The sugar industry is third largest industry in the country. About 60% of the world sugar production is made from sugarcane. The sugarcane is crushed in the sugar mill and the juice extracted by heavy rollers.
The juice contains saccharose, glucose, laevulose, organic salts and acids in solution and is mixed with biogases fibers, clay, colouring matter, albumen and pectin in suspension. Clarification is obtained through heating and the addition of lime based precipitants. Once clarified the juice is concentrated by vacuum evaporation until it precipitates in the form of grayish crystals.
The concentrated juice or molasses contains 45% of water. Centrifuge treatment produces granulated sugar of a greyish hue (brown sugar), however, while sugar is obtained by a refining process. In the refineries, the brown sugar is dissolved with various chemicals (sulphuric anhydride, phosphoric acid) and is filtered with or without bone black depending upon the desired purity. The filtered syrup evaporates in vacuum until it crystallizes; centrifugation is then applied until a white crystalline powder is obtained.
Sugarcane is grown in tropical and subtropical zones where certain diseases and pathological conditions are endemic. These are made worse by poverty and by environmental and working conditions (temperature up to 40°C and humidity as high as 80%).
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The worker is obliged to large quantities of liquid, fumes and gases may be given off at various stages of the refining process (carbon dioxide, sulphurdioxide, carbon monoxide, hydrochloric acid fumes). The fumes and steam given off are troublesome and sometimes toxic. Dust with residue from the
ovens can irritate the respiratory tract and bagassosis has been reported in the past.
In some pates of the factory (as near turbines), noise levels may exceed tolerable limits. Decomposing organic matter gives off unpleasant odors (suppurated hydrogen). The commonest injuries are heatstroke, various kinds of dermatitis, conjunctivitis, burns and falls. The incidences of dental decay are fairly high. Morbidity is in general 50% higher than in other branches of industry. Tuberculosis, alcoholism and chronic fatigue are characteristic in tropical countries and these are diseases which are peculiar to the area.
Cane sugar industry is one of the most polluting industries in India. Sugar mills discharge large amount of wastewater having low pH with high concentration of suspended solids, dissolved solids, BOD and COD. Bureau of Indian Standards presented data on the average volume of wastewater generated per tone of cane crushed and the wastewater quality based on data collection, Huascaran and Chakra borty reported that the sugar mill wastewaters are amenable to treatment by anaerobic digestion followed by stabilization in anaerobic oxidation pond.
Ketter and Huchabay suggested that besides process changes for reducing the wastewater, volume and good housekeeping, marooning and stabilization by organisms in Methanogenic system is necessary. Satyabaldieva et.al. Used waste water characteristics to optimise organic matter removal by coagulation. Sinha and Thakur reported studies on anaerobic digestion of cane sugar waste water.
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Vander Meer and Lettings have developed up flow anaerobic sludge blanket reactors for the treatment of sugarmill wastewater. Garcia et.al. Reported studies on sugar refinery waste water treatment in acidification lagooning. They have reported 95% BOD removal. Vanden Borg et.al. Studied the treatment of sucrose waste water at high organic loading rates in anaerobic down flow stationary fixed film reactors.
Manjunath studied anaerobic digestion of sugar mill waste water. Although lot of work has been carried out on treatment of sugar mill waste waters using differential biological methods, not much information is available on the treatment of sugar mill waste water in an up flow anaerobic filter.