Biodegradation of linear alkylbenzene sulfonates and their degradation intermediates in seawater

Exploring the potential of bacterial-augmented floating treatment wetlands for the remediation of detergent-contaminated water

Due to industrialization and urbanization, the use of detergents inadvertently led to contamination of aquatic environments, thus posing potential threat to aquatic organisms and human health. One of the main components of detergents is linear alkylbenzene sulfonate (LAS), which can cause toxic effects on living organisms, particularly aquatic life in the environment. In this study, floating treatment wetlands (FTWs) mesocosms were developed and augmented with LAS-degrading bacteria. The plant species, Brachiaria mutica (Para grass), was vegetated to establish FTWs and bacterial consortium (1:1:1:1) of Pseudomonas aeruginosa strain PJRS20, Bacillus sp. BRRH60, Acinetobacter sp. strain CYRH21, and Burkholderia phytofirmans Ps.JN was augmented (free or immobilized) in these mesocosms. Results revealed that the FTWs removed LAS from the contaminated water and their augmentation with bacteria slightly increased LAS removal during course of the experiment. Maximum reduction in LAS concentration (94%), chemical oxygen demand (91%), biochemical oxygen demand (93%), and total organic carbon (91%) was observed in the contaminated water having FTWs augmented with bacterial consortium immobilized on polystyrene sheet. This study highlights that the FTWs supported with immobilized bacteria on polystyrene sheets can provide an eco-friendly and sustainable solution for the remediation of LAS-bearing water, especially for developing countries like Pakistan.

Effects of internal hydrophilic groups of a newly developed sustainable anionic surfactant on biodegradability and ecotoxicity

Recently, a new sustainable anionic surfactant called bio-based internal olefin sulfonate (Bio IOS) has been developed. This surfactant enables excellent water solubility and high surface activity. It has a unique structure of long hydrophobic alkyl chains (C16 to C18) with two types of hydrophilic groups in its midsection, which distinguish it from other conventional anionic surfactants. However, the effects of the specific structural features of the surfactant on its environmental properties and the consequent effects on the environment remain unclear. In this study, we investigated the environmental fate and ecotoxicity of Bio IOS and the effects of the types and positions of hydrophilic groups on biodegradability and ecotoxicity. Biodegradation studies demonstrated that Bio IOS was readily biodegradable with >99.5% removal in wastewater treatment activated sludge (test concentration: 1 mg/L) and a fast half-life of 5.8 h in river water (test concentration: 10 μg/L); the excellent biodegradability was likely due to the high water solubility attributed to the internal hydrophilic groups. Meanwhile, moderately toxic effects were observed, whereby the 50% lethal and effect concentrations of the three freshwater species were above 1 mg/L. Ecotoxicity studies with different types and positions of hydrophilic groups revealed that hydroxyalkane sulfonate was less toxic and that toxicity was reduced in the presence of more internally located hydrophilic groups. These findings suggest that the hydroxyl group and the internal positions of hydrophilic groups that constitute the molecular configuration resembling two separate shorter alkyl chains may reduce the adverse effects on organisms despite the long alkyl chains.

Distribution and diagenetic fate of synthetic surfactants and their metabolites in sewage-impacted estuarine sediments

Surfactants are high production volume chemicals used in numerous domestic and industrial applications and, after use, the most abundant organic contaminants in wastewater. Their discharge might jeopardize the receiving aquatic ecosystems, including sediments, where they tend to accumulate. This is the first comprehensive study on their distribution and fate in this environmental compartment as we performed simultaneous analysis of the three main classes of surfactants (anionic: LAS; nonionic: NPEO and AEO; cationic: DTDMAC, DADMAC, BAC, and ATMAC) and some of their transformation products (SPC, NP, NPEC, and PEG). To account for spatial and time trends, surface sediments and dated cores were collected from Jamaica Bay, a heavily sewage-impacted estuary in New York City. The concentrations of surfactants in surface sediments were between 18 and > 200 μg g^-1 and showed slight variation (<10%) over different sampling years (1998, 2003 and 2008). Cationic surfactants were found at the highest concentrations, with DTDMAC accounting for between 52 and 90% of the total sum of target compounds. Vertical concentration profiles in dated cores from the most contaminated station, in the vicinity of the biggest local sewage treatment plant (STP), indicated two sub-surface surfactant peaks in the mid-1960s (469 μg g^-1) and late 1980s (572 μg g^-1) coinciding with known STP upgrades. This trend was observed for most target compounds, except for DADMAC, C22ATMAC, and PEG, which showed a continuous increase towards the top of the cores. In-situ degradation was studied by comparing sediment core samples taken 12 years apart (1996 and 2008) and revealed a net decrease in PEG and specific surfactants (BAC, ATMAC, NPEO, and AEO) accompanied by growing concentrations of metabolites (SPC, NP, and NPEC). DTDMAC, DADMAC, and LAS, however, remained stable over this period, suggesting recalcitrant behavior under the anaerobic conditions in Jamaica Bay sediments.

