LINEAR ALKYLBENZENE SULFONATE (LAS) - UNEP Chemicals

OECD SIDS LINEAR ALKYLBENZENE SULFONATE (LAS)
(C) Conc. In sludge 30.2; 12.8; 11.4; 7.0 and 7.5 g LAS/kg of dry matter
(from 5 plants)
Remarks: (A) Plants with aeration/settling system
(B) Plants with activated sludge & aerobic digestion of sludges system
(C) Plants with activated sludge & anaerobic digestion of sludges.
The concentrations in sludge correlate with water hardness. The higher the
water hardness, the greater the amount of calcium-precipitated LAS in the
sludge. For example, the water hardness that resulted in the 30.2 g/kg value
was >500 mg/L as calcium carbonate. This level of hardness is very high and
is 2-3 times higher than the more typical range of 200-300 mg/L as calcium
carbonate. The amount of LAS physically removed to the sludge during
primary settleing versus biodegradaded can be seen in the following table.
Treatment Plant Physical
LAS
Water Hardness
(all from category C) Removal Biodegradation (as mg/L CaCO3)
Alicante 35% 68.2% >500
Sevilla S.E. 30% 75.6% 220
Sevilla N. 27% 87% 315
La China (Madrid) 16% 91%