Environmental Health Practice Questions

Q: All of the following are essential for a well to meet the criteria of a sanitary well, EXCEPT:

No user should have to carry water more than 500 metres. ### Explanation In Community Medicine, a **Sanitary Well** is defined by specific structural and locational criteria designed to prevent waterborne diseases (like Cholera and Typhoid). **1. Why Option C is the Correct Answer:** The distance a user travels to collect water is a **service level/accessibility criterion**, not a structural requirement for the well itself to be considered "sanitary." According to the *Operational Guidelines for Jal Jeevan Mission*, the goal is to provide water within the household premises or within a distance of **100 meters** in rural areas. The 500-meter limit is an outdated or irrelevant metric for defining the sanitary integrity of a well. **2. Analysis of Incorrect Options (Sanitary Requirements):** * **Option A (Location):** A sanitary well must be located at least **15 meters (50 feet)** away from sources of contamination (latrines, soakage pits) to prevent sub-surface seepage of pathogens. * **Option B (Consumer Responsibility):** For a well to remain sanitary, the community must be educated on its proper use (e.g., not washing clothes near the well, using a dedicated bucket). Maintenance is a shared responsibility. * **Option C (Parapet Wall):** A parapet wall of at least **70–75 cm** is essential to prevent surface washings, animals, and children from falling into the well. **High-Yield NEET-PG Pearls:** * **Lining:** The well should be lined with bricks or stones up to a depth of at least **6 meters (20 feet)** to prevent sub-soil seepage. * **Platform:** A cement-concrete apron/platform should extend **1 meter** all around the well with a outward slope. * **Disinfection:** The most common method for well disinfection is **Bleaching Powder**. The standard dose is roughly 2.5g per 1000 liters to achieve a residual chlorine of 0.5 mg/L after 1 hour of contact time.

Q: Which method is used for the disposal of chemical waste under Biomedical waste management guidelines?

Incineration. **Explanation:** Under the **Biomedical Waste Management (BMWM) Rules**, chemical waste is categorized under **Yellow Bag** waste. The preferred method for its disposal is **Incineration** (specifically high-temperature incineration >1200°C for hazardous chemicals) or disposal in a **Secured Landfill**. **Why Incineration is Correct:** Chemical waste often contains toxic organic compounds or hazardous substances that require thermal decomposition to be neutralized. Incineration ensures the complete combustion of these chemicals, reducing them to non-toxic ash and gases, thereby preventing environmental contamination and chemical hazards. **Analysis of Incorrect Options:** * **Autoclaving (Option B):** This is a method of sterilization using pressurized steam. It is used for **Red Bag** waste (infected plastics) and **Yellow Bag** waste like soiled cotton/dressings, but it is ineffective for chemicals as it does not neutralize chemical toxicity. * **Microwaving (Option C):** Similar to autoclaving, this uses radiant energy to disinfect waste. It is used for infectious waste but is not suitable for chemical or pharmaceutical waste. * **Recycling (Option D):** While some metals or glass may be recycled after disinfection, raw chemical waste is hazardous and cannot be recycled due to the risk of toxicity and environmental persistence. **High-Yield NEET-PG Pearls:** * **Yellow Bag:** Includes human anatomical waste, animal waste, soiled waste, expired/discarded medicines, and **chemical waste**. * **Cytotoxic Drugs:** Must be incinerated at temperatures **>1200°C** (Yellow bag with "Cytotoxic" label). * **Chemical Liquid Waste:** Requires pre-treatment (neutralization) before being discharged into the drain/effluent treatment plant (ETP). * **Chlorinated Plastic Bags:** Should **never** be incinerated as they release toxic dioxins and furans.

Q: Sullage consists of:

Wastewater from kitchen. ### Explanation **Sullage** is a specific term used in environmental sanitation to describe wastewater that does **not** contain human excreta. It originates from domestic activities such as kitchens, bathrooms, and laundries. **1. Why Option D is Correct:** Sullage refers to "greywater." It includes wastewater from kitchen sinks, washbasins, and showers. While it contains organic matter (food particles) and detergents, it is significantly less pathogenic than sewage because it lacks fecal contamination. **2. Analysis of Incorrect Options:** * **Option A (Solid vegetable waste matter):** This is categorized as **Refuse** or "Garbage." Refuse refers to solid waste, whereas sullage is strictly liquid waste. * **Option B (Inorganic waste):** This refers to non-biodegradable dry refuse (e.g., glass, plastic, metals). Sullage is liquid and primarily organic in nature. * **Option C (Waste containing human excreta):** This is defined as **Sewage**. Sewage is a mixture of sullage and "night soil" (human excreta). It is highly hazardous and requires more complex treatment than sullage. **3. High-Yield Facts for NEET-PG:** * **Sewage vs. Sullage:** Sewage = Sullage + Night Soil (Human excreta). * **Sewer:** The underground pipe/conduit that carries sewage. * **Sewerage:** The entire infrastructure (pipes, pumps, treatment plants) designed to remove and treat sewage. * **BOD (Biochemical Oxygen Demand):** A key indicator of water pollution. Sewage has a much higher BOD compared to sullage. * **Health Impact:** Improper disposal of sullage leads to stagnant pools, which act as breeding grounds for *Culex* mosquitoes (vector for Filariasis).

