78 Questions
EASY What is the primary purpose of removing suspended solids in water treatment?
To reduce disinfection costs
What is the size of suspended solids that can be removed in the first stage of water treatment?
Greater than 2 microns
What happens to suspended solids if not removed in water treatment?
They cause deposits, erosion, and plugging of equipment
What type of water is likely to have high levels of suspended solids?
River and lake water
What is the purpose of a settling pond or basin?
To slow or delay the velocity of water and allow suspended solids to settle
How do clarifiers differ from settling ponds?
Clarifiers have features that promote the continuous removal of solids deposited by sedimentation
What is the typical residence time for water in a clarifier?
An hour or two
How is water introduced in a typical clarifier?
From the center
What is the primary function of the filter in the treatment process?
To catch suspended solids in the water
What happens to the pressure drop across the filter as it screens out more solids?
It increases
What is the primary use of activated carbon filters in industry?
To remove chlorine from municipal source water
What happens to the chlorines in water when they pass through an activated carbon filter?
They are reduced to non-oxidative chlorides
What is the result of heating carbonaceous material to about 1000°C with steam?
The material is transformed into activated carbon
What is the purpose of backwashing and regenerating activated carbon filters?
To restore the filter's effectiveness
What is the unique property of activated carbon that makes it useful for adsorption?
Its high surface area to mass ratio
What is the equivalent surface area of one teaspoon of activated carbon?
A football field
What is the purpose of adding alum or synthetic polymer coagulant in the clarifier?
To speed up the settling time of particles
What is the main function of a clarifier?
To remove suspended solids from the water
What type of particles are less than 1 μm in size and carry a slight electric charge?
Colloidal particles
What is the purpose of the rake in the clarifier?
To remove particles from the bottom of the clarifier
What is the purpose of the filter medium in a pressure filter?
To trap suspended particles in its pores
What is the consequence of inadequate backwash flow in a filter?
Trapped solids will not come free
What is the purpose of the filter-aid in a filter-aid tubular filter?
To pre-coat the tubes and prolong the filter run
What is the purpose of the compressed air in the upper part of the filter housing in a filter-aid tubular filter?
To force water through the tubes in the reverse direction during backwashing
What type of filters are similar to an oil filter in an automotive engine?
Cartridge filters
What is the consequence of excessive backwash flow in a filter?
The filter medium is entrained and removed to waste
MEDIUM What is the primary purpose of adding alum or a synthetic polymer coagulant in the clarifier?
To neutralize the particles and speed up the settling time
What is the function of the rake in the clarifier?
To remove the sludge from the bottom of the clarifier
What is the purpose of the filter medium in a pressure filter?
To remove the suspended particles from the water
What happens to the filter cake in a filter-aid tubular filter when it needs to be replaced?
It gets removed and replaced with new filter-aid
What is the purpose of the compressed air in the upper part of the filter housing in a filter-aid tubular filter?
To force water through the tubes in the reverse direction during backwashing
What is the consequence of inadequate backwash flow in a filter?
Trapped solids will not come free, making the backwash ineffective
What is the purpose of a clarifier in water treatment?
To remove suspended solids from the water
What type of particles are less than 1 μm in size and carry a slight electric charge?
Colloidal particles
What is the result of excessive backwash flow in a filter?
The filter media gets removed to waste, making the filter ineffective
What type of filters are similar to an oil filter in an automotive engine?
Cartridge filters
What is the primary purpose of the filter in the treatment process?
To remove suspended solids from the water
What happens to the water as it passes through the filter?
It gets clarified and sent to the next stage
What is the purpose of monitoring the pressure drop across the filter?
To determine when to replace the filter cartridge
What is the primary use of activated carbon filters in water treatment?
To remove taste or odors from the water
What is the result of adsorption of organics onto the activated carbon?
The removal of taste or odors from the water
What is the unique property of activated carbon that makes it useful for adsorption?
High surface area to mass ratio
What is the purpose of backwashing and regenerating activated carbon filters?
To restore the filter's effectiveness
What happens to the carbon atoms during the production of activated carbon?
They are removed as they react with steam
What is the primary benefit of removing suspended solids in the first stage of water treatment?
