Linear Alkylbenzene Sulfonate Removal Research Articles

Efficient and sustainable removal of linear alkylbenzene sulfonate in a membrane biofilm: Oxygen supply dosage impacts mineralization pathway

Linear alkylbenzene sulfonate (LAS) can be thoroughly mineralized within sufficient oxygen (O2), but which is energy intensive and may causes serious foaming problem. Although cometabolism can achieve efficient LAS removal within a wide range of O2 dosages, how O2 dosage systematically affects LAS metabolic pathway is still unclear. Here, membrane aerated biofilm reactor (MABR) enabled accurate O2 delivery and bulk dissolved oxygen (DO) control. MABR achieved efficient removal of LAS (>96.4 %), nitrate (>97.8 %) and total nitrogen (>96.2 %) at the three target DO conditions. At high DO condition (0.6 mg/L), LAS was efficiently removed by aerobic mineralization (predominant) coupled with aerobic denitrification biodegradation with the related functional enzymes. Pseudomonas, Flavobacterium, Hydrogenophaga, and Pseudoxanthomonas were dominant genus contributing to four possible LAS aerobic metabolic pathways. As O2 dosage reduced to only 29.7 % of the demand for LAS mineralization, O2 facilitated LAS activation, benzene-ring cleavage and a portion of respiration. NO3--N respiration-induced anaerobic denitrification also contributed to ring-opening and organics mineralization. Desulfomicrobium and Desulfonema related two possible anaerobic metabolic pathways also contributed to LAS removal. The findings provide a promising strategy for achieving low-cost high LAS-containing greywater treatment.

Removal of linear alkylbenzene sulfonate by electrocoagulation/flotation using a cylindrical vertical reactor

This study proposes a vertical electrocoagulation/flotation reactor model and evaluates its efficiency through hydraulic tests and the removal of linear alkylbenzene sulfonate (LAS), a common wastewater surfactant. Residence time distribution assays and computational fluid dynamics verified the fluid flow pattern. Response surface methodology (RSM) was used to assess the impact of pH, electric current, and sodium chloride concentration on LAS removal. Ecotoxicity tests using Artemia salina detected no toxic byproducts from electrocoagulation/flotation (ECF). Adsorption kinetics and isotherms were used to evaluate the removal behavior of LAS, which showed the highest efficiencies with an electric current of 1.5 A, a pH of 5.73, and a NaCl concentration of 4652.4 mg/L. The electric current and pH were the most influential variables. The ecotoxicity assay indicated no toxic byproduct generation, even at high chloride concentrations, and increased LAS biodegradability posttreatment. Adsorption kinetics followed a pseudo-first-order model at 20 mg/L and a pseudo-second-order model at 240 mg/L. The Freundlich isotherm indicated a high affinity between the LAS and aluminum hydroxide flakes, achieving nearly 90 % removal in 30 min at an energy cost of 5.25 Wh.

Laboratory and field studies on the effect of geoenvironmental factors on the removal of linear alkylbenzene sulfonate during riverbank filtration

Laboratory and field studies on the effect of geoenvironmental factors on the removal of linear alkylbenzene sulfonate during riverbank filtration

Linear Alkylbenzene Sulfonate Removal by Oxidative Ozonation Coupled with UV/H2O2 Oxidative Process

In this study, the results of the application of advanced oxidative processes to remove linear alkylbenzene sulfonate (LAS) from wastewater produced in the laundry industry are presented. Photocatalysis with UV radiation and oxygen peroxide (H2O2) was applied followed by ozonation (O3). LAS removal was higher than 90% in the first 60 min. H2O2 application based on COD reached its most effective concentration for the rate of [1:2.5] with O3 acting as a polishing agent. Excessive foam formation caused by the bubbling effect led to the necessity of introducing a lag into the process, retarding the O3 application in 30 min. Therefore, complete oxidation was achieved with a low concentration of LAS, and no foam was observed by the end of the process. The best COD removal results were achieved when low doses of H2O2 were applied. Using UV/H2O2/O3, 51.2% removal was achieved.

