Unit 3: Water Pollution: Sources, Parameters, Health Effects, and Diseases

Water pollution refers to the contamination of water bodies, such as rivers, lakes, oceans, groundwater, and aquifers, typically due to human activities. This contamination negatively affects aquatic ecosystems, human health, and various beneficial uses of water.

Sources of Surface and Ground Water Pollution

Water pollution can originate from various sources, categorized broadly into point and non-point sources.

Sources of Surface Water Pollution

Surface water includes rivers, lakes, ponds, and oceans.

• Point Sources: These are identifiable and localized sources from which pollutants are discharged directly into a water body.

  Examples:

  • Industrial discharge pipes dumping chemical waste or heated water.
  • Sewage treatment plant outfalls releasing treated (or sometimes untreated) wastewater.
  • Oil spills from tankers or offshore drilling rigs.
  • Factories releasing heavy metals, acids, or toxic chemicals.

• Non-Point Sources: These are diffuse and widespread sources where pollution originates from various locations and enters water bodies through runoff or atmospheric deposition. It is often difficult to pinpoint the exact origin of non-point pollution.

  Examples:

  • Agricultural runoff containing pesticides, herbicides, fertilizers (nitrates and phosphates), and animal waste.
  • Urban runoff carrying oil, grease, chemicals, pet waste, and litter from streets and parking lots.
  • Stormwater runoff from construction sites, eroding soil, and sediment.
  • Atmospheric deposition of pollutants from air pollution settling into water bodies.

Sources of Ground Water Pollution

Groundwater is water located beneath the Earth's surface in aquifers. Pollution often occurs when contaminants seep through the soil.

• Septic Systems: Malfunctioning or improperly maintained septic tanks can leach pathogens (bacteria, viruses) and nitrates into groundwater.
• Landfills: Leakage from landfills can release leachate, a toxic liquid containing heavy metals, organic chemicals, and pathogens, into groundwater.
• Agricultural Activities: Excessive use of fertilizers and pesticides can seep into the ground and contaminate aquifers. Animal feedlots also contribute nitrates and pathogens.
• Industrial Spills and Leaks: Chemicals from industrial sites, underground storage tanks (e.g., gasoline stations), and hazardous waste sites can leak and migrate into groundwater.
• Mining Activities: Acid mine drainage can release heavy metals and acidic water into groundwater.
• Saltwater Intrusion: Over-pumping of groundwater in coastal areas can draw saltwater into freshwater aquifers, contaminating them.

Water Quality Parameters and Standards

Water quality is assessed by measuring various physical, chemical, and biological parameters against established standards to determine its suitability for different uses (e.g., drinking, irrigation, recreation).

Physical Parameters

• Temperature: Affects dissolved oxygen levels and aquatic life metabolism. Higher temperatures reduce oxygen solubility.
• Turbidity: A measure of water clarity; caused by suspended solids (silt, clay, organic matter). High turbidity reduces light penetration, affecting photosynthesis and clogging fish gills.
• Color: Can indicate the presence of dissolved organic material, metals, or industrial waste.
• Odor: Indicates the presence of certain chemicals, organic decomposition, or microbial activity.
• Total Suspended Solids (TSS): The dry weight of particles retained by a filter; contributes to turbidity.

Chemical Parameters

• pH: Measures acidity or alkalinity (scale 0-14). Pure water has a pH of 7. Most aquatic life thrives in a pH range of 6.5-8.5.
• Dissolved Oxygen (DO): The amount of oxygen dissolved in water, crucial for aquatic life respiration. Low DO indicates pollution (e.g., from organic matter decomposition). Typical values for healthy water are 5-9 mg/L.
• Biochemical Oxygen Demand (BOD): The amount of oxygen consumed by microorganisms while decomposing organic matter in water over a specific period (usually 5 days at 20°C). High BOD indicates high organic pollution.
• Chemical Oxygen Demand (COD): The amount of oxygen required to chemically oxidize all organic and inorganic pollutants in water. COD is generally higher than BOD.
• Hardness: Caused by dissolved calcium (Ca²⁺) and magnesium (Mg²⁺) ions. Hard water can cause scale buildup.
• Alkalinity: Water's capacity to neutralize acids; primarily due to bicarbonate, carbonate, and hydroxide ions. Acts as a buffer against pH changes.
• Chlorides: Naturally occurring, but high levels can indicate sewage contamination, industrial waste, or saltwater intrusion.
• Nitrates (NO₃^-) and Phosphates (PO₄^3-): Essential plant nutrients, but excessive levels (from fertilizers, sewage) lead to eutrophication.
• Heavy Metals: Toxic metals like lead, mercury, cadmium, arsenic. Even in trace amounts, they can be highly toxic to humans and aquatic life.

Biological Parameters

• Coliform Bacteria: A group of bacteria present in the digestive tracts of warm-blooded animals and in the environment. Their presence indicates potential fecal contamination.
• Fecal Coliform and E. coli: Specific types of coliform bacteria strongly associated with fecal matter. E. coli is a primary indicator of fecal contamination and the potential presence of pathogenic organisms.

Water Quality Standards

Water quality standards are legal limits and guidelines set by regulatory bodies (e.g., World Health Organization (WHO), Environmental Protection Agency (EPA) in the USA) for various pollutants in water. These standards define the maximum permissible concentrations of contaminants for different water uses, ensuring public health and environmental protection. They help in monitoring, assessing, and managing water quality.

Eutrophication

Eutrophication is the process where a body of water becomes overly enriched with nutrients, leading to excessive growth of algae and aquatic plants