Page History

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Concentric well screen filter design
Offset filter bed design
Single 55 gallon barrel filter schematic
55 Gallon Barrel Filters with Shared Clear Well
Single 55 gallon barrel filter schematic
Height required to attain backwash velocity (with headloss calculations)

Factors to

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consider for operation:

1)a. Sand level monitoring
b. Pressure across filters
c. -Plexi-glass viewing strip on barrel side
2)Pressure across filters-when do the filters need to be back-washed?
-piezometer
3)Backwash Velocity- achieve bed expansion without losing sand
-Gate valve on siphon tube
4)Flow distribution during backwash
d. Bypass entire system-avoiding shocks to the system
5)Bypass -for seasons when filtration is unnecessary

Discussion topics

a. 7 backwash 1 problems/feasibility
b. Inclusion of clear well
c. Backwash with raw water1)8 parallel filters: where 7 down-flow filters backwash 1 filter
-Problem: not flexible for variable plant flow rates
-If multiple filters are dirty, can not achieve desired backwash velocity
2)Clear well might be necessary
-Constant backwash velocity
-If multiple filters are dirty, filters can still be back-washed
3)Backwash from sedimentation tank
-Is using raw water for backwash okay?
-At end of backwash ~6 inches of dirty water is retained in bed, so the first distribution of water after backwash will have high turbidity

Future work

Bench top model:
-Test how changing the height difference (between the water level in the clear well to the bottom of the siphon) influences backwash velocities.
-Fine-tune the backwash velocity using a gate valve on the siphon tube.