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behaviour of las


Sludge Amended Soils

The use of sludge from Wastewater Treatment Plants in agricultural soil amendment is a frequent practice in most European countries, although with a variable degree of application from one country to another.

Surfactants are present in sludge of wastewater treatment works due to their physical - chemical properties and their ability to adsorb / precipitate. The occurrence and effects of surfactants on sludge amended soils has been widely investigated with a rich data base on LAS augmented by limited information on other surfactants. It is estimated that between 10 and 20% of the surfactant load to a WWTP escape the biological treatment due to precipitation / adsorption into the primary sludge ending up in the final sludge. LAS in sludge degrades rapidly and extensively in sludge amended soils as well as during the composting of sludge.

Summary of Data of LAS Occurrence and Behavior in Sludge Amended Soils.

Typical LAS conc. in anaerobic sludge in Europe

0.5 - 10 g/Kg d.s

LAS removal in sludge amended soils

> 98%

Half life of LAS in sludge amended soils

10 - 30 days

LAS removal during composting

> 99%

          No accumulation detected in soils after several years of continuous application of sludge.
          No LAS has been found in water percolating through soil. The migration (leaching) potential is limited to the first few cm of soil thickness.
          No intact LAS is adsorbed by plants growing in sludge amended soils.

Key references

Berna JL, J Ferrer, A Moreno, D Prats, F Ruiz Bevia, The fate of LAS in the environment, Tenside Surf. Det. 26: 101-107, 1989

DiCorcia A, R Samperi, A Belloni, A Marcomini, M Zanette, K Lemr, L Cavalli, Riv. It. Sostanze Grasse LXXI: 467-475, 1994

Feijtel-a TCJ, E Matthijs, A Rottiers, GBJ Rijs, A Kiewiet, A de Nijs, AISE/CESIO environmental surfactant monitoring programme. Part 1: LAS monitoring study in "de Meer" STP and receiving river "Leidsche Rijn", Chemosphere 30: 1053-1066, 1995

Holt MS, Matthijs E, Waters J, The concentrations and fate of LAS in sludge amended soils, Wat. Res 23: 749-759, 1989

Prats-b D, M Rodriguez, MA Muela, JM Llamas, J Ferrer, A Moreno, JL Berna, AM Nielsen, C Naylor, Elimination of LAS in sewage biosolids by composting, 5th World CESIO Congress V.2: 1475-1488, 2000, Firenze, Italy

Sànchez Leal J, MT Garcià, R Tmàs, J Ferrer, C Bengoechea, Tenside Surf. Det. 31: 253-256, 1994

Solbè J, JL Berna, L Cavalli, TCJ Feijtel, KK Fox, J Heinze, SJ Marshall, W de Wolf, Terrestrial risk assessment of LAS in sludge-amended soils, 5th World CESIO Congress V.2: 1433-1438, May-June 2000, Firenze, Italy