Surfactant Linear Alkylbenzene Sulfonate Research Articles

Study of the Effect of the Surfactant Linear Alkylbenzene Sulfonate (LAS) on the Coagulation of Aged Microplastic

Objective: Evaluate the effect of linear alkylbenzene sulfonate (LAS) surfactant on the coagulation of aged microplastic. Theoretical Framework: Chemical coagulation is one of the steps adopted in water treatment that can help remove microplastics. During coagulation, suspended particles agglomerate, increasing the efficiency of removing these particles in the sedimentation stage. However, when coagulation occurs in the presence of surfactants, evidence points to deficits in removal capacity. Method: Using Jar Test tests, the optimal parameters for microplastic removal were determined with aluminum sulfate as a coagulating agent in the presence and absence of the surfactant linear alkyl benzene sulfonate (LAS). The LAS concentrations studied were in the range of 20 mg/L to 300 mg/L. Microplastic removal efficiency was evaluated by measuring turbidity. Results and Discussions: The combination of pH and coagulant concentration values that best suited the system were 5.0 and 4.25 mg/L, respectively. Due to the addition of surfactants, a decrease in removal efficiency was observed, with an average value ranging from 94.79% to 76.50% due to the interaction of polyethylene spheres with the surfactant. Research Implications: As explained, due to the coexistence of microplastics and surfactants in the aqueous environment, studies that describe chemical coagulation under these conditions have great value for optimizing treatment systems and technologies. Research Originality/Value: The use of aged microplastics aims to approximate their natural occurrence.

A novel in situ method for linear alkylbenzene sulfonate quantification in environmental samples using a digital image-based method.

Surfactants from detergents, when inadequately treated in sewage treatment plants, are carried away into estuaries, resulting in the contamination of aquatic environments. It is thus necessary to develop rapid and efficient techniques that are capable of effectively monitoring these pollutants. In this context, for the first time in the literature, this study reports the development and application of a digital image-based (DIB) method for the in situ quantification of the anionic surfactant linear alkylbenzene sulfonate (LAS) in water bodies using a smartphone. The DIB method is a highly effective modern detection method based on methylene blue, which is employed as a modified alternative technique to the spectrophotometric method and commonly used in environmental studies; in the DIB method, the images of interest are obtained using a smartphone and the analyses are carried out using free software Color grab. The results obtained from the application of the DIB method showed that the method possesses high precision and accuracy, with a linear calibration curve in the range of 0.15 to 4.5 mg L-1, R2 = 0.993, a limit of detection of 6.0 μg L-1, and recovery rates ranging from 82.7% to 114%. The efficacy of the proposed method was evaluated by comparing its results with those of spectrophotometry (used as a reference method) through the analysis of environmental samples obtained from the Capibaribe River Estuary using methylene blue. No statistically significant differences were observed between the results obtained from the DIB and the spectrophotometric method. The innovative method proposed in this study is fast, economical and environmentally friendly; the technique involves the use of only a few microliters of samples and generates little waste compared to spectrophotometry. In addition, the proposed method is applicable for in situ analyses, allowing real-time monitoring of LAS in different types of aquatic environments.

Aplikasi Surfaktan Alami dan Sintetis untuk Meningkatkan Penghilangan Total Petroleum Hidrokarbon dari Tanah Tercemar

Environmental pollution by petroleum hydrocarbons (total petroleum hydrocarbons) is an environmental problem affecting human health and the environment. Innovative and sustainable treatment methods are needed to solve this problem. One remediation technique that can be used is soil washing. Soil washing is a remediation technique using surfactants as a contaminant washing solution. This research study investigated the washing of soil contaminated by used motor oil using green and synthetic surfactants. The type of natural surfactant used was saponin at a concentration of 10,000 mg/L and synthetic surfactant Linear Alkylbenzene Sulfonate (LAS) at 800 mg/L. The effect of washing time and stirring speed on TPH reduction efficiency was also tested through a series of laboratory tests. Based on the statistical results, the three factors, namely surfactant type, washing time, and stirring speed, significantly influenced TPH removal. Optimum removal efficiency with LAS surfactant was obtained under washing time between 70 - 90 minutes and stirring speed between 40 - 50 rpm. Meanwhile, saponin surfactant at washing time is 60 - 80 minutes, and stirring speed is 48 - 50 rpm.

