The top several inches of the sand has to be removed regularly usually by hand due to the mass of growing material schmutzdecke that collects in the filter.
Water treatment slow sand filter diagram.
Lab effectiveness field effectiveness and health impact.
It is very old type water filtration or water treatment system.
Early slow sand filters typically have filter rates of 0 05 gpm ft2 of surface area and require large filter areas.
Provides hydraulic head pressure to push water through the sand filter below.
Slow sand filter biological filter elements of a slow sand filter 1.
The slow sand water filter in water treatment field slow sand filter is the large scale water filter.
In a study water was obtained from sample taps of water treatment plants from three local reservoirs.
Feed turbidity in one study ranged from 1 86 to 3 9 ntu.
1 4 hydraulic conductivities for slow sand filters 19 1 5 summary of designs of slow sand filters in europe as reported by hazen with units adjusted to fit those used in this manual 21 1 6 design criteria for slow sand filters for rural water supplies 26 2 1 present and projected flow data for village of 100 mile house bc 35.
Crushed rock is the best type of filtration sand since it has less chance of being contaminated with pathogens or organic material.
Bed of graded sand on a support of gravel 3.
Well water in most cases needs only disinfection because it is already clear.
Distribute the water and prevent disturbing the sand near the filter wall.
Depth varies from 1 1 5meters serves two important purposes.
Sand and gravel preparation selecting and preparing the filtration sand and gravel is crucial for the treatment efficiency of the sand filter.
It poured through a slow sand filter and results showed that turbidity decreased to a mean of 1 45.
The key components of a slow sand filter are as follows.
Slow sand filter lab effectiveness studies with a mature biolayer have shown 99 98 protozoan 90 99 bacterial and variable viral reduction.
A system of filter control valves 1.
The treatment required is not always the same.
Several types of filters are used for water treatment.
Surface water quite commonly needs coagulation sedimentation filtration and disinfection.
A provides a constant head of water this overcomes the resistance of the filter bed.
Water with high turbidity looks dirty due to sand silt and clay floating in the water.
Some household treatment methods and their effectiveness are summa rized in table 6 1 whereas the following household and community water treatment technologies are described in greater detail.
Users can maintain flow rate by cleaning the filter through agitating the top level of sand or by pre treating turbid water before filtration.
The diagram below shows a simplified schematic of a sand filter.
In the slow sand filter water entering first through about 32 36 inches of sand then through a multi size layer of gravel this layer is known as schmutzdecke which is german for dirty skin before entering the under drain.
Treatment qf raw water raw water is the term used to refer to water which needs treatment.
Household water treatment systems boiling.
