300+ REAL TIME WASTE WATER Engineering Objective Questions & Answers 2023

250+ TOP MCQs on Principles of House Drainage and Answers

Waste Water Engineering Multiple Choice Questions on “Principles of House Drainage”.

1. The sewers should be laid ______
a) Below the building
b) Side of the building
c) Within the building
d) Across the building

Answer: b
Clarification: It is advisable to lay sewers by the side of the building rather than below the building. The drains should be laid at an angle of 180˚ between the inspection manholes.

2. What is the angle between the drains and inspection manholes?
a) 45˚
b) 90˚
c) 135˚
d) 180˚

Answer: d
Clarification: The drains should be laid at an angle of 180˚ between the inspection manholes. Drains from different houses should be connected to public sewers only if the level permits.

3. The entire system should be ventilation free.
a) True
b) False

Answer: b
Clarification: The entire sewer system should have proper ventilation. The house drainage should be containing enough number of traps at suitable points for the efficient functioning of it. The joints should be watertight.

4. _________ is the removal of excess surface water from the land to enhance crop growth.
a) Sewer drainage
b) Agricultural drainage
c) Municipal drainage
d) Soil drainage

Answer: b
Clarification: Agricultural land drainage is the removal of excess surface and subsurface water from the land to enhance crop growth, including the removal of soluble salts from the soil.

5. Which of the following is not correct with respect to installing the drainage system in the waterlogged land?
a) Increase in water amount in soil
b) Reduction in water amount on soil
c) Discharge of water through the system
d) Reducing waterlogging

Answer: a
Clarification: The direct effects of installing a drainage system in the waterlogged land are the reduction in the average amount of water in the soil mass and on the surface soil inducing drier soil conditions.

6. Which of these is negative effect owing to the drier soil conditions?
a) Aeration of soil
b) Soil structure
c) Availability of nitrogen
d) Irrigation efficiency

Answer: d
Clarification: Aeration of the soil increases with improved soil structure and availability of the nitrogen. Irrigation efficiency is negative.

7. Which of these is a positive effect owing to the drier soil conditions?
a) Irrigation efficiency
b) Risk of drought
c) Organic matter
d) Crop production

Answer: d
Clarification: The positive effects are increased aeration of the soil, stabilized soil structure, higher availability of nitrogen in the soil, higher and more diversified crop production and better workability of the land.

8. Which of these is a positive effect owing to the discharge?
a) Leaching of nutrients
b) Environmental damage
c) Interference with infrastructural elements of land
d) Removal of salts

Answer: d
Clarification: Positive effects owing to the discharge are the removal of salts or other harmful substances from the soil, availability of drainage water for various purposes.

9. What is the time required for the depletion of oxygen in soil by waterlogging?
a) 6-12 hours
b) 1-2 days
c) 3-6 days
d) 1-4 weeks

Answer: b
Clarification: The adverse effects of drainage may be broadly classified as impaired crop growth, formation of water logged soils waterlogging- causes oxygen deficits in soils, usually within 1-2 days.

10. What is the average land coverage of vertisols in Ethiopia?
a) 5 million ha
b) 10 million ha
c) 13 million ha
d) 16 million ha

Answer: c
Clarification: Vertisols (deep black clay soils) cover about 13 million ha in Ethiopia. The highland Vertisols above 1500 m altitude cover 7.6 million ha, of which 1.93 million ha are currently cropped (about 23% of all Ethiopian crop land).

11. What is the power of diminishment of van der Waals force with respect to distance?
a) 2
b) 4
c) 6
d) 8

Answer: c
Clarification: Water molecules are attracted to solid surfaces by various types of London-van der Waals forces. These are strong, but very short-range forces; they diminish with about the sixth power of the distance.

250+ TOP MCQs on Pumps & Pumping Stations – 2 and Answers

Waste Water Engineering Interview Questions and Answers on “Pumps & Pumping Stations – 2”.

1. Pumping stations are necessary where pressures have to be decreased.
a) True
b) False
Answer: b
Clarification: Pumping stations are necessary where water is pumped directly into system o where pressure has to be increased because there is an insufficient difference in water levels in gravity flow distribution systems.

