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Question 1
ప్రశ్న 1
What is the principal objective of disinfection in a drinking-water treatment system?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Disinfection is principally intended to control disease-producing microorganisms in treated drinking water. It provides a microbiological barrier after the preceding physical and chemical treatment processes. Disinfection does not normally remove hardness, dissolved salts or all suspended matter. Effective upstream clarification and filtration improve disinfection reliability by reducing particle shielding and disinfectant demand. Therefore Option B is correct.
వివరణ:
Question 2
ప్రశ్న 2
When chlorine is added to water, which free-chlorine species are primarily responsible for disinfection after hydrolysis?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Chlorine reacts with water and forms free available chlorine species. The principal disinfecting forms in the normal drinking-water pH range are hypochlorous acid, HOCl, and hypochlorite ion, OCl-. Their relative proportions depend strongly on pH. Hypochlorous acid is generally the more effective disinfecting form of the two. Therefore Option A is correct.
వివరణ:
Question 3
ప్రశ్న 3
What is the general effect of increasing water pH on free-chlorine disinfection effectiveness, other conditions being comparable?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The equilibrium between hypochlorous acid and hypochlorite ion is pH dependent. As pH increases, a greater fraction of the free chlorine occurs as hypochlorite ion. Hypochlorous acid has stronger germicidal effectiveness than hypochlorite ion under otherwise comparable conditions. Consequently higher pH can require greater concentration or contact time for equivalent disinfection. Therefore Option B is correct.
వివరణ:
Question 4
ప్రశ్న 4
How is chlorine demand defined in current CPHEEO terminology?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Chlorine reacts with organic matter, ammonia and various inorganic reducing substances before a residual remains. CPHEEO defines chlorine demand as the difference between chlorine added and chlorine residual after a specified contact period. The demand therefore depends on both water quality and the conditions under which it is measured. Contact time, pH, temperature, chlorine dose and the desired residual form can influence the measured demand. Therefore Option B is correct.
వివరణ:
Question 5
ప్రశ్న 5
A treated water receives a chlorine dose of 2.6 mg/L and has a measured residual chlorine of 0.4 mg/L after the specified contact period. What is its chlorine demand under these conditions?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Chlorine demand equals applied chlorine minus the residual measured after the specified contact period. The applied dose is 2.6 mg/L and the residual is 0.4 mg/L. Therefore the demand is 2.6 - 0.4 = 2.2 mg/L. This result applies to the stated test conditions because demand can change with contact time and water characteristics. Therefore Option C is correct.
వివరణ:
Question 6
ప్రశ్న 6
What does the breakpoint represent during chlorination of water containing ammonia and other chlorine-consuming substances?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Initially, added chlorine is consumed by reducing substances and reactions with ammonia. Combined chlorine residuals such as chloramines can then form and change as the chlorine dose increases. With further addition, these combined forms are substantially oxidized and the residual may pass through a minimum region. Beyond the breakpoint, additional chlorine increasingly appears as free available residual chlorine. Therefore Option B is correct.
వివరణ:
Question 7
ప్రశ్న 7
Which statement best describes prechlorination in a conventional water-treatment plant?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Prechlorination means applying chlorine at an early point before the final treatment stages. Depending on raw-water conditions, it may assist with biological growth, taste and odour problems or oxidation of certain constituents. Its use must be evaluated carefully because chlorine can react with natural organic matter and form disinfection by-products. Modern process selection should therefore consider raw-water quality and the consequences of the application point. Therefore Option A is correct.
వివరణ:
Question 8
ప్రశ్న 8
What is the principal purpose of postchlorination in a conventional drinking-water treatment plant?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Postchlorination is the principal final chlorination step in many conventional treatment plants. Chlorine is applied after the major particle-removal processes, particularly filtration. This allows effective disinfection of the clarified and filtered water under controlled conditions. The dose must also provide the required residual protection through subsequent storage and distribution. Therefore Option A is correct.
