Grit chambers

Grit chambers are basin to remove the inorganic particles to prevent damage to the pumps, and to prevent their accumulation in sludge digestors.

1. GRIT CHAMBERS 4/26/2016 1 ASHWANI KUMAR 1NT12CV064

2. GRIT Grit is the heavy mineral material found in raw sewage, and it may contain sand, gravel, silt, cinders, broken glass, small fragments of metal and other small inorganic solids. S ubsiding velocities or specific gravity substantially greater than those of organic putrescible solids in water. Ex-eggshells, bone chips, sand, gravel, silt etc.. 4/26/2016 2

3. GRIT CHAMBER Grit chamber is the second unit operation used in primary treatment of wastewater and it is intended to remove suspended inorganic particles such as sandy and gritty matter from the wastewater limited to municipal wastewater Grit chambers are provided to protect moving mechanical equipment from abrasion and abnormal wear; avoid deposition in pipelines, channel, and conduits; and to reduce frequency of digester cleaning 4/26/2016 3

4. TYPES OF GRIT CHAMBERS Horizontal Flow Grit Chamber Aerated Grit Chamber 4/26/2016 4

5. HORIZONTAL FLOW GRIT CHAMBER Velocity maintained is 0.3 m/s Permit the heavier grit to settle but carry organic particles To maintain a constant velocity of flow, a control section is placed at the end of the channel. A control section varies with the c/s area of the flow in the section in direct proportion to the flow. 4/26/2016 5

6. 4/26/2016 6 Fig: Horizontal Flow Grit Chamber

7. DESIGN OF GRIT CHAMBERS Settling velocity Overflow rate Detention period Bottom scour Velocity control devices Number of units Dimensions of each unit 4/26/2016 7

8. AERATED GRIT CHAMBER It consists of a standard spiral flow aeration tank provided with air diffusion tubes placed on one side of the tank. G rit particles tend to settle down to the bottom of the tank at rates dependant upon the particle size and the bottom velocity of roll of the spiral flow, which depends on the rate of air diffusion through diffuser tubes and shape of aeration tank. The lighter organic particles are carried with roll of the spiral motion 4/26/2016 8

9. 4/26/2016 9 Fig: Aerated grit chamber

10. DISPOSAL OF GRIT Clean grit is characterized by the lack of odour It is included when detention time is more or flow through velocity is less Disposed by dumping or burying or by sanitary landfill Unwashed grit acts a soil conditioner and will give good yeild 4/26/2016 10

11. 4/26/2016 11 THANK YOU