2. The most expensive part is the energy supply for pumps.
a) True
b) False
Answer: a
Clarification: Pumping stations are situated where water has to be pumped into a distribution system or where pressure levels are to be increased. This requires high energy supplies and is expensive.

3. To reduce the expenses, the pumps must have a high degree of ________
a) Flow rate
b) Efficiency
c) Power
d) Intake
Answer: b
Clarification: To reduce the expenses, the pumps must have a high degree of efficiency and must be maintained properly. To guarantee safe water quality, cross connection of drinking water and waste removal systems must be avoided.

4. What are the facilities including pumps and other equipment for pumping fluids from one place to another called?
a) Pumping facilities
b) Pumping stations
c) Pumping house
d) Pump and equipment facilities
Answer: b
Clarification: Pumping stations are used for a variety of infrastructures such as the supply of water to canals, the drainage of low-lying land and the removal of sewage to processing sites.

5. What is a building where the pumps are located and operated called?
a) Pumping station
b) Pump house
c) Pumping facility
d) Pumping house
Answer: b
Clarification: A building where the pumps are located and operated is called a pump house. This consists of pumps of an irrigation system with a pressurized water filtration system.

6. In duplex pump stations, the pumps shall be of __________
a) Same pressure
b) Same efficiency
c) Same capacity
d) Different capacity
Answer: c
Clarification: In duplex pump stations, the pumps shall be of the same capacity. If pumps are in series it is required to meet the capacity of total dynamic head requirement, each set of pumps in series shall be viewed as a single pumping unit.

7. The road way to the pumping station must be a _______
a) Hard surface
b) Muddy road
c) Hilly road
d) Smoother path
Answer: a
Clarification: The road way to the pumping station must be an all-weather roadway. The road way must be provided on a hard surface. Muddy roads lead to inconvenience during the rainy season.

8. In a desalination plant in order to provide high pressure greater than the osmotic pressure which type of pump is selected?
a) Reciprocating Pump
b) Positive Displacement Pump
c) Booster Pump
d) Multistage Pump
Answer: d
Clarification: Multistage Pumps have two/more impellers and a corresponding number of volute cases. Since there are multiple volute cases the pressure obtained is more than that obtained by a single stage pump. However, the volume of the fluid handled remains constant in both the cases.

9. Generally, what is the Material of Construction of the casing of the pumps which are used in a desalination plant?
a) Cast Iron
b) Bronze
c) Stainless Steel SS 304 GRADE
d) Stainless Steel SS 316 L Grade
Answer: d
Clarification: The inlet water of any desalination plant would have a minimum TDS of 25,000 ppm. Since this water has high concentration of ions it can easily corrode the inner parts of the pump. Hence the quality of Steel of 316 L is preferred.

10. Which type of pump is used when chemicals are to be dosed in water treatment plant?
a) Plunger Pump
b) Positive Displacement Pump
c) Vertical Turbine Pump
d) Jet Pump
Answer: b
Clarification: Positive Displacement Pump is used to pump liquids with high viscosity. These are also known as a reciprocating pump. These pumps are used when the fluid to be pumped is at low flow and high pressure.

11. Which is the part of the pump which prevents the flow of water from the volume to enter back to the impeller?
a) Shaft
b) Bearing
c) Mechanical seal
d) Wear rings
Answer: d
Clarification: Water from the high pressure zone of the volute could re-enter the impeller. In order to prevent this a physical separation between the high and low pressure side is provided. Wear ring provides a flow restriction in order to prevent the water from entering the impeller again.

12. For a mechanical seal which is the normal leakage rate?
a) 30-50 drops of seal water/min
b) 40-60 drops of seal water/min
c) 20-40 drops of seal water/min
d) 20-60 drops of seal water/min
Answer: d
Clarification: A normal leakage rate is 20-60 drops of seal water/min. If it is below 20 drops of seal water/min then the operator should gradually loosen the packing gland nuts. He should observe the leakage rate after loosening the gland.