A study on adsorption of anionic surfactant from water during riverbank filtration

Riverbank filtration (RBF) is a low-cost and environmentally friendly alternative to advanced treatment technologies for pre-treatment or removal of various synthetic organic micro-pollutants from surface water. Through laboratory-scale batch tests employing aquifer soil with varying fine content and particle size, the removal of Linear Alkylbenzene Sulfonate (LAS) from river water during riverbank filtration (RBF) was investigated to determine its adsorption behavior. In addition to it, the effect of adsorbent dosage (3–60 g/L), adsorbate conc. (2–60 mg/L), contact time (10–240 min), agitation speed (80–200 rpm), and pH (2 to 10) on the adsorption for nine types of aquifer soil were studied in batch experiments. The optimal conditions for maximum rate of LAS adsorption on aquifer soil were found to be as initial LAS conc. of 15 mg/L, pH at 7, contact time of 150 min, agitation speed at 160 rpm and adsorbent dosage of 15 g/L respectively. The removal efficiency of LAS was obtained as 88.9% for aquifer soil with 15% fine content and 86.3% for fine sand at an adsorbent dose of 15 g/L, initial LAS conc. of 15 mg/l, neutral pH, agitation speed of 160 rpm, and contact time of 150 mins. Equilibrium data were fitted to Langmuir and Freundlich isotherms, and Langmuir isotherm (R2 = 0.99) was revealed to be the best fit of these models. From multiple linear regression, the LAS removal by soil samples was found to be strongly associated with all five geo-environmental factors (R2 = 0.91). So during the design of the RBF system, suitable contact time or travel time should be maintained in addition to the selection of proper aquifer site conditions for the RBF.

Comparison of the Efficiency of Ultraviolet/Ultrasonic (UV/US) and Ultraviolet/Zinc Oxide (UV/ZnO) Technologies as Advanced Oxidation Processes in the Removal of Linear Alkylbenzene Sulfonate (LAS), an Anionic Detergent, from Aqueous Media

Surfactants are one of the most commonly found xenobiotics in municipal and industrial wastewater. The purpose of this study was to compare ultraviolet/ultrasonic (UV/US) and ultraviolet/zinc oxide (UV/ZnO) processes in the removal of LAS from aqueous media.In this study, a medium-pressure UV lamp (125 W), an ultrasonic device (400 W and 42 kHz), and ZnO nanoparticles (NPs) were used. The concentration of LAS was 0.5, 14, and 21 mg/L in all experiments. Contact time of 8, 16, and 24 minutes, pH of 3, 7, and 11, and NP concentrations of 50, 100, 150 mg/L were selected. Detergent extraction was performed using methylene blue active substances.The results showed that the efficiency of UV/US process in the removal of LAS was 89.35%, while the removal efficiency of UV/ZnO process was 81.27%. In both processes, the rate of detergent removal increased by elongating the contact time from 8 to 24 minutes. The efficiency of UV/US process in LAS removal was greater than that of the UV/ZnO process. The findings showed that the removal efficiency of UV/US process was directly correlated with pH, while it had an inverse correlation with the removal efficiency of UV/ZnO process.

Quantitative determination of linear alkylbenzene sulfonate (LAS) concentration and simultaneous power generation in a microbial fuel cell-based biosensor

Linear alkylbenzene sulfonate (LAS), one of the most widely used synthetic surfactants in laundry detergent industry, is considered a hazardous contaminant in wastewater. In the present study, a microbial fuel cell (MFC) based biosensor is developed to quantitively determine the LAS concentration in wastewater. To do so, the developed MFC is fed with LAS concentration of 60 mg l−1. Finally, a sustained biofilm is formed after almost 34 days and the highest open circuit potential of 425 mV is recorded. The maximum power and current densities of 75 mW m−3 and 663 mA m−3 are obtained, respectively; and the internal resistance of the MFC-based biosensor is calculated to be about 1 kΩ. After 98 h, LAS removal and coulombic efficiency are 90% and 65%, respectively. A linear correlation between the current density and LAS concentration (in the range of 10–120 mg l−1) is obtained. Furthermore, a comprehensive model is used to interpret the output electrical signal of the MFC representing temporal and spatial distributions of different microorganisms as well as the hierarchal processes of the LAS biodegradation. The competition between electrogens and methanogens in the biofilm; and also, the effect of external resistance on electrogen concentration are shown as well. Besides, the MFC-based biosensor desirably performed as a power generator and purifier in addition to being an accurate biosensor.

