Anaerobic biodegradability testing of surfactants

Environmental Safety of the Use of Major Surfactant Classes in North America

This paper brings together over 250 published and unpublished studies on the environmental properties, fate, and toxicity of the four major, high-volume surfactant classes and relevant feedstocks. The surfactants and feedstocks covered include alcohol sulfate or alcohol sulfate (AS), alcohol ethoxysulfate (AES), linear alkylbenzene sulfonate (LAS), alcohol ethoxylate (AE), and long-chain alcohol (LCOH). These chemicals are used in a wide range of personal care and cleaning products. To date, this is the most comprehensive report on these substance's chemical structures, use, and volume information, physical/chemical properties, environmental fate properties such as biodegradation and sorption, monitoring studies through sewers, wastewater treatment plants and eventual release to the environment, aquatic and sediment toxicity, and bioaccumulation information. These data are used to illustrate the process for conducting both prospective and retrospective risk assessments for large-volume chemicals and categories of chemicals with wide dispersive use. Prospective risk assessments of AS, AES, AE, LAS, and LCOH demonstrate that these substances, although used in very high volume and widely released to the aquatic environment, have no adverse impact on the aquatic or sediment environments at current levels of use. The retrospective risk assessments of these same substances have clearly demonstrated that the conclusions of the prospective risk assessments are valid and confirm that these substances do not pose a risk to the aquatic or sediment environments. This paper also highlights the many years of research that the surfactant and cleaning products industry has supported, as part of their environmental sustainability commitment, to improve environmental tools, approaches, and develop innovative methods appropriate to address environmental properties of personal care and cleaning product chemicals, many of which have become approved international standard methods.

Priority and emerging pollutants in sewage sludge and fate during sludge treatment

This paper aims at characterizing the quality of different treated sludges from Paris conurbation in terms of micropollutants and assessing their fate during different sludge treatment processes (STP). To achieve this, a large panel of priority and emerging pollutants (n=117) have been monitored in different STPs from Parisian wastewater treatment plants including anaerobic digestion, thermal drying, centrifugation and a sludge cake production unit. Considering the quality of treated sludges, comparable micropollutant patterns are found for the different sludges investigated (in mg/kg DM - dry matter). 35 compounds were detected in treated sludges. Some compounds (metals, organotins, alkylphenols, DEHP) are found in every kinds of sludge while pesticides or VOCs are never detected. Sludge cake is the most contaminated sludge, resulting from concentration phenomenon during different treatments. As regards treatments, both centrifugation and thermal drying have broadly no important impact on sludge contamination for metals and organic compounds, even if a slight removal seems to be possible with thermal drying for several compounds by abiotic transfers. Three different behaviors can be highlighted in anaerobic digestion: (i) no removal (metals), (ii) removal following dry matter (DM) elimination (organotins and NP) and iii) removal higher than DM (alkylphenols - except NP - BDE 209 and DEHP). Thus, this process allows a clear removal of biodegradable micropollutants which could be potentially significantly improved by increasing DM removal through operational parameters modifications (retention time, temperature, pre-treatment, etc.).

Bacteria inside semiconductors as potential sensor elements: biochip progress

It was discovered at the beginning of this Century that living bacteria-and specifically the extremophile Pseudomonas syzgii-could be captured inside growing crystals of pure water-corroding semiconductors-specifically germanium-and thereby initiated pursuit of truly functional "biochip-based" biosensors. This observation was first made at the inside ultraviolet-illuminated walls of ultrapure water-flowing semiconductor fabrication facilities (fabs) and has since been, not as perfectly, replicated in simpler flow cell systems for chip manufacture, described here. Recognizing the potential importance of these adducts as optical switches, for example, or probes of metabolic events, the influences of the fabs and their components on the crystal nucleation and growth phenomena now identified are reviewed and discussed with regard to further research needs. For example, optical beams of current photonic circuits can be more easily modulated by integral embedded cells into electrical signals on semiconductors. Such research responds to a recently published Grand Challenge in ceramic science, designing and synthesizing oxide electronics, surfaces, interfaces and nanoscale structures that can be tuned by biological stimuli, to reveal phenomena not otherwise possible with conventional semiconductor electronics. This short review addresses only the fabrication facilities' features at the time of first production of these potential biochips.

