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Question 1
ప్రశ్న 1
What is the principal role of a conventional rapid gravity filter in a surface-water treatment plant?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Rapid gravity filtration normally follows coagulation, flocculation and clarification in a conventional surface-water treatment train. The filter removes residual suspended matter and floc that escape the sedimentation process. Removal occurs within a granular medium, usually sand or an appropriate multi-media arrangement. Effective filtration also improves the reliability of subsequent disinfection by reducing particulate shielding of microorganisms. Therefore Option B is correct.
వివరణ:
Question 2
ప్రశ్న 2
What provides the principal driving force through a conventional rapid gravity filter?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
A rapid gravity filter is an open filter in which water moves through the media under available hydraulic head. This head is progressively consumed by resistance through the media, retained solids, underdrains and outlet system. As solids accumulate during a filter run, the head loss across the bed increases. When the allowable hydraulic resistance is approached, the filter normally requires cleaning. Applied pressure rather than an open gravitational head characterizes a pressure filter.
వివరణ:
Question 3
ప్రశ్న 3
Which statement most accurately compares a pressure filter with a rapid gravity filter?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
CPHEEO states that the removal mechanism in pressure filtration is essentially the same as in rapid sand filtration. The principal difference is that the media are enclosed in a pressure vessel through which water is forced under applied pressure. Pressure filters are compact and can be useful for smaller plants and applications such as iron or manganese removal. Pretreatment remains essential where the raw-water characteristics require it. Their enclosed construction also makes observation and inspection of media and washing more difficult than in an open gravity filter.
వివరణ:
Question 4
ప్రశ్న 4
According to current MoHUA/CPHEEO engineering guidance, what is the standard filtration-rate range for a conventional rapid sand gravity filter?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Current CPHEEO guidance gives the standard conventional rapid-sand filtration rate as about 80 to 100 L/m²/min. This is equivalent to approximately 4.8 to 6.0 m³/m²·h. The manual further indicates that the average filtration rate should generally be 5.5 m/h or less. When the specified overloading check is applicable, the rate with a bed out of service should remain below 6 m³/m²·h. Therefore Option C is correct.
వివరణ:
Question 5
ప్రశ్న 5
Which combination correctly represents current CPHEEO guidance for conventional rapid-sand filter media?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Current CPHEEO guidance specifies conventional rapid-filter sand principally in terms of effective size and uniformity coefficient. The effective size is generally about 0.45 to 0.70 mm. The uniformity coefficient should be not less than about 1.3 and not more than about 1.7. The sand should also be hard, resistant and substantially free from clay, soft grains and objectionable impurities. Therefore Option B is correct.
వివరణ:
Question 6
ప్రశ్న 6
What is the principal function of graded gravel beneath the sand bed of a conventional rapid gravity filter?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The graded gravel layer provides mechanical support beneath the finer filter sand. It helps prevent loss of sand into larger openings associated with some types of underdrain systems. Proper grading also assists the hydraulic transfer of filtrate toward the drains during normal filtration. During backwashing it helps distribute upward flow without excessive local disturbance of the sand. Therefore Option D is correct.
వివరణ:
Question 7
ప్రశ్న 7
Which statement correctly describes the functions of a rapid-filter underdrain system?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
During filtration, water that has passed through the media must be collected across the filter floor. The underdrain system performs this collection function while keeping hydraulic losses within the design range. During backwashing, flow is reversed and the underdrain distributes cleaning water upward through the bed. Poor distribution can create dirty zones, local media movement and ineffective washing. Therefore Option A is correct.
వివరణ:
Question 8
ప్రశ్న 8
Which statement best describes the normal development of head loss during a rapid gravity filter run?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
A freshly washed rapid filter offers comparatively low resistance to flow. Current CPHEEO guidance indicates an initial loss of head of about 0.2 to 0.3 m. As suspended material accumulates within the bed, resistance and head loss progressively increase. The manual notes approximately 1.8 to 2.0 m as a usual terminal head-loss range before cleaning. Therefore Option C is correct.
