Sugar factory waste characteristics

A)    Floor washings and boiler blowdown:-
A considerable amount of waste water results from floor washings which contain oil and grease and spillover of juice etc. The BOD concentration of this waste may be in the range of 1000 to 1500 mg/l. The boiler blowdown may not contain any organic pollutants, however, the inorganic contents are high.

B)    Soda and Acid wash waters:-
It is general practice to clean heat exchangers and evaporators with caustic soda and hydrochloric acid in order to remove scale on the surface of tubings. Normally the caustic soda washings are stored and reused for next cleaning operation. However, most of the sugar factories discharge this waste stream into drains. If recycling is followed, not only the problem of disposal of waste would be solved but a considerable saving of chemicals can be achieved. After the equipment is boiled with caustic soda and rinsed with fresh water, the equipment is treated with dilute hydrochloric acid along with an inhibitor. This wastewater is discharged into drains, as the recovery of dilute HCL may not prove to be economical.

The washings of soda and acid contribute considerable amount of organic and inorganic pollution load and would lead to shock load on wastewater treatment plants. These washings should be stored in the holding tank and discharged in a gradual manner into waste treatment plant or allowed to dry in evaporation pits and the sludge can be disposed off in low lying areas.

C)    Excess condensate turbine overflow:-
The condensate does not normally contain any pollutants and is used as boiler feed water, washing operations, imbibition water etc. It may so happen sometimes that it may get contaminated with juice due to entrainment in which case it is let out into wastewater gutter. The treatment requirement in this case is nominal and can be let out directly as irrigation water after cooling or can be stored in a pond to percolate into ground which would help to recharge ground water table.

D)    Condenser cooling water:-
In some industries mini cooling towers are used to cool waters and recycle back for process. Condenser cooling water is recirculated unless it gets contaminated with juice due to defective entrainment separators, faulty operation beyond the design rate capacity of evaporators etc. If it gets contaminated the water would go into drain invariably. The best way is to avoid entrainments and if it is not possible to recharge into groundwater after neutralisation.

E)    Sulphur and lime house:-
The washing of sulphur and lime house may contribute a inorganic solids concentration. The sulphur burner and compressor cooling waters can be recycled after passing through spray pond / cooling tower.

F)    Vacuum filter washing:-
The filter is washed occasionally and this would contribute considerable amount of suspended solids. This waste contains both organic and inorganic pollutants. The waste streams may be diverted to holding tank.

Waste water streams.
The characteristics of industrial streams as well as combined effluents are given below

Sr. No	Type of waste	Oil & Grease	pH	COD	BOD	TS	TDS	SS	Chloride
1	Mill house	40-80	6.0-7.7	1500-2000	800-900	600 -800	300 -400	300-400	60-80
2	Boiler Blow down	20-40	9.0-10.0	300-500	200-300	3000-3500	2800-3400	100-200	80-160
3	Floor washing	100-400	5.0-6.0	4000-6000	2000-3000	3000-4000	2500-3400	500-600	40-60
4	Pan section	20-40	4.0-4.5	800-1000	200-300	1000-1200	800 -900	200-300	100-150
5	Boiling House	10-20	4.0-4.5	800-2000	450-850	1000-1900	900-1700	100-200	30-50
6	Filter washing	Nil	4.5-7.0	10,000-15,000	4,000-6,000	15,000-20,000	12,000-15,000	3,000-5,000	200-300
7	Cleaning waste	100-200	4.0-5.0	4,000-6,000	2,000-3,000	7,000-8,000	6,500-7,000	500-1,000	150-200
8	Excess condensate	Nil	6.0-7.0	100 -300	50-100	500 -800	400 –600	100-200	30-50
9	Spray pond overflow	Nil	7.0-7.5	100-300	50-100	600-1000	500 -800	100-200	30-50
10	Combined	100-150	5.0-5.5	2000-3000	800-1200	2500-3000	1000-2000	300-400	80-100

Note : All values except pH are in mg/l.