Section 2. BREWERY AND DISTILLERY WASTES
TREATMENT OF DISTILLERY WASTEWATER (SPENT WASH)
INDIAN EXPERIENCE
T. Damodara Rao, Executive Engineer
Tamil Nadu Water Supply and Drainage Board
Madras, India
T. Viraraghavan, Professor
Faculty of Engineering
University of Regina
Regina, Saskatchewan
Canada S4S OA2
INTRODUCTION
It is reported that 141 distilleries are working in India consuming approximately 2.2 million tonnes
of molasses producing about 500 million litres of alcohol [1]. The largest number (approximately 30)
of distilleries are located in Uttar Pradesh, while 15 distilleries operate in Tamil Nadu. The phenomenal growth of the sugar industry in India resulted in an excessive production of molasses, a byproduct which is used in the manufacture of alcohol. The industrial process adopted by the distilleries
is nearly the same viz., fermenting the diluted molasses with yeast and distilling the alcohol produced
by passing a counter current of steam while allowing the fermented wash to come down a tall column.
Only about 10% of the molasses is utilized in the process, and the major remaining portion ends
up as an effluent in the process. The liquid wastes from the process mainly consist of spent wash
besides yeast waste sludge and floor washings. Yeast waste sludge is separated out, dried on land
nearby and used as animal feed. The resulting spent wash is highly coloured, high in total solids and
organic matter; it has to be rendered environmentally acceptable for final disposal. This paper discusses the methods investigated, adopted and proposed for the treatment of distillery spent wash in
India.
CHARACTERISTICS OF DISTILLERY SPENT WASH
The characteristics of spent wash from molasses distilleries reported by some investigators in India
are shown in Table I. The wastewater is characterized by high BOD (40 000 to 50 000 mg/1), low pH
(3.5 to 4.5), high dissolved solids (70 000 to 80 000 mg/1), high level of sulphates (4 000 to 8 000
mg/1) and considerable amounts of potassium (8 000 to 12 000 mg/1); the wastewater is highly colored
and has a distinct "molasses" odor. Thus distillery effluent (spent wash) resulting from a cane molasses based alcohol industry is one of the highly polluting industrial effluents.
RESULTS FROM EXPERIMENTAL (BENCH-SCALE AND PILOT-SCALE) SYSTEMS
A considerable amount of work has been carried out by a number of investigators in India to
find an acceptable and economical solution to the treatment and disposal of distillery wastewater.
Anaerobic Digestion Studies
Sen and Bhaskaran [5] carried out laboratory studies to determine the optimum condition for
high rate digestion of molasses distillery waste. It was found that anaerobic digestion of this waste
was possible at 37 C using digested cow dung as seed at a BOD loading of 3 kg/m'/d, corresponding
to a detention time of ten days. Anaerobic digestion resulted in 90% BOD removal and the final
effluent had a BOD less than 1000 mg/1. The gas contained 60% methane. De et al. [6] used diluted
spent wash in anaerobic digestion studies and concluded that 1:3 dilution was optimum to obtain a
BOD removal efficiency of approximately 90% at a detention time of 5 days at a BOD loading of
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