A STUDY ON REUSE OF WATER IN A WOOLEN MILL
Hu Jiajun, Professor
Cal Bute, Professor
Gao Tingyao, Associate Professor
Gu Youghin, Lecturer
Wang Huizheng, Lecturer
Department of Environmental Engineering
Tongji University
Shanghai 2000092
China
INTRODUCTION
In the Shanghai Second Woolen Mill, there are two workshops discharging colored wastewater
(top dyeing workshop and dyeing-finishing workshop). Main raw materials are wool and synthetic
fiber. Products are woolen and blend fabrics. Dyestuffs used are acidic mordant dyes, disperse dyes,
sulfur dyes, neutral dyes, reactive dyes and direct dyes. Also, different dyeing auxiliaries are used. The
Shanghai Environmental Protection Bureau demands treatment of colored wastewater.
From September 1974 through June 1976, field experiments were carried out under the conditions
in this mill, resulting in making use of biotower-flotation process and working out design parameters
and flowsheet. Consequent design and construction followed. At the end of 1979, construction of the
treatment facilities was finished. The facilities were put into operation and since then the effluent has
been meeting the criteria for discharge but has a distinct tint to exclude it from reuse. In order to make
use of the effluent and further improve the environmental quality, it was sought to upgrade the treatment process in use so as to further reduce color of the effluent for recycle. So research was carried
out in 1982, resulting in the development of a coagulation-adsorption process for decolorization by
which the effluent could be recycled with only insignificant modification of the existing facilities.
EXPERIMENTS ON BIOLOGICAL TREATMENT
Biotower
The area available for constructing the treatment works was only 250 m2. In making plans for experimentation, a biotower was chosen. The filter media of the experimental biotower was honey-comb
plastic blocks.
The effect of hydraulic loading rate was evaluated after the biotower had run as smoothly as
expected. After a two-month operation period, it was found that when the hydraulic loading rate was
lower than 80 m3/m2/day, the openings of the 19 mm honey-comb media were clogged. Thereafter
25 mm-blocks were used, and the hydraulic loading rate was raised. When the loading rate was up to
120-160 m3/m2/day, the effluent met the national criteria for discharge. BOD5 and COD removal
was 70-90% and 65-75%, respectively.
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