WATER POLLUTION-UEN008_0fe359ef8ccb0e8422428a676eb79fca

Water Pollution

Definition

Contamination of water bodies, primarily due to human activities such as industrial discharges, agricultural runoff, wastewater disposal, and urban development.

Water Bodies Affected

  • Lakes: Stagnant bodies of water that can accumulate pollutants, leading to eutrophication and loss of biodiversity.

  • Rivers: Flowing water bodies impacted by both point and non-point sources of pollution, affecting aquatic ecosystems along their banks.

  • Aquifers: Underground layers of water-bearing rock that can become contaminated, leading to severe groundwater pollution and scarcity.

  • Groundwater: Water located beneath the earth's surface that is often a source of drinking water and can be polluted from surface activities.

Impact

  • Change in water composition can lead to loss of beneficial uses such as drinking, recreation, agriculture, and habitat for wildlife. Polluted water can pose health risks to humans and animals, disrupt ecosystems, and contribute to climate change.

Water Cycle

Overview

  • The continuous movement of water through evaporation, condensation, precipitation, infiltration, and runoff is crucial for maintaining the balance of ecosystems.

Characteristics of Water Pollution

Physical Characteristics

  • Solids: Excess sediment can cause turbidity, impacting photosynthesis in aquatic plants.

  • Temperature: Changes in water temperature can affect oxygen levels and aquatic life.

  • Colour: Can indicate the presence of certain pollutants, affecting aquatic visibility.

  • Odour: Unpleasant smells may indicate pollution or sick waterways.

  • Turbidity: High turbidity levels can block sunlight and disturb aquatic habitats.

  • Oil and Grease: Hazardous pollutants that form films on water bodies, disrupting oxygen transfer.

  • Conductivity: High levels can signify presence of dissolved salts and pollutants.

Chemical Characteristics

  • Organics: Proteins, carbohydrates, lipids, surfactants, phenols, pesticides, and emerging organics that pose risk to health and environment.

  • Inorganics: Elements like pH, chlorides, alkalinity, nitrogen, phosphorus, and heavy metals which contribute to water toxicity and eutrophication.

  • Gases: Oxygen, hydrogen sulfide, and methane levels are critical for aquatic life; their imbalance can indicate pollution.

  • Aggregate Organics: Biological Oxygen Demand (BOD), Chemical Oxygen Demand (COD), and Total Organic Carbon (TOC) are parameters that indicate organic matter pollution.

Biological Characteristics

  • Pathogens: Disease-causing microorganisms that can contaminate water supply and threaten public health.

  • Indicators: Presence of certain species can signal the level of water quality; may include sensitive aquatic macroinvertebrates.

Sources of Water Pollution

  • Point Sources: Identifiable sources of pollution such as discharge pipes from factories or sewage treatment plants.

  • Non-Point Sources: Diffuse sources like agricultural runoff, urban stormwater, and atmospheric deposition that are harder to regulate.

Major Water Pollutants

Categories of Pollutants

  • Biodegradable Organic Matter: Organic waste that can decompose, but in high quantities can lead to oxygen depletion.

  • Suspended, Colloidal, and Dissolved Solids: Material that can cloud water and impede aquatic life.

  • Nutrients: Nitrogen and phosphorus, when in excess, can lead to algal blooms and eutrophication.

  • Pathogens: Bacteria, viruses, and protozoa can originate from sewage and runoff.

  • Soaps, Detergents, and Color-Causing Substances: These pollutants can alter water chemistry and aesthetics.

Persistent Pollutants

  • Synthetic Chemicals: Substances like heavy metals (lead, cadmium, mercury) that resist degradation and accumulate in ecosystems over time.

Categories of Pollutants

  • Fund Pollutants: Degradable pollutants that can be absorbed or broken down by the environment (e.g., organic matter).

  • Stock Pollutants: Pollutants that accumulate and have little to no absorptive capacity (e.g., heavy metals).

Dissolved Oxygen (DO)

Importance

  • Indicator of water quality, essential for the survival of aerobic aquatic organisms. Low levels can lead to fish kills and biodiversity loss.

Measurement

  • Expressed in mg/L; maximum saturation level for most freshwaters is usually around 10 mg/L at 16°C.

Oxygen Sources

  • Sources include diffusion from air, aeration from wind and waves, and photosynthesis by aquatic plants.

Biological Oxygen Demand (BOD)

Definition

  • The amount of oxygen required to decompose organic matter present in water, indicating pollution levels.

BOD Test

  • Conducted over 5 days (BOD5) under dark conditions at 20°C to prevent photosynthetic activity from influencing results.

Factors Influencing BOD

  • Key factors include temperature, time, and light conditions that can affect microbial activity and decomposition rates.

Chemical Oxygen Demand (COD)

Definition

  • Measures the total pollution potential from organic matter in water, including both biodegradable and non-biodegradable substances.

Difference from BOD

  • COD is generally higher than BOD because it quantifies all chemicals that can be oxidized, while BOD measures only what can be biologically degraded.

Measurement Process

  • Involves chemical oxidation using potassium dichromate in an acidic medium to quantify oxygen demand.

Key Relationship

  • BOD and COD Relationship: COD values will generally be greater than BOD due to the inclusion of non-biodegradable materials in COD measurements.

  • BOD/COD Ratio: A higher ratio indicates efficient biological treatment and suggests more biodegradable organic matter.

Physical Parameters of Water Quality

  • Solids: Evaluate total solids, total volatile solids, total suspended solids, and total dissolved solids for water quality assessment.

  • Turbidity & Color: Light transmission and color are crucial for aquatic ecology; high turbidity can impede plant growth and aquatic visibility.

Wastewater Treatment

Phases

  • Primary Treatment: Involves the physical removal of solid waste and sediments from wastewater.

  • Secondary Treatment: Biological treatment phase aimed at removing dissolved and suspended organic matter.

  • Tertiary Treatment: Advanced processes that remove remaining contaminants and nutrients from the water, often using filtration and chemical processes.

Disinfection of Water

Methods

  • Employs chemical (e.g., chlorine, ozone), physical (e.g., UV radiation), and mechanical (e.g., filtration) methods to eliminate pathogens from water.

Ideal Disinfectant Characteristics

  • Effective against a broad spectrum of microbes, stable in storage, and should not produce harmful by-products or corrode infrastructure.

Final Notes

  • Understanding water pollution and its treatment is crucial to achieving sustainable development and protecting the quality of water essential for human health and environmental balance. Implementing practices that reduce pollution can help preserve water resources for future generations.