Linear alkylbenzene sulfonate (LAS) can become attached (adsorbed) to sewage sludge before it enters wastewater treatment systems and, while continuing to biodegrade, can be present in sewage sludge following treatment. Similarly, LAS f rom sludges can sometimes be found in soil mixtures shortly after treated sludges are applied to agricultural lands as fertilizer. Concentrations of LAS in these "sludge-amended soils" rapidly decrease with time. Studies show that LAS levels typically fou nd in treated sludge are safe. Thirty years of hazard assessments show that any trace amounts of LAS present and breaking down in soil do not harm plants, earthworms and soil bacteria.
Following standard aerobic treatment, levels of LAS in sludge drop considerably. Post-treatment concentrations average 152 milligrams per kilogram (mg/kg).(2)
Studies on agricultural lands fertilized by treated sludge -- "sludge amended soils" -- have found that any remaining LAS biodegrades, or breaks down, rapidly. The half-life (the time it takes for half a substance to break down) o f LAS in sludge applied to soil is between five and 33 days.(6) A similar study on sludge-amended soils found LAS half-lives ranging from seven to 22 days.(7-8)
Soil studies in areas where LAS in sludge was applied for over 10 years demonstrate that LAS levels quickly decrease from 50 mg/kg to a range of zero to 5 mg/kg after application.(9,10)
A 1987 study on farm fields showed that LAS concentrations at 42 sites where sludge had recently been applied dropped significantly, from initial concentrations of 2.6 to 66.4 mg/kg to concentrations of zero to 2.5 mg/kg.(7,8 )
In another study, 98 percent of the remaining LAS in two soil types mineralized, or biodegraded completely, within 76 and 106 days, respectively.(11)
LAS effect levels for test crops (including sorghum, wheat, corn and sunflower) range from 167 mg/kg to more than 407 mg/kg (for most plant species tested). These levels are three to several hundred times higher than even initial concentrations of LAS present before degradation in sludge-amended soils.(12)
Crops are usually planted at least a month after sewage sludge is added, allowing sufficient time for much, if not all, of the LAS to disappear. What little LAS remains biodegrades completely during the growing season, with LAS le vels quickly decreasing to a range of zero to 5 mg/kg.(9,10,13)
2. McAvoy, D. C., W. S. Eckhoff and R. A. Rapaport. "Fate of Linear Alkylbenzene Sulfonate in the Environment." Environ. Toxicol. Chem. 12, 977-987 (1993).
3. Rapaport, R. A. and W. S. Eckhoff. "Monitoring Linear Alkyl Benzene Sulfonate in the Environment: 1973-1986." Environ. Toxicol. Chem. 9, 1245-1257 (1990).
4. Takada, H. and R. Ishiwatari. "Linear Alkylbenzene in Urban Riverine Environments in Tokyo: Distribution, Source and Behavior." Environ. Sci. Technol. 21, 875-883 (1987).
5. Cowan, C.E., R.J. Larson, T.C. Feijtel and R.A. Rapaport. "An Improved Model for Predicting the Fate of Consumer Product Chemicals in Wastewater Treatment Plants." Wat. Res. 27, 561-573 (1993).
6. Knaebel, D. B., T. W. Federle and J. R. Vestal. "Mineralization of Linear Alkylbenzene Sulfonate and Linear Alcohol Ethoxylate in 11 Contrasting Soils." Environ. Toxicol. Chem. 9, 981-988 (1990).
7. Waters, J., M. S. Holt and E. Matthijs. Tenside Surf. Det. 26, 129 (1989).
8. Holt, M. S., E. Matthijs and J. Waters. Water Research 23, 749 (1989).
9. de Hanau, H., E. Matthijs and W.D. Hopping. Int. J. Anal. Chem. 26, 279 (1986).
10. Giger, W., A. C. Alder, P. H. Brunner, A. Marcomini, and H. Seigrist. "Behavior of LAS in Sewage and Sludge Treatment and in Sludge-Treated Soil." Tenside Surf. Det. 26, 95-100 (1989).