Removing heavy metals and reducing other treatment costs
How do suspended solids behave in water?
They sink or float with gravity
What is the primary difference between a settling pond and a clarifier?
The residence time of the water
Why is filtration used to remove suspended solids from groundwater?
Because it is necessary to remove suspended solids that are not removed by settling or clarifying
What is the purpose of the continuous removal of solids deposited by sedimentation in a clarifier?
To prevent the accumulation of solids at the bottom of the clarifier
What happens to the suspended solids in a settling pond or clarifier?
They settle to the bottom by gravity
Why is it necessary to remove suspended solids from water?
To prevent operational issues in the treatment process
What is the result of water flowing through a settling pond or clarifier?
The suspended solids settle to the bottom of the tank by gravity
HARD What is the primary benefit of removing suspended solids in the first stage of water treatment?
Reducing the need for disinfection
What is the primary purpose of a clarifier?
To remove suspended solids from the water
What is the primary difference between a settling pond and a clarifier?
A clarifier has a continuous removal of solids
Why is filtration used to remove suspended solids from groundwater?
Because filtration is a more effective method
What happens to suspended solids in a settling pond or clarifier?
They settle to the bottom
What is the primary purpose of a settling pond or basin?
To reduce the velocity of water
What happens to the pressure drop across a filter as it screens out more solids?
It increases
What is the primary benefit of removing suspended solids in the first stage of water treatment?
Reducing the need for disinfection
What is the primary mechanism by which activated carbon filters remove taste or odor from water?
Adsorption of the organics onto the activated carbon
What is the primary advantage of using activated carbon filters in industry?
They can selectively remove chlorine and other oxidizing agents
What is the primary reason why filters need to be replaced in the water treatment process?
The pressure drop across the filter becomes too high
What is the primary purpose of heating carbonaceous material to about 1000°C with steam?
To create a large surface area for adsorption
How does the filter material catch suspended solids in the water treatment process?
Through a physical barrier that traps the solids
What is the primary benefit of using filters in the water treatment process?
To remove suspended solids and clarify the water
What is the primary purpose of monitoring the pressure drop across the filter?
To determine when the filter needs to be replaced
What is the primary advantage of using activated carbon filters in water treatment?
They can remove a wide range of contaminants from water
What is the primary reason why colloidal particles are difficult to remove in a clarifier?
They carry a slight electric charge
What is the purpose of the distribution plate in a pressure filter?
To distribute the water evenly onto the filter medium
What happens to the filter cake in a filter-aid tubular filter when it needs to be replaced?
It is removed and replaced with new filter aid
What is the primary advantage of using a filter-aid tubular filter over a pressure filter?
It has a longer filter run
What is the consequence of excessive backwash flow in a pressure filter?
The filter medium is removed and needs to be replaced
What is the primary purpose of adding a coagulant to the water in a clarifier?
To neutralize the electric charge of colloidal particles
What is the purpose of the compressed air in the upper part of the filter housing in a filter-aid tubular filter?
To force the water through the filter in the reverse direction
What is the primary difference between a cartridge filter and a pressure filter?
The type of filter medium used
What is the consequence of inadequate backwash flow in a pressure filter?
The filter cake is not removed
What is the primary purpose of using a clarifier in water treatment?
To remove suspended particles
Study Notes
Water Treatment Stage 1: Removal of Suspended Solids
- Suspended solids are particles greater than 2 microns that do not dissolve as ions and can be removed by gravity.
- Removing suspended solids also removes other harmful substances like heavy metals and reduces treatment costs.
- Suspended solids can cause operational issues like deposits, erosion, and plugging of equipment if not removed.
Settling Pond/Basin
- A settling pond or basin slows or delays the velocity of water, allowing suspended solids to settle to the bottom by gravity.
- Examples of common settling basins are cooling water basins and inlet water basins.
Clarifier
- A clarifier is a large settling tank that uses gravity to settle out particles.
- Clarifiers have features that promote the continuous removal of solids deposited by sedimentation.
- Residence time for water in a clarifier is around an hour or two, compared to a number of days for a typical settling pond.