వివరణ:
Question 9
ప్రశ్న 9
In rapid filtration, what does filter breakthrough principally mean?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
A rapid-filter run can terminate because the available head is exhausted or because filtrate quality deteriorates. Breakthrough refers to the latter condition, when particulate matter begins appearing in the filter effluent at an unacceptable level. It can occur before the nominal terminal head loss is reached. Continuing filtration after breakthrough can compromise downstream treatment and drinking-water quality. Therefore Option B is correct.
వివరణ:
Question 10
ప్రశ్న 10
Why should development of negative pressure within a rapid filter bed be avoided?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Excessive head loss can cause pressure at some depth in the filter to fall below atmospheric pressure. Dissolved gases can then come out of solution and accumulate as bubbles in the pores. The resulting air binding reduces the effective cross-sectional area available for water flow. This produces nonuniform filtration and can accelerate further head-loss development. Therefore Option D is correct.
వివరణ:
Question 11
ప్రశ్న 11
A water-treatment plant must filter 36 MLD at a design filtration rate of 5 m³/m²·h. What total operating filter area is required?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
A flow of 36 MLD equals 36,000 m³/day. Dividing by 24 gives an hourly flow of 1,500 m³/h. Required operating filter area equals flow divided by the filtration rate. Hence A = 1,500/5 = 300 m². Therefore Option B is correct.
వివరణ:
Question 12
ప్రశ్న 12
For the 36 MLD plant above, each rapid-filter unit is to have an area of 60 m². If the full stated flow must still be handled at 5 m³/m²·h with one filter out of service, what minimum number of installed units is required?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The required operating filter area is 300 m². Each filter unit provides 60 m² of effective area. Five operating units are therefore required to provide 5 × 60 = 300 m². To retain five operating units while one unit is unavailable, six units must be installed. Therefore Option C is correct.
వివరణ:
Question 13
ప్రశ్న 13
Six rapid-filter units of 60 m² each serve a 36 MLD plant. If one unit is out of service, what filtration rate is carried by each of the five remaining equal units?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
With one unit out of service, the five operating filters provide a combined area of 300 m². The total flow is 36,000 m³/day, which equals 1,500 m³/h. The actual rate is therefore 1,500/300 = 5.0 m³/m²·h. This remains below the CPHEEO upper conventional rate of 6 m³/m²·h. Therefore Option A is correct.
వివరణ:
Question 14
ప్రశ్న 14
A rapid-filter unit has an effective area of 60 m² and an adopted length-to-width ratio L/W = 1.5. What are its approximate plan dimensions?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Let the width be B and the length be 1.5B. The area condition is therefore 1.5B² = 60. Solving gives B approximately 6.32 m and L approximately 9.49 m. The adopted ratio of 1.5 lies within the current CPHEEO preferred filter-box range of roughly 1 to 1.66 for the stated type of arrangement. Therefore Option D is correct.
వివరణ:
Question 15
ప్రశ్న 15
What is the principal purpose of backwashing a rapid sand filter?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Suspended material accumulates in a rapid-filter bed throughout a filter run. This accumulation progressively increases hydraulic resistance and can ultimately cause deterioration of filtrate quality. Backwashing cleans the bed by sending water upward through the media, commonly after air scour in current conventional designs. The expanded and agitated bed releases accumulated deposits that are carried into wash-water gutters. Therefore Option B is correct.
వివరణ:
Question 16
ప్రశ్న 16
According to current MoHUA/CPHEEO guidance for conventional rapid sand filters using air scour followed by water wash, which water-backwash condition is appropriate?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Current CPHEEO guidance describes air scour followed by a high-rate water wash for conventional rapid sand filters. Air scour is applied first, after which wash water is introduced upward through the underdrain system. The recommended conventional water-wash rate is approximately 24 to 40 m/h of filter-bed area. The stated water-wash duration is about 10 minutes. Therefore Option C is correct.
వివరణ:
Question 17
ప్రశ్న 17
A rapid-filter bed has an area of 50 m² and is backwashed at 36 m/h. What wash-water discharge is required?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Wash-water discharge equals backwash rate multiplied by filter-bed area. Thus Q = 36 × 50 = 1,800 m³/h. Dividing by 3,600 seconds per hour gives 0.50 m³/s. A wash rate of 36 m/h lies within the current CPHEEO conventional water-backwash range. Therefore Option A is correct.