Removal of linear alkylbenzene sulfonate (LAS) by a cetyltrimethylammonium bromide (CTAB)-aided coagulation-filtration process

ABSTRACT This paper reports on the removal of linear alkylbenzene sulfonate (LAS) by conventional and cetyltrimethylammonium bromide (CTAB)-aided coagulation-filtration processes. The addition of CTAB led to the formation of CTAB-LAS aggregates, whose surface charge was negative at a CTAB-LAS molar ratio < 1 and positive at a molar ratio > 1. The efficacy of the coagulation-filtration process strongly depended on the electrostatic interactions between hydroxide floc and both free LAS and CTAB-LAS aggregate. Since free LAS is anionic, its adsorption onto the hydroxide floc was enhanced when the floc was positively charged. Ferric hydroxide floc (pH < 6.0) and aluminum hydroxide floc (pH < 7.4) showed positive surface charges and were thereby effective in removing free LAS. The optimal coagulation pH for removing the CTAB-LAS aggregate depended on the CTAB/LAS molar ratio. A higher coagulation pH was effective in removing LAS under the CTAB/LAS molar ratio > 1. However, in this case, excessive free CTAB remained after coagulation-filtration. Therefore, the lower coagulation pH with a CTAB/LAS molar ratio < 1, with the hydroxide floc and CTAB-LAS aggregate being positively and negatively charged, respectively, was recommended for LAS removal. In chemical industry wastewater, the optimal CTAB dose was higher than that in synthetic wastewater due to coexistent chemicals scavenging CTAB. Consequently, coagulation-filtration using a ferric chloride coagulant under the CTAB/LAS molar ratio of 0.7–2.0 and pH 4.5 was recommended for LAS removal from chemical industry wastewater, where the observed LAS removal efficiency reached 91 ± 3% without any deterioration of COD removal.

Simultaneous removal of phenol and linear alkylbenzene sulfonate from automotive service station wastewater: Optimization of coupled electrochemical and physical processes

ABSTRACT This work investigates the feasibility of the coupled electrochemical (electrocoagulation/flotation) and physical processes (sedimentation, sand filtration, and activated carbon) for the treatment of automotive service wastewater (ASWW). The impacts of critical parameters, viz. pH solution, reaction time and current intensity on linear alkylbenzene sulfonate (LAS), and phenol removal efficiencies as well as energy consumption and operating cost are studied. Central composite design results reveal that at the optimum conditions, LAS and phenol removal efficiencies, energy consumption and operating cost are obtained 96.7%, 87.65%, 15.99 Wh, 0.001 US$, respectively. This process reveals a feasible technology for phenol and LAS removal from ASWW.

Removal of linear alkylbenzene sulfonate and turbidity from greywater by a hybrid multi-layer slow sand filter microfiltration ultrafiltration system

In this study, a new hybrid system using multi-layer slow sand filter (MSSF), micro filter (MF) and ultra filter (UF) was investigated for the chemical oxygen demand (COD), linear alkylbenzene sulfonate (LAS), total suspended solid (TSS) and turbidity removal from the greywater at different organic loading rates (OLRs) (3.15–19.28 gCOD/(L.d) in a laboratory scale over a period of 157 days. The best removal efficiencies for COD, LAS, TSS, and turbidity were 98.22, 99.97, 99.99, and 99.98 percent, respectively using the MSSF-MF-UF hybrid system. The best removal efficiencies of LAS were 86.7, 89.6, and 98.37 percent, respectively in the OLR of 3.15 gCOD/(L.d). The scanning electron microscopy (SEM) images confirmed that biofilm grew appropriately in the media using the MSSF. Moreover, the increase of OLRs in the hybrid system decreased the removal efficiency levels of COD, LAS, TSS, and turbidity. However, the average effluents of LAS, TSS, and turbidity in the hybrid system were 0.04 mg/L, 1.55 mg/L, and 1.04 NTU, respectively for all OLRs, which were lower than the standard measures for reuse of water. In fact, the combination of biological process (MSSF) with membrane process (MF and UF) led to a more effective LAS and suspended solids (SS) removal in the grey water. Therefore, the combination of MSSF-MF-UF can be applied for removal of LAS and SS.

