Accumulation of linear alkylbenzenesulphonate surfactants in sewage sludges

Effects of nonionic surfactants on life history traits of Drosophila melanogaster

Surfactants are used for a variety of applications such as emulsifiers, solubilizers, or foaming agents. Their intensive production and use in pharmaceutical, cosmetic and agricultural products have resulted in their continuous discharge in the environment, especially via wastewaters. Surfactants have become a threat to living organisms as they interact with, and disrupt, cell membranes and macromolecules. Their effects have mainly been studied in aquatic species; however, terrestrial organisms are also threatened by these emerging contaminants. This study investigates the effects of two widely used nonionic surfactants, Tween-20 and Triton X-100, on key traits of larvae and adults of the fruit fly Drosophila melanogaster. We assessed the toxicity of the two surfactants on viability, development time, body size and food intake of the flies. The results revealed that both surfactants induced toxic effects on the drosophila flies leading to decreased viability, delayed development and lowered food consumption at the highest tested concentrations. Both surfactants proved to be toxic to flies, and, for all tested traits, Triton X-100 appeared more toxic than Tween-20. Our results might extend to other invertebrates. The widespread use of these substances, which then end up in the environment, should be regulated to mitigate their impacts on biodiversity and ecosystems.

Synthetic surfactants in Swiss sewage sludges: Analytical challenges, concentrations and per capita loads

Surfactants are high-production-volume chemicals that are among the most abundant organic pollutants in municipal wastewater. In this study, sewage sludge samples of 36 Swiss wastewater treatment plants (WWTPs), serving 32% of the country's population, were analyzed for major surfactant classes by liquid chromatography mass spectrometry (LC-MS). The analyses required a variety of complementary approaches due to different analytical challenges, including matrix effects (which can affect adduct ion formation) and the lack of reference standards. The most abundant contaminants were linear alkylbenzene sulfonates (LAS; weighted mean [WM] concentration of 3700 μg g^-1 dry weight), followed by secondary alkane sulfonates (SAS; 190 μg g^-1). Alcohol polyethoxylates (AEO; 8.3 μg g^-1), nonylphenol polyethoxylates (NPEO; 16 μg g^-1), nonylphenol (NP; 3.1 μg g^-1), nonylphenol ethoxy carboxylates (NPEC; 0.35 μg g^-1) and tert-octylphenol (tert-OP, 1.8 μg g^-1) were present at much lower concentrations. This concentration pattern agrees with the production volumes of the surfactants and their fates in WWTPs. Branched AEO homologues dominated over linear homologues, probably due to higher persistence. Sludge concentrations of LAS, SAS, and NP were positively correlated with the residence time in the anaerobic digester. Derivation of the per capita loads successfully revealed potential industrial/commercial emission sources. Comparison of recent versus historic data showed a decrease in NPEO and NP levels by one or two orders of magnitude since their ban in the 1980s. By contrast, LAS still exhibit similar concentrations compared to 30 years ago.

Surfactants in aquatic and terrestrial environment: occurrence, behavior, and treatment processes

Surfactants belong to a group of chemicals that are well known for their cleaning properties. Their excessive use as ingredients in care products (e.g., shampoos, body wash) and in household cleaning products (e.g., dishwashing detergents, laundry detergents, hard-surface cleaners) has led to the discharge of highly contaminated wastewaters in aquatic and terrestrial environment. Once reached in the different environmental compartments (rivers, lakes, soils, and sediments), surfactants can undergo aerobic or anaerobic degradation. The most studied surfactants so far are linear alkylbenzene sulfonate (LAS), quaternary ammonium compounds (QACs), alkylphenol ethoxylate (APEOs), and alcohol ethoxylate (AEOs). Concentrations of surfactants in wastewaters can range between few micrograms to hundreds of milligrams in some cases, while it reaches several grams in sludge used for soil amendments in agricultural areas. Above the legislation standards, surfactants can be toxic to aquatic and terrestrial organisms which make treatment processes necessary before their discharge into the environment. Given this fact, biological and chemical processes should be considered for better surfactants removal. In this review, we investigate several issues with regard to: (1) the toxicity of surfactants in the environment, (2) their behavior in different ecological systems, (3) and the different treatment processes used in wastewater treatment plants in order to reduce the effects of surfactants on living organisms.

Simplified spectrophotometric method using methylene blue for determining anionic surfactants: applications to the study of primary biodegradation in aerobic screening tests

In the present work, we propose a simplified spectrophotometric method for determining anionic surfactants, based on the formation of the ionic pair anionic surfactant-methylene blue (AS-MB). This method, in relation to the conventional analytic procedure, considerably reduces not only the quantity of chloroform used in extracting the ionic pair formed, but also the time and the quantity of sample necessary to perform the assay, eliminating the filtration stage. The method has been simplified by displacing the transfer equilibrium of the ionic pair AS-MB towards the organic phase, augmenting the volumetric relationship of chloroform/sample. The method proposed has been applied in the study of primary biodegradation kinetics of linear alkylbenzenesulfonate (LAS).

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.

