EFFECT OF THREE FRACTIONS EXTRACTED FROM AN AEROBIC AND AN ANAEROBIC SEWAGE SLUDGE ON THE WATER STABILITY AND SURFACE AREA OF SOIL AGGREGATES

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Abstract
We sequentially extracted two sludges with boiling ethyl ether, ethyl alcohol, and water and then added suitable amounts of the resulting fractions-namely, (1) fats, waxes, and oils; (2) resins; and (3) water-soluble polysaccharides-to 1− to 2-mm aggregates of two soils. The concentration of the added fractions ranged from 0 to 2.5 percent by weight of the dry soil. After drying the aggregates, we measured their stability to wet-sieving and their nitrogen surface areas (SA). Water stability increased markedly with ether- and alcohol-soluble fractions. The stabilizing effect of the water-soluble fractions was poor for the soil richer in clay and absent for the soil richer in silt. For both sludges the water stability of the soil aggregates improved as more hydrophobic substances were extracted with ether. Surface areas of aggregates decreased after all treatments. The reduction of SA was not affected by the kind of sludge and only slightly influenced by the kind of fraction. We sequentially extracted two sludges with boiling ethyl ether, ethyl alcohol, and water and then added suitable amounts of the resulting fractions-namely, (1) fats, waxes, and oils; (2) resins; and (3) water-soluble polysaccharides-to 1− to 2-mm aggregates of two soils. The concentration of the added fractions ranged from 0 to 2.5 percent by weight of the dry soil. After drying the aggregates, we measured their stability to wet-sieving and their nitrogen surface areas (SA). Water stability increased markedly with ether- and alcohol-soluble fractions. The stabilizing effect of the water-soluble fractions was poor for the soil richer in clay and absent for the soil richer in silt. For both sludges the water stability of the soil aggregates improved as more hydrophobic substances were extracted with ether. Surface areas of aggregates decreased after all treatments. The reduction of SA was not affected by the kind of sludge and only slightly influenced by the kind of fraction. © Williams & Wilkins 1983. All Rights Reserved.