SUGAR INDUSTRY :

India is the largest producer of sugar in the World and per capita consumption of sugar in the country is 13,4 kilograms per annum, There are about 400 operating sugar mills, located mainly in the states of Uttar Pradesh Maharastra Andhra Pradesh, Karnataka and Tamil Nadu, During 1993-94, these industries have produced 98 Iakh tonnes of sugar. It is a seasonal industry and operates for about 6 months in a year, normally from October to March.

Pollution Problems
sugar mills consume around 1,500-2,000 litres of water and generate about 1,000 litres of wastewater for per tonne of cane crushed, the effluent is mainly floor washing wastewater and condensate water, Leakage in valves and glands of the pipeline add sugarcane juice, syrup and molasses in the effluent, The sugar mill effluent has a BOD of 1,000-1,500 mg/litre, but appears relatively clean initially, However after stagnating for sometime, it turns black and start emitting foul odour, If untreated effluent is discharged,in water courses, It depletes dissolved oxygen In water and makes the environment unfit for aquatic life. If untreated effluent is discharged on land, decaying organic solids and oil and grease clog the soil pores.

Most of the use bagasse as a Sugar mills fuel in boilers, which produces particulate matter, oxides of nitrogen, carbon, sulphur and water The vapours, The particulate matter, usually referred to as fly ash, consists of ash, unburnt bagasse and carbon practicles. Fly ash is very light therefore, if pollution control equipments are not Installed, it escapes in the atmosphere through chimney and travels long distances. In such conditions, nearby population suffer from dizziness and irritation in eyes, nose, throat and lungs. The heavier particles, if settle on vegetation then it damages them Among the solid waste generated by sugar mills, lime sludge and press mud are important. For purifying the sugarcane juice from organic matter, dirt and other impurities, milk of lime is In generates lime sludge. The impurities from the sugarcane juice is either vacuum filtered or press have filtered and removed as press mud. In addition to these, solid wastes are also generated from the pollution control facilities, like ETP sludge and flyash collected from the dusting devices.

Pollution Standards
The pollution standards stipulate that BOD of effluent should be less than 30 mg/lltre for disposal into inland surface waters and less than 100 mg / litre for disposal on land. BOD can be 500 mg / litre, in case land application effluent is envisaged as a secondary treatment system for further removal of BOD.

Regardlng water consumption and effluent generation, specified standards are 1 ,000 Iltres and 400 litres respectively for per tonne of cane crushed.

As per general emission standards, particulate matter is required to be within 150 mg/Normal cubic metre. In case of horse shoe/pulsating grate and spreader stroker bagasse fired boilers, the particulate matter emission is required to be within 500 mg/ Normal cubic metre and 800 mg/ Normal cubic metre respectively

Pollution Control
There is scope of recycling and reuse of water in sugar mills thereby minimising water consumption and ultimately effluent quantity. The recycling and reuse of hot condensate water can reduce the water consumption to as low as. 100-200 litres, as against 1,500-2,000 litres per tonne of cane crushed. Proper housekeeping, periodic checking and maintenance of pipe joints, valves and glands further reduces the water consumption and effluent quantity .The effluents from the sugar industry can be treated added. The preparation of milk of the lime by conventional biological treatment systems. general, anaerobic biological processes (oxidation ponds and biomethanation) several advantages over aerobic processes (aerated lagoons, activated sludge process). Anaerobic processes are easier to control and operate, produce a lower quantity of sludge and their costs are lower. Anaerobic processes decompose the organic compounds in an atmosphere free of oxygen and consequently require significantly less energy as compared to aerobic processes.

Among the air pollution control of treated equipments; wet collectors and multi-cyclones, can reduce particulate matter in boiler emissions by 90% or more. These equipments can reduce ..the concentration of particulate matter to 450 mg/ Normal cubic metre.

Double Sulphitation Process, already adopted by most of the sugar industries, reduces the quantity of lime sludge and press mud to a I great extent. The lime sludge is usually dumped in low lying areas, whereas press mud is sold to farmers as it can be used as manure. Bagasse is either used as fuel or sold to pulp and paper industry which use them as raw materials.. Molasses produced in sugar industry is raw materials for fermentation industries.

The table 7 reveals that a sugar mill requires only ariund 180 litre of water per tonne of cane as against the stipulate limit of 1,000 litres, if the condensate water is properly utilised and cooling water is recycled.

Table 7 : Water Balance Sheet for Sugar Industry
S.No.
Water Available/Required
Credit
Use
Balance
  
(per tonne of cane crushed)
1.
Quantity of water available as hot condensate (after accounting for all losses in bagass, molassess, press mud etc.



0.5 m3


-


-
2.
Water required at various sections of the mill,
(i) imbibition
--
0.20 m3
--
(ii) Lime preparation
--
0.02 m3
--
(iii) Evaporator pans
--
0.05 m3
--
 (iv) Boiler feed
--
0.01 m3
--
 (v) Cooling water *
--
0.04 m3
--
  
Sub Total   0.05 m3
0.68 m3
--
3.
Extra Water Required   
* With closed loop cooling water system for recycling.

Biogas from Press Mud
Press mud, which is discarded as a solid waste from sugar mills and used as a manure or as a landfill, is found to be an useful substrate for biogas production. Based on the studies conducted by the Department of Agriculture of the Annamalai University, Tamil Nadu, the Ministry of Non-Conventional Energy Sources, Govt. of India, selected M/S Ugar Sugar Works ltd., Karnataka for a demonstration plant including biogas distribution system to 120 families residing in the factory complex.

The results indicated biogas production upto 80 Nm3/tonne of fresh press mud. The effluent slurry is also useful as a nutrient rich fertilizer.


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