Synthesis and evaluation of core–shell nanocomposites for the photodegradation of liner alkyl-benzene sulfonate water contaminations

Linear alkyl-benzene sulfonate surfactants (LAS) are a major pollutant source of sewage and wastewater. They trigger severe impact on the environmental fauna and flora. Current research explores the synthesis of three different core–shell nanocomposites (CSNCs) containing titania through an inexpensive oxidative polymerization technique. The fabricated CSNCs were evaluated for the photocatalytic degradation of LAS water contaminations. The selected CSNCs investigated for this study were the TiO2/poly(aniline-co-pyrrole) and TiO2/ poly(aniline-co-3-Me-thiophene) as well as the TiO2/terpolymer (aniline-pyrrole-m-aminobenzoic acid). The structure of the formed nanocomposites was confirmed by varied characterization spectroscopy. The core–shell structure of the nanocomposites was confirmed by scanning electron micrographs and transmission electron microscopy. The CSNCs exhibited intensive photo catalytic degradation efficacy toward LAS under visible light exposure in comparison with the exposure in their absence. The parameters optimizing their photovoltaic degradation efficiency were assessed. The presented approach implies that an effective, economical, and environmentally friendly synthetic setup was achieved to produce novel CSNCs with high potential as LAS photodegradation agents.

Toxicity test of LC-50 (Lethal Concentration) surfactant LAS (Linear Alkylbenzene Sulfonate) against white snapper (Lates calcarifer) fingerlings on a laboratory scale

LAS (Linear Alkylbenzene Sulfonate) surfactants are the main cleaning agents from the anionic group found in detergents that are widely used in Indonesia. LAS decomposes in surface water for 1-2 days, in sediments it decomposes for 1-3 days, in marine and estuarine systems it decomposes for 5-10 days. LAS is generally degraded by as much as 90% within 3 months, with a time ranging from 5-30 days (World Health Organization, 1996). LAS surfactants can cause damage to the gill epithelium and blockage of branchiola channels in fish. This study aims to determine the toxic effect of LAS surfactant on the survival of white snapper (Lates calcarifer) fry and to determine the toxicity value of LC50 (Lethal Concentration) of LAS surfactant to white snapper (Lates calcarifer) fry on a laboratory scale. This research was carried out on September 21 – October 04, 2021 at the Marine Science Laboratory, Faculty of Agriculture, Malikussaleh University using laboratory experimental methods with 5 treatments, namely: control treatment A (0 ppm), B (0.83 ppm), C (1.58 ppm). ), D (2.16 ppm), and E (2.91 ppm). The results of this study cause barramundi to experience irregular movements, mouth opening and operculum tend to be fast and irregular, scales are pale and peeling, and cause death, LAS surfactants affect water quality such as pH and dissolved oxygen, but have no effect on salinity and temperature. The 24-hour LC50 value is 1.95 ppm, the 48-hour LC50 value is 1.86 ppm, the 72-hour LC50 value is 1.70 ppm, and the 96-hour LC50 value is 1.58 ppm.Key words : LAS surfactant; LC50; toxicity; white snapper

Toxicity test of LC-50 (Lethal Concentration) surfactant LAS (Linear Alkylbenzene Sulfonate) against white snapper (Lates calcarifer) fingerlings on a laboratory scale

