Why this chapter matters for UPSC: Wastewater and sanitation are core GS3 topics — Swachh Bharat Mission (rural + urban), AMRUT sewage treatment, NAMAMI Gange (untreated sewage is the biggest source of river pollution), and open defecation impacts on public health are all directly tested in Prelims and Mains.

PART 1 — Quick Reference Tables

Wastewater Treatment Stages

Stage Process Removes
Screening Physical bars filter out large objects Rags, sticks, cans, large debris
Primary treatment (settling) Wastewater held in settling tank; solids sink (sludge); oil/grease float (scum) ~50–60% suspended solids; some BOD
Secondary treatment (biological) Aeration tank: Air pumped in → aerobic bacteria decompose organic matter → activated sludge; settling tank; chlorination ~85–95% BOD; dissolved organics
Tertiary treatment Advanced filtration, UV/ozone disinfection, chemical treatment Nutrients (N, P), pathogens, micropollutants
Sludge treatment Anaerobic digestion → biogas + treated sludge (used as fertiliser) Converts sludge to useful byproducts

India's Sanitation Statistics

Indicator Value Year
Open Defecation Free (ODF) villages ~6 lakh+ Gram Panchayats declared ODF Swachh Bharat Mission Gramin
Rural toilet coverage ~100% (declared); actual use still improving SBM-G
Urban sewage treatment capacity ~31,841 MLD (million litres per day) CPCB 2022
Urban sewage generation ~72,368 MLD CPCB 2022
Sewage treated ~44% of generated sewage CPCB 2022
Ganga untreated sewage ~2,950 MLD discharged untreated into Ganga towns Namami Gange data

PART 2 — Detailed Notes

Sources and Composition of Wastewater

Key Term

Types of wastewater:

Domestic sewage:

  • Kitchen, bathroom, toilet water
  • Contains: Organic matter, pathogens (bacteria, viruses, parasites), nutrients (N, P), soaps/detergents, medicines
  • Relatively dilute; biodegradable if treated

Industrial effluent:

  • From factories, manufacturing plants
  • Contains: Heavy metals (lead, mercury, chromium), toxic chemicals, acids/alkalis, dyes, oils — depending on industry
  • Often much more toxic than domestic sewage
  • Must be treated at source (CETP — Common Effluent Treatment Plants for industrial clusters, ETP at individual factories)
  • Key polluting industries in India: Tanneries (Kanpur, chromium pollution), dyeing units (Tirupur, textile chemicals), pulp and paper mills, fertiliser/chemical plants

BOD (Biochemical Oxygen Demand):

  • Amount of oxygen needed by bacteria to decompose organic matter in water
  • High BOD = high organic pollution = low dissolved oxygen = fish kills
  • Clean water: BOD < 2 mg/L; Heavily polluted: BOD > 10 mg/L; Ganga in urban stretches: BOD often 10–50 mg/L

Swachh Bharat Mission and Sanitation

UPSC Connect

UPSC GS2/GS3 — Swachh Bharat Mission:

Swachh Bharat Mission — Gramin (SBM-G):

  • Launched: October 2, 2014 (Gandhi Jayanti); Phase 2: 2020–2025
  • Goal: Eliminate open defecation; construct household toilets; promote hygiene behaviour change
  • Achievement (Phase 1, 2014–2019): ~10 crore toilets built; all states declared ODF
  • Concerns: "ODF but not ODF+" — toilets built but not always used (behavioural change harder than construction); structural quality issues (some latrines unusable)
  • Phase 2 (ODF Plus): Focus on sustainable sanitation — ODF sustainability, solid and liquid waste management, biodegradable waste composting, plastics management

Swachh Bharat Mission — Urban (SBM-U):

  • Focus: Eliminate open defecation in cities, solid waste management (segregation, processing), faecal sludge management
  • 100% household toilet coverage in cities
  • Swachhata Survekshan: Annual survey ranking cities on cleanliness; Indore has consistently been India's cleanest city for 7+ consecutive years

