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📌 The Question:
“Membrane Bioreactors” are often discussed in the context of:

(a) Assisted reproductive technologies
(b) Drug delivery nanotechnologies
(c) Vaccine production technologies
(d) Wastewater treatment technologies

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✅ Correct Answer: (d) Wastewater treatment technologies

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⚡ Lightning Classroom Explanation:

A Membrane Bioreactor (MBR) is an advanced wastewater treatment technology that integrates:

• Biological treatment (activated sludge process), and
• Membrane filtration (microfiltration / ultrafiltration)

🔬 The membrane replaces the traditional sedimentation tank.

👉 Because membrane pore sizes are extremely small (often < 0.1 micrometre), MBR systems:

• Remove suspended solids
• Trap bacteria and pathogens
• Produce very high-quality treated effluent

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🧠 Curiosity Raiser:
👉 Why is MBR preferred in urban & water-scarce regions?
Because the treated water is clean enough for reuse in industries, landscaping, and groundwater recharge.

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📚 Enrich Notes (UPSC Value-Add):

• Smaller land footprint than conventional STPs
• High capital cost, but lower long-term operational footprint
• Widely used in Smart Cities, industrial effluent treatment, and sewage reuse projects
• Important for circular water economy and SDG-6 (Clean Water & Sanitation)

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🕊️ IAS Monk Whisper:
“When water is treated wisely, cities breathe easier.”