MAIN FINDING

Chronology of major synthetic surfactants are illustrated in the dated sediment cores, as well as their different diagenetic fates.

Evaluation of the anaerobic biodegradation of linear alkylbenzene sulfonates (LAS) using OECD 308 water/sediment systems

Linear alkylbenzene sulfonates (LAS) are the most widely used anionic surfactants in household detergents and cleaning products. We have evaluated LAS anaerobic degradation in sediments following OECD 308 guidelines. Four different classes of sediments were collected from non-polluted areas and tested to check the influence of: fine and coarse texture, low and high organic carbon content, and freshwater and marine origin. The concentrations of LAS and possible degradation metabolites in sediment and water phases were monitored by high resolution mass spectrometry over an incubation period of 160 days. LAS removal was between 0 and 63%, depending on the sediment used, and it was accompanied by formation of sulfophenyl carboxylic acids (SPCs). The best results were observed for marine sediments having low organic carbon and silt + clay contents (0.5% and 13%, respectively), whereas degradation was negligible in freshwater sediments. The large differences in degradation observed across the sediments tested were attributed to their physicochemical properties influencing LAS bioavailability and the heterogeneity of microbial communities. Further research is also needed to address some shortcomings observed during the application of the OECD 308 and to ensure that test results obtained with these guidelines model anaerobic biodegradation under realistic environmental conditions.

Effects of extreme rainfall events on the distribution of selected emerging contaminants in surface and groundwater: The Guadalete River basin (SW, Spain)

This study is focused on the Guadalete River basin (SW, Spain), where extreme weather conditions have become common, with and alternation between periods of drought and extreme rainfall events. Combined sewer overflows (CSOs) occur when heavy rainfall events exceed the capacity of the wastewater treatment plants (WWTP), as well as pollution episodes in parts of the basin due to uncontrolled sewage spills and the use of reclaimed water and sludge from the local WWTP. The sampling was carried out along two seasons and three campaigns during dry (March 2007) and extreme rainfall (April and December 2010) in the Guadalete River, alluvial aquifer and Jerez de la Frontera aquifer. Results showed minimum concentrations for synthetic surfactants in groundwater (<37.4μg·L^-1) during the first campaign (dry weather conditions), whereas groundwater contaminants increased in December 2010 as the heavy rainfall caused the river to overflow. In surface water, surfactant concentrations showed similar trends to groundwater observations. In addition to surfactants, pharmaceuticals and personal care products (PPCPs) were analyzed in the third campaign, 22 of which were detected in surface waters. Two fragrances (OTNE and galaxolide) and one analgesic/anti-inflammatory (ibuprofen) were the most abundant PPCPs (up to 6540, 2748 and 1747ng·L^-1, respectively). Regarding groundwater, most PPCPs were detected in Jerez de la Frontera aquifer, where a synthetic fragrance (OTNE) was predominant (up to 1285ng·L^-1).

Degradation kinetics of pharmaceuticals and personal care products in surface waters: photolysis vs biodegradation

Poor removal of many pharmaceuticals and personal care products (PPCPs) in sewage treatment leads to their discharge into the receiving waters, where they may cause negative effects. Their elimination from the water column depends of several processes, including photochemical and biological degradation. We have focused this research on comparing the degradation kinetics of a wide number (n=33) of frequently detected PPCPs considering different types of water, pH and solar irradiation. For those compounds that were susceptible of photodegradation, their rates (k) varied from 0.02 to 30.48h^-1 at pH7, with the lowest values for antihypertensive and psychiatric drugs (t_1/2>1000h). Modification of the pH turned into faster disappearance of most of the PPCPs (e.g., k=0.072 and 0.066h^-1 for atenolol and carbamazepine at pH4, respectively). On the other hand, biodegradation was enhanced by marine bacteria in many cases, for example for mefenamic acid, caffeine and triclosan (k=0.019, 0.01 and 0.04h^-1, respectively), and was faster for anionic surfactants. Comparing photodegradation and biodegradation processes, hydrochlorothiazide and diclofenac, both not biodegradable, were eliminated exclusively by irradiation (t_1/2=0.15-0.43h and t_1/2=0.14-0.17h, respectively). Salicylic acid and phenylbutazone were efficiently photo (t_1/2<3h) and biodegraded (t_1/2=116-158h), whereas some compounds such as ibuprofen, carbamazepine and atenolol had low degradation rates by any of the processes tested (t_1/2=23-2310h), making then susceptible to persist in the aquatic media.