13. In order to reduce the operation and maintenance which of the following characteristics of a pump should be considered?
a) Efficiency of the pump
b) Flow rate
c) NPSH
d) Head
Answer: a
Clarification: Higher the efficiency of the pump lesser will be the power consumed. Hence the electricity consumed by the pump would be low. This will result in a lesser maintenance cost of the pump.

14. Which type of impeller is usually preferred when handling liquids with solids?
a) Closed impeller
b) Open impeller
c) Single suction impeller
d) Double suction impeller
Answer: b
Clarification: Open impellers are used to handle water with a large concentration of solid. Also open impellers get damaged more than the closed impellers as the vanes are exposed directly. These impellers usually handle water which is at a low pressure.

15. Which type of pump is used when the efﬂuent should be pumped back into the plant for use as service water?
a) Vortex Pump
b) Vertical Turbine Pump
c) Sump pump
d) Rotary pump
Answer: b
Clarification: The construction of the turbine pumps enables to handle clean water. Line shaft turbine pump has been used t0 draw water from deep wells. In case the effluent has to be pumped back as service water then Vertical Turbine pumps are apt for the same application.

16. Which formula is used to calculate the head for centrifugal pumps?
a) H=P(PSIG)X144/Specific gravity
b) H=P(PSIG)X2.31/Specific gravity
c) H=P(ft)X144/Specific gravity
d) H=P(ft)X2.31/Specific gravity
Answer: b
Clarification: As pressure increases head too increases. Similarly sp. Gravity is inversely proportional. This formula holds good when the head is measured at psig.

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250+ TOP MCQs on Methods for Treatment of Wastewater – 2 and Answers

Waste Water Engineering Question Paper on “Methods for Treatment of Wastewater – 2”.

1. What is the method of treatment used when the TSS in the sample is high?
a) Ultrafiltration
b) High rate solid contact clarifier
c) Pressure Sand filter
d) Activated Carbon filter
Answer: b
Clarification: High rate solid contact clarifier is used to treat samples with very high TSS. The other methods namely ultrafiltration and pressure sand filter cannot treat samples with very high TSS. This is because the filters will get clogged.

2. Which type of treatment does clarification fall in?
a) Secondary treatment
b) Primary treatment
c) Preliminary treatment
d) Tertiary treatment
Answer: b
Clarification: Clarification is classified as Primary treatment. Influent with high TSS can be treated here. The COD associated TSS also gets reduced in this stage.

3. Which of these remove coarse materials?
a) Coarse screen
b) Grit chamber
c) Fine screen
d) Commutors
Answer: a
Clarification: Coarse screens remove coarse materials. The size of the coarse screen is 6mm-25mm. These coarse screens maybe manual or mechanically driven.

4. Which type of treatment is the coarse screen?
a) Preliminary treatment
b) Primary treatment
c) Secondary treatment
d) Tertiary treatment
Answer: a
Clarification: Coarse screens are classified as preliminary treatment. This is mainly to remove grit, sand particles. This prevents clogging of the pipe and pump.

5. Tube settlers are classified as which type of treatment?
a) Tertiary treatment
b) Secondary treatment
c) Preliminary treatment
d) Primary treatment
Answer: b
Clarification: Tube settlers are classified as secondary treatment. These are used mainly to remove TSS. Tube settlers will be followed generally after a clarifier and a flocculator.

6. Activated Carbon is classified as which type of treatment?
a) Preliminary treatment
b) Primary treatment
c) Secondary treatment
d) Tertiary treatment
Answer: d
Clarification: Activated Carbon is classified as tertiary treatment. This works on the principle of adsorption. Pressure sand filter is usually prior to the activated carbon filter.

7. Which of these is used to remove odour?
a) Ultrafiltration
b) Pressure sand filter
c) Activated carbon
d) Nano filter
Answer: c
Clarification: Activated carbon filters are used to remove odour. This is also used to reduce COD by removing organics. The treatment process works on the principal of adsorption.

8. Reverse Osmosis is which type of treatment?
a) Primary treatment
b) Preliminary treatment
c) Secondary treatment
d) Tertiary treatment
Answer: d
Clarification: Reverse Osmosis is classified as tertiary treatment. This is mainly used to remove ions. This results in the reduction of total dissolved salts.

