APPLICATION OF CHEMICAL COAGULATION AND LAND SYSTEM
FOR IMPROVING BIOLOGICAL WOOL SCOURING WASTEWATER
TREATMENT
AUen C. Chao, Assistant Professor
North Carolina State University
Dept. of Civil Eng.
Raleigh, North Carolina  27650
Wan-fa Yang, Professor & Director
Sze-Kung Tseng, Associate Professor
Graduate Institute of Environmental Engineering
National Taiwan University
Taipei, Taiwan
Republic of China
INTRODUCTION
Biological wastewater treatment systems, such as activated sludge processes or trickling
filters [ 1 ], have been widely employed for treating the wastewater from wool scouring plants
to meet stringent effluent limitations. The wool scouring wastewater usually contains significant quantities of grease, suspended solids and organic matter. The grease constitutes a special
treatment problem because it is not readily biodegradable.  Its presence in the wastewater tends
to coat biological floes and reduces the oxygen transfer rate, thus interfering with the operation of the biological process.
In-process recovery may greatly reduce the quantity of grease in the processed wastewater
[2, 3], but its concentration in the final discharge may still be too high to be properly treated
in a biological system. Therefore, removing grease from wool scouring wastewater before it
reaches the treatment plant will enhance the efficiency of the biological system.
Various physiochemical and biological pretreatment methods can be employed to achieve
removal of grease with the associated suspended solids and organic matter. Their application
for management of wool scouring wastewater depends primarily on many objective factors in
addition to technical feasibilities.
This paper presents approaches to solve this problem for wool scouring plants located in two
distinct geographical regions. These plants have similar wool scouring processes and in-process
wool grease recovery facilities and discharge wastewaters of the same characteristics. Because
of the geological and environmental differences of the plant locations, two entirely different
methods have been or will be adopted to reduce the wastewater loads on the biological treatment plants and to increase the treatment efficiencies.
Plant A is typical of most wool scouring plants currently operated in the United States,
Australia and New Zealand, and has a plant-owned wastewater treatment system for treating
the process water and other minor streams generated by the plant (Table I). This plant is located in a rural area with vast land available for future expansion. Thus, a land disposal system
has been incorporated into the existing biological system to achieve better effluent quality.
Plants B and C are representative of those located in industrial parks in some southeastern
Asian areas such as Taiwan (Table I). The wool scouring wastewater is mixed with other industrial wastewater streams and treated in a central system owned and operated by the
industrial park. Land is very restricted so that future expansion of the treatment system is
limited to processes requiring little space. Chemical coagulation and dissolved air flotation have
been selected for reducing the grease content of the wastewater to be treated in a biological
central plant.
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