- Water flows from the center of the clarifier to the bottom, then upwards to the weirs, and particles settle out and are removed by a rake.
Coagulation
- Colloidal particles (less than 1 μm in size) can be difficult to remove in a clarifier due to their slight electric charge.
- Alum (aluminum sulfate) or a synthetic polymer coagulant can be added to neutralize the particles, allowing them to combine and settle to the bottom of the clarifier.
Filtration
- Filtration is used to remove the last of the suspended particles after initial removal of suspended solids.
- Common types of filters include pressure filters, filter-aid tubular filters, cartridge filters, and activated carbon filters.
Pressure Filter
- A pressure filter has a filter medium (usually sand, anthracite coal, or calcite) that the water flows through.
- Suspended particles adhere to the surface of the medium and get trapped in pores.
- The filtered water is collected in the under-bed collection system.
- Filters become plugged with suspended particles over time and must be backwashed.
Filter-Aid Tubular Filter
- A filter-aid tubular filter consists of a closed cylindrical housing with screen-type cylindrical tubes covered in Dacron or polyethylene filter cloth.
- A slurry of filter-aid (usually diatomaceous earth or volcanic ash) is fed through the inlet at the beginning of the filter cycle.
- The filter-aid pre-coats the tubes, and additional filter cake forms, increasing filtration effectiveness.
- Backwashing involves closing the inlet and outlet valves, opening the drain valve, and using compressed air to loosen the filter cake.
Cartridge Filter
- A cartridge filter is a simple system similar to an oil filter in an automotive engine.
- Water flows around the outer space of the filter and then through the filter, catching suspended solids.
- The clarified water then goes through the middle of the filter and out to the next stage in the treatment process.
- The filter cartridge is replaced once the pressure drop across the filter becomes too high.
Activated Carbon Filter
- An activated carbon filter is used to remove taste or odors from water, and to remove chlorine, especially from municipal source water.
- Activated carbon is produced from carbonaceous material, transformed into activated carbon by heating to about 1000°C with steam, and in the absence of oxygen.
- Each teaspoon of activated carbon has a total surface area equal to that of a football field.
- Activated carbon filters are not very effective against dissolved solids and should be placed in the process after the removal of solids.
Water Treatment Stage 1: Removal of Suspended Solids
- Suspended solids are particles greater than 2 microns that do not dissolve as ions and can be removed by gravity.
- Removing suspended solids also removes other harmful substances like heavy metals and reduces treatment costs.
- Suspended solids can cause operational issues like deposits, erosion, and plugging of equipment if not removed.
Settling Pond/Basin
- A settling pond or basin slows or delays the velocity of water, allowing suspended solids to settle to the bottom by gravity.
- Examples of common settling basins are cooling water basins and inlet water basins.
Clarifier
- A clarifier is a large settling tank that uses gravity to settle out particles.
- Clarifiers have features that promote the continuous removal of solids deposited by sedimentation.
- Residence time for water in a clarifier is around an hour or two, compared to a number of days for a typical settling pond.
- Water flows from the center of the clarifier to the bottom, then upwards to the weirs, and particles settle out and are removed by a rake.
Coagulation
- Colloidal particles (less than 1 μm in size) can be difficult to remove in a clarifier due to their slight electric charge.
- Alum (aluminum sulfate) or a synthetic polymer coagulant can be added to neutralize the particles, allowing them to combine and settle to the bottom of the clarifier.
Filtration
- Filtration is used to remove the last of the suspended particles after initial removal of suspended solids.
- Common types of filters include pressure filters, filter-aid tubular filters, cartridge filters, and activated carbon filters.
Pressure Filter
- A pressure filter has a filter medium (usually sand, anthracite coal, or calcite) that the water flows through.
- Suspended particles adhere to the surface of the medium and get trapped in pores.
- The filtered water is collected in the under-bed collection system.
- Filters become plugged with suspended particles over time and must be backwashed.
Filter-Aid Tubular Filter
- A filter-aid tubular filter consists of a closed cylindrical housing with screen-type cylindrical tubes covered in Dacron or polyethylene filter cloth.
- A slurry of filter-aid (usually diatomaceous earth or volcanic ash) is fed through the inlet at the beginning of the filter cycle.