9. Which is usually prior to reverse osmosis?
a) Ultrafiltration
b) Activated carbon filter
c) Clarifier
d) Tube settler
Answer: a
Clarification: Ultrafiltration is usually prior to reverse osmosis. This is to remove the TSS present in the sample. Reverse osmosis reduces the total dissolved solids in the water sample.

10. What does zero discharge actually refer to?
a) There is zero discharge of ions
b) The reject is recycled from every part of the treatment plant
c) The reject is not rejected out. Influent equals effluent
d) 100 percent efficient plant
Answer: b
Clarification: Zero discharge usually refers to the treatment plant in which the reject from each part of the treatment plant is recycled. The reject is fed as the influent and once again treated. The removal efficiency of the pollutants is approximately 97-98%.

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250+ TOP MCQs on Trickling Filters – 1 and Answers

Waste Water Engineering Multiple Choice Questions on “Trickling Filters – 1”.

1. Who used the trickling filter for the first time?
a) Didden
b) Streeter
c) Thomas
d) Newton
Answer: a
Clarification: Trickling filter consists of a fixed bed of rocks, lava, coke, gravel and polyurethane over which sewage or other wastewater flows downward and causes a layer of microbial slime. It was first used by Didden.

2. Splashing helps in improving aerobic conditions.
a) True
b) False
Answer: a
Clarification: Splashing, diffusion, etc. increases aerobic conditions and it is increased either by forced-air flowing through the bed or natural convection of air if the filter medium is porous.

3. Trickling filter can also be called as a biofilter.
a) True
b) False
Answer: a
Clarification: The systems like trickling filter and biofilter have also been described as roughing filters, intermittent filters, packed media bed filters, alternative septic systems, percolating filters, attached growth processes, and fixed film processes.

4. The supernatant from the tank flows into a ____
a) Trickling filter
b) Dosing device
c) Pumping station
d) Sedimentation tank
Answer: b
Clarification: The supernatant from the tank flows into a dosing device, often a tipping bucket which delivers flow to the arms of the filter. The flush of water flows through the arms and exits through a series of holes pointing at an angle downwards.

5. __________ in trickling filter contains many species like bacteria and round worms.
a) Treated water
b) Wastewater
c) Biofilm
d) Air influent
Answer: c
Clarification: The bio-film that develops in a trickling filter may become several millimeters thick and is typically a gelatinous matrix that contains many species of bacteria, ciliates and amoeboid protozoa, annelids, round worms and insect larvae and many other micro fauna.

6. Which of the following is not used as a media for trickling filters?
a) Sand
b) Geotextiles
c) Gravel
d) Paper
Answer: d
Clarification: Trickling may have a variety of types of filter media used to support the biofilm. Coke, pumice, plastic matrix material, open-cell polyurethane foam, clinker, gravel, sand and geotextiles are the most common type of media used.

7. Which of the following causes thickening of the biofilm?
a) Reduction of intake wastewater
b) Rapid growth of organisms
c) Reduction in air supply
d) Increase in acidity
Answer: b
Clarification: At certain times of the year, especially in the spring, rapid growth of organisms in the film may cause the film to be too thick and it may slough off in patches leading to the “spring slough”.

8. What is the shape of a typical trickling filter?
a) Circular
b) Cylindrical
c) Square
d) Rectangular
Answer: a
Clarification: A typical trickling filter is circular and between 10 meters and 20 meters across and between 2 meters to 3 meters deep. A wall, circular, often of brick, contains a bed of filter media which in turn rests on a base of under-drains.

9. What is the depth of the trickling filter?
a) 0.5-1 m
b) 1-1.5 m
c) 1.5-2 m
d) 2-3 m
Answer: d
Clarification: A typical trickling filter is circular and between 10 meters and 20 meters across and between 2 meters to 3 meters deep. A circular wall, often of brick, contains a bed of filter media which in turn rests on a base of under-drains.

10. The spindle is provided at the ______ to support perforated plates.
a) Edge
b) Bottom
c) Top
d) Centre
Answer: d
Clarification: On the top of the filter media, in the centre is a spindle supporting two or more horizontal perforated pipes which extend to the edge of the media.

