A Biological Treatment for Color Removal in Distillery Effluents
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Date
2013
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Publisher
Uva Wellassa University of Sri Lanka
Abstract
Distilleries are one of the industries generating enormous amount of wastewater which is about 10–15 L of effluent for the production of 1 L of alcohol. The fermentation of carbohydrates present in molasses is carried out by yeasts, which yields ethyl alcohol. The pH of the raw
molasses is adjusted to 4 - 4.5 to prevent bacterial growth and then fermented liquor containing
alcohol is degasified and alcohol is separated, leaving behind the waste called “spent wash”.
The spent wash is the major polluting waste of the distillery, which has very high Biological
Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) values. The COD often crosses
and BOD reaches7×10 mgL (Goel, 2006).The waste is dark brown in
color due to caremalization of some sugar. It also contains nearly 2% of the dark brown
recalcitrant pigment called melanoidin, which does not get degraded easily by microorganisms,
posing a great difficulty in its removal. Molasses has very high quantity of fermentable sugars.
These sugars react with amino acids and undergo Maillard reaction and then polymerize to form
melanoidin, which is a major color containing compound in the distillery effluent. Putrescible
organics like skatole, indole and other sulfur compounds produces obnoxious smell in the
effluent and when it comes in contact with high temperature, becomes more toxic to aquatic
biota. The waste has substantial quantities of dissolved solids and suspended solids with high
. The pH of spent wash remains in the
acidic range varying from 3 to 5.4 (Goel, 2006). The distillery waste also has high quantities of
potassium along with sulphates.
Melanoidin containing distillery effluents require pretreatment before safe disposal into the
environment, because the direct disposal causes serious soil and water pollution by inducing
coloration and eutrophication problems in aquatic environments- which leads to reduction of
sunlight penetration in water bodies. Additionally, it in turn decreases both photosynthetic
activity and DO concentration affecting the normal life cycle of aquatic fauna and flora (Goel,
2006). Further, it causes reduction in soil alkalinity, inhibition of seed germination and damage
to vegetation upon land disposal. Treatment of distillery wastewaters by physical or chemical
methods was found not feasible due to the high cost and generation of secondary pollutants. But
compared to them biological treatments are more economical and environmental friendly. Many
fungi species have the ability of removing color from wastewaters. Especially white rot fungi
exhibit extensive bioremediation activities that are mainly based upon their capabilities to
produce extracellular lignin modifying enzymes (Pant and Adholeya, 2007). In this research we
studied several white rot fungi activity towards decolorization of distillery effluents.
Methodology
Ten polyporusbasidiomycetes white rot fungi species were collected for distillery waste water
treatment from Matara area.Effluent was collected from Pelwatte distillery inButtala. Effluent
was dark brown in color, semi liquid and a dense material. About 5mm squares were cut from
collected basidiocarps and placed on PDA plates and were incubated for 7 days. Among them,
five fungal species were selected for the experiment due to their rapid growth.
Above efficiently growing five fungal specieswere isolated using streak plate method. Streaked
cultures were incubated again for 7 days.Then, using these cultures new plates were prepared by
spread plate method incubatingagain for seven days.
Description
Keywords
Materials Sciences, Materials Sciences, Biological Treatment, Biochemistry, Waste Water Treatment