11.9 Granular Filtration

Question 1

what are the three basic methods for controlling the filtration rate and distributing the flow to the filters?

Answer 1

modulation control valve, influent weir splitting, declining-rate filtration

Question 2

what is the modulating control valve system equipped with?

Answer 2

flow meter and a control valve

Question 3

water flows in through a common channel and is split equally to all operating filters by the weir

Answer 3

influent weir splitting system

Question 4

declining rate filtration system: each filter receives a different flow depending on the accumulated __________

Answer 4

headloss

Question 5

which filters receive the greatest flow in declining rate filtration systems?

Answer 5

cleanest

Question 6

develops in a filter when the summation of headlosses from the media surface downward exceeds the depth of water to that point

Answer 6

negative head

Question 7

when shallow water operating depths are provided, negative head develops a ________ _________ into the media

Answer 7

short distance

Question 8

negative head may cause bubbles of dissolved _______ and _______ to come out of the solution

Answer 8

oxygen and nitrogen

Question 9

reduction of effective filtering area as a result of bubbles being stuck in the bed

Answer 9

air binding

Question 10

what are three indicators for evaluating the performance of the filter

Answer 10

filtered water turbidity, length of filter run, ratio of backwash water to filtered water