LAS (Linear Alkylbenzene Sulfonate) surfactants are the main cleaning agents from the anionic group found in detergents that are widely used in Indonesia. LAS decomposes in surface water for 1-2 days, in sediments it decomposes for 1-3 days, in marine and estuarine systems it decomposes for 5-10 days. LAS is generally degraded by as much as 90% within 3 months, with a time ranging from 5-30 days (World Health Organization, 1996). LAS surfactants can cause damage to the gill epithelium and blockage of branchiola channels in fish. This study aims to determine the toxic effect of LAS surfactant on the survival of white snapper (Lates calcarifer) fry and to determine the toxicity value of LC50 (Lethal Concentration) of LAS surfactant to white snapper (Lates calcarifer) fry on a laboratory scale. This research was carried out on September 21 – October 04, 2021 at the Marine Science Laboratory, Faculty of Agriculture, Malikussaleh University using laboratory experimental methods with 5 treatments, namely: control treatment A (0 ppm), B (0.83 ppm), C (1.58 ppm). ), D (2.16 ppm), and E (2.91 ppm). The results of this study cause barramundi to experience irregular movements, mouth opening and operculum tend to be fast and irregular, scales are pale and peeling, and cause death, LAS surfactants affect water quality such as pH and dissolved oxygen, but have no effect on salinity and temperature. The 24-hour LC50 value is 1.95 ppm, the 48-hour LC50 value is 1.86 ppm, the 72-hour LC50 value is 1.70 ppm, and the 96-hour LC50 value is 1.58 ppm.Key words: LAS surfactant; LC50; toxicity; white snapper

In Silico Analysis to Define Microbial Common Core Associated with Degradation of Anionic Surfactant Linear Alkylbenzene Sulfonate (Las)

In Silico Analysis to Define Microbial Common Core Associated with Degradation of Anionic Surfactant Linear Alkylbenzene Sulfonate (Las)

Electrocoagulation Method Using Al/Graphite Electrode for Removal Surfactant LAS (Linear Alkylbenzene Sulfonate)

An increasing number of laundries have caused water contamination by surfactants. One commonly used surfactant is LAS (Linear Alkylbenzene Sulfonate), a material difficult to decompose, polluting the environment. Electrocoagulation was carried out using Al/Graphite electrode, applied to LAS surfactant artistic waste. This study aims to determine the functional ability of the Al/Graphite electrode in reducing surfactant through electrocoagulation. Various variations were carried out, on the voltage parameters (3,6,9,12) Volt; NaCl concentration (0;0.4;0.8;1.2;1.6;2) g/L; pH (3,5,7,9,11) and time (10,20,30,40,50) minutes. To analyze the changes in the sample before and after electrocoagulation, characterization was carried out using a UV-VIS spectrophotometer and FTIR. A kinetic study was conducted to determine the reaction order of electrocoagulation surfactant. Based on a study, removal at condition voltage 9 Volt, initial pH of the solution 9, electrocoagulation time 50 minute, and the addition of NaCl electrolyte 2 g/L, obtained surfactant concentration was 0,785 mg/L with removal efficiency 97,45%. UV-VIS spectra show a decreased absorption at a wavelength of 653 nm. FTIR spectra showed the presence of absorption on the same functional groups, which indicated that most of the surfactant pollutants could be separated from the wastewater through the electrocoagulation process. The second-order reaction was obtained in the surfactant electrocoagulation process.

Adsorption mechanism on surfactant removal using eggshell waste and rice straw as economically biosorbent

Adsorption is an effective process to remove organic compounds, including surfactants. In this research, rice straw (JP) and eggshell waste (CT) would be tested as economically adsorbents of surfactant. This research aims to determine the effect of pH, adsorbent dose, initial concentration, and particle size on adsorption effectivity, find out kinetics, removal efficiency and desorption ability of adsorbents. Anionic surfactant Linear Alkylbenzene Sulfonate (LAS) was determined by using MBAS method. A preliminary test was conducted to examine which adsorbent is the potential to be used in the main experiment. Adsorbent selected from the preliminary test was CT2 and JP1. Surfactant removal at an acidic solution was better than in an alkaline solution. The particle size of adsorbent was not influencing much at removal of surfactant. As increasing dosage, removal efficiency increases. Removal efficiency decreases as initial concentration is increased. Isotherm D-R fitted well for both adsorption and desorption using JP; therefore Langmuir isotherm fitted well for CT. Removal efficiency of LAS adsorption was better using JP than CT adsorbent. Desorption release at CT was 9.68-20.94%, while for JP was 8.51-12.20%. Pseudo-second order and second-order models fitted data well for adsorption kinetics. Physisorption was dominant in the adsorption process.

The identification and performance assessment of dominant bacterial species during linear alkylbenzene sulfonate (LAS)-biodegradation in a bioelectrochemical system.