Distribution of anionic and nonionic surfactants in a sewage-impacted Mediterranean coastal lagoon: inputs and seasonal variations

In this work we have monitored the seasonal inputs, occurrence and distribution of the world's most widely used surfactants (linear alkylbenzene sulfonates, LAS, nonylphenol polyethoxylates, NPEOs, and alcohol polyethoxylates, AEOs) in Mar Menor lagoon (SE Spain) and its main tributary (El Albujón) for the first time. Concentration of target compounds was determined in both surface waters and sediments after solid phase extraction and pressurized liquid extraction, respectively, followed by liquid chromatography-mass spectrometry (LC-MS). There were significant differences in surfactant fluxes from El Albujón towards Mar Menor depending on the season and the day of the week, with maximum estimated annual inputs being detected for LAS (406 kg) and their metabolites, sulfophenyl carboxylic acids (482 kg). Average concentrations of surfactants in the lagoon were between 44 and 1665 μg/kg in sediment, and between 0.3 and 63 μg/L in water. These levels were significantly higher for samples collected near the shore than for those measured inside the lagoon itself. Overall, the occurrence and distribution of surfactants in the system could be explained due to a combination of different sources (surface and groundwater inputs, treated and untreated wastewater effluents, towns, ports, etc.) and simultaneous in-situ physicochemical and biological processes, with an special emphasis on degradation during warmer months.

Phosphorylation of histone H2AX generated by linear alkylbenzene sulfonates and its suppression by UVB exposure

We previously demonstrated that the nonionic surfactants, nonylphenol polyethoxylates (NPEOs) induced the phosphorylation of histone H2AX (γ-H2AX), accompanied by DNA double-strand breaks (DSBs), and that exposure to ultraviolet (UV) degraded NPEOs, which sometimes enhanced their DNA-damaging ability. In this study, we showed that linear alkylbenzene sulfonates (LAS), general anion surfactants, also generated DSBs with γ-H2AX, and this ability was attenuated by UVB exposure. In the human breast adenocarcinoma cell line, MCF-7, γ-H2AX was generated in a dose-dependent manner immediately after cells were treated with LAS, and this was attributed to the formation of DSBs and was independent of cell cycle phases. The ability to generate γ-H2AX was markedly reduced in LAS exposed to UVB. HPLC analysis revealed that LAS were a mixture of various alkyl chain lengths, the peaks of which were detected at individual retention times. UVB evenly decreased all peaks of LAS, without migration of peaks to other retention times, which indicated that UVB may degrade the benzene ring of LAS, but did not shorten the alkyl chains. UVB is an important environmental factor in the degradation of LAS exhibiting the ability to induce DSBs, the most serious type of DNA damage.

Degradation of surface-active compounds in a constructed wetland determined using high performance liquid chromatography and extraction spectrophotometry

Degradation of anionic and nonionic surfactants in a constructed wetland with horizontal subsurface flow was studied using high performance liquid chromatography and extraction spectrophotometry. The ratio of individual homologues of linear alkylbenzene sulfonates (LAS) and the efficiency of their removal were studied. Tridecyl-, dodecyl-, undecyl-, and decylbenzene sulfonates were removed with efficiencies of 92.9%, 84.3%, 64.7%, and 41.1%, respectively. These differences are due to sequential shortening of the alkyl chain in homologues during degradation (the higher homologue can provide the lower one). The formation of sulfophenyl carboxylic acids during ω-oxidation of the alkyl chain followed by successive α- and/or β-oxidation is also a possible mechanism for removal of LAS. Solid phase extraction using Chromabond® HR-P columns was used for preconcentration of the analytes prior to their determination by HPLC. Methylene blue active compounds were determined using extraction spectrophotometry. The average efficiency of their removal was 84.9% in this case. The efficiency of nonionic surfactant removal (98.2%) was significantly higher in comparison to that for anionic surfactants. The concentration of the endocrine disruptor nonylphenol (a product of nonylphenol polyethoxylate surfactant degradation) determined in the profile of the wetland was beneath the limit of detection (0.4 μg/L). The average outflow concentrations of anionic and nonionic surfactants determined by spectrophotometry were 0.54 and 0.021 mg/L, respectively. The average outflow concentrations of decyl- and tridecylbenzene sulfonates determined by HPLC were 0.195 and 0.015 mg/L. Efficiencies of 86.4% and 92.2% were obtained for removal of organic compounds as indicated by chemical and biochemical oxygen demand (COD(Cr) and BOD(5)). These results demonstrate the suitability of the constructed wetland for degrading surface-active compounds.