వివరణ:
Question 9
ప్రశ్న 9
Which statement correctly describes superchlorination followed by dechlorination?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Superchlorination involves applying a chlorine dose substantially higher than that required for ordinary residual chlorination. It may be used for strong oxidation or for particular taste, odour or contamination problems. Such a high dose can leave an undesirable residual chlorine concentration after the required reaction period. Dechlorination is then used to reduce the excess chlorine to an acceptable concentration. Therefore Option A is correct.
వివరణ:
Question 10
ప్రశ్న 10
According to current MoHUA/CPHEEO guidance, what minimum residual chlorine should normally be maintained at the critical point in a drinking-water distribution system?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Current CPHEEO guidance specifies a minimum residual chlorine of 0.2 mg/L at the critical point in the distribution system. The residual demonstrates that some disinfectant protection remains after satisfying chlorine demand along the system. During monsoon or epidemic conditions, the guidance allows the target to be raised to about 0.5 mg/L. The chlorine dose at the plant must be adjusted so that the desired critical-point residual is actually achieved. Therefore Option B is correct.
వివరణ:
Question 11
ప్రశ్న 11
A water-treatment plant treats 25 MLD and applies chlorine at 2.4 mg/L. What mass of chlorine is required per day?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
A useful unit relationship is that 1 mg/L applied to 1 MLD corresponds to 1 kg/day of chemical. The chlorine requirement is therefore 25 × 2.4 kg/day. This gives 60 kg/day. The value represents the chlorine corresponding to the stated dose before allowing for chemical purity or additional operational reserve. Therefore Option C is correct.
వివరణ:
Question 12
ప్రశ్న 12
A plant requires 60 kg/day of available chlorine. If a sodium hypochlorite product contains 12 percent available chlorine by mass, what product mass is theoretically required per day?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Only 12 percent of the supplied product is available chlorine under the stated assumption. The product mass is therefore the required available-chlorine mass divided by 0.12. Thus the required quantity is 60/0.12 = 500 kg/day. Multiplying 500 kg/day by 0.12 returns the required 60 kg/day of available chlorine. Therefore Option C is correct.
వివరణ:
Question 13
ప్రశ్న 13
What detention time does current MoHUA/CPHEEO guidance recommend as a practice for a dedicated chlorine contact tank used for postchlorination?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The current CPHEEO engineering manual recommends a dedicated chlorine contact tank or chamber for postchlorination. As a design practice, the recommended detention time is 30 minutes. The tank should be arranged to promote effective horizontal flow and reduce undesirable short-circuiting. Adequate chlorine distribution and hydraulic contact are essential because disinfection depends on both concentration and exposure time. Therefore Option C is correct.
వివరణ:
Question 14
ప్రశ్న 14
A water-treatment plant supplies 24 MLD. What theoretical chlorine-contact-tank volume is required for a nominal detention time of 30 minutes?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
A flow of 24 MLD equals 24,000 m3/day. Dividing by 1,440 minutes per day gives approximately 16.67 m3/min. The required nominal contact volume is 16.67 × 30. This gives approximately 500 m3. Therefore Option B is correct.
వివరణ:
Question 15
ప్రశ్న 15
A 120 MLD water-treatment plant adopts the current CPHEEO 30-minute chlorine-contact-tank detention period. What total nominal tank volume is required, and how should it be divided if two equal compartments are adopted as recommended for plants above 100 MLD?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
A flow of 120 MLD equals 120,000 m3/day or approximately 83.33 m3/min. For 30 minutes, the nominal volume is 83.33 × 30 = 2,500 m3. Current CPHEEO guidance specifies two compartments for chlorine contact tanks serving plants above 100 MLD. If divided equally, each compartment therefore has a nominal volume of 1,250 m3. Therefore Option C is correct.
వివరణ:
Question 16
ప్రశ్న 16
Why are baffles provided in a chlorine contact tank?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
An unbaffled tank can permit some water to move rapidly from inlet to outlet along preferential paths. Such short-circuiting reduces the effective contact time available for disinfection. Baffles lengthen and control the hydraulic flow path through the contact tank. Better hydraulic efficiency makes the actual disinfectant exposure more representative of the intended design contact period. Therefore Option A is correct.