The anionic surfactant linear alkylbenzene sulfonate (LAS) is a major chemical constituent of detergent formulation. Regarding the recalcitrant nature of sulfonoaromatic compounds, discharging these substances into wastewater collection systems is a real environmental issue. A study on LAS biodegradation based on bioelectrochemical treatment and in the form of developing a single-chamber microbial fuel cell with air cathode is reported in the present work. Pretreatment study showed LAS concentration of 60ppm resulted in the highest anaerobic LAS removal of 57%; so, this concentration was chosen to run the MFC. After the sustained anodic biofilm was formed, LAS degradation rate during 4days in MFC was roughly 76% higher than that in the serum bottle, which indicated the role of the bioelectrochemical process in improving anaerobic LAS removal. Additionally, through 16S rRNA gene sequencing, the dominant bacterial species in the biofilm was identified as Pseudomonas zhaodongensis NEAU-ST5-21(T) with about 98.9% phylogenetic similarity and then a pathway was proposed for LAS anaerobic biodegradation. The MFC characteristics were assessed by pH monitoring as well as scanning electron microscopy and current density evolution.

Highly Efficient Degradation of Linear Alkylbenzene Sulfonate Surfactant by MIL‐53 (Fe) Metal Organic Framework Derived Electro‐Fenton Applicable in Water Treatments

AbstractMIL‐53 (Fe) Metal‐organic framework (MOF) was synthesized by a hydrothermal method and characterized by SEM, XRD, FT‐IR, and Brunauer‐Emmett‐Teller techniques. The synthesized MOF was successfully applied as an efficient catalyst in Electro‐Fenton degradation of linear alkylbenzene sulfonate (LAS) surfactant, so that degradation rate constant, Kapp, for LAS degradation showed significantly higher amounts in presence of Fe MOF. Effect of experimental parameters on Electro‐Fenton degradation including pH, MOF amount, applied current, Fe (II) concentration, and electrodes distance were investigated and optimized amounts were found. Applying of MOF caused efficient removal of LAS in compared to when MOF was not applied. Catalytic electrochemical degradation in this work showed removal of more than 98 % of initial surfactant in 150 min which was completely satisfying for LAS removal.

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.

Study of the pollution by surfactants in a river of a high Andean micro basin

The surfactants linear alkylbenzene sulfonate (LAS), is used in large quantities in modern society, and wastewater containing it can contaminate groundwaters through runoff and sewers. The study aimed to determine the level of LAS in the Huatanay river; in Cusco city, Peru. Water samples were taken from nine points along the river, in the rainy and dry season in 2018. LAS surfactants were determined spectrometrically using methylene blue as indicator; dissolved oxygen (DO) and conductivity were also determined; both were correlated through Pearson coefficient at 5% significance, and analyzed in triplicate. The concentration of LAS in the dry season varied between 0.01 to 23.17 mg/L and in rains from 0.09 to 1.47 mg/L; the DO level shows values between 0.11 to 5.04 mg O2/L, and the conductivity varied from 777.7 to 2688.9 µS/cm. In conclusion, high levels of LAS considerably decrease the DO and increase the conductivity.

Revealing the Origin of the Specificity of Calcium and Sodium Cations Binding to Adsorption Monolayers of Two Anionic Surfactants.

The studied anionic surfactants linear alkyl benzene sulfonate (LAS) and sodium lauryl ether sulfate (SLES) are widely used key ingredients in many home and personal care products. These two surfactants are known to react very differently with multivalent counterions, including Ca2+. This is explained by a stronger interaction of the calcium cation with the LAS molecules, compared to SLES. The molecular origin of this difference in the interactions remains unclear. In the current study, we conduct classical atomistic molecular dynamics simulations to compare the ion interactions with the adsorption layers of these two surfactants, formed at the vacuum-water interface. Trajectories of 150 ns are generated to characterize the adsorption layer structure and the binding of Na+ and Ca2+ ions. We found that both surfactants behave similarly in the presence of Na+ ions. However, when Ca2+ is added, Na+ ions are completely displaced from the surface with adsorbed LAS molecules, while this displacement occurs only partially for SLES. The simulations show that the preference of Ca2+ to the LAS molecules is due to a strong specific attraction with the sulfonate head-group, besides the electrostatic one. This specific attraction involves significant reduction of the hydration shells of the interacting calcium cation and sulfonate group, which couple directly and form surface clusters of LAS molecules, coordinated around the adsorbed Ca2+ ions. In contrast, SLES molecules do not exhibit such specific interaction because the hydration shell around the sulfate anion is more stable, due to the extra oxygen atom in the sulfate group, thus precluding substantial dehydration and direct coupling with any of the cations studied.