11. While designing a trickling filter what would be the depth assumed?
a) 12-15m
b) 4-12 m
c) 16-20 m
d) 20-25 m
Answer: b
Clarification: The depth for trickling filters would be mostly assumed as 4-12 m. Other than this, a trickling filter constitutes a waste water dosing system. Also it constitutes a drain.

12. What is necessary prior to trickling filters?
a) Secondary clarification
b) MBBR
c) Grit chamber
d) Primary clarification
Answer: d
Clarification: Primary clarification is necessary prior to trickling filters. Screening of the materials prior to letting it into the trickling filter is necessary. This is done to prevent clogging.

13. Which type of bacteria are used in trickling filters?
a) Facultative
b) Nitrifying
c) Anaerobic
d) Blue-green bacteria
Answer: a
Clarification: Facultative bacteria are used in trickling filters. Pseudomonas and Alcaligenes are some of the strains used in these filters. Also, Flavobacterium and Achromobacter are also used in this type of treatment.

14. For rock packing low- rate trickling filters what is the hydraulic loading assumed?
a) 1-4 m³/m².d
b) 4-8 m³/m².d
c) 8- 12 m³/m².d
d) 12-15 m³/m².d
Answer: a
Clarification: 1-4 m³/m².d is the hydraulic rate considered for rock type of packing in trickling filters. The other type of packing is plastic. While designing this type of packing the hydraulic rate of this would be different.

15. For rock type of packing in intermediate filtration trickling filters what is the hydraulic rate considered?
a) 4-10 m³/m².d
b) 10-15 m³/m².d
c) 20-25 m³/m².d
d) 25-30 m³/m².d
Answer: a
Clarification: For rock type packing in intermediate filtration trickling type filters, the hydraulic rate considered is 4-10 m³/m².d. In case of high filtration rock type trickling filters packing it is considered as 10-75 m³/m².d. For plastic packing type in trickling filters, the hydraulic rate is different.

16. For rock type of roughing packing trickling filter what will be the hydraulic loading rate?
a) 40-200 m³/m².d
b) 300 m³/m².d
c) 500 m³/m².d
d) 600 m³/m².d
Answer: a
Clarification: For rock type of rough packing trickling filter, the hydraulic loading rate is 40-200 m³/m².d.High organic loaded waste water have been treated by rough packing filters. However this only partially removes the BOD.

17. For rock type low filtration rate trickling filters what would be the organic loading rate assumed?
a) 0.07-0.22 kg BOD/m³d
b) 0.24-0.48 kg BOD/m³d
c) 0.4-2.4 kg BOD/m³d
d) >2.4 kg BOD/m³d
Answer: a
Clarification: For rock type of low filtration rate trickling filters the organic load assumed is 0.07-0.22 kg BOD/m³d. Intermediate rate filtration filters would have different organic load. It is around 0.24-0.48 kg BOD/m³d.

18. For rock type high filtration rate trickling filters what would be the organic loading rate assumed?
a) 0.07-0.22 kg BOD/m³d
b) 0.24-0.48 kg BOD/m³d
c) 0.4-2.4 kg BOD/m³d
d) >2.4 kg BOD/m³d
Answer: c
Clarification: For rock type of high filtration rate tricking filters, the organic load assumed is 0.4-2.4 kg BOD/m³d. Intermediate rate filtration trickling filters would have different organic load. It is around 0.24-0.48 kg BOD/m³d.

19. For plastic type high filtration rate trickling filters what would be the organic loading rate assumed?
a) 0.07-0.22 kg BOD/m³d
b) 0.24-0.48 kg BOD/m³d
c) 0.5 kg BOD/m³d
d) 0.6-3.2 kg BOD/m³d
Answer: d
Clarification: For plastic type of high filtration rate trickling filters, the organic load assumed is 0.6-3.2 kg BOD/m³d. Roughing rock type of trickling filter has a different organic loading rate. It is > 1.5 kg BOD/m³d.