వివరణ:
Question 17
ప్రశ్న 17
In disinfection practice, what does the simplified CT concept represent?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The CT concept combines disinfectant concentration and exposure time into a single disinfection-performance parameter. In its simplest form, CT is concentration multiplied by effective contact time. For chlorine, the appropriate required CT depends on factors such as microorganism, temperature, pH and disinfectant form. A calculated CT therefore cannot be judged adequate without reference to the applicable treatment objective and conditions. Therefore Option A is correct.
వివరణ:
Question 18
ప్రశ్న 18
If the relevant residual disinfectant concentration is 0.50 mg/L and the effective contact time is 30 minutes, what is the corresponding CT value?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
CT is calculated as disinfectant concentration multiplied by effective contact time. The concentration is 0.50 mg/L and the time is 30 minutes. Therefore CT = 0.50 × 30 = 15 mg·min/L. The calculation alone does not establish whether this CT is adequate for every pathogen or set of operating conditions. Therefore Option B is correct.
వివరణ:
Question 19
ప్రశ్న 19
A chlorine contact basin has an effective water volume of 600 m3 and carries 30 MLD. What is its nominal hydraulic detention time?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The plant flow is 30,000 m3/day. Dividing by 1,440 gives approximately 20.833 m3/min. The detention time is volume divided by flow, or 600/20.833. This gives approximately 28.8 minutes. Therefore Option C is correct.
వివరణ:
Question 20
ప్రశ్న 20
A nominal chlorine contact time is 30 minutes, but hydraulic evaluation indicates an effective contact-time factor of 0.70. If the disinfectant residual used for the CT calculation is 0.60 mg/L, what effective CT results?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The effective contact time is 0.70 × 30 = 21 minutes. CT is then the specified residual concentration multiplied by this effective time. Thus CT = 0.60 × 21 = 12.6 mg·min/L. This example illustrates why nominal basin volume alone can overstate actual disinfectant exposure when hydraulic short-circuiting occurs. Therefore Option B is correct.
వివరణ:
Question 21
ప్రశ్న 21
A treated water has a chlorine demand of 1.7 mg/L after the specified contact period, and the design requires a residual of 0.3 mg/L at that point. What chlorine dose is theoretically required?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Chlorine demand equals applied dose minus residual chlorine. Rearranging gives required dose equal to demand plus desired residual. The required dose is therefore 1.7 + 0.3 = 2.0 mg/L. Actual plant dosage should subsequently be adjusted from measured residual and changing water-quality conditions. Therefore Option C is correct.
వివరణ:
Question 22
ప్రశ్న 22
An 18 MLD plant applies chlorine at 1.8 mg/L. What theoretical daily chlorine requirement corresponds to this dose?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
For water-treatment dosing, 1 mg/L applied to 1 MLD corresponds numerically to 1 kg/day. The chlorine requirement is therefore 18 × 1.8 kg/day. This equals 32.4 kg/day. Chemical purity, standby capacity and operational reserve would be considered separately in an actual chlorination installation. Therefore Option C is correct.
వివరణ:
Question 23
ప్రశ్న 23
What is meant by rechlorination in a drinking-water supply system?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Chlorine residual gradually decays as treated water travels through reservoirs and distribution mains. Long travel times or continued chlorine demand can cause the residual to fall below the desired value at remote locations. Rechlorination provides an additional controlled chlorine application at an appropriate downstream point. Its purpose is to restore adequate disinfectant protection without unnecessarily overchlorinating water at the original plant. Therefore Option A is correct.
వివరణ:
Question 24
ప్రశ్న 24
Which comparison between chlorine, ozone and ultraviolet disinfection is most accurate at an introductory water-treatment level?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Chlorination is widely valued because a measurable disinfectant residual can persist after treatment and provide protection in distribution. Ozone is a powerful oxidant and disinfectant but decays rapidly and does not ordinarily provide the same persistent distribution residual. Ultraviolet radiation inactivates microorganisms while water passes through the UV reactor but likewise does not establish a continuing chemical residual. Systems using ozone or UV may therefore require an additional strategy where distribution-system residual protection is needed. Therefore Option A is correct.