Evaluation of the Photosonolysis Process Efficacy for the Removal of Anionic Surfactant Linear Alkyl Benzene Sulfonate from Aqueous Solutions

In this study, the experiments on the sulfonate linear alkylbenzene (LAS) solution were performed using the methylene blue active substances (MBAS) method. The effectiveness of the sonochemical and photochemical reactors for LAS degradation was evaluated with an emphasis on the effect of the contact time, pH values, type of process and initial concentrations. The experiments were carried out at the initial concentrations of 0.5 mg/L, 14.00 mg/L and 21.00 mg/L, the contact time of 8, 16, and 24 minutes, pH of 3, 7, and 11, the ultrasonic frequency of 42 kHz, the acoustic power value of 160 W, an ultraviolet lamp with 150W power and the wavelength of 254 nm. This study showed that the LAS degradation was increased along with the contact time. In addition, at alkaline pH, the removal efficiency increased as well. Overall, the results obtained from this research demonstrated that by themselves, both the sonochemical and photochemical reactors may not be useful for completely reducing the complex wastewaters with high surfactant loads, but the succession of the UV/US process has a significant effect on the removal of anionic detergents. These findings demonstrated the removal efficiency under alkaline conditions and the contact time of 24 minutes was equal to 96.97 percent.

Effect of Fine Bubbles on Removal of Linear Alkyl Benzene Sulfonate Surfactant during the Rinsing Stage of Laundry Washing

AbstractThe use of fine bubbles is a promising approach to remove surfactant efficiently during the rinsing process of clothing, to fulfill a requirement. Therefore, the influence of fine bubbles on the removal performance of surfactant from cloth during the rinse process of pulsator washing machine (top loading type) was investigated. The test apparatus was assembled by connecting a microbubble generation tank and a small washing machine with tubes and circulating fine bubble water to a small washing machine. Swatches of cloth with a specified amount of linear alkylbenzene sulfonate (LAS) adsorbed from aqueous solution, were rinsed with tap water, and the LAS concentration in the rinse water was examined with an HPLC system equipped with a high‐precision fluorescence detector. The average bubble diameter of the fine bubble water used was 0.13–1.4 μm. In the rinsing experiment, no difference was found in the final LAS removal efficiency between water with and without bubbles; but the former increased the LAS removal rate during the initial stage of rinsing. This tendency was particularly noticeable when the stirring power of the washing machine was weak. Therefore, it was concluded that the fine bubble effect on the removal of the surfactant is mainly a kinetic effect rather than an equilibrium effect.

Reusability Enhancement of Taste Sensor Using Lipid Polymer Membranes by Surfactant Cleaning Treatment

The aim of our study was to enhance the reusability of a taste sensor by increasing the efficiency of the cleaning process. In this paper, we proposed a surfactant cleaning method for two types of bitterness sensor using lipid polymer membranes with high hydrophobicity. To select suitable surfactants for cleaning, the usability of four types of surfactant with different polarities and ionicities was evaluated. Among these surfactants, the anionic surfactant linear alkylbenzene sulfonate (LAS) showed no impact on the initial membrane potential and completely removed residue substances of high-concentration quinine hydrochloride adsorbed on the bitterness sensor used for hydrochloride salts. On the other hand, the amphoteric surfactant lauryl dimethylaminoacetic acid (LDA) showed no impact on the initial membrane potential and almost completely removed residue substances of high-concentration iso- $\alpha $ acid adsorbed on the bitterness sensor used for acidic bitter materials. Moreover, we found that the combined use of the conventional cleaning solution and LDA acid solution in turn greatly improved the reusability of an astringency sensor in multiple measurements of black tea.

