2.19     EFFLUENT TREATMENT PROCESS

The mill plant effluent contains oil and fibre. This effluent is therefore subjected to deskimming operation in mill plant itself to free it from oil and fibre and mixed with other factory effluents. The combined effluents are treated in preliminary and secondary treatment as described below. The flow diagram of effluent treatment plant is given in Figure-

i. Preliminary Treatment:

Combined effluent from common drainage is lead to the effluent treatment plant. It is passed through bar screen, grit   chamber and oil separator and then received in a neutralizer cum equalization tank of about 30 min holding capacity. Lime/caustic soda is added to raise the effluent pH to about 7.0-7.5 and also to. precipitate some of the inorganic dissolved solids. The neutralized effluent is' passed through the primary classifier of 2.5 to 3.0 hr. detention period. The sludge collected at the bottom is pumped to sludge drying bed for denaturing. The clear overflow from the classifier is passed to biological treatment plant for secondary treatment. In the primary treatment, the grit fiber and suspended solids are removed by screens. The BOD is reduced by 15% . However the BOD reduction has not been considered while designing the secondary treatment plant.

ii Secondary Treatment :

This plant consists of the stage wise activated sludge aerobic treatment process. Each stage consists of the aeration tank with fixed surface aerators and secondary clarifies. The effluents containing suspended active Biodegradable suspended mass clarified in respective secondary clarifies. In respective secondary clarifies. Sludge settled at the clarifies is recycled to aeration tank to maintain the concentration of mixed liquor suspended solids (MLSS) tank at the desired level. The excess active sludge from secondary clarifies is pumped to sludge drying beds. The clear effluent from clarifies is collected in a polishing pond of about 8 hours capacity and then let out to agricultural land for irrigation

AGRICULTURAL LAND FOR LETTING OUT TREATED EFFLUENT                     

A total of 80 acres agricultural land is provided for utilizing the treated effluent for irrigation purpose for cultivation of sugar cane/seed development.