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.

Metabolic routes involved in the removal of linear alkylbenzene sulfonate (LAS) employing linear alcohol ethoxylated and ethanol as co-substrates in enlarged scale fluidized bed reactor

In this study, the microbial community characterization and metabolic pathway identification involved in the linear alkylbenzene sulfonated (LAS) degradation from commercial laundry wastewater in a fluidized bed reactor (FBR) on an increased scale were performed using the Illumina MiSeq platform. Ethanol and non-ionic surfactant (LAE, Genapol C-100) were used as co-substrates. The FBR was operated in five operational phases: (I) synthetic substrate for inoculation; (II) 7.9 ± 4.7 mg/L LAS and 11.7 ± 6.9 mg/L LAE; (III) 19.4 ± 12.9 mg/L LAS, 19.6 ± 9.2 mg/L LAE and 205 mg/L ethanol; (IV) 25.9 ± 11 mg/L LAS, 19.5 ± 9.1 mg/L LAE and 205 mg/L ethanol and (V) 43.9 ± 18 mg/L LAS, 25 ± 9.8 mg/L LAE and 205 mg/L ethanol. At all operation phases, organic matter was removed from 40.4 to 85.1% and LAS removal was from 24.7 to 56%. Sulfate-reducing bacteria (SRB) were identified in the biofilm of FBR in all operational phases. Although the LAS promoted a toxic effect on the microbiota, this effect can be reduced when using biodegradable co-substrates, such as ethanol and LAE, which was observed in Phase IV. In this phase, there was a greater microbial diversity (Shannon index) and higher microorganism richness (Chao 1 index), both for the Domain Bacteria, and for the Domain Archaea.

Evaluation of anionic surfactant removal by anaerobic degradation of commercial laundry wastewater and domestic sewage

ABSTRACTAn expanded granular sludge bed reactor was evaluated for the anaerobic digestion of commercial laundry wastewater and domestic sewage focused on the removal of linear alkylbenzene sulfonate (LAS). The reactor was operated in three stages, all under mesophilic conditions and with a hydraulic retention time of 36 h. At stage I, the laundry wastewater was diluted with tap water (influent: 15.3 ± 4.9 mg LAS/L); at stage II, 50% of the feed volume was domestic sewage and 50% was a mixture of tap water and laundry wastewater (influent: 15.8 ± 4.9 mg LAS/L); and at stage III, only domestic sewage was used as a diluent of the laundry wastewater (influent: 24.1 ± 4.1 mg LAS/L). Due to the addition of domestic sewage the organic compounds content and LAS in the influent increased. Under such conditions, it was observed that LAS removal rate decreased from 77.2 ± 14.9% (stage I) to 55.3 ± 18.4% (stage III). Statistical tests indicated that the decrease of the LAS removal rate was significant and indicated a correlation between the removal of LAS and specific organic loading rate. The analysis of 16S rRNA gene sequencing revealed genera similar to Geobacter, Desulfovibrio, Syntrophomonas, Syntrophus, Desulfobulbus, Desulfomonile, and Desulfomicrobium, which were related to the degradation of LAS.

