ESS 4.4 Water Pollution

Water pollution

Contamination of water bodies by harmful substances or waste.

Pollutant

Any chemical, physical, or biological substance that degrades water quality.

Point source pollution

Pollution coming from a single, identifiable source (like a factory pipe).

Non-point source pollution

Pollution coming from many diffuse sources (like farms or cities).

Sewage

Wastewater from homes and industries that can pollute rivers and seas.

Agricultural run-off

Water from farms carrying fertilizers, pesticides, or manure into waterways.

Industrial effluent

Liquid waste discharged from factories into the environment.

Urban run-off

Rainwater washing pollutants from cities (like oil, metals, and litter) into drains.

Oil spill

Accidental release of oil into oceans or rivers, harming marine life.

Solid waste disposal

Dumping of garbage that can leach toxins into water sources.

Organic pollution

Pollution from natural materials (e.g., sewage, food waste) that deplete oxygen as they decompose.

Plastic debris

Human-made plastics accumulating in oceans and waterways.

Microplastics

Tiny plastic particles (less than 5 mm) that enter food chains.

Biodegradable

Able to be broken down by microorganisms.

Bioaccumulation

Gradual buildup of a substance (like mercury) in an organism.

Biomagnification

Increase in toxin concentration as it moves up the food chain.

Water quality

A measure of the chemical, physical, and biological characteristics of water.

Dissolved oxygen (DO)

The amount of oxygen available in water for organisms to breathe.

Biochemical oxygen demand (BOD)

Amount of oxygen microorganisms need to break down organic matter; high BOD = pollution.

Indicator species

Organisms whose presence or absence reflects pollution levels.

Biotic index

A scale showing water quality based on species diversity and tolerance to pollution.

Eutrophication

Excess nutrients (mainly nitrates and phosphates) causing algae overgrowth and oxygen loss.

Algal bloom

Rapid increase in algae population due to nutrient enrichment.

Anoxic / hypoxic water

Water with very low or no oxygen, unable to support most life.

Ecosystem services

Benefits humans gain from clean water (drinking, recreation, biodiversity).

Management levels of eutrophication

Reducing nutrients at the source, controlling release, and restoring ecosystems.

Primary treatment

Removal of large solids from sewage by settling and screening.

Secondary treatment

Biological process where bacteria break down organic waste.

Tertiary treatment

Final purification stage removing nutrients, bacteria, or chemicals.

Water quality index (WQI)

A numerical indicator summarizing overall water quality.

WHO guidelines

Standards set by the World Health Organization for safe drinking water.

Citizen action

Efforts by individuals or groups to monitor and reduce water pollution.

Persistent pollutants

Substances that resist natural breakdown (e.g., PCBs, DDT).

Endocrine disruptors

Chemicals (like tributyltin) that interfere with hormones in animals and humans.

Thermal pollution

Release of warm water from industry that lowers dissolved oxygen levels.

Toxins

Poisonous substances produced by algae or human activity that harm organisms.

Harmful algal bloom (HAB)

Algal bloom that releases toxins dangerous to humans and wildlife.

Hypoxia

Low oxygen condition in water, often due to eutrophication and warming.

Anoxia

Complete absence of oxygen in water.

Sewage treatment process

Stages that clean wastewater before release: pre-treatment, primary, secondary, tertiary.

Activated sludge

Microorganisms used in secondary sewage treatment to break down waste.

Ozone treatment

Advanced method in tertiary treatment that disinfects and removes pollutants.

Micropollutants

Trace contaminants like pharmaceuticals that persist after treatment.

Biogas

Renewable gas produced from sewage sludge decomposition.

Water pollution index

Composite measure combining chemical and biological indicators of contamination.

Anoxic zone expansion

Growth of oxygen-free zones in oceans due to global warming and eutrophication.

Drinking water standards

Legal water quality limits set by local or national governments.