Q: Softening of water is recommended when the hardness exceeds which of the following levels?

150 mg/litre. **Explanation:** The correct answer is **150 mg/litre**. Water hardness is primarily caused by the presence of calcium and magnesium bicarbonates, sulfates, and chlorides. While hardness is not a direct health hazard, it has significant economic and aesthetic implications, such as excessive soap consumption and scaling in pipes. According to standard public health guidelines (Park’s Preventive and Social Medicine), the recommendation for water softening is based on the following thresholds: * **Hardness 150 mg/L:** Softening is recommended to prevent scale formation and ensure effective lathering of soap. **Analysis of Options:** * **A (50 mg/L):** This is the threshold below which water is classified as "soft." No softening is required at this level. * **B (75 mg/L) & C (100 mg/L):** While water in this range is considered "moderately hard," it is still acceptable for most municipal supplies. Softening is not strictly recommended until the level exceeds 150 mg/L. **High-Yield NEET-PG Pearls:** 1. **Hardness Classification:** 0-50 (Soft), 50-150 (Moderately Hard), 150-300 (Hard), >300 (Very Hard). 2. **Temporary Hardness:** Caused by carbonates/bicarbonates of Calcium and Magnesium; removed by **boiling** or adding **lime**. 3. **Permanent Hardness:** Caused by sulfates, chlorides, and nitrates; removed by **base exchange process (Permutit)** or soda ash. 4. **Health Link:** Some epidemiological studies suggest a weak inverse correlation between water hardness and cardiovascular disease (hard water may be protective), though this remains a topic of debate.

Q: What is the quantitative requirement of water in urban areas per day?

150 liters per capita. ### Explanation **Correct Answer: C. 150 liters per capita** In Community Medicine, the quantitative requirement of water is determined by the environment and the level of development. According to the **Bureau of Indian Standards (BIS: 1172)** and the **Manual on Water Supply and Treatment**, the standard water requirement for an average urban area with a full sewerage system is **150 to 200 liters per capita per day (lpcd)**. The figure of **150 lpcd** is the benchmark used for planning urban water supply schemes in India. This volume accounts for domestic needs (drinking, cooking, bathing, flushing), as well as institutional and minor commercial requirements. **Analysis of Incorrect Options:** * **Option A (220 liters):** This exceeds the standard requirement for typical Indian urban settings. While some metropolitan cities may aim higher, it is not the standard benchmark for exams. * **Option B (100 liters):** This is generally considered the requirement for **urban areas without a sewerage system** or for smaller towns. It is insufficient for a fully functional urban infrastructure. * **Option D (300 liters):** This is an overestimation. Such high consumption is usually seen only in highly industrialized cities or developed Western nations. **High-Yield NEET-PG Pearls:** * **Rural Water Requirement:** The minimum requirement for rural areas (under the Jal Jeevan Mission) is **55 lpcd**. * **Basic Survival:** The absolute minimum water required for survival (physiological needs) is approximately **2–3 liters per day**, but for "basic hygiene," the WHO recommends at least **20 lpcd**. * **Water Quality:** Remember that quantity is secondary to quality; for urban supply, the residual chlorine should be **0.5 mg/L** after a contact time of 30 minutes.

Q: Which of the following statements about bleaching powder is true?

It is not used for disinfection of faces and urine.. ### Explanation **Bleaching Powder (Chlorinated Lime)** is a widely used disinfectant in public health, but its efficacy is highly dependent on its chemical stability and the presence of organic matter. **Why Option D is Correct:** Bleaching powder is **not** recommended for the disinfection of feces and urine. This is because chlorine is rapidly neutralized by organic matter. Feces and urine contain high concentrations of organic compounds that "consume" the available chlorine, rendering it ineffective unless used in impractical quantities. For excreta disinfection, **Cresol** or **8% Lime (Calcium Hydroxide)** are preferred. **Analysis of Incorrect Options:** * **Option A:** Fresh bleaching powder contains approximately **33% available chlorine**, not 100%. This is a high-yield number for exams. * **Option B:** There is no "100% solution" of bleaching powder. For general environmental disinfection, a 1% solution is typically used. For feces, even if it were used, the concentration required would be much higher, but it remains suboptimal due to the organic load. * **Option C:** Bleaching powder is **unstable**. It loses its chlorine content rapidly when exposed to air, light, or moisture. It must be stored in a cool, dark, and dry place in airtight containers. **High-Yield NEET-PG Pearls:** 1. **Horrocks’s Apparatus:** Used to estimate the dose of bleaching powder required to disinfect a given quantity of water. 2. **Contact Time:** For effective water disinfection, the contact time for chlorine should be at least **30 to 60 minutes**. 3. **Free Residual Chlorine:** The recommended level in drinking water is **0.5 mg/L** after 1 hour of contact. 4. **OT Test (Orthotolidine):** Used to detect both free and combined chlorine; however, the **OTA (Orthotolidine-Arsenite) Test** is superior as it distinguishes between the two.