20. For rock type low filtration rate trickling filters what would be the recycling ratio assumed?
a) 0
b) 1-2
c) >2
d) >3
Answer: a
Clarification: For rock type low filtration, the recycling ratio would be 0. In case of intermediate filtration, this ratio is a little higher. It is around 0-1.

250+ TOP MCQs on Sequential Batch Reactor & BOD Removal Methods and Answers

Waste Water Engineering written test Questions & Answers on “Sequential Batch Reactor & BOD Removal Methods”.

1. SBR is a type of ________
a) Aerobic process
b) Activated sludge process
c) Anaerobic process
d) Chemical process
Answer: b
Clarification: Sequencing batch reactors (SBR) or sequential batch reactors are a type of activated sludge process for the treatment of wastewater. SBR reactors treat wastewater such as sewage or output from anaerobic digesters or mechanical biological treatment facilities in batches.

2. The one tank is aerating and filling while the other one is decant.
a) True
b) False
Answer: a
Clarification: The tanks have a “flow through” system, with raw wastewater (influent) coming in at one end and treated water (effluent) flowing out of the other. One tank is in settle/decant mode the other is aerating and filling in multiple tank systems.

3. Bio-selectors direct the flow.
a) True
b) False
Answer: a
Clarification: In some systems, tanks contain a section known as the bio-selector, which consists of a series of walls or baffles which direct the flow either from side to side of the tank or under and over consecutive baffles.

4. ___________ helps to mix the incoming influent and the returned activated sludge.
a) Walls
b) Orifice
c) Manifold
d) Bio-selector
Answer: d
Clarification: This helps to mix the incoming Influent and the returned activated sludge (RAS), beginning the biological digestion process before the liquor enters the main part of the tank.

5. How is mixing done in SBR?
a) Manual
b) Mechanical
c) Air stripping
d) Agitation by air
Answer: b
Clarification: The inlet valve opens and the tank is being filled in, while mixing is provided by mechanical means (no air). This stage is also called the anoxic stage.

6. In which stage of the SBR is aeration performed?
a) First
b) Second
c) Third
d) fourth
Answer: b
Clarification: The fixed or floating mechanical pumps are used or air is transferred into fine bubble diffusers fixed to the floor of the tank during the second stage aeration of the mixed liquor.

7. In which stage are the aeration and mixing avoided?
a) First
b) Second
c) Third
d) Fourth
Answer: c
Clarification: No aeration or mixing is provided in the third stage and the settling of suspended solids starts. During the fourth stage, the outlet valve opens and the “clean” supernatant liquor exits the tank.

8. The multiplication of _________ is encouraged by the addition of oxygen.
a) Bacteria
b) Aerobic bacteria
c) Anaerobic bacteria
d) Fungi
Answer: b
Clarification: Aeration times vary according to the plant size and the composition/quantity of the incoming liquor, but are typically 60 to 90 minutes. The multiplication of aerobic bacteria is encouraged by the addition of oxygen.

9. ______ is used to remove phosphorus compounds from the liquor.
a) Aluminium nitrate
b) Aluminium phosphate
c) Aluminium sulphate
d) Sodium nitrate
Answer: c
Clarification: To remove phosphorus compounds from the liquor, aluminium sulphate (alum) is often added during this period. It reacts to form non-soluble compounds, which settle into the sludge in the next stage.

10. The _________ is usually the same length in time as the aeration.
a) Screening stage
b) Mixing stage
c) Clarification stage
d) Settling stage
Answer: d
Clarification: The settling stage is usually the same length in time as the aeration and during this stage, the sludge formed by the bacteria is allowed to settle to the bottom of the tank.

11. Which part of the tank is suitable for anaerobic bacteria to flourish?
a) Top
b) Bottom
c) Sides
d) Middle zone
Answer: b
Clarification: The aerobic bacterium multiplies until the dissolved oxygen is all used up. The bottom conditions are more suited for the anaerobic bacteria to flourish.

12. ______ is removed by Anammox.
a) Nitric oxides
b) Nitrate
c) Nitrite
d) Ammonia
Answer: d
Clarification: An anaerobic process uses anoxic methods to remove ammonia, such as the removal of ammonia via Anammox or the study of slow-growing micro-organisms.

