Effect of air space

180/120 = 100/x
x = 100/1.5 = 67%
6. Mean flow rate (%): The mean flow rate (%) of all phase was also calculated by adding the
flow rate (%) of each phase and dividing by the total number of phase.
7. Time required for volume of water to be filtered (min): This is the time that is required for
certain volume of water to be filtered.
8. Mean time required for volume of water to be filtered (min): The mean time required for
volume of water to be filtered was calculated by adding all the total time required for volume
of water to be filtered for each phase and dividing by the total number of phase.
Arsenic concentration of filtered water (ppb): This data defines the As concentration in the
filtered water

, ANNEX B Table Of Data Obtained During The field Study

Bishow Nath Chaudhary (20 liters. water used)

Raw samples: 250 ppb( before filtration)
Phase 1:
After filtration:

Volume of Amount Flow liter Flow Mean Arsenic
water of water Rate per rate in flow conc. of
filtered in the (sec hour terms rate (%) filtered
(L) basin (%) per 100 of % water(ppb)
ml)
2 100% 2 180 100% 100% 30
4 88% 2 180 100% 100% 30
6 75% 3 120 67% 89% 20
8 63% 3 120 67% 89% 20
10 50% 4 90 50% 67% 20
12 38% 4 90 50% 62% 20
14 25% 7 51 29% 36% 10
16 13% 11 33 18% 24% 10
18 0% 21 17 10% 13% 10


Raw samples: 250 ppb (before filtration)
Phase 2:
After filtration:
Volume of Amount Flow liter Flow Arsenic
water of water Rate per rate in conc. of
filtered in the (sec per hour terms filtered
(L) basin 100 ml) of % water(ppb)
(%)
2 100% 3 120 100% 20
4 88% 3 120 100% 20
6 75% 3 120 100% 20
8 63% 3 120 100% 20
10 50% 4 90 75% 10
12 38% 4 90 75% 10
14 25% 7 51 43% 10
16 13% 10 36 30% 10
18 0% 20 18 15% 10