Determination of Alcohol Ethoxylate Components in Sewage Sludge

An analytical method has been developed for the determination of alcohol ethoxylate (AE) components in sewage sludge. The method has been extensively ring tested in several industrial laboratories and concentrations in sludge samples from a number of EU countries have been obtained. The method is based on a methanol soxhlet extraction of centrifuged sludge, which is then cleaned up using an alumina column, followed by derivatisation with naphthoyl chloride and a further alumina column clean-up. The extract is analysed using high performance liquid chromatography (HPLC) with fluorescence detection. The method is capable of determining alcohol ethoxylate components in the range of C12–C18 alkyl chain lengths with an ethoxylate chain of EO4 up to approximately EO20 in sludge samples. The detection limit is approximately 20–30 mg kg−1 of total AEs in dry weight of sludge. Using the method, sludges from several European Sewage Treatment Plants (STP) were analysed. The concentration of the AEs, which are primarily linear, in digestor inlet averaged 1164 mg kg−1 (550–2947 mg kg−1) and in outlet sludges the mean value obtained was 167 mg kg−1 (<22–468 mg kg−1). At those plants in which concentrations were monitored in both inlet and outlet sludges, removal of the AEs by anaerobic digestion at the STP averaged 82% (range 61–93%). The interlaboratory relative standard deviation of the procedure was around 40% for the digester sludges analysed. The method developed provides a more accurate estimate of the environmental level of AE components compared to existing colorimetric approaches, but the method will over-estimate the concentration of alcohol ethoxylates in sludges due to the non-specific nature of the detection. However, it is sufficiently robust and accurate to estimate alcohol ethoxylates in sludges and hence concentrations that could be applied to soil.

Effects of household detergent on anaerobic fermentation of kitchen wastewater from food waste disposer

This study examines the effects of household detergent on anaerobic methane fermentation of wastewater from food waste disposers (FWDs). Anaerobic toxicity assay (ATA) demonstrated that methane production substantially decreased at a higher detergent concentration. The Gompertz three-parameter model fitted well with the ATA results, and both the extent of methane production (M) and methane production rate (R(m)) obtained from the model were strongly affected by the concentration of the detergent. The 50% inhibitory concentration (IC(50)) of the detergent was 603 mg/L based on R(m). Results from fatty acid methyl esters (FAMEs) analysis of microbial culture revealed that deterioration of methane fermentation was attributed to impaired structure of anaerobic microbial membrane due to detergent. This study suggests that wastewater from FWD could be used for methane production, but it is necessary to reduce the concentration of detergent prior to anaerobic fermentation.

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.

New sample treatment for the determination of alkylphenols and alkylphenol ethoxylates in agricultural soils

A new sample treatment for alkylphenols (AP) and alkylphenol ethoxylates (APEO) determination in agricultural soil samples has been developed. In a first stage these compounds were isolated from soil by pressurized liquid extraction (PLE) using methanol. In a second stage the extracts were cleaned up and pre-concentrated by solid-phase extraction (SPE) using ENV+cartridges. The effect of different variables on PLE and SPE was also studied. In the last place, separation and quantification of analytes were performed by liquid chromatography with fluorescence detection (LC-FD) and gas chromatography coupled to mass spectrometry (GC-MS). Quantification limits (QL) ranged from 20 to 200 ng g(-1) for LC-FD and from 3 to 126 ng g(-1) for GC-MS. This method was satisfactorily applied in a study field designed to evaluate the environmental behaviour of APEOs in agricultural soils.