11. Figge, K. and P. Schoberl. "LAS and the Application of Sewage Sludge in Agriculture." Tenside Surf. Det. 26, 122-128 (1989).
12. Mieure, J. P., J. Waters, M. S. Holt and E. Mathijs. "Terrestrial Safety Assessment of Linear Alkylbenzene Sulfonate." Chemosphere 21, 251-262 (1990).
13. Berna, J. L., J. Ferrer, A. Moreno, D. Prats, and F. Ruiz Bevia. "The Fate of LAS in the Environment." Tenside Surf. Det. 26, 101-107 (1989).
Giger, W., P. H. Brunner, M. Ahel, J. McEvoy, A. Marcomini and C. Schaffner. "Organische Waschmittelinhaltsstaffe und deren Abbauproduckte in Abwasser und Klarschlamm." Gas-Wasser-Abwasser 67, 111-122 (1987).
Hand, V. C. and G. K. Williams. "Structure-Activity Relationships for Sorption of Linear Alkylbenzene Sulfonates." Environ. Sci. Technol. 21, 370-373 (1987).
Hand, V. C., R. A. Rapaport and C. A. Pittinger. "First Validation of a Model for the Adsorption of Linear Alkylbenzene Sulfonate to Sediment and Comparison to Chronic Effects Data." Chemosphere 21, 741-750 (1990).
Litz, N., H. W. Doering and H. P. Blume. "The Behavior of Linear Alkylbenzene Sulfonates in Different Soils: A Comparison Between Field and Laboratory Studies." Ecotox. Environ. Saf. 14, 103-116 (1987).
McAvoy, J. And W. Giger. "Determination of linear alkylbenzene sulfonates in sewage sludge by high resolution gas chromatography/mass spectometry." Environ. Sci. Technol. 20, 376-383 (1986).
McAvoy, D. C., C. E. White, B. L. Moore and R. A. Rapaport. "Chemical Fate and Transport in a Domestic Septic System: Sorption and Transport of Anionic and Cationic Surfactants." Environ. Toxicol. Chem. 13, 213-221 (1994).
Orth, R. G., R. L. Powell, G. Kutey and R. A. Kimerle. "Impact of Sediment Partitioning Methods on Environmental Safety Assessment of Surfactants." Environ. Toxicol. Chem. 14, 337-343 (1995)
Shimp, R. J., E. V. Lapsins and R. M. Ventullo. "Chemical Fate and Transport in a Domestic Septic System: Biodegradation of Linear Alkylbenzene Sulfonate (LAS) and Nitrilotriacetic Acid (NTA)." Environ. Toxicol. Chem. 13, 205-212 (1994).
Shutter, S. B., E. A. Sudicky and W. D. Robertson. "Chemical Fate and Transport in a Domestic Septic System: Application of a Variably Saturated Model for Chemical Movement." Environ. Toxicol. Chem. 13, 223-231 (1994).
Urano, K., M. Saito and C. Murato. "Adsorption of Surfactants on Sediments." Chemosphere 13, 293-300 (1984).
Vandomi, M. V., L. Goldberg-Federico. Riv. Ital. Sostanze Grasse 50, 185 (1973).
# # #
INDEX OF CLER FACT SHEETS
- Executive Summary
- Recent Developments
- LAS Biodegradation and
Removal In Sewage Treatment
- LAS Biodegradation and
Safety in Rivers and Streams
- LAS Biodegradation and
Safety in Sediments
- LAS Biodegradation and
Safety in Sludge and Soils
- LAS Biodegradation and
Safety Under Anaerobic Conditions
- Biodegradation and
Safety of Commercial LAS
- Environmental and Other
Benefits of Replacing ABS With LAS
- Test Methods for Biodegradation
- Laboratory Versus Field
Safety Assessment Studies
- Oleochemical and Petrochemical Surfactants