Three-dimension oxygen gradient induced low energy input for grey water treatment in an oxygen-based membrane biofilm reactor.

Grey water (GW) containing high levels of linear alkylbenzene sulfonates (LAS) can be a threat to human health and organisms in the environment if not treated properly. Although aerobic treatment could achieve high organics removal efficiency, conventional aeration can lead to serious foaming and energy waste. Here, we systematically evaluated an oxygen based membrane biofilm reactor (O2-MBfR) for its capacity to simultaneously remove organics and nitrogen from GW. The dissolved oxygen (DO) concentration inside the reactor was maintained at 0.4 mg/L by gradually controlling the lumen air pressure. Results showed that the O2-MBfR achieved high removal efficiency of total chemical oxygen demand (TCOD), total linear alkylbenzene sulfonates (LAS) and total nitrogen (TN) of 89.7%, 99.1% and 78.1%, respectively, with a hydraulic retention time (HRT) of 7.5 h. Lower HRT (7.0 h) led to the accumulation of LAS in the biofilm, which caused cell lysis and damaged the O2-MBfR system, leading to a discernible and continuous decline of the reactor performance. The O2-MBfR design completely eliminated foaming formation and the three-dimension oxygen gradient design led to low air pressure inside the membrane fiber, which enabled the high removal efficiency for both organics and nitrogen with low energy input and GW treatment cost, providing the fundamental knowledge for practical application of O2-MBfR in wastewater treatment.

Novel synthetic clays for the adsorption of surfactants from aqueous media.

The aim of this work was to assess for the first time the use of two high-charge swelling micas (Na-Mica-4 and C18-Mica-4) for the removal of four linear alkylbenzene sulfonates (LAS) from aqueous samples. To this end, Na-Mica-4 was synthesized and organically functionalized with cations of octadecylamine to obtain C18-Mica-4. Na-Mica-4 and C18-Mica-4 were characterized by X-Ray diffraction, Zeta potential, specific surface area and thermogravimetric analysis before and after the adsorption experiments. LAS removal studies were carried out in water samples spiked with a LAS mixture (10 mg L-1). Removal rates with C18-Mica-4 were between 94% and 97% at pH = 2, and between 98% and 99% at pH = 5 after 1 h. For the same amount of Na-Mica-4, removal rates were between 54% and 81% at pH = 2, and between 24% and 66% at pH = 5 after seven days. No significant effects on the removal rates of C18-Mica-4 were observed for pH values between 0.5 and 9. The experimental equilibrium data were fitted to 30 min, with removal rates of up to 98% in all the experiments. C18-Mica-4 characterization tests indicate that LAS adsorption occurs in the interlayer space. Finally, C18-Mica-4 was applied successfully to the removal of the target compounds from influent and effluent wastewater, surface water and tap water samples.

Ionic-liquid-modified magnetic nanoparticles as a solid-phase extraction adsorbent coupled with high-performance liquid chromatography for the determination of linear alkylbenzene sulfonates in water samples.

Novel ionic-liquid-functionalized Fe3 O4 magnetic nanoparticles were synthesized by the thiol-ene click reaction. The prepared functionalized Fe3 O4 nanoparticles possessed multiple interactions, such as electrostatic, hydrophobic, and π-π interactions. The functionalized Fe3 O4 nanoparticles were characterized by using Fourier transform infrared spectroscopy, X-ray diffraction, vibrating sample magnetometry, and transmission electron microscopy. Four kinds of linear alkylbenzene sulfonates, namely, sodium decylbenzenesulfonate, sodium undecylbenzene sulfonate, sodium dodecylbenzenesulfonate, and sodium tridecylbenzenesulfonate, were selected as model compounds to evaluate the applicability of adsorbents for extraction and subjected to high-performance liquid chromatography analysis. In addition, the effects of various parameters, such as sorbent amount, pH value, ionic strength, sample volume, extraction time, and elution conditions on extraction efficiency were studied in detail. Under the optimum conditions, good linearities were attained, with correlation coefficients between 0.9912 and 0.9968. The proposed method exhibited limits of detection ranging from 0.061 to 0.099 µg/L for all the target analytes. The spiked recoveries of the target analytes in real water samples ranged from 86.3 to 107.5%, with relative standard deviations lower than 7.96%. The enrichment factors of the analytes ranged from 364 to 391, indicating that the obtained functionalized Fe3 O4 nanoparticles can effectively extract trace target analytes from environmental water samples.

