BIOLOGICAL TREATMENT OF CHEMICALLY FLOCCULATED AGRO-INDUSTRIAL WASTE FROM THE WOOL SCOURING INDUSTRY BY AN AEROBIC PROCESS WITHOUT SLUDGE RECYCLE ANDREW J. POOLE 1 *, RALF CORD-RUWISCH 2 and F. WILLIAM JONES 1 CSIRO Division of Wool Technology, Belmont, Vic. 3216, Australia and 2 School of Biological and Environmental Sciences, Murdoch University, Murdoch, WA 6150, Australia (First received April 1998; accepted in revised form September 1998) AbstractÐA new agro-industrial euent known as Sirolan CF euent is the aqueous phase remaining after the chemical ¯occulation of wool scouring euent by the Sirolan CF process. This euent has been characterized, and shown to be eectively treated by biological degradation. It has a high concen- tration of organic material (5750 mg/L COD), with a low BOD 5 /COD ratio (0.29). Aerobic biological treatment was tested using laboratory and pilot scale reactors, and shown to remove essentially all BOD 5 , solvent extractable material and detergent activity. Maximum removal of the COD was 65% leaving a 2000 mg/L residual component of nonbiodegradable organic material. The combined pro- cesses of Sirolan CF and biological treatment removed over 90% of the COD and all solvent extracta- ble material from raw wool scouring euent. This compares favourably to existing treatment systems, and represents a viable and attractive alternative to treat this extremely polluted wastewater. # 1999 CSIRO. Published by Elsevier Science Ltd Key wordsÐwool scouring, agro-industry, wastewater, Sirolan CF, biodegradation, aerobic, chemostat. INTRODUCTION The worldwide annual production of wool is pro- jected to reach to 1.6 million tonnes (clean weight) by the year 2001 (IWS, 1996). The scouring (washing) of this wool removes an approximately equal weight of contaminants and uses around 10 m 3 of water per tonne of raw wool. The wastewater produced is the most contaminated in the textile industry, and one of the most polluted agro-industrial euents. It consists of a stable emulsion of wool wax in an aqueous sol- ution containing dissolved organic and inorganic compounds. The principal environmental threat comes from the extremely high oxygen demand of typically 45,000 mg/L chemical oxygen demand (COD) (Genon et al., 1984). This cannot be lowered through improved scouring techniques since the scouring process is one of contaminant extraction. Indeed, rationalized water usage in recent times has led to more concentrated euents. This means specialized treatment systems are required, however none of the currently used chemical, physical, bio- logical or combined processes have proved wholly satisfactory due to environmental or economic reasons. Seventy-®ve percent of the total COD in wool scouring euent comes from the emulsi®ed wool wax, and recently a chemical ¯occulation process (Sirolan CF) has been developed which removes over 95% of wool wax (Bateup et al., 1996). The sludge produced may be used in composting or soil dressing as a means of disposal. The ¯ow-down from the process (Sirolan CF euent) contains the water soluble organic and inorganic compounds washed from the raw wool, known as ``suint'' (Truter, 1956), which is a highly colored mixture of mainly potassium salts of fatty acids, as well as peptides (Mozes, 1982). The residual pollutant con- centration of approximately 5000±15000 mg/L COD is still unacceptably high and further treat- ment is required. MATERIALS AND METHODS The present study characterizes the Sirolan CF euent, and investigates in batch and continuous culture exper- iments whether it can be eectively treated by an aerobic biological system to remove the water soluble pollutants. The incubation parameters used were: dissolved oxygen (DO) >50% of saturation, pH 7 and 308C. Euent was obtained from a pilot Sirolan CF system operated at a commercial wool scouring plant in Melbourne, Australia. The euent did not putrefy when in storage due to its low pH (pH < 4). Wat. Res. Vol. 33, No. 9, pp. 1981±1988, 1999 # 1999 CSIRO. Published by Elsevier Science Ltd Printed in Great Britain 0043-1354/99/$ - see front matter PII: S0043-1354(98)00391-1 *Author to whom all correspondence should be addressed. [Tel.: +61-3-5246-4000; fax: +61-3-5246-4057; e-mail andrew.poole@dwt.csiro.au]. 1981