 88-97% of the original material. These DATS and iso-LAS biodegradation intermediates continued to mineralize in simulated receiving water and soil environments at rates similar to that of sulfophenyl carboxylate (SPC) intermediates of a standard LAS.
International Journal of Photoenergy, 2005
The effects of the photochemical pre-treatment by using a pilot-plant UV/H 2 O 2 process on the biodegradability of aqueous linear alkylbenzene sulfonate (LAS) were studied. It was observed that the photochemical pre-treatment of the LAS solutions by UV-254/H 2 O 2 increased the biodegradability of LAS solutions. Aqueous solutions with higher concentrations of LAS (> 100 mg/L) were non-biodegradable. The ratio of BOD 5 /COD of the pre-treated LAS solutions was increased, indicating that the pre-treated LAS solutions were more biodegradable. This ratio was improved as the LAS solutions were more pre-treated. Also, the biodegradability factor for the pre-treated LAS solutions was increased as the time of the photochemical pre-treatment was increased.
Biodegradation of linear alkylbenzene sulfonates in sulfate-leached soil mesocosms
Chemosphere, 2003
Surface active agents (surfactants) are chemical compounds which are massively used as raw material in detergent production. Synthetic type surfactants are often used because they perform better and more economical compared to natural detergents. Linear Alkyl Benzene Sulfonate (LAS) is one of synthetic surfactants that is widely used. Although LAS is biodegradable, its introduction to the environment in big amount harms the water bodies. Research on biodegradation of LAS with 100 ppm, 400 ppm, 700 ppm, 1000 ppm and 1500 ppm concentrations was conducted by using consortium of bacteria comprises of Pseudomonas aeroginosa, Bacillus subtilis, Bacillus aglomerans, Bacillus cereus, Bacillus alvae. Experiments were carried out in twelve days, in 29 o C temperature with initial total inoculum bacteria 1,59 x 10 8 CFU/mL. Results showed that this type of bacterial consortium could live until 1500 ppm in LAS environment. However, significant growth rate did not occurr, 0.039 -0.042 hour -1 and not too efficiently reduce Chemical Oxygen Demand (COD) for those systems. Surface tension in several variated concentration of LAS: 0 ppm >100 ppm >400 ppm >700 ppm, LAS 700 ppm = 1000 ppm = 1500 ppm.
Wet Air Oxidation of Aqueous Solutions of Linear Alkylbenzene Sulfonates
Industrial & Engineering Chemistry Research, 2000
The semibatch wet air oxidation of aqueous solutions of linear alkylbenzene sulfonate (LAS), an anionic surfactant, has been investigated at temperatures of 453 and 473 K, total pressures of 2.8 and 3.3 MPa, and reaction times varying from 40 to 390 min. The concentration of total organic carbon, chemical oxygen demand, and active detergent were followed throughout the reaction, the main intermediates formed were identified by means of electrospray-MS and highperformance liquid chromatography, and a mechanism describing LAS oxidation was proposed. It was found that LAS could easily be oxidized at 473 K to yield a group of molecules with short alkyl chains that do not behave as active detergents. The segments of alkyl chains broken off the reaction intermediates appear primarily as short-chain organic acids that are resistant to total oxidation. Oxidation experiments were also performed at 473 K with solutions of 4-hydroxybenzene sulfonic acid, an intermediate formed during the oxidation of LAS. It was found that 4-hydroxybenzene sulfonic acid could easily be oxidized. Figure 7. Principal reaction pathways for the oxidation of LAS. Xn ) (CH2)nC6H4SO3 -. For Ri, i ) 1-4 with R1 ) CH3, R2 ) CH2-OH, R3 ) CHO, and R4 ) COOH.
Chemosphere, 2006
The degradation of linear alkylbenzene sulfonates and their degradation intermediates (sulfophenylcarboxylic acids) has been characterized at 9°C in an activated sludge pilot plant. After an adequate adaptation period (20 days), LAS primary degradation exceeds 99% and takes place preferentially for long alkyl chain homologues and external isomers. LAS homologues in the reactor are preferentially sorbed onto particulate matter, while sulfophenylcarboxylic acids (SPCs) are present predominantly in solution, due to their lower hydrophobicity. During the adaptation period the most abundant LAS biodegradation intermediates were long chain sulfophenylcarboxylic acids (SPCs) (C 9 -C 13 SPC). However once this system is fully adapted, the microorganisms are capable of degrading SPCs efficiently. SPCs with 7-9 carbon atoms in the carboxylic chain predominate due to their degradation being slower than for the rest of the SPCs. The presence of C 13 SPC confirms that LAS degradation in wastewater starts with a x-oxidation on the alkylic chain. A preferential degradation of SPC isomers of the types 2/C n SPC to 6/C n SPC was also detected, as shown by the relatively higher SPC concentrations of the remaining ones.
Effect of temperature on the biodegradation of linear alkylbenzene sulfonate and alcohol ethoxylate
Journal of Surfactants and Detergents, 2006
The effect of temperature on the biodegradation of linear alkylbenzene sulfonate (LAS) and alcohol ethoxylate (AE) was evaluated using method OECD 303 A, Confirmatory test (Husmann units). The experiments were performed using an initial surfactant concentration of 10 mg/L and working temperatures of 25, 15, and 9°C, keeping the biodegradation units inside a thermostatic chamber. In all cases, the removal of both surfactants tested, LAS and AE, was higher than 90%, regardless of the temperature used in the test. We observed that longer acclimation periods were needed by the microorganisms at lower temperatures.
Biodegradation of Linear Alkylbenzene Sulfonates and Their Degradation Intermediates in Seawater
Environmental Science & Technology, 2004
A bacterial consortium capable of degrading the linear alkylbenzene sulfonate (LAS) was isolated from the wastewater treatment plant. The bacterial consortium consisted of two members, Pantoea agglomerans and Serratia odorifera 2. Cells were grown evenly together in a minimal medium (M9) and nutrient broth (NB). The bacterial consortium was able to grow in the minimal medium containing LAS as the only carbon source. The percentage degradation of 200 ppm LAS by this bacterial consortium was better when cells were grown in NB (∼70%) than in the M9 medium (36%). Also, the degradation ability by the bacterial consortium was very much higher than by its individual cells. This work shows that the two bacteria complement each other in the degrading ability of LAS, indicating catabolic cooperation between the two consortium members. An incubation temperature of 32 • C, an agitation rate of 250 rev min −1 , and the addition of different carbon and nitrogen sources all independently caused complete mineralization of 200 mg L −1 LAS within 48-72 h.