Effects of hydraulic retention time, co-substrate and nitrogen source on laundry wastewater anionic surfactant degradation in fluidized bed reactors

The aim of this study was to evaluate the influence of hydraulic retention time (HRT) on linear alkylbenzene sulfonate (LAS) removal in fluidized bed reactors (FBRs). FBR1 (HRT of 8h) and FBR2 (HRT of 12h) were fed laundry wastewater with 18.6±4.1 to 27.1±5.6mg/L of LAS in the following conditions: ethanol and nitrate addition (Phases I, II and III), nitrate (Phase IV), ethanol (Phase V) and laundry wastewater (Phase VI). LAS removal was 93±12% (FBR1) and 99±2% (FBR2). In FBR1, nitrate influenced significantly on LAS removal (99±3% – Phase IV) compared to the phase without nitrate (90±15% – Phase V). In FBR1 the absence of ethanol was more favourable for LAS removal (99±3% – Phase IV) compared to ethanol addition (87±16% – Phase II). In FBR2, 99±2% LAS removal was found up to 436days. By microbial characterization were identified bacteria as Acinetobacter, Dechloromonas, Pseudomonas and Zoogloea.

Evaluation of anionic surfactant removal in anaerobic reactor with Fe(III) supplementation

The objective of this study was to evaluate the removal of linear alkylbenzene sulfonate (LAS) associated with Fe(III) supplementation using an expanded granular sludge bed (EGSB) reactor. The reactor was inoculated with a granular sludge and fed with synthetic wastewater containing a specific LAS load rate (SLLR) of 1.5 mg gVS−1 d−1 (∼16.4 mgLAS L−1 influent) and supplied with 7276 μMol L−1 of Fe(III). The biomasses from the inoculum and at the end of the EGSB-Fe operation (127 days) were characterized using 16S rRNA Ion Tag sequencing. An increase of 20% in the removal efficiency was observed compared to reactors without Fe(III) supplementation that was reported in the literature, and the LAS removal was approximately 84%. The Fe(III) reduction was dissimilatory (the total iron concentration in the influent and effluent were similar) and reached approximately 64%. The higher Fe(III) reduction and LAS removal were corroborated by the enrichment of genera, such as Shewanella (only EGSB-Fe - 0.5%) and Geobacter (1% - inoculum; 18% - EGSB-Fe). Furthermore, the enrichment of genera that degrade LAS and/or aromatic compounds (3.8% - inoculum; 29.6% – EGSB-Fe of relative abundance) was observed for a total of 20 different genera.

Methanogenic activity inhibition by increasing the linear alkylbenzene sulfonate (LAS) concentration

ABSTRACTThe effect of the initial concentration of linear alkylbenzene sulfonate (LAS) on specific methanogenic activity (SMA) was investigated in this work. Six anaerobic flasks reactors with 1 L of total volume were inoculated with anaerobic sludge (2 g VSS L−1). The reactors were assayed for 42 days, and fed with volatile fatty acids, nutrients, and LAS. The initial LAS concentrations were 0, 10, 30, 50, 75, and 100 mg L−1 for the treatment flasks T1 (control), T2, T3, T4, T5, and T6, respectively. When compared with T1, T2 exhibited a 30% reduction in maximum SMA and total methane production (TMP). In treatment T3 through T6, the reductions were 44–97% (T3–T6) for SMA, and 30–90% (T3–T6) for TMP. Total LAS removal increased following the increase in the initial LAS concentration (from 36% at T1 to 76% at T6), primarily due to the high degree of sludge adsorption. LAS biodegradation also occurred (32% in all treatments), although this was most likely associated with the formation of non-methane intermediates. Greater removal by adsorption was observed in long-chain homologues, when compared to short-chain homologues (C13 > C10), whereas the opposite occurred for biodegradation (C10 > C13). The C13 homologue was adsorbed to a great extent (in mass) in T4, T5 and T6, and may also have inhibited methane formation in these treatments.

Removal of linear alkyl benzene sulfonate from aqueous solutions by functionalized multi-walled carbon nanotubes

This paper explores the possibility of employing Oxidized Multiwalled Carbon Nanotubes (MWCNT-COOH) for the removal of toxic Linear Alkyl benzene Sulfonate (LAS). LAS is among the most toxic industrial and house hold waste surfactants. This study discusses the feasibility of removing LAS from aqueous solutions using MWCNT-COOH. The effects of operational parameters such as solution pH, LAS concentration and contact time on the removal of LAS were studied. The four linear forms of Langmuir, Freundlich, Dubinin Radushkevich (D-R) and Temkin models were applied to determine the best fit of equilibrium expressions. Our results showed that the experimental adsorption isotherm complies with Freundlich model. The maximum adsorption capacity was determined to be 62.5mg/g with an initial LAS concentration of 4mg/L at pH3 in 45min. Fitting of the experimental results to kinetic models showed the relevance of the pseudo second-order (R2>0.99) model for LAS. Our results confirmed that MWCNT-COOH would be promising adsorbents for LAS removal in aqueous solution.