Anaerobic Biodegradation of Detergent Surfactants

Detergent surfactants can be found in wastewater in relevant concentrations. Most of them are known as ready degradable under aerobic conditions, as required by European legislation. Far fewer surfactants have been tested so far for biodegradability under anaerobic conditions. The natural environment is predominantly aerobic, but there are some environmental compartments such as river sediments, sub-surface soil layer and anaerobic sludge digesters of wastewater treatment plants which have strictly anaerobic conditions. This review gives an overview on anaerobic biodegradation processes, the methods for testing anaerobic biodegradability, and the anaerobic biodegradability of different detergent surfactant types (anionic, nonionic, cationic, amphoteric surfactants).

A tiered approach for aquatic risk assessment of alcohol ethoxylates

An environmental risk assessment approach for alcohol ethoxylate (AE) mixtures was recently published which required the concentrations of the AE homologues in a mixture. The application of this approach can be limited in certain circumstances because AE homologue concentrations would generally not be available without environmental monitoring and would be difficult to estimate by exposure modeling. A tiered assessment approach was proposed in this study which required AE homologue concentrations only in the last tier. A key parameter in the tiered approach was based on Monte Carlo simulation in which simulated AE mixtures were decomposed into plausible combinations of homologues. The value of this parameter was determined so that the probability of false-negative conclusions in the tiered risk assessment approach was minimized. The use of the tiered approach was demonstrated.

Anaerobic nonylphenol ethoxylate degradation coupled to nitrate reduction in a modified biodegradability batch test

The aim of this work was to elucidate the role of nitrate as a terminal electron acceptor on the biodegradation of NPEO. We have characterized the products of NPEO degradation by mixed microbial communities in anaerobic batch tests by means of HPLC, (1)H NMR and GC-MS. Anaerobic degradation of NPEO was strictly dependent on the presence of nitrate. Within seven days of anoxic incubation, NP2EO appeared as the major degradation product. After 21 days, NP was the main species detected, and was not degraded further even after 35 days. Nitrate concentration decreased in parallel with NPEO de-ethoxylation. A transient accumulation of nitrite was observed within the time period in which NP formation reached its maximum production. The observed generation of nonylphenol coupled to nitrate reduction suggests that the microbial consortium possessed an alternate pathway for the degradation of NPEO, which was not accessible under aerobic conditions.

The chronic toxicity of alcohol alkoxylate surfactants on anaerobic granular sludge in the pulp and paper industry

The chronic toxicity of an alcohol alkoxylate surfactant used in the pulp and paper industry was observed in methanogenic consortia under unfed conditions. Methanogenic inhibition was not observed until 250 h of famine conditions while in the presence of the surfactant. The delayed onset of inhibition is likely due to the amount of time necessary for the surfactant to partition into the cellular membrane which uncouples cellular energy conservation mechanisms and exhausts internal energy reserves necessary to maintain homeostasis.

Fate, behavior and effects of surfactants and their degradation products in the environment

Surfactants are widely used in household and industrial products. After use, surfactants as well as their products are mainly discharged into sewage treatment plants and then dispersed into the environment through effluent discharge into surface waters and sludge disposal on lands. Surfactants have different behavior and fate in the environment. Nonionic and cationic surfactants had much higher sorption on soil and sediment than anionic surfactants such as LAS. Most surfactants can be degraded by microbes in the environment although some surfactants such as LAS and DTDMAC as well as alkylphenols may be persistent under anaerobic conditions. LAS were found to degrade in sludge amended soils with a half-lives of 7 to 33 days. Most surfactants are not acutely toxic to organisms at environmental concentrations and aquatic chronic toxicity of surfactants occurred at concentrations usually greater than 0.1 mg/L. However, alkylphenols have shown to be capable of inducing the production of vitellogenin in male fish at a concentration as low as 5 microg/L. More toxicity data are needed to assess the effects on terrestrial organisms such as plants.