- The filter-aid pre-coats the tubes, and additional filter cake forms, increasing filtration effectiveness.
- Backwashing involves closing the inlet and outlet valves, opening the drain valve, and using compressed air to loosen the filter cake.
Cartridge Filter
- A cartridge filter is a simple system similar to an oil filter in an automotive engine.
- Water flows around the outer space of the filter and then through the filter, catching suspended solids.
- The clarified water then goes through the middle of the filter and out to the next stage in the treatment process.
- The filter cartridge is replaced once the pressure drop across the filter becomes too high.
Activated Carbon Filter
- An activated carbon filter is used to remove taste or odors from water, and to remove chlorine, especially from municipal source water.
- Activated carbon is produced from carbonaceous material, transformed into activated carbon by heating to about 1000°C with steam, and in the absence of oxygen.
- Each teaspoon of activated carbon has a total surface area equal to that of a football field.
- Activated carbon filters are not very effective against dissolved solids and should be placed in the process after the removal of solids.
Water Treatment Stage 1: Removal of Suspended Solids
- Suspended solids are particles greater than 2 microns that do not dissolve as ions and can be removed by gravity.
- Removing suspended solids also removes other harmful substances like heavy metals and reduces treatment costs.
- Suspended solids can cause operational issues like deposits, erosion, and plugging of equipment if not removed.
Settling Pond/Basin
- A settling pond or basin slows or delays the velocity of water, allowing suspended solids to settle to the bottom by gravity.
- Examples of common settling basins are cooling water basins and inlet water basins.
Clarifier
- A clarifier is a large settling tank that uses gravity to settle out particles.
- Clarifiers have features that promote the continuous removal of solids deposited by sedimentation.
- Residence time for water in a clarifier is around an hour or two, compared to a number of days for a typical settling pond.
- Water flows from the center of the clarifier to the bottom, then upwards to the weirs, and particles settle out and are removed by a rake.
Coagulation
- Colloidal particles (less than 1 μm in size) can be difficult to remove in a clarifier due to their slight electric charge.
- Alum (aluminum sulfate) or a synthetic polymer coagulant can be added to neutralize the particles, allowing them to combine and settle to the bottom of the clarifier.
Filtration
- Filtration is used to remove the last of the suspended particles after initial removal of suspended solids.
- Common types of filters include pressure filters, filter-aid tubular filters, cartridge filters, and activated carbon filters.
Pressure Filter
- A pressure filter has a filter medium (usually sand, anthracite coal, or calcite) that the water flows through.
- Suspended particles adhere to the surface of the medium and get trapped in pores.
- The filtered water is collected in the under-bed collection system.
- Filters become plugged with suspended particles over time and must be backwashed.
Filter-Aid Tubular Filter
- A filter-aid tubular filter consists of a closed cylindrical housing with screen-type cylindrical tubes covered in Dacron or polyethylene filter cloth.
- A slurry of filter-aid (usually diatomaceous earth or volcanic ash) is fed through the inlet at the beginning of the filter cycle.
- The filter-aid pre-coats the tubes, and additional filter cake forms, increasing filtration effectiveness.
- Backwashing involves closing the inlet and outlet valves, opening the drain valve, and using compressed air to loosen the filter cake.
Cartridge Filter
- A cartridge filter is a simple system similar to an oil filter in an automotive engine.
- Water flows around the outer space of the filter and then through the filter, catching suspended solids.
- The clarified water then goes through the middle of the filter and out to the next stage in the treatment process.
- The filter cartridge is replaced once the pressure drop across the filter becomes too high.
Activated Carbon Filter
- An activated carbon filter is used to remove taste or odors from water, and to remove chlorine, especially from municipal source water.
- Activated carbon is produced from carbonaceous material, transformed into activated carbon by heating to about 1000°C with steam, and in the absence of oxygen.
- Each teaspoon of activated carbon has a total surface area equal to that of a football field.
- Activated carbon filters are not very effective against dissolved solids and should be placed in the process after the removal of solids.
Learn about the first stage of water treatment, removing suspended solids, and its importance in reducing treatment costs and preventing operational issues.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