Health impact of sanitation:

  • Open defecation → faecal-oral disease transmission → diarrhoea, cholera, typhoid, polio
  • Child stunting: Open defecation near homes → environmental enteropathy → children don't absorb nutrients → stunting despite adequate food intake
  • Reducing open defecation = one of most cost-effective public health interventions

WASH:

  • Water, Sanitation, and Hygiene — the UN framework linking all three
  • SDG 6: Clean water and sanitation for all by 2030
  • India's progress: Rapid on sanitation access (SBM); still challenges on water quality (JJM) and hygiene behaviour

Water Pollution and Treatment

Explainer

India's water pollution crisis:

Main sources:

  1. Untreated sewage: ~50–60% of urban sewage not treated; discharged directly into rivers
  2. Industrial effluent: ~40% untreated; heavy metals, dyes, chemicals
  3. Agricultural runoff: Fertilisers (nitrates, phosphates) → eutrophication; pesticides
  4. Solid waste: Plastics and garbage dumped in rivers (riverfront management needed)
  5. Religious practices: Idol immersion (metals + paints → river), floral offerings

Most polluted rivers in India:

  • Ganga (from Kanpur and Varanasi stretches — tanneries, sewage, industrial)
  • Yamuna (Delhi stretch: Nearly dead; 77% of Delhi's sewage enters Yamuna)
  • Sabarmati (Ahmedabad industrial stretch)
  • Cooum and Adyar (Chennai urban rivers)

Namami Gange Programme:

  • Launched: 2015; Budget: ₹20,000 crore; implementing body: NMCG (National Mission for Clean Ganga) under Jal Shakti Ministry
  • Key interventions: Sewage treatment plants (STPs), industrial effluent treatment, river front development (ghats), biodiversity conservation (Gangetic dolphin, mahseer fish), afforestation of Ganga corridor
  • Status: ~170+ STPs commissioned; Ganga declared pollution-free in small stretches; significant work remaining

Gangetic River Dolphin:

  • National Aquatic Animal of India (declared 2009)
  • Endangered; found in Ganga-Brahmaputra system
  • Blind (uses echolocation); indicator species for river health
  • Population: ~3,700–4,000 estimated (improving with better river management)

Exam Strategy

Prelims traps:

  • SBM-G launched October 2, 2014 (Gandhi Jayanti) — year is important; October 2 date is important
  • Indore = cleanest city (Swachhata Survekshan 7+ consecutive years)
  • BOD = biochemical oxygen demand — high BOD = polluted water; low dissolved oxygen → fish kills
  • Namami Gange = 2015 (NOT SBM which is 2014) — different programmes; Ganga-specific
  • Ganga = National River (designated 2008); Gangetic dolphin = National Aquatic Animal (2009)
  • Sewage treatment deficit: India treats only ~44% of generated sewage; untreated sewage = biggest source of river pollution
  • CETP = Common Effluent Treatment Plant — for industrial clusters (tanneries, dyeing units); different from STP (Sewage Treatment Plant) which is for domestic sewage

Previous Year Questions

Prelims:

  1. The Swachh Bharat Mission (Gramin) was launched on which day and year?
    (a) August 15, 2014
    (b) October 2, 2014
    (c) January 26, 2015
    (d) April 22, 2014

  2. The "Gangetic River Dolphin" is significant because it is:
    (a) The state animal of Assam
    (b) India's National Aquatic Animal and an indicator species for river health
    (c) The rarest dolphin species in the world
    (d) Found only in the Brahmaputra, not the Ganga

  3. "BOD" (Biochemical Oxygen Demand) is used to measure:
    (a) The amount of dissolved oxygen in water
    (b) The amount of organic pollution in water (oxygen needed to decompose organic matter)
    (c) The acidity of water
    (d) The concentration of heavy metals in water