వివరణ:
Question 18
ప్రశ్న 18
For the 50 m² filter above, if the 36 m/h water-backwash rate is maintained for 10 minutes, what wash-water volume is used?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The backwash discharge is 1,800 m³/h. Ten minutes equals one-sixth of an hour. The volume used is therefore 1,800 × 10/60 = 300 m³. This calculation is based only on the water-wash stage specified in the question. Therefore Option C is correct.
వివరణ:
Question 19
ప్రశ్న 19
A 12 MLD treatment plant uses 300 m³ of water for one filter wash during a particular day. What percentage of that day's 12,000 m³ treated-water volume does this single wash represent?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The daily treated-water volume is 12 MLD, or 12,000 m³. The stated single wash consumes 300 m³. The percentage is 300/12,000 × 100 = 2.50 percent. This is simply the percentage represented by the stated wash and should not be interpreted as a universal fixed wash-water allowance for every plant. Therefore Option B is correct.
వివరణ:
Question 20
ప్రశ్న 20
If wash-water storage is selected to provide two complete 10-minute washes of the same 50 m² filter at 36 m/h before replenishment, what useful water volume is required, neglecting dead storage and other service-water demands?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
One 10-minute wash uses 300 m³ under the stated design conditions. Providing storage for two complete washes therefore requires twice this volume. The required useful wash-water storage is 2 × 300 = 600 m³. Dead storage, chemical-service requirements and operational reserves have explicitly been excluded from the calculation. Therefore Option C is correct.
వివరణ:
Question 21
ప్రశ్న 21
A rapid-filter sand bed is 0.70 m deep in its undisturbed state. If backwashing expands the bed by 40 percent of its original depth, what is the expanded bed depth?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
A 40 percent expansion means that the final depth is 140 percent of the initial undisturbed depth. Therefore the expanded depth is 0.70 × 1.40 = 0.98 m. This is equivalent to an increase in depth of 0.28 m. It lies within the traditional design concept of expanding rapid-filter sand to about 130 to 150 percent of its undisturbed condition during effective washing. Therefore Option A is correct.
వివరణ:
Question 22
ప్రశ్న 22
What is the principal purpose of auxiliary air scour or surface-wash action during rapid-filter cleaning?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Deposited material can adhere strongly to filter grains and can accumulate in localized dirty zones. Water wash alone may not always provide sufficient agitation for effective release of this material. Air scour produces strong grain agitation before the main water wash in the current conventional CPHEEO arrangement. Surface-wash systems can serve a similar auxiliary cleaning purpose in appropriate designs. Therefore Option D is correct.
వివరణ:
Question 23
ప్రశ్న 23
According to current CPHEEO guidance, which statement regarding pressure-filter filtration rate is correct?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Current CPHEEO guidance gives a pressure-filter filtration rate of approximately 6,000 to 15,000 L/m²·h. This is equivalent to about 6 to 15 m³/m²·h. Pressure filters contain the underdrain, gravel and media inside a closed vessel through which water flows under pressure. The manual notes that pressure filters are useful for smaller or specialized applications but are not recommended for large community supplies because of their operational disadvantages. Therefore Option B is correct.
వివరణ:
Question 24
ప్రశ్న 24
A small pressure-filter installation must treat 3.0 MLD continuously at an explicitly selected filtration rate of 10 m³/m²·h. What total operating filter area is required?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
A flow of 3.0 MLD equals 3,000 m³/day. Dividing by 24 gives an hourly flow of 125 m³/h. At the stated filtration rate of 10 m³/m²·h, required area is 125/10 = 12.5 m². The selected filtration rate lies within the current CPHEEO pressure-filter range. Therefore Option C is correct.