Ultrasound-assisted sample preparation for simultaneous extraction of anionic, cationic and non-ionic surfactants in sediment.

Despite their very wide use in various fields, knowledge concerning surfactants in environmental solid matrices is generally poor. One of the difficulties encountered in the analysis of surfactants is their very diverse physicochemical properties which require different extraction techniques. The objective of this work was therefore to develop an extraction method in sediments that allows the simultaneous analysis of anionic, cationic and non-ionic surfactants. Different extraction techniques (salting-out, ultrasound), solvents and additives were compared. The optimized method, followed by analysis by coupling liquid chromatography with tandem mass spectrometry, was then validated and applied to real samples in which the analytes were quantified by matrix matched calibration. Optimization of the extraction parameters showed different trends depending on the surfactant family. However, ultrasound assisted extraction with a 90/10 acetonitrile/water mixture at 1% acetic acid and 0.1 M EDTA showed the best results overall. The quantification limits obtained, between 6.4 µg/kg for linear alkylbenzene sulfonate (LAS) C10 and 158 µg/kg for 1-laureth sulfate, allow the analysis of traces in sediments. Eighteen of the 27 targeted surfactants were thus detected. The highest concentrations were found for LAS and quaternary ammoniums. Strong correlations between concentrations of different homologues of the same families of surfactants were observed.

Growth and antioxidant response in Spirodela polyrrhiza under linear alkylbenzene sulfonate, naphthalene and their joint stress.

The synthetic organic surfactants linear alkylbenzene sulfonate (LAS) and polycyclic aromatic hydrocarbon naphthalene (NAP), two common organic pollutants, are frequently detected in freshwater environments. However, the combined ecotoxicological risks associated with these pollutants have not been fully elucidated. The present study investigated the effects of individual and combined treatments of LAS and NAP on the growth and physiological responses of Spirodela polyrrhiza. The results showed that LAS was the main compound toxic to S. polyrrhiza in a dose-dependent manner. The peroxidase (POD) enzyme and catalase (CAT) enzyme are the main antioxidant enzymes protecting S. polyrrhiza from LAS stress. When exposed to NAP stress alone, only slightly reversible damage was observed as the exposure time was extended (14 days). The antioxidant enzyme systems (including superoxide dismutase (SOD), CAT and POD) showed positive responses. Synergistic effects were induced with LAS-NAP mixtures (≥ 5 + 5 mg L-1), and LAS played a major toxic role. The POD enzyme was a sensitive protective enzyme in duckweed during the joint exposure to LAS + NAP. The results indicate that LAS or NAP may cause serious damage to S. polyrrhiza and aggravate ecotoxicity in aquatic ecosystems.

Screening and mutagenesis of high-efficient degrading bacteria of linear alkylbenzene sulfonates.

As a widely used detergent, anionic surfactant linear alkylbenzene sulfonates (LAS) is a common toxic pollutant in wastewater. In this study, Pseudomonas sp. strain H6 was isolated from activated sludge and municipal wastewater, which had good degradation effect on LAS. The results showed that strain H6 could grow with LAS as the sole carbon source. When the concentration of LAS was less than 100 mg/L, strain H6 could degrade more than 80% of the LAS within 24 h. Meanwhile, the growth of strain H6 increased with the increase of LAS concentration, reaching the maximum growth at the presence of 100 mg/L LAS. When the concentration of LAS was over 100 mg/L, strain H6's cell growth and degradation of LAS showed a downward trend due to the strong toxicity of LAS, and the degradation rate of LAS almost tended to zero with 500 mg/L LAS. Further mutagenesis analysis of strain H6 showed that positive mutation occurred under ultraviolet and nitrite mutagenesis with using ampicillin to increase the screening pressure, and the degradation rate of LAS was 44.91% higher than that of original strain.

Deterioration of biological pollutants removal induced by linear alkylbenzene sulphonates in sequencing batch reactors: Insight of sludge characteristics, microbial community and metabolic activity.