Q: In which process does aerobic digestion of sludge primarily occur?

Activated sludge. **Explanation:** The **Activated Sludge Process** is a biological method of secondary sewage treatment that relies on **aerobic digestion**. In this process, sewage is passed into an aeration tank where it is mixed with "activated sludge" (a mixture of aerobic bacteria and protozoa). Large amounts of air are pumped into the tank, providing the oxygen necessary for these microorganisms to oxidize organic matter into carbon dioxide, water, and nitrogenous compounds. This is the most common method used for large-scale urban sewage treatment. **Analysis of Incorrect Options:** * **Trickling Filter:** While also an aerobic process, it involves sewage trickling over a bed of stones covered in a biological film. It is less efficient than the activated sludge process and does not involve the "digestion of sludge" in the same suspended-growth manner. * **Broad Irrigation:** This is a method of land disposal where raw or partially treated sewage is used to water crops. It relies on natural soil filtration and surface oxidation rather than a controlled aerobic digestion process. * **Septic Tank:** This is a primary treatment unit that works on the principle of **anaerobic digestion**. Solids settle at the bottom and are decomposed by anaerobic bacteria in the absence of oxygen. **High-Yield Pearls for NEET-PG:** * **BOD (Biochemical Oxygen Demand):** The Activated Sludge process can reduce BOD by 85–95%. * **Indicator of Pollution:** High BOD indicates high organic pollution; drinking water should ideally have a BOD of zero. * **Septic Tank Retention:** The recommended detention period for a septic tank is 12–24 hours. * **Secondary Treatment:** Both Trickling Filters and Activated Sludge are forms of secondary (biological) treatment.

Question 1

All of the following are essential for a well to meet the criteria of a sanitary well, EXCEPT:

Accepted Answer

No user should have to carry water more than 500 metres

Answer

Located at least 15m away from possible sources of contamination

Answer

Consumer responsibility

Answer

A parapet wall up to a height of at least 70-75cm

Question 2

The amount of good quality bleaching powder required for chlorinating a round well measuring 4 meters in diameter and with a water column depth of 6 meters, to achieve a residual chlorine level indicated by the Horrocks' test giving a definite blue color in the 3rd cup onwards, is?

Accepted Answer

993.8 grams

Answer

99.38 grams

Answer

9.938 grams

Answer

0.9938 grams

Question 3

Which method is used for the disposal of chemical waste under Biomedical waste management guidelines?

Accepted Answer

Incineration

Answer

Autoclaving

Answer

Microwaving

Answer

Recycling

Question 4

Sullage consists of:

Accepted Answer

Wastewater from kitchen

Answer

Solid vegetable waste matter

Answer

Inorganic waste

Answer

Waste containing human excreta

Question 5

All are TRUE regarding bacteriological surveillance of drinking water quality EXCEPT:

Accepted Answer

Clostridium perfringens is routinely used for bacteriological surveillance of drinking water.

Answer

Fecal streptococci are the indicator of recent contamination of water.

Answer

Clostridium perfringens indicate remote contamination.

Answer

Screening test for coliform in drinking water is the presumptive coliform test.

Question 6

What is true about incineration?

Accepted Answer

65% pharmaceutical waste, 15% lime, 15% cement, and 5% water

Answer

85% pharmaceutical waste and 15% cement

Answer

75% pharmaceutical waste, 15% cement, and 10% water

Answer

70% pharmaceutical waste, 20% cement, and 10% lime

Question 7

Softening of water is recommended when the hardness exceeds which of the following levels?

Accepted Answer

150 mg/litre

Answer

50 mg/litre

Answer

75 mg/litre

Answer

100 mg/litre

Question 8

What is the quantitative requirement of water in urban areas per day?

Accepted Answer

150 liters per capita

Answer

220 liters per capita

Answer

100 liters per capita

Answer

300 liters per capita

Question 9

Which of the following statements about bleaching powder is true?

Accepted Answer

It is not used for disinfection of faces and urine.

Answer

It contains 100% available chlorine.

Answer

A 100% solution is used for disinfection of faces.

Answer

It is a stable compound on storage.

Question 10

In which process does aerobic digestion of sludge primarily occur?

Accepted Answer

Activated sludge

Answer

Trickling filter

Answer

Broad irrigation

Answer

Septic tank

Environmental Health — MCQs

Environmental Health — MCQs

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