Filtration Flashcards
The typical filter run time for a high rate filter system is between __ and __ hours. 24 hours is an average high rate filter run time.
12 and 36 hours
The action of straining suspended particles plays a ___ role during filtration. Filtration depends on a combination of physical and chemical mechanisms, ___ being the most important.
Minor
Adsorption
A diatomaceous earth filter uses ___ for filtration.
Pressure
Coating the sides of uncovered sedimentation basins with ___ ___ and ___ can eliminate slime growths.
Copper sulfate and Lime
Operators that run a ______ ___ ______ process have as their objective the production of pinfloc for easier flotation and removal.
Dissolved air flotation
The filtration media in a slow sand filter is ___.
Unstratified
___ to ___ % of the water produced by a conventional rapid sand filter is used for backwashing.
2 to 4 %
___ plates are usually inclined at 45 degrees.
Lamella
The ___ process is eliminated by direct filtration.
Sedimentation
A backwash rate that is too ___ can cause gravel displacement which can lead to a ___ ___.
High
Sand Boil
When treating low turbidity water and operating a filter for one week between backwashes, ___ ___ can still occur even though the water quality is high.
Floc breakthrough
High rate filters operate in the range of _ to _ gpm/ft2.
3.0 to 8.0 gpm/ft2
A difference in ___ between anthracite and sand causes the anthracite to remain on top of the sand following a backwash. Sand has a higher ___ than anthracite.
Density, density
___ tube settlers are inclined about 5 degrees.
Horizontal
Slow sand filters have a ___.
Schmutzdecke (biological mat) on top.
Cleaning is accomplished by scraping the top inch of sand and schmutzdecke off the filter
It takes several days to re-establish the schmutzdecke after cleaning
Filtered water must be wasted until the schmutzdecke is reestablished
This process can be repeated until the sand depth reaches about 2 ft (starts with 3 1/2 ft sand depth).