Enantioselective degradation and unidirectional chiral inversion of 2-phenylbutyric acid, an intermediate from linear alkylbenzene, by Xanthobacter flavus PA1

Microbial degradation of the chiral 2-phenylbutyric acid (2-PBA), a metabolite of surfactant linear alkylbenzene sulfonates (LAS), was investigated using both racemic and enantiomer-pure compounds together with quantitative stereoselective analyses. A pure culture of bacteria, identified as Xanthobacter flavus strain PA1 isolated from the mangrove sediment of Hong Kong Mai Po Nature Reserve, was able to utilize the racemic 2-PBA as well as the single enantiomers as the sole source of carbon and energy. In the presence of the racemic compounds, X. flavus PA1 degraded both (R) and (S) forms of enantiomers to completion in a sequential manner in which the (S) enantiomer disappeared much faster than the (R) enantiomer. When the single pure enantiomer was supplied as the sole substrate, a unidirectional chiral inversion involving (S) enantiomer to (R) enantiomer was evident. No major difference was observed in the degradation intermediates with either of the individual enantiomers when used as the growth substrate. Two major degradation intermediates were detected and identified as 3-hydroxy-2-phenylbutanoic acid and 4-methyl-3-phenyloxetan-2-one, using a combination of liquid chromatography-mass spectrometry (LC-MS), and (1)H and (13)C nuclear magnetic resonance (NMR) spectroscopy. The biochemical degradation pathway follows an initial oxidation of the alkyl side chain before aromatic ring cleavage. This study reveals new evidence for enantiomeric inversion catalyzed by pure culture of environmental bacteria and emphasizes the significant differences between the two enantiomers in their environmental fates.

LAS degradability by marine biofilms derived from seawater in Spain and Sweden

Marine biofilms were established on glass beads with or without deliberate pre-exposure to LAS (20 μg/L) in Spain (Cadiz) and Sweden (Kristineberg). The ability of each community to mineralize LAS (100 μg/L) was then assessed in biometers at four experimental temperatures (between 6 and 21°C). Genetic diversity and biomass of the biofilms were assessed by genetic fingerprinting (DGGE) and direct bacterial counts. With biofilms from Sweden, where LAS was not detected in seawater (n = 3), deliberate pre-exposure to LAS resulted in lower genetic diversity and higher mineralization rate constant; however, with biofilms from Spain, where 6.4 ± 3.9 μgLAS/L (n = 3) was measured during the colonization, pre-exposure did not affect the bacterial community. Bacterial acclimation therefore appeared to have been induced at environmental concentrations < 6 μgLAS/L. Environmental pre-exposure was not a pre-requisite for featuring the full consortia of LAS degraders in the biometers. The mineralization rate was described using an Arrhenius equation at experimental temperatures within the typical annual range; however, they departed from this model below this range.

Linear alkylbenzene sulfonate (LAS) in water of Lake Dianchi--spatial and seasonal variation, and kinetics of biodegradation

For the purpose of elucidating the environmental characteristics of anion surfactants [linear alkylbenzene sulfonates (LAS)] in the water of Lake Dianchi, a sampling investigation in the field from October 2006 to July 2007 and a batch of biodegradation experiments in the laboratory were carried out. The results showed that concentrations of LAS ranged from 18.6 to 260.1 μg L(-1), and the average concentration was 52.6 μg L(-1) in Lake Dianchi. The highest concentrations of LAS were found in the Northwest region, and the distribution of LAS varied through seasons, with much lower concentrations in fall than in any other seasons. LAS can be primarily biodegraded by microorganisms in the lake water, and the percentage of degradation was >97% after 28 days. Biodegradation of LAS was well-fitted with the kinetic model presented in this paper, and the half-lives ranged from 3.2 to 16.3 days. Temperature, pH, and initial concentrations could affect the biodegradation of LAS, among which temperature was the major factor influencing on biodegradation of LAS in water of Lake Dianchi.

