Mechanism of aerobic biological destabilisation of wool scour effluent emulsions.
Wool scouring effluent is a highly polluted industrial wastewater in which the main pollutant, wool wax, is held in a stable oil-in-water emulsion by non-ionic detergent. The use of microbial action to cause emulsion destabilisation has been proposed as a new treatment strategy for this effluent stream. This strategy aims at improving aerobic treatment performance by physically removing the high-COD, slowly bio-degradable wool wax from the system without bio-degradation. The mechanism by which an aerobic-mixed culture destabilises the wool scouring effluent emulsion was investigated. Our results show that destabilisation is due to partial bio-degradation of both the scouring detergent and the wool wax. Cleavage of the wool wax esters was the first stage in wax degradation, when 40-50% of wax was de-emulsified. Over the same period, detergent degradation was low, at 7-21%. With further incubation, detergent degradation increased, aiding further breakdown of the emulsion. The degradation of the detergent, a nonylphenol ethoxylate, resulted in both a reduction in molar concentration (of up to 82%) and a shortening of the ethoxylate chain length. The latter reduced the hydrophile-lipophile balance (HLB) from 12 to approximately 7, thereby reducing the ability of the residual detergent to stabilise the emulsion. Analysis of the emulsified and de-emulsified wax fractions could not identify a group of compounds that were preferentially de-emulsified based on molecular weight or polarity. These findings will assist in using a de-emulsification strategy in both existing and new treatment systems in order to save on aeration costs and treatment times for biological treatment of this highly polluted wastewater.
Poole
Andrew J
AJ
CSIRO Textile and Fibre Technology, Belmont 3216, Vic., Australia. andrew.j.poole@csiro.au
Cord-Ruwisch
Ralf
R
William Jones
F
F
D000818:Animals; D001420:Bacteria, Aerobic; D001673:Biodegradation, Environmental; D019149:Bioreactors; D003902:Detergents / Q000737:chemistry; D004655:Emulsions; D005026:Ethylene Glycols / Q000737:chemistry; D006868:Hydrolysis; D007220:Industrial Waste; D008970:Molecular Weight; D013997:Time Factors; D014865:Waste Disposal, Fluid / Q000379:methods*; D018508:Water Purification / Q000379:methods*; D014885:Waxes / Q000737:chemistry; D014935:Wool
D003902:Detergents; D004655:Emulsions; D005026:Ethylene Glycols; D007220:Industrial Waste; D014885:Waxes; C021754:terics