వివరణ:
Question 25
ప్రశ్న 25
Consider the following statements about drinking-water chlorination: I. Chlorine demand is the difference between chlorine applied and residual chlorine after a specified contact period. II. Breakpoint chlorination can produce an increasing free chlorine residual after chlorine-consuming and combined-chlorine reactions have largely been satisfied. III. Current CPHEEO guidance recommends about 30 minutes detention for a dedicated postchlorination contact tank. IV. Current CPHEEO guidance requires at least about 0.2 mg/L residual chlorine at the critical point of the distribution system under normal conditions. Which option is correct?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Statement I correctly states the CPHEEO definition of chlorine demand. Statement II correctly describes the essential behavior of breakpoint chlorination. Statement III is correct because current CPHEEO engineering guidance recommends a 30-minute chlorine contact-tank detention period as a practice. Statement IV is correct because the guidance specifies a minimum residual chlorine of 0.2 mg/L at the critical distribution point under normal conditions. 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 destroy or inactivate pathogenic microorganisms to reduce the risk of waterborne disease సమాధానం: B.
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Question 2 ప్రశ్న 2Answer: A. Hypochlorous acid and hypochlorite ion సమాధానం: A.
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Question 3 ప్రశ్న 3Answer: B. More chlorine exists as hypochlorite ion, so free-chlorine disinfection generally becomes less effective సమాధానం: B.
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Question 4 ప్రశ్న 4Answer: B. Chlorine applied minus residual chlorine after a specified contact period సమాధానం: B.
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Question 5 ప్రశ్న 5Answer: C. 2.2 mg/L సమాధానం: C.
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Question 6 ప్రశ్న 6Answer: B. The stage after major chlorine demand and combined-chlorine reactions have been satisfied, beyond which additional chlorine produces an increasing free residual సమాధానం: B.
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Question 7 ప్రశ్న 7Answer: A. Chlorine is applied before major treatment units, such as near the raw-water intake or early in the treatment process, for specified process objectives సమాధానం: A.
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Question 8 ప్రశ్న 8Answer: A. To add chlorine to treated water after filtration so that final disinfection and an appropriate distribution-system residual can be achieved సమాధానం: A.
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Question 9 ప్రశ్న 9Answer: A. A comparatively high chlorine dose is applied for strong oxidation or disinfection, followed by removal of excess residual chlorine when necessary సమాధానం: A.
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Question 10 ప్రశ్న 10Answer: B. 0.2 mg/L సమాధానం: B.
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Question 11 ప్రశ్న 11Answer: C. 60 kg/day సమాధానం: C.
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Question 12 ప్రశ్న 12Answer: C. 500 kg/day సమాధానం: C.
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Question 13 ప్రశ్న 13Answer: C. 30 minutes సమాధానం: C.
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Question 14 ప్రశ్న 14Answer: B. 500 m3 సమాధానం: B.
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Question 15 ప్రశ్న 15Answer: C. 2,500 m3 total, 1,250 m3 per compartment సమాధానం: C.
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Question 16 ప్రశ్న 16Answer: A. To promote a controlled flow path and reduce hydraulic short-circuiting so that more of the water receives adequate contact సమాధానం: A.
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Question 17 ప్రశ్న 17Answer: A. The product of disinfectant residual concentration C and effective contact time T సమాధానం: A.
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Question 18 ప్రశ్న 18Answer: B. 15 mg·min/L సమాధానం: B.
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Question 19 ప్రశ్న 19Answer: C. 28.8 min సమాధానం: C.
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Question 20 ప్రశ్న 20Answer: B. 12.6 mg·min/L సమాధానం: B.
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Question 21 ప్రశ్న 21Answer: C. 2.0 mg/L సమాధానం: C.
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Question 22 ప్రశ్న 22Answer: C. 32.4 kg/day సమాధానం: C.
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Question 23 ప్రశ్న 23Answer: A. Additional chlorine application at an appropriate downstream point to restore or maintain the required residual during storage or distribution సమాధానం: A.
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Question 24 ప్రశ్న 24Answer: A. Chlorine can provide a persistent distribution-system residual, whereas ozone and ultraviolet treatment do not normally provide the same lasting disinfectant residual సమాధానం: A.
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Question 25 ప్రశ్న 25Answer: D. I, II, III and IV సమాధానం: D.