13. How many types of BOD are present?
a) 1
b) 2
c) 3
d) 4
Answer: b
Clarification: BOD can be used as a gauge of the effectiveness of wastewater treatment plants. It is listed as a conventional pollutant in the U.S. Clean Water Act. The two major types of BOD are soluble BOD and insoluble BOD.

14. BOD is a physical procedure for determining DO needed for aerobic biological organisms.
a) True
b) False
Answer: b
Clarification: BOD is a chemical procedure for determining the amount of dissolved oxygen needed by aerobic biological organisms in a body of water to break down organic material.

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250+ TOP MCQs on Disc Filtration – 1 and Answers

Waste Water Engineering Multiple Choice Questions on “Disc Filtration – 1”.

1. Disc filter is similar to a screen filter.
a) True
b) False
Answer: a
Clarification: A disc filter is a type of water filter used primarily in irrigation, similar to a screen filter, except that the filter cartridge is made of a number of plastic discs stacked on top of each other like a pile of poker chips.

2. Filtration is based on colour of particles.
a) True
b) False
Answer: b
Clarification: The filtration quality is based on the quantity and size of particles that the filtering element is able to retain. Higher quality filtration simply means cleaner water. This depends on the geometry of the channels, including the size, length, angle and number of generated intersection points.

3. Which of the following parameter is used by disc filters?
a) Size
b) Colour
c) Taste
d) Smell
Answer: a
Clarification: Higher quality filtration simply means cleaner water. This depends on the geometry of the channels, including the size, length, angle and number of generated intersection points.

4. Discs are colour coded to denote _______
a) Water level
b) Wastewater level
c) Velocity
d) Level of filtration
Answer: d
Clarification: The discs are typically colour coded to denote the level of filtration. Filtration quality is usually measured in microns, based on the smallest size particle filtered. The typical range is from 25 microns for the finest level of filtration to 400 microns for the coarsest.

5. What is the common unit used to measure filtration quality?
a) Litre
b) Cumic
c) Microns
d) Galloon
Answer: c
Clarification: Filtration quality is usually measured in microns, based on the smallest size particle filtered. The typical range is from 25 microns for the finest level of filtration to 400 microns for the coarsest.

6. What is the value for the finest level of filtration?
a) 5 microns
b) 15 microns
c) 20 microns
d) 25 microns
Answer: d
Clarification: The typical range is from 25 microns for the finest level of filtration to 400 microns for the coarsest. The filtration quality is given as the equivalent mesh size of a comparable screen filter.

7. What is the value for coarse filtration?
a) 100 microns
b) 200 microns
c) 300 microns
d) 400 microns
Answer: d
Clarification: Sometimes the filtration quality is given as the equivalent mesh size of a comparable screen filter. When using mesh sizes, 40 is the coarsest and 600 is the finest or highest level of filtration.

8. What is the smallest mesh size of the filter is used?
a) 250
b) 400
c) 550
d) 600
Answer: d
Clarification: Mesh sizes usually range from 40 to 600. When using mesh sizes, 40 is the coarsest and 600 is the finest or highest level of filtration.

9. What is the maximum mesh size being used?
a) 20
b) 40
c) 45
d) 55
Answer: b
Clarification: When using mesh sizes, 40 is the coarsest and 600 is the finest or highest level of filtration. The filtration quality is given as the equivalent mesh size of a comparable screen filter.

10. In which year was the disc filter developed?
a) 1922
b) 1930
c) 1932
d) 1936
Answer: d
Clarification: In 1936 disc filter was originally developed to filter hydraulic fluid in the B-17 bomber. In these filters, the discs were made of stainless steel and brass. This type of filter began to be used in Israel to filter irrigation water in the 1960s.

11. Which of the following is an advantage of disc filter?
a) Flush water
b) Area
c) Speed
d) Cost
Answer: a
Clarification: In 1936 disc filter was originally developed to filter hydraulic fluid in the B-17 bomber. In these filters, the discs were made of stainless steel and brass. This type of filter was used in Israel in the 1960s to filter irrigation water.