Environmental Health Practice Questions

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.

Q: Which of the following methods is used to treat Category 4 and Category 7 waste?

Autoclaving. ### Explanation The classification and management of Biomedical Waste (BMW) are governed by the **BMW Management Rules (2016)**. To answer this question, we must identify the waste types associated with these categories: * **Category 4:** Waste Sharps (Needles, syringes with fixed needles, scalpels, blades). * **Category 7:** Solid Waste (Tubing, catheters, intravenous sets, gloves). **Why Autoclaving is Correct:** According to the guidelines, both Category 4 (Sharps) and Category 7 (Recyclable plastic waste) must undergo **disinfection** before final disposal or recycling. **Autoclaving** (or microwaving/hydroclaving) is the preferred method for sterilization/disinfection of these categories. For Category 4, autoclaving is followed by shredding or mutilation to prevent reuse and ensure safety. **Analysis of Incorrect Options:** * **A. Incineration:** Used primarily for **Category 1 (Human Anatomical Waste)** and **Category 2 (Animal Waste)**. It is contraindicated for plastics (Category 7) because burning PVC releases toxic dioxins and furans. * **C. Deep Burial:** This is a localized solution permitted only in rural or remote areas where a Common Bio-medical Waste Treatment Facility (CBWTF) is unavailable, specifically for anatomical waste. * **D. Disposal in Landfill:** Waste must be treated (autoclaved/shredded) before reaching a sanitary landfill. Only "Secured Landfills" are used for the disposal of incineration ash. **High-Yield Clinical Pearls for NEET-PG:** * **Color Coding:** Category 4 (Sharps) goes into **White (Translucent)** puncture-proof containers. Category 7 (Recyclable plastics) goes into **Red** bags/containers. * **The "No-Burn" Rule:** Never incinerate chlorinated plastics or metals. * **Cytotoxic Drugs:** These belong to Category 5 and must be incinerated at high temperatures (>1200°C) or returned to the manufacturer.

Question 1

Sullage consists of:

Accepted Answer

Wastewater from kitchen

Answer

Solid vegetable waste matter

Answer

Inorganic waste

Answer

Waste containing human excreta

Question 2

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 3

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 4

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 5

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 6

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 7

In which process does aerobic digestion of sludge primarily occur?

Accepted Answer

Activated sludge

Answer

Trickling filter

Answer

Broad irrigation

Answer

Septic tank

Question 8

Which type of sand filter is more effective for the removal of bacteria?

Accepted Answer

Slow sand filter is more effective

Answer

Rapid sand filter is more effective

Answer

Both are equally effective

Answer

Rapid sand filter removes 70% of bacteria

Question 9

What is a characteristic feature of a slow sand filter?

Accepted Answer

Can be operated by personnel with limited technical expertise.

Answer

Requires a small installation area.

Answer

The filter is cleaned by backwashing.

Answer

Primarily used for large urban water supplies.

Question 10

Which of the following methods is used to treat Category 4 and Category 7 waste?

Accepted Answer

Autoclaving

Answer

Incineration

Answer

Deep burial

Answer

Disposal in landfill

Environmental Health — MCQs

Environmental Health — MCQs

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