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

StageProcessRemoves
ScreeningPhysical bars filter out large objectsRags, 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 treatmentAdvanced filtration, UV/ozone disinfection, chemical treatmentNutrients (N, P), pathogens, micropollutants
Sludge treatmentAnaerobic digestion → biogas + treated sludge (used as fertiliser)Converts sludge to useful byproducts

India's Sanitation Statistics

IndicatorValueYear
ODF Plus villages (SBM-G Phase 2)>95% villages declared ODF Plus (late 2025)Swachh Bharat Mission Gramin Phase 2
ODF Plus (Model) villages>83% villagesSBM-G; Jal Shakti Ministry 2025
Rural toilet coverage~100% (declared); actual use still improvingSBM-G
Urban sewage treatment capacity~31,841 MLD (million litres per day)CPCB 2022
Urban sewage generation~72,368 MLDCPCB 2022
Sewage treated~44% of generated sewageCPCB 2022
Namami Gange STP capacity3,976 MLD across 173 STPs (FY 2025-26)NMCG

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, 2020–2025): Focus on sustainable sanitation — ODF sustainability, solid and liquid waste management, biodegradable waste composting, plastics management. [Additional] Status (late 2025): Over 95% of villages declared ODF Plus; 83%+ declared ODF Plus (Model) status. 5.27 lakh villages have solid waste management; 5.41 lakh have liquid waste management arrangements. Total Phase 2 outlay: ₹1.41 lakh crore.

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 8 consecutive years (Swachhata Survekshan 2024–25, results July 2025)

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
  • [Additional] Status (FY 2025-26): 173 STPs commissioned with combined capacity of 3,976 MLD; Asia's largest STP (564 MLD) commissioned in Delhi (2025). NMCG targets 7,000 MLD total sanctioned capacity by December 2026. Significant work remaining to achieve zero-discharge goal.

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: ~6,327 (6,324 Gangetic + 3 Indus dolphins; Project Dolphin first systematic survey 2021–23; 'Population Status of River Dolphin in India 2024' report released by PM on World Wildlife Day, 3 March 2024)

[Additional] 18a. Faecal Sludge Management (FSM) — The Missed Half of India's Sanitation Story

The chapter (and most public discussion) focuses on Sewage Treatment Plants (STPs) that handle wastewater from piped sewage networks. But ~60–70% of urban India's households are on on-site sanitation — septic tanks, pit latrines, and single-pit systems — whose sludge is managed (or mismanaged) separately.

UPSC Connect

[Additional] Faecal Sludge and Septage Management (FSSM) — GS2/GS3 (Sanitation / Governance):

The distinction — STP vs FSTP:

  • STP (Sewage Treatment Plant): Treats wastewater that flows through a piped sewer network to a centralised plant
  • FSTP (Faecal Sludge Treatment Plant): Treats the thick sludge (septage) that accumulates in septic tanks, pit latrines, and holding tanks — collected by suction trucks and transported to the treatment plant
  • Both are necessary because India has two parallel sanitation realities: ~30–40% of urban households connected to sewers (going to STPs), and ~60–70% on on-site systems (whose sludge requires FSTP)

National Policy on Faecal Sludge and Septage Management (FSSM Policy):

  • Issued by Ministry of Urban Development (MoUD) in February 2017 — India's first dedicated national FSSM policy
  • Mandates that all Urban Local Bodies (ULBs) must have a plan for managing faecal sludge from on-site sanitation systems
  • Key objectives: Ensure safe emptying, transport, treatment, and disposal/reuse of faecal sludge; prevent contamination of water bodies; recover resources (biogas, organic fertiliser from sludge)

AMRUT and FSSM:

  • AMRUT (Atal Mission for Rejuvenation and Urban Transformation, 2015–2022): Includes septage management as a component for cities
  • AMRUT 2.0 (2021–2026): Explicitly includes sewerage and septage infrastructure; 102 lakh sewer/FSSM connections planned across 485 AMRUT cities
  • Uttar Pradesh: From 1 FSTP in 2018 to 59 FSTPs operational — largest state-scale FSSM programme in India
  • Nationally: Over 1,000 FSTPs built across India under various missions

Why this matters:

  • Improperly managed faecal sludge is a major source of groundwater contamination in urban areas (septic tank overflow, illegal discharge)
  • Manual scavenging — the practice of manually cleaning dry latrines and septic tanks without protective equipment — is linked to inadequate FSSM infrastructure; still persists despite being banned (Prohibition of Employment as Manual Scavengers and their Rehabilitation Act, 2013)
  • SDG 6.2 requires "safely managed sanitation for all" — piped sewage alone cannot achieve this; FSSM is essential to close the sanitation gap

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 8 consecutive years as of 2024–25)
  • 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

Practice 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