Biodegradation of linear alkylbenzene sulfonate in commercial laundry wastewater by an anaerobic fluidized bed reactor

The biodegradation of linear alkylbenzene sulfonate (LAS) from commercial laundry wastewater was evaluated in an anaerobic fluidized bed reactor (FBR) fed with synthetic substrate (598 mg L−1 to 723 mg L−1 of organic matter) supplemented with 9.5 ± 3.1 mg L−1 to 27.9 ± 9.6 mg L−1 of LAS. The average chemical oxygen demand (COD) removal efficiency was 89% and the biodegradation of LAS was 57% during the 489 days of anaerobic FBR. Higher levels of volatile fatty acids (VFA) were observed in the effluent at the stage with the best LAS removal performance. Increasing the surfactant concentration did not increase the VFA production in the effluent. The predominant VFAs after the addition of LAS were as follows: isovaleric acid and valeric acid, followed by propionic acid, caproic acid and formic acid. The similarities of 64% and 45% to Archaea and Bacteria domains were observed in the samples taken in the operating period of anaerobic FBR fed with 23.6 ± 10 mg L−1 and 27.9 ± 10 mg L−1 of LAS. During the operation stages in the reactor, Gemmatimonas, Desulfobulbus and Zoogloea were determined as the most abundant genera related to surfactant degradation using 454-Pyrosequencing.

Investigating the removal of linear alkyl benzene sulfonate from aqueous solution by ultraviolet irradiation and hydrogen peroxide process

This study investigated the efficiency of ultraviolet radiation and hydrogen peroxide for the removal of linear alkylbenzene sulfonate (LAS) from aqueous solutions. Methylene blue active substances assay and spectrophotometry were used to determine the amount of anionic and residual surfactants. The effect of H2O2 concentration, initial concentration of surfactant, pH, and length of UV radiation were examined. The potential for use of UV/H2O2 to degrade LAS was analyzed statistically using multiple linear regression analysis. The results showed that after 20 min of contact time, ultraviolet radiation alone removed 38.44% of the LAS. The use of hydrogen peroxide alone for 10, 20, and 30 min showed no effect on the removal of LAS. The removal rates for the combination UV/H2O2 at 10, 20, and 30 min were 86.2, 90, and 96.5%, respectively. The results of this study showed that the use of ultraviolet radiation and hydrogen peroxide individually for degradation of anionic surfactant was not effective, but the combination of UV/H2O2 was effective for the removal of anionic detergents.

Microbial diversity and the implications of sulfide levels in an anaerobic reactor used to remove an anionic surfactant from laundry wastewater

The objective of this study was to evaluate the removal of linear alkylbenzene sulfonate (LAS) from commercial laundry wastewater using an expanded granular sludge bed (EGSB) reactor with two specific LAS loading rates (SLLRs), 1.0 and 2.7mgLASgVS−1d−1. The biomass was characterized using denaturing gradient gel electrophoresis (DGGE) and 16S Ion Tag sequencing. Higher LAS removal (92.9%) was observed in association with an SLLR of 1.0mgLASgVS−1d−1 than with an SLLR of 2.7mgLASgVS−1d−1 (58.6%). A relationship between the S−2 concentration in the effluent and the surfactant removal efficiency was observed. This result is indicative of the inhibition of LAS-removing microbiota at S−2 concentrations greater than 20mgSL−1. By using DGGE, microbial stratification was observed in the reactor in association with granule size, even though the reactor is considered to be a completely mixed regime. The RDP-classifier identified 175 genera, 33 of which were related to LAS degradation.