వివరణ:
Question 25
ప్రశ్న 25
Consider the following statements about rapid filtration: I. Conventional rapid gravity filters normally operate at much higher loading rates than slow sand filters. II. Head loss increases as solids accumulate during a filter run. III. Backwashing reverses cleaning flow and expands or agitates the media to remove accumulated solids. IV. A filter run should not be continued merely because terminal head loss has not been reached if filtrate quality has already deteriorated. Which option is correct?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Statement I is correct because conventional rapid filters operate at hydraulic loading rates many times those of slow sand filters. Statement II is correct because accumulated impurities increase the hydraulic resistance of the granular bed. Statement III is correct because effective rapid-filter cleaning uses reverse wash flow and media agitation or expansion. Statement IV is correct because deterioration of filtrate quality or breakthrough is independently sufficient reason to terminate a filter run. Therefore all four statements are correct and Option D is the valid answer.
వివరణ:
Answer Key సమాధానాల పట్టిక
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Question 1 ప్రశ్న 1Answer: B. To remove remaining suspended and flocculated impurities from clarified water by passage through granular media సమాధానం: B.
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Question 2 ప్రశ్న 2Answer: C. Available hydraulic head due to gravity across the filter system సమాధానం: C.
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Question 3 ప్రశ్న 3Answer: A. The basic filtration mechanism is similar, but a pressure filter operates in a closed vessel under pressure and is generally more suited to smaller or specialized installations సమాధానం: A.
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Question 4 ప్రశ్న 4Answer: C. 4.8–6.0 m³/m²·h సమాధానం: C.
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Question 5 ప్రశ్న 5Answer: B. Effective size 0.45–0.70 mm and uniformity coefficient 1.3–1.7 సమాధానం: B.
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Question 6 ప్రశ్న 6Answer: D. To support the sand and provide a suitable hydraulic interface with the underdrain system సమాధానం: D.
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Question 7 ప్రశ్న 7Answer: A. It collects filtered water during normal operation and distributes backwash water uniformly as practicable during cleaning సమాధానం: A.
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Question 8 ప్రశ్న 8Answer: C. Head loss is relatively low after washing and increases as retained solids clog the pore spaces సమాధానం: C.
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Question 9 ప్రశ్న 9Answer: B. Previously retained or incoming particles begin to pass through sufficiently to cause unacceptable deterioration of filtrate quality సమాధానం: B.
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Question 10 ప్రశ్న 10Answer: D. Because dissolved gases may be released and cause air binding, disrupting normal filter hydraulics సమాధానం: D.
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Question 11 ప్రశ్న 11Answer: B. 300 m² సమాధానం: B.
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Question 12 ప్రశ్న 12Answer: C. 6 సమాధానం: C.
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Question 13 ప్రశ్న 13Answer: A. 5.0 m³/m²·h సమాధానం: A.
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Question 14 ప్రశ్న 14Answer: D. 9.49 m × 6.32 m సమాధానం: D.
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Question 15 ప్రశ్న 15Answer: B. To reverse cleaning flow through the media and remove accumulated solids so that hydraulic capacity and filtration performance can be restored సమాధానం: B.
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Question 16 ప్రశ్న 16Answer: C. Approximately 24–40 m/h of filter-bed area for about 10 minutes సమాధానం: C.
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Question 17 ప్రశ్న 17Answer: A. 1,800 m³/h, equivalent to 0.50 m³/s సమాధానం: A.
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Question 18 ప్రశ్న 18Answer: C. 300 m³ సమాధానం: C.
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Question 19 ప్రశ్న 19Answer: B. 2.50% సమాధానం: B.
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Question 20 ప్రశ్న 20Answer: C. 600 m³ సమాధానం: C.
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Question 21 ప్రశ్న 21Answer: A. 0.98 m సమాధానం: A.
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Question 22 ప్రశ్న 22Answer: D. To improve cleaning of dirty media and help prevent mud balls, clogged zones and ineffective backwashing సమాధానం: D.
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Question 23 ప్రశ్న 23Answer: B. A pressure-filter range of about 6–15 m³/m²·h is identified, with water passing through a closed vessel under pressure సమాధానం: B.
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Question 24 ప్రశ్న 24Answer: C. 12.5 m² సమాధానం: C.
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Question 25 ప్రశ్న 25Answer: D. I, II, III and IV సమాధానం: D.