Application of liquid chromatography–electrospray-tandem mass spectrometry for the identification and characterisation of linear alkylbenzene sulfonates and sulfophenyl carboxylates in sludge-amended soils

A novel procedure was developed for the simultaneous determination of linear alkylbenzene sulfonates (LAS) and their major metabolites, sulfophenyl carboxylates (SPC), in sludge-amended soil. After pressurised liquid extraction with methanol/water (90:10) and a clean-up on C18 solid-phase extraction cartridges, final analysis was done by ion-pair liquid chromatography-electrospray-tandem mass spectrometry (LC-ESI-MS/MS). With this method, SPC with 5-13 carbon atoms in the aliphatic side chain were identified for the first time in agricultural soils treated with sewage sludge. Quantification of LAS and SPC in soil from 10 field sites, which differed in the history of sludge application, gave total concentrations of 120-2840 microg kg(-1) for LAS and of 4-220 microg kg(-1) for SPC. The data provided evidence for rapid biodegradation of LAS in the initial phase after sludge amendment with a transitory build-up of high concentrations of, mainly, short-chain SPC. Trace amounts of residual LAS and SPC were detected in soils having received the last sludge treatment 10 days to 4 years prior to sampling.

Toxicity of linear alkylbenzene sulfonate in anaerobic digestion: influence of exposure time

The inhibition of anaerobic digestion by the anionic surfactant linear alkylbenzene sulfonate was studied. The development of bacterial activity during several weeks was monitored by performing batch degradation tests with acetate and propionate. In the first phase the decay of activity without surfactant addition was studied. After the addition of the surfactant an immediate inhibition was detected. Subsequently, the degradation activity continued to decrease with increasing exposure time. Both, the immediate inhibition and the rate of the subsequent decrease of activity were dependent on the surfactant concentration. A kinetic model is presented that describes this behavior. A surfactant concentration of 14 mg L(-1) causes a 50% immediate inhibition of acetate degradation (27 mg L(-1) in the case of propionate degradation). Additionally, each 12 mg L(-1) of surfactant increases the decay rate of acetate degradation activity by a factor 10 (23 mg L(-1) for propionate degradation). A deviation from this model occurs at low surfactant concentrations (<3 mg L(-1)), where a slight stimulation of bacterial activity was observed. The above-mentioned concentrations refer to measured surfactant concentrations. These were substantially lower than the nominal concentrations (added surfactant per volume). This discrepancy is explained by adsorption of the surfactant to the biomass. Finally, the importance of the presented kinetic model and the significance of surfactant toxicity for anaerobic digestion are discussed.

Formation of metabolites during biodegradation of linear alkylbenzene sulfonate in an upflow anaerobic sludge bed reactor under thermophilic conditions

Biodegradation of linear alkylbenzene sulfonate (LAS) was shown in an upflow anaerobic sludge blanket reactor under thermophilic conditions. The reactor was inoculated with granular biomass and fed with a synthetic medium and 3 micromol/L of a mixture of LAS with alkylchain length of 10 to 13 carbon atoms. The reactor was operated with a hydraulic retention time of 12 h with effluent recirculation in an effluent to influent ratio of 5 to 1. A sterile reactor operated in parallel revealed that sorption to sludge particles initially accounted for a major LAS removal. After 8 days of reactor operation, the removal of LAS in the reactor inoculated with active granular biomass exceeded the removal in the sterile reactor inoculated with sterile granular biomass. The effect of sorption ceased after 185 to 555 h depending on the LAS homologs. 40% of the LAS was biodegraded, and the removal rate was 0.5 x 10(-6) mol/h/mL granular biomass. Acidified effluent from the reactor was subjected to dichloromethane extraction followed by gas chromatography/mass spectrometry. Benzenesulfonic acid and benzaldehyde were detected in the reactor effluent from the reactor with active granular biomass but not in the sterile and unamended reactor effluent. Benzenesulfonic acid and benzaldehyde are the first identified degradation products in the anaerobic degradation of LAS.

The biodegradation of surfactants in the environment

The possible contamination of the environment by surfactants arising from the widespread use of detergent formulations has been reviewed. Two of the major surfactants in current use are the linear alkylbenzene sulphonates (LAS) and the alkyl phenol ethoxylates (APE). These pass into the sewage treatment plants where they are partially aerobically degraded and partially adsorbed to sewage sludge that is applied to land. The biodegradation of these and a range of other surfactants both in wastewater treatment plants and after discharge into natural waters and application to land resulting in sewage sludge amended soils has been considered. Although the application of sewage sludge to soil can result in surfactant levels generally in a range 0 to 3 mg kg(-1), in the aerobic soil environment a surfactant can undergo further degradation so that the risk to the biota in soil is very small, with margins of safety that are often at least 100. In the case of APE, while the surfactants themselves show little toxicity their breakdown products, principally nonyl and octyl phenols adsorb readily to suspended solids and are known to exhibit oestrogen-like properties, possibly linked to a decreasing male sperm count and carcinogenic effects. While there is little serious risk to the environment from commonly used anionic surfactants, cationic surfactants are known to be much more toxic and at present there is a lack of data on the degradation of cationics and their fate in the environment.