Modeling kinetic processes controlling hydrogen and acetate concentrations in an aquifer-derived microcosm

Groundwater contaminants may degrade via fermentation to intermediate species, which are subsequently consumed by terminal electron-accepting processes (TEAPs). A numerical model of an aquifer-derived laboratory microcosm is developed to simulate the dynamic behavior of fermentation and respiration in groundwater by coupling microbial growth and substrate utilization kinetics with a formulation that also includes aqueous speciation and other geochemical reactions including surface complexation, mineral dissolution, and precipitation. The model is used to test approaches that currently make use of H2(aq) to diagnose prevalent TEAPs in groundwater. Competition between TEAPs is integral to the conceptual model of the simulation, and the results indicate that competitive exclusion is significant but with some overlap found in the temporal sequence of TEAPs. Steady-state H2(aq) concentrations observed during different TEAPs do not differ significantly. The results are not consistent with previous applications of the partial equilibrium approach since most TEAP redox pairs exhibit free energies that suggest a particular process is able to proceed, yet observations here show that this process does not proceed.

Potential for anaerobic conversion of xenobiotics

This review covers the latest research on the anaerobic biodegradation of aromatic xenobiotic compounds, with emphasis on surfactants, polycyclic aromatic hydrocarbons, phthalate esters, polychlorinated biphenyls, halogenated phenols, and pesticides. The versatility of anaerobic reactor systems regarding the treatment of xenobiotics is shown with the focus on the UASB reactor, but the applicability of other reactor designs for treatment of hazardous waste is also included. Bioaugmentation has proved to be a viable technique to enhance a specific activity in anaerobic reactors and recent research on reactor and in situ bioaugmentation is reported.

Environmental properties and effects of nonionic surfactant adjuvants in pesticides: a review

Little is known about the environmental fate of adjuvants after application on the agricultural land. Adjuvants constitute a broad range of substances, of which solvents and surfactants are the major types. Nonionic surfactants such as alcohol ethoxylates (AEOs) and alkylamine ethoxylates (ANEOs) are typically examples of pesticide adjuvants. In view of their chemical structure this paper outlines present knowledge on occurrence, fate and effect on the aquatic and terrestrial environment of the two adjuvants: AEOs and ANEOs. Both AEOs and ANEOs are used as technical mixtures. This implies that they are not one single compound but a whole range of compounds present in different ratios. Structurally both groups of substances have a mutual core with side chains of varying lengths. Each of these compounds besides having the overall ability to distribute between different phases also possesses some single compound behaviour. This is reflected in the parameters describing the fate e.g. distribution coefficient, leaching, run-off, adsorption to soil, degradation and effects of these substances. The adsorption behaviour of ANEOs in contrast to AEOs is particularly variable and matrix dependent due to the ability of the compound to ionise at environmentally relevant pH. Probably because the compounds exceeds high soil adsorption and are easily degradable which is reflected in the low environmental concentrations generally found in monitoring studies. The compounds generally possess low potency to both terrestrial and aquatic organisms. The major environmental problem related to these compounds is the ability to enhance the mobility of other pollutants in the soil column.

Biological activity and environmental impact of anionic surfactants

The newest results concerning the biological activity and environmental fate of anionic surfactants are collected and critically evaluated. The chemical and physicochemical parameters related to the biological activity and the field of application are briefly discussed. Examples on the effect of anionic surfactants on the cell membranes, on the activity of enzymes, on the binding to various proteins and to other cell components and on their human toxicity are presented and the possible mode of action is elucidated. The sources of environmental pollution caused by anionic surfactants are listed and the methods developed for their removal from liquid, semiliquid and solid matrices are collected. Both the beneficial and adversary effects of anionic surfactants on the environment are reported and critically discussed. It was concluded that the role of anionic surfactants in the environment is ambiguous: they can cause serous environmental pollution with toxic effect on living organisms; otherwise, they can promote the decomposition and/or removal of other inorganic and organic pollutants from the environment. The relationship between their chemical structure, physicochemical parameters, biological activity and environmental impact is notwell understood. A considerable number of data are needed for the development of new anionic surfactants and for the successful application of the existing ones to reduce the adversary and to promote beneficial effects.