Aerobic biodegradation of linear alkylbenzene sulfonates and sulfophenylcarboxylic acids for different salinity values by means of continuous assays

Aerobic biodegradation of linear alkylbenzene sulfonates (LAS) and sulfophenylcarboxylic acids (SPCs) in water, at different salinity values, has been studied. Three experiments have been carried out employing a staircase model system with continuous dosage of LAS to the system and using concentrations of LAS of the same order as those detected in littoral waters receiving urban wastewater discharges. LAS biodegradation was observed to be almost complete (showing a great extent), and in all cases exceeds 98.4%. At the very low concentration values of LAS utilized in the experiments, no significant variations in the biodegradation of LAS due to the effect of the different salinity values assayed were observed. The biodegradation intermediates detected for all the cases were sulfophenylcarboxylic acids with carboxylic chains of between five and 13 carbon atoms. The detection of C13-SPC (which is only produced by C13-LAS) confirms the existence of omega-oxidation. The total disappearance of SPCs in all cases indicates that mineralization of LAS at the concentrations tested was complete.

Anaerobic degradation pathway of linear Alkylbenzene sulfonates (LAS) in sulfate-reducing marine sediments

Linear alkylbenzene sulfonates (LAS) are among the principal synthetic surfactants used worldwide. Their presence in the environment has been reported in a significant number of studies, and it has been generally assumed that LAS are not biotransformed in the absence of oxygen. However, laboratory experiments performed by our group using anoxic marine sediments have reported LAS degradation percentages that can reach up to 79% in 165 days. Here, we show for the first time the initial reaction metabolites (generated via fumarate addition to the LAS molecules), their biotransformation into sulfophenyl carboxylic acids (SPC), and the progressive degradation of these by successive beta-oxidation reactions. Advanced mass spectrometry has been used to carry out the identification of these compounds. This is the first time that an anaerobic degradation pathway for LAS is described, and these results represent a significant advance in understanding the final fate of these and other similar compounds in anoxic environments.

Exposure of the marine deposit feeder Hydrobia ulvae to sediment associated LAS

Linear Alkylbenzene Sulfonates (LAS) effects (mortality, egestion rate, behaviour) on the marine deposit feeder Hydrobia ulvae were assessed in whole-sediment and water-only systems. The results were combined with a bioenergetic-based kinetic model of exposure pathways to account for the observed toxicity. The 10-d LC50 value based on the freely dissolved fraction was 9.3 times lower in spiked sediment (0.152 +/- 0.001 (95% CI) mg/L) than in water-only (1.390 +/- 0.020 (95% CI) mg/L). Consequently, the actual 10-d LC50 value (208 mg/kg) was overestimated by the Equilibrium Partitioning calculation (1629 mg/kg). This suggests that the sediment associated LAS fraction was bioavailable to the snails. It could also be due to modifications in physiological parameters in absence of sediment, the organism natural substrate.

Influence of the hydrophilic moiety of anionic and nonionic surfactants on their aerobic biodegradation in seawater

The extent and kinetics of the primary biodegradation have been characterized for the most commonly-used surfactants, employing four homologues with the same alkyl chain: dodecyl ethoxy sulfate (C(12)AES), sodium dodecyl sulfate (SDS), dodecyl alcohol ethoxylate (C(12)AEO) and dodecyl benzenesulfonate (C(12)LAS). A brief acclimatization period has been required to enable an effective degradation of C(12)LAS and C(12)AES to take place, but this lag phase has not been detected for SDS and C(12)AEO. Primary biodegradation percentages at the end of these experiments were higher than 99%, showing a fast degradation rate in all cases (average half-life lower than 2 days). The secondary biodegradation of C(12)LAS was also monitored. C(12)LAS external isomers, which are predominant, are preferentially degraded by successive beta-oxidations, generating significant amounts of external even isomers of sulfophenylcarboxylic acid (SPC) (mainly 2,3PhiC(4,6)SPCs). In ontrast, internal isomers are converted into internal odd isomers of SPC (mostly 4,5PhiC(5,7)SPCs) by omega-oxidation followed by alpha-oxidation and/or beta-oxidations.

