Many studies have been conducted in the U.S. and Europe in recent years on linear alkylbenzene sulfonate (LAS) in sewage treatment. These studies demonstrate that LAS is rapidly biodegraded and extensively removed during biological trea tment in municipal sewage treatment plants and in household septic systems.
- In
the U.S., 75% of sewage is treated in municipal treatment plants
while 25% is treated in household septic systems, mostly in
suburban and rural areas.(1)
- Biodegradation
of LAS begins in raw sewage before reaching the sewage treatment
plant.(2-4)
- From
1987 through 1989, 50 U.S. sewage treatment plants (STPs) were
monitored for LAS concentrations. Testing of incoming water
(influent), outgoing water (effluent) and solids (sludge) show
extensi ve removal of LAS from wastewater. Indeed, LAS was more
efficiently removed than were other biodegradable materials,
measured as the biochemical oxygen demand, or BOD.(5)
- Most
U.S. STPs are activated sludge units, which typically remove
more than 99 percent of the LAS present in sewage. Other systems,
such as rotating biological contactors (RBCs) and oxidation
ditche s, have LAS removal rates ranging from 96 to 99 percent.
Less efficient and less widely used trickling filter systems
remove 77 percent when used alone, but reach more effective
removal levels when coupled with methods such as sand filtration.(5)
- Comparison
of the performance of activated sludge treatment plants with
those from an earlier (1973 through 1986) U.S. monitoring study
(6) shows that LAS removal during sewage treatment has improved
over the years, probably due to more efficient treatment plant
operation.
- Most
of the LAS removal is due to rapid and complete biodegradation
during sewage treatment.(5,7,8)
- Consequently,
LAS concentrations in water and sediments of rivers and streams
receiving treated wastewater are very low and pose no risk to
the environment. The remaining LAS will continue to rapidl y
biodegrade (See "LAS Biodegradation and Safety in Rivers
and Streams" and "LAS Biodegradation and Safety in
Sediments").
- Sludge from sewage treatment is incinerated, put in landfills or applied to land as a soil conditioner or fertilizer. LAS levels in sludge applied to soil are very low and pose no risk to the environment. Remaining LAS continues to rapidly biodegrade (See "LAS Biodegradation and Safety in Sludges and Soils").
- Numerous studies of sewage treatment plants in Europe have demonstrated that LAS rapidly biodegrades and is extensively removed during biological treatment.(3,4,9-14)
- LAS biodegrades rapidly in the soil under the percolation field of a household septic system. Consequently, LAS is efficiently removed in septic systems and poses no risk to groundwater resources.(15-17)
- Sludge from sewage treatment is incinerated, put in landfills or applied to land as a soil conditioner or fertilizer. LAS levels in sludge applied to soil are very low and pose no risk to the environment. Remaining LAS continues to rapidly biodegrade (See "LAS Biodegradation and Safety in Sludges and Soils").
2. Moreno, A., J. Ferrer and J.L. Berna. "Biodegradability of LAS in a Sewer System." Tenside Surf. Det. 27, 312-315 (1990).
3. Cavalli, L., A. Gellera and A. Landone. "LAS Removal and Biodegradation in a Wastewater Treatment Plant." Environ. Toxicol. Chem. 12, 1777-1788 (1993).
4. Snchez Leal, J., M.T. Garca, R. Toms, J. Ferrer and C. Bengoechea. "Linear Alkylbenzene Sulfonate Removal." Tenside Surf. Det. 31, 253-256 (1994).
5. 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).
6. Rapaport, R.A. and W.S. Eckhoff. "Monitoring linear alkyl benzene sulfonate in the environment: 1973-1986." Environ. Toxicol. Chem. 9, 1245-1257 (1990).
7. Rapaport, R.A., R.J. Larson, D.C. McAvoy, A.M. Nielsen and M. Trehy. "The Fate of Commercial LAS in the Environment." 3rd CESIO International Surfactants Congress & Exhibition -- A World Market, Proceedings, Section E, pp. 78- 87 (London, June 1-5, 1992).
8. Trehy, M.L., W.E. Gledhill, J.P. Mieure, J.E. Adamove, A.M. Nielsen, H.O. Perkins and W.E. Eckhoff. "Environmental Monitoring for Linear Alkylbenzene Sulfonates, Dialkyltetralin Sulfonates and Their Biodegradation Intermediates." Environ. Toxicol. Chem., 15, 233-240 (1996).
9. 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).
10. Berna, J.L., A. Moreno and J. Ferrer. "An Assessment of the Ultimate Biodegradation of LAS." Tenside Surf. Det. 30, 217-222 (1993).
12. Di Corcia, A., R. Samperi, A. Bellioni, A. Marcomini, M. Zanette, K. Lemr, and L. Cavalli. "LAS pilot study at the "Roma-Nord" sewage treatment plant and in the Tiber river." Riv.Ital. Sost. Grasse 71, 467-475 (1994 ).
13. Schberl, P., H. Klotz, R. Spilker and L. Nitschke. "Alkylbenzolsulfonat-(LAS-)Monitoring." Tenside Surf. Det. 31, 243-252 (1994).
14. Waters, J. and J. Feijtel. "AIS/CESIO Environmental Surfactant Monitoring Program: Outcome of Five National Pilot Studies on Linear Alkylbenzene Sulfonate (LAS)." Chemosphere 30, 1939-1956 (1995).
15. 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).
16. 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 (199 4).
17. 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).
- Birch,
R.R. "Prediction of the Fate of Detergent Chemicals During
Sewage Treatment." J. Chem. Tech. Biotechnol. 50,
411-422 (1991).
- Cowan,
C.E., R.J. Larson, T.C.J. 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).
- Painter, H.A. "Anionic Surfactants" The Handbook of Environmental Chemistry, Vol. 3, Part F, pp. 1-88 (Springer-Verlag, New York, NY, 1992). Last updated on May 1996
# # #
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