Degradation of surfactant waste of leather tanning using Fe2O3/activated carbon catalyst

The development of the tannery industry in addition to being beneficial for the economic growth of the community also has a negative impact on the environment due to the disposal of waste produced. Components of waste produced from the leather tanning industry include residual protein and fat, surfactants, anti-bacterial, anti-fungal, coloring and tanning agents. One component that is found in surfactants and often pollutes waters is alkyl benzene sulfonate and linear alkyl benzene sulfonate surfactants. Alkyl benzene sulfonate (ABS) is an anionic surfactant that has a very long and branched carbon chain that is difficult to degrade by microorganisms in nature. Characterization and testing of the activity of porous/activated carbon catalysts will be carried out. The type of porous activated carbon used is coconut shell carbon with microspores character. The stages of this research consisted of the process of impregnation of iron oxide on porous carbon, the surfactant waste degradation process and the characterization of the catalysts produced. Based on the research that has been done, it can be concluded that the catalyst Fe2O3/coconut shell activated carbon is very effective to be applied for the degradation of surfactant waste. The degradation capacity of surfactant wastes increases with increasing concentration of active site Fe. The capacity of the surfactant waste degradation reaction using coconut shell catalyst at t = 3 hours for variations in the concentration of Fe 2%, 4% and 6% respectively 6.77 mmol/gram catalyst, 3.18 mmol/gram catalyst and 1.61 mmol/gram catalyst. The data show that the surfactant waste degradation reaction capacity increases with the increase in the composition of iron oxide added to the surface of the porous carbon support.

Biokinetics of the anionic surfactant linear alkylbenzene sulfonate (LAS) in the marine fish Sparus aurata: Investigation via seawater and food exposure pathways

Uptake and depuration kinetics of [14C]C12-6-linear alkylbenzene sulfonate (LAS) in the fish Sparus aurata were determined during experimental exposure via seawater or food separately under laboratory conditions. The fish concentrated LAS from seawater (using realistic contaminant concentrations) with a mean BCF value of 20 ± 2 L kg−1 reached within 3 days and following a one-compartment exponential model. High differences in BCF were noted among organs, with values ranking in the order gall bladder (1400 ± 600 L kg−1) >> digestive tract (52 ± 9 L kg−1) > liver (38 ± 4 L kg−1) > gills (16 ± 3 L kg−1) > skin (13 ± 2 L kg−1) > head (9 ± 1 L kg−1) > muscles (4 ± 1 L kg−1). After three days of exposure, 14C activity decreased in gall bladder while it remained constant in other organs. Biotransformation and elimination processes could explain this phenomenon observed in gall bladder. LAS depuration was rapid in all organs (with up to 90% elimination within 2 days) and depuration kinetics was best fitted by a two-compartment exponential-model. When fish were fed with radiolabeled food, ingested LAS was transferred to organs within the first hours following the feeding. Model best describing depuration kinetics of LAS in the whole fish indicated that the contaminant can be considered as not assimilated.

Laundry wastewater and domestic sewage pilot-scale anaerobic treatment: Microbial community resilience regarding sulfide production

In this study, the removal of anionic surfactant Linear Alkylbenzene Sulfonate (LAS) from laundry wastewater was evaluated in co-digestion with domestic sewage, using a pilot-scale Expanded Granular Sludge Bed reactor. Surfactant influent concentration was enhanced from 5 ± 3 mg LAS L−1 (stage I) to 19 ± 10 mg LAS L−1 (stage II) and 36 ± 19 mg LAS L−1 (stage III) throughout reactor operation. Sulfide levels higher than 20 mg L−1 influenced LAS removal efficiency, which decreased from 71% to 55% and 32% in stage I, II and III, respectively. Acclimation of microbial population was verified and higher relative abundance of the genera similar to Cytophaga, Bacteroides, Syntrophus and Syntrophobacter in the early stages (adaptation and stage I) was replaced by higher relative abundance of the genera Anaerophaga, Nitrosovibrio, Sulfurovum and Desulfovibrio in the last stages (stage II and III).