Equilibrium partitioning theory to predict the sediment toxicity of the anionic surfactant C(12)-2-LAS to Corophium volutator

The study of the effect of the sorption of linear alkylbenzene sulfonates (LAS) on the bioavailability to marine benthic organisms is essential to refine the environmental risk assessment of these compounds. According to the equilibrium partitioning theory (EqP), the effect concentration in water-only exposure will be similar to the effect concentration in the sediment pore water. In this work, sorption and desorption experiments with two marine sediments were carried out using the compound C(12)-2-LAS. The effect of the sediment sorption on the toxicity of benthic organisms was studied in water-only and in sediment bioassays with the marine mud shrimp Corophium volutator. In addition, three common spiking methods were tested for its application in the toxicity tests, as well as the stability of the surfactant during the water-only and sediment-water test duration. LC50 values obtained from water-only exposure showed a good correspondence with the pore water concentrations calculated from the sorption and desorption isotherms in the spiked sediments.

Aerobic biodegradation of polyethylene glycols of different molecular weights in wastewater and seawater

In order to distinguish between aerobic biodegradation of synthetic polymers in fresh and seawater, polyethylene glycols (PEGs) were systematically and comparatively investigated in inocula from municipal wastewater and seawater aquarium filters for the first time. The molecular weight (MW) of the PEGs, (HO(CH(2)CH(2)O)(n)H, n=3-1350) as representatives of water-soluble polymers, ranged from 250 to 57,800Da. The biodegradation was observed by removal of dissolved organic carbon and carbon dioxide production by applying standardized ISO and OECD test methods. Specific analyses using liquid chromatography mass spectrometry (LC-MS) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) were performed. All PEGs selected were completely biodegradable in freshwater media within 65d. PEGs with an MW up to 14,600Da have a similar degradation pathway which is characterized by gradual splitting of C(2)-units off the chain resulting in formation of short-chain PEGs. In artificial seawater media, full biodegradation of PEGs up to 7400Da required more time than in freshwater. PEGs with MW 10,300 and 14,600Da were only partially degraded whereas PEGs with MW 26,600 and 57,800Da were not degraded for a period of 135d. The biodegradation pathway of PEG 250 and PEG 970 in seawater is similar to that for freshwater. For PEGs having an MW from 2000 to 10,300Da, the degradation pathway in seawater differs from the pathway of the shorter PEGs.

The behaviour of linear alkyl benzene sulphonate under direct discharge conditions in Vientiane, Lao PDR

Direct discharge of untreated sewage to surface waters is a common practice in many parts of the world. However, relatively little is known about the behaviour of synthetic organic pollutants under these conditions. This paper describes a sampling campaign designed to track changes in water quality in a surface water system in Vientiane (Lao PDR) receiving significant quantities of untreated waste water. The study was based on following in-channel transport using a fluorescent tracer injected as a pulse, with a focus on the anionic surfactant linear alkylbenzene sulphonate (LAS) and ammonia. Water samples were collected at a number of stations with sampling times estimated to coincide with solute time-of-travel. The reduction in LAS concentration with flow-time could be approximated by first-order kinetics with a half life of about 7 h. Free ammonia concentrations decreased more slowly than LAS and remained above the level believed to be toxic for sensitive aquatic species along the entire channel. Changes in the ratios of LAS alkyl chain homologues to total LAS concentrations suggest a preferential removal of longer chain lengths. The role of biodegradation in the removal of LAS was confirmed by the presence of LAS metabolites (sulphophenylcarboxylates, SPCs) which increased systematically (as a fraction of LAS remaining) with flow-time.

Presence of surfactants and their degradation intermediates in sediment cores and grabs from the Cadiz Bay area

The occurrence and distribution of the major surfactants--LAS, AES, APEOs and AEOs--and their degradation intermediates--SPCs, AP and APECs--in a marine-estuarine environment at Spain are presented. Results show that their concentration in surface sediments is clearly correlated with their usage and the existence of wastewater discharges. The degradation processes appear to lead to the formation of SPCs in the case of LAS, and to the shortening of the average ethoxylated chain length in the case of NPEOs, AEOs and AES. Vertical profiles for AEOs and AES are reported for the first time and present the highest values nearest the surface, followed by a sharp decrease with depth for all surfactants, as well as the appearance of degradation intermediates in deeper sedimentary layers. Shorter LAS homologues and SPCs tend to be present in pore water while strongly non-polar intermediates like NP are firmly attached to the sediments.

Removal of linear alkylbenzene sulfonates and their degradation intermediates at low temperatures during activated sludge treatment

The degradation of linear alkylbenzene sulfonates and their degradation intermediates (sulfophenylcarboxylic acids) has been characterized at 9 degrees 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 omega-oxidation on the alkylic chain. A preferential degradation of SPC isomers of the types 2phiC(n)SPC to 6phiC(n)SPC was also detected, as shown by the relatively higher SPC concentrations of the remaining ones.