Linear alkylbenzene sulfonates (LAS) are widely detected in wastewater, and pose potential risks to environment. The influences of LAS on the typical pollutants removal in sequencing batch reactors (SBRs) were evaluated. The results indicated that the removal efficiency of COD, NH4+ and PO43- was respectively reduced by 10.5-27.5%, 5.4-7.3% and11.6-28.9% with the exposure of 10-50 mg/L LAS. Mechanisms investigation found that LAS disrupted the sludge structure and reduced the biomass in reactors due to the saponification effects. Also, the presence of LAS altered the microbial community of activated sludge, and reduced the abundances of functional bacterial responsible for pollutants removal (i.e.Candidatus Accumulibacter, Nitrospira, Denitratisoma and etc.). Moreover, the LAS exhibited negative impacts on the microbial activity with increased LDH release but decreased ATP concentration. The genes expressions for microbial metabolism (i.e. carbohydrate metabolisms, energy metabolism) and typical pollutants removal (i.e. electron transport, phosphonate transport) were all downregulated in LAS-exposed SBRs.

Treatment of grey water (GW) with high linear alkylbenzene sulfonates (LAS) content and carbon/nitrogen (C/N) ratio in an oxygen-based membrane biofilm reactor (O2-MBfR).

Grey water (GW) containing high levels of linear alkylbenzene sulfonates (LAS) can be a threat to the human health and organisms in the environment if not treated properly. Although aerobic treatment may achieve high GW treatment efficacy, conventional aeration can lead to serious foaming. Here, we firstly and systematically evaluated an oxygen-based membrane biofilm reactor (O2-MBfR) for its capacity to simultaneous remove organics and nitrogen from greywater with high LAS levels and carbon/nitrogen (C/N) ratios. After a five-day startup period, multifarious microorganisms formed multifunctional biofilms and the MBfR achieved high removal rates of chemical oxygen demand (COD), LAS, and total nitrogen (TN) of 88.4%, 95.6%, and 80%, respectively, with a hydraulic retention time of 7.86 h. Higher organics loading (5.53 g TCOD/m2-day) caused cell lysis and damaged the O2-MBfR system, leading to a discernible and continuous decline of the reactor performance. The O2-MBfR design completely eliminated foaming formation. LAS -biodegrading-rich genus containing Clostridium, Parvibaculum, Dechloromonas, Desulfovibrio, Mycobacterium, Pseudomonas, and Zoogloea enable the nearly complete removal of LAS even under high C/N conditions. Results demonstrated that the O2-MBfR technology is feasible for treating GW containing high LAS and C/N ratio, while remaining free of foaming formation, and at a low cost due to high O2 utilization rates.

Occurrence and potential environmental risk of surfactants and their transformation products discharged by wastewater treatment plants.

Seven-day composite effluent samples from a German monitoring campaign including 33 conventional wastewater treatment plants (WWTP) were analyzed for linear alkylbenzene sulfonates (LAS) and alkyl ethoxysulfates (AES) and were screened by wide-scope suspect screening for 1564 surfactants and their transformation products (TPs) by UHPLC-ESI-QTOF-MS. Corresponding seven-day composite influent samples of selected WWTPs showed high influent concentrations as well as very high removal rates for LAS and AES. However, average total LAS and AES effluent concentrations were still 14.4 µg/L and 0.57 µg/L, respectively. The LAS-byproducts di-alkyl tetralin sulfonates (DATSs), the TPs sulfophenyl alkyl carboxylic acids (SPACs) and sulfo-tetralin alkyl carboxylic acids (STACs) reached maximum effluent concentrations of 19 µg/L, 17 µg/L and 5.3 µg/L, respectively. In many cases the sum of the concentration of all LAS-related byproducts and TPs surpassed the concentration of the precursors. High concentrations of up to 7.4 µg/L were found for 41 polyethylenoglycol homologs. Quantified surfactants and their TPs and by-products together accounted for concentrations up to 82 µg/L in WWTP effluents. To determine the risk of individual surfactants and their mixtures, single homologs were grouped by a "weighted carbon number approach" to derive normalized Predicted No-Effect Concentrations (PNEC), based on experimental ecotoxicity data from existing risk assessments, complemented by suitable Quantitative Structure-Activity Relationships (QSAR) predictions. Predicted Environmental Concentrations (PEC) were derived by dividing effluent concentrations of surfactants by local dilution factors. Risks for all analyzed surfactants were below the commonly accepted PEC/PNEC ratio of 1 for single compounds, while contributions to mixture toxicity effects from background levels of LAS and DATS cannot be excluded. Maximum LAS concentrations exceeded half of its PNEC, which may trigger country-wide screening to investigate potential environmental risks.

Promoting waste activated sludge reduction by linear alkylbenzene sulfonates: Surfactant dose control extracellular polymeric substances solubilization and microbial community succession.