Environmental fate of alkylphenols and alkylphenol ethoxylates--a review

Alkylphenol ethoxylates (APEs) are widely used surfactants in domestic and industrial products, which are commonly found in wastewater discharges and in sewage treatment plant (STP) effluents. Degradation of APEs in wastewater treatment plants or in the environment generates more persistent shorter-chain APEs and alkylphenols (APs) such as nonylphenol (NP), octylphenol (OP) and AP mono- to triethoxylates (NPE1, NPE2 and NPE3). There is concern that APE metabolites (NP, OP, NPE1-3) can mimic natural hormones and that the levels present in the environment may be sufficient to disrupt endocrine function in wildlife and humans. The physicochemical properties of the APE metabolites (NP, NPE1-4, OP, OPE1-4), in particular the high K(ow) values, indicate that they will partition effectively into sediments following discharge from STPs. The aqueous solubility data for the APE metabolites indicate that the concentration in water combined with the high partition coefficients will provide a significant reservoir (load) in various environmental compartments. Data from studies conducted in many regions across the world have shown significant levels in samples of every environmental compartment examined. In the US, levels of NP in air ranged from 0.01 to 81 ng/m3, with seasonal trends observed. Concentrations of APE metabolites in treated wastewater effluents in the US ranged from < 0.1 to 369 microg/l, in Spain they were between 6 and 343 microg/l and concentrations up to 330 microg/l were found in the UK. Levels in sediments reflected the high partition coefficients with concentrations reported ranging from < 0.1 to 13,700 microg/kg for sediments in the US. Fish in the UK were found to contain up to 0.8 microg/kg NP in muscle tissue. APEs degraded faster in the water column than in sediment. Aerobic conditions facilitate easier further biotransformation of APE metabolites than anaerobic conditions.

Anaerobic digestion of alcohol sulfate (anionic surfactant) rich wastewater--batch experiments. Part I: influence of the surfactant concentration

Textile wet processing wastewater (e.g., from cotton desizing) contains high concentrations of surfactants as well as readily biodegradable compounds like starch and other carbohydrates. Decyl sulfate (DS, surfactant) and soluble starch were used as model pollutants for biodegradation batch experiments. Very high loadings of the biomass were applied (DS: 21.7-217 g/kg cell dry weight (CDW); starch: 910 g/kg cell dry weight) to study inhibitory effects of the surfactant on the degradation cascade of the biopolymer. The starch hydrolysis was inhibited above sludge loadings of 65 g DS/kg CDW. Acidogenesis was the degradation step with the highest resistance towards inhibitory effects of the surfactant, whereas methanogenesis proved to be the most sensitive. The effects of the surfactant were described by the change of the methane evolution, which was reduced by 50% in 87 days with an addition of 58 g DS/kg CDW. The surfactant caused a high temporary accumulation of intermediates like volatile fatty acids. At the highest loading (217 g DS/kg CDW) the conversion of the substrate to methane was only minor.

Effect of the alkyl chain length on the anaerobic biodegradability and toxicity of quaternary ammonium based surfactants

The anaerobic biodegradability and toxicity to methanogenic gas production of different alkyl chain length homologs of quaternary ammonium based surfactants were examinated. Two series of these cationic surfactants were selected: alkyl trimethyl ammonium and alkyl benzyl dimethyl ammonium compounds. A simple anaerobic gas production test containing municipal digester solids as a source of anaerobic bacteria was used. Under the applied methanogenic conditions, the cationic surfactants tested showed a very poor primary biodegradation and no evidence of any extent of ultimate biodegradation was observed. The toxicity of quaternary ammonium based surfactants to methanogenic gas production decreased with increasing the alkyl chain length.