Terrestrial risk assessment for linear alkyl benzene sulfonate (LAS) in sludge-amended soils

A comparison of the estimated environmental concentration and the effect concentrations (in the laboratory or field) in the receiving compartment form the basis of environmental risk assessments. This paper reviews processes that critically influence the fate of LAS in the terrestrial environment. Concentrations of LAS in sludge are quite high due to sorption to primary sludge, precipitation of Ca and Mg-salts of LAS, and lack of biodegradation under anaerobic digestion. This implies that when sludge is applied to soil e.g. as a fertilizer, considerable amounts of this important surfactant may enter the terrestrial environment. Influence of aerobic situations on LAS concentrations during sludge storage needs further research to allow incorporation into the risk assessment. Aerobic biodegradation in soil is considered the most important removal mechanism of LAS loading to the terrestrial environment through sludge-amendment. Sorption plays a role in determining the residence time of a chemical in the soil, hereby enabling more time for biodegradation to occur. In addition, sorption may affect the expression of effects of surfactants towards benthic and soil dwelling organisms and plants. Another factor that needs further attention is the form of LAS in the environment, which is not similar to the commercial material applied in detergents. The differential sorption and biodegradation of the LAS components lead to a shift in the alkyl chain length (homologue), and phenylisomer distribution towards increased hydrophobicity. Also, occurrence of Ca/Mg-salts in the environment versus the Na-salt for the commercial material critically impacts the extrapolation of effects data obtained in lab studies (mostly performed with the commercial material) to the field. The literature data were used in combination with strategies and methods provided by the European Union Technical Guidance Document in support of risk assessment of new and notified substances (1996) for the prediction of environmental concentrations of LAS entering the soil system through sludge applications. Soil biodegradation is an essential, necessary element for the PEC-calculations of LAS. The initial realistic worst case assessment presented indicates no human health risks exists with indirect exposure to LAS through either food or drinking water. Also, current LAS use does not pose a risk to terrestrial organisms such as plants and invertebrates.

Sources, behaviour and fate of organic contaminants during sewage treatment and in sewage sludges

Recent concern over the environmental impact of sewage sludge application to agricultural land has drawn particular attention to the wide range of organic contaminants that may enter sewage treatment processes and persist in biosolids for disposal. This paper discusses processes influencing the fate and behaviour of organic contaminants during wastewater treatment and reviews literature relating to specific contaminants identified in sewage sludge. The difficulties associated with the development of specific methods for the analysis of trace residues of organic contaminants in complex matrices such as sludge are discussed. Some potential issues relating to impact of sewage sludge disposed to agricultural land are also considered.

Surfactants and complexing agents: new tasks for specimen banking?

Surfactants and complexing agents are chemical products that are released into the environment in large amounts after being used in cleaning processes, mineral flotation, pesticide formulations, etc. Although these compounds are largely degraded during sewage treatment in industrialized countries, significant amounts will be found in sediments or sewage sludges. Furthermore, large concentrations of these compounds can be found in small rivers and brooks in the vicinity of outfalls of sewage treatment plants. Since these compounds can be expected to alter the organic matrix of the soil (surfactants) or to remobilize heavy metals from soils or sediments (complexing agents), their occurrence in the environment and their effects have to be investigated to estimate their long-term risk potential. This could be a new task for specimen banking. To this end, (a) sensitive and specific detection methods for surfactants and complexing agents have to be developed at concentrations relevant to environmental occurrence, and (b) the effect of surfactants and complexing agents on the distribution of organic and inorganic pollutants in environmental compartments has to be investigated. Preliminary investigations show significant synergistic or antagonistic effects of various surfactants on the adsorption of pollutants at clay minerals.

Chronic toxicities of surfactants and detergent builders to algae: a review and risk assessment

Surfactants are high volume chemicals used primarily in detergent products and are found in natural waters. The toxic effects of representative surfactants on aquatic life have been determined and summarized in greater detail for animal test species than for aquatic vegetation. This paper summarizes the chronic toxicity levels for algae, an important trophic level in aquatic ecosystems. Toxic effects have been determined for a few commercially important surfactants and primarily for cultured freshwater algae under the controlled conditions of the laboratory where inhibition, and in some cases, stimulation have been observed. The reported toxicities of surfactants have varied widely over several orders of magnitude and the effect levels are compound and species-specific. Species sensitivity can vary as much as three orders of magnitude to the same surfactant and the effects of different surfactants on the same algal species can vary as much as four orders of magnitude. Therefore, data generalizations and extrapolations are difficult but anionic and nonionic surfactants and detergent builders are relatively non-toxic when compared to various cationic monoalkyl and dialkyl quaternary ammonium salts. Recent toxicity studies conducted in the field monitoring the effects of several surfactants used in commercial products on various structural and functional parameters of natural algal communities have shown toxicity to be less in many cases than that predicted from laboratory tests. Furthermore, the field-derived effect levels typically exceed the reported measured environmental levels of the corresponding surfactants indicating the likelihood of no impact. Additional field studies are needed to substantiate this trend for these and other commercially important surfactants particularly for natural saltwater algal assemblages for which the toxicity data base is unavailable.