Short-time aerobic digestion (STAD) was proved to promote the reduction of waste activated sludge (WAS). This study systematically disclosed the influential characteristics and mechanisms of linear alkylbenzene sulfonates (LAS) dosage on the reduction of WAS in STAD system. Flow cytometer (FC) combined with SYTOX Green (SG) dye was used to differentiate extracellular polymeric substances (EPS) release and cell lysis of WAS during STAD process. LAS lower than 0.10 g/g total suspended solids (TSS) brought about EPS solubilization and the decrease of sludge floc size, and the accumulated soluble microbial products (SMP) could be biodegraded by heterotrophs. Moreover, the activity of microorganisms (denoted as specific oxygen uptake rate (SOUR)) and proportion of bacteria functional for LAS and SMP biodegradation dramatically increased, leading to a high LAS biodegradation rate (kLAS) and increased WAS biodegradation rate (kCOD, WAS). Even more LAS (> 0.10 g/g TSS) caused cell lysis, leading to the decreased kTCOD and kLAS, and therefore inhibit the reduction of WAS. High WAS reduction and LAS biodegradation rate were achieved at the LAS dosage of 0.10 g/g TSS in STAD system. This study lays the foundation for improving WAS reduction by optimizing surfactant dose in STAD system.

Efficiency of ultrasound for degradation of an anionic surfactant from water: Surfactant determination using methylene blue active substances method.

The removal of a surfactant from wastewater is usually difficult due to its toxicity and low biodegradability. The aim of this study was to apply sonoreactor for degradation of an anionic surfactant from aqueous solution. An ultrasonic bath with frequency of 130 kHz was used to investigate the effects of different operational parameters such as sonication time, initial concentration and power. In this study, experiments of linear alkylbenzene sulfonates solution were performed using methylene blue active substances method. Experiments were performed at initial concentrations of 0.2 , 0.5 , 0.8 and 1 mg/L, frequency of 130 kHz, acoustic powers value of 400 and 500 W, temperature of 18-20 °C and pH value of 6.8-7. This study showed that linear alkylbenzene sulfonates degradation rate was found to increase with increasing sonication time and power. In addition, as the concentration increased, the linear alkylbenzene sulfonates degradation rate decreased in the ultrasonic reactor. •Surfactants are one of the largest groups of pollutants which exist in almost all urban and many industrial wastewaters.•Ultrasonic reactors alone may not be useful for reducing completely complex wastewaters of high surfactant load.•Application of ultrasonic reactors in combination with other treatment processes including Ozone, UV irradiation, chlorination, Fenton, nanoparticles and H2O2 could be used as a pre-treatment unit in a sequential chemical and biological treatment process.

Formation and toxicity of halogenated disinfection byproducts resulting from linear alkylbenzene sulfonates.

Linear alkylbenzene sulfonates (LAS) are an important group of organic pollutants in urban wastewater effluents. The practice of using seawater for toilet flushing results in saline wastewater effluents, which contain high levels of bromide ions. Chlorine is most commonly used in wastewater disinfection. During chlorination of freshwater or saline wastewater effluents, some halogenated disinfection byproducts (DBPs) resulting from LAS could be formed. In this study, the overall formation of halogenated DBPs resulting from LAS was quantified by total organic halogen (TOX) measurement. Polar halogenated DBPs resulting from LAS were detected with a novel precursor ion scan method. The structures and formation pathways of the major ones were tentatively proposed. The overall toxicity of different scenarios of LAS samples was evaluated with embryos of a marine polychaete Platynereis dumerilii. The results demonstrate that chlorinated DBPs were generated during chlorination of LAS without bromide, while brominated DBPs were generated during chlorination of LAS with bromide. The TOX concentrations were relatively low, indicating that LAS were not quite reactive with halogen. The major polar chlorinated and brominated DBPs resulting from LAS were proposed to be 2,6-dichloro-3,5-dihydroxy-4-dodecylbenzenesulfonic acid and 2,6-dibromo-3,5-dihydroxy-4-dodecylbenzenesulfonic acid, which belong to a group of DBPs with similar structures but different halogen atoms, and their formation pathways were tentatively proposed. The results also reveal that the undisinfected LAS sample was the least toxic, followed by the chlorinated LAS sample without bromide, and the chlorinated LAS sample with bromide was the most toxic.

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.

γ-H2AX induced by linear alkylbenzene sulfonates is due to deoxyribonuclease-1 translocation to the nucleus via actin disruption.

Phosphorylation of histone H2AX (γ-H2AX) occurs following formation of DNA double strand breaks (DSBs). Other types of DNA damage also generate DSBs through DNA replication and repair, leading to the production of γ-H2AX. In the present study, we demonstrated that linear alkylbenzene sulfonates (LAS), the most widely used and non-genotoxic anionic surfactants, could generate γ-H2AX via a novel pathway. Breast adenocarcinoma MCF-7 cells were treated with five kinds of LAS with alkyl chains ranging from 10 to 14 carbon units (C10-C14LAS). The generation of DSBs and subsequent production of γ-H2AX increased in a manner that depended on the number of carbon units in LAS. γ-H2AX could also be generated with non-cytotoxic doses of LAS and was independent of the cell cycle, indicating the non-apoptotic and DNA replication-independent formation of DSBs. The generation of γ-H2AX could be attenuated by EGTA and ZnCl2, deoxyribonuclease-1 (DNase I) inhibitors, as well as by the knockdown of DNase I. LAS weakened the interaction between DNase I and actin, and the enhanced release of DNase I was dependent on the number of carbon units in LAS. DNase I released by the LAS treatment translocated to the nucleus, in which DNase I attacked DNA and generated γ-H2AX. These results suggested that the LAS-induced generation of γ-H2AX could be attributed to the translocation of DNase I to the nucleus through the disruption of actin, and not to LAS-induced DNA damage.

Occurrence of surfactants in wastewater: hourly and seasonal variations in urban and industrial wastewaters from Seville (Southern Spain).

Surfactants are daily discharged to the environment from urban and industrial activities. The assessment of the risk derived from the presence of these compounds in the environment requires a deep knowledge about their sources and their distribution in wastewater treatment plants (WWTPs). However, in spite of several studies reporting their presence in WWTPs, only a small number is focused on their different sources. In this work, the distribution of anionic (linear alkylbenzene sulfonates) and non-ionic (nonylphenol ethoxylates) surfactants in WWTPs and in urban and industrial wastewater collection systems has been investigated. Seasonal and daily variability was also assessed. Concentrations of linear alkylbenzene sulfonates in influent and effluent wastewaters ranged from 1155 to 9200 µg L(-1), and from below limit of detection to 770 µg L(-1), respectively, whereas the concentrations of nonylphenol ethoxylates were significantly lower. Linear alkylbenzene sulfonates were efficiently removed (>96%), while mean removal rates of nonylphenol ethoxylates were significantly lower (<20%). Studies carried out in different seasons revealed seasonal discharge patterns from both urban and industrial activities. The analysis of wastewater collection systems showed a major contribution of linear alkylbenzene sulfonates from urban areas while, in the case of nonylphenol ethoxylates, their major contribution came from industrial activities. In all cases the discharge patterns of surfactants were related with the water consumption.

Determination of non-ionic and anionic surfactants in industrial products by separation on a weak ion-exchanger, derivatization and liquid chromatography.

A method for the determination of priority surfactants, including fatty alcohol ethoxylates (FAE), alkylether sulfates (AES) and linear alkylbenzene sulfonates (LAS) is described. The samples were diluted with 50% methanol at pH 4 prior to solid-phase extraction on a weak anionic exchanger (WAX). The AES and LAS surfactant classes were retained, whereas the non-ionic components, including most FAE oligomers were eluted. After washing the WAX cartridge to remove cations, the remaining hydrophobic FAE oligomers were eluted using hot 80% methanol at pH 4 (at ca. 50°C). These two eluates were combined to constitute the non-ionic fraction. Then, AES and LAS were eluted using 80% MeOH with 3M NH3 followed by 95% methanol with 0.75M NH3. The two eluates obtained in basic media were combined to constitute the anionic fraction. The solvents were evaporated, the residues were dissolved in 1,4-dioxane, and esterification of the alcohols and transesterification of AES with phthalic anhydride was performed. Separation of the derivatized oligomers was achieved by gradient elution on a C8 column with acetonitrile/water in the presence of 0.1% acetic acid and 0.1M NaClO4. The chromatogram of the non-ionic fraction showed the peaks of the resolved FAE oligomers. The chromatogram of the anionic fraction showed the peaks of the LAS homologues well resolved from those of the AES oligomers. The method was applied to laundry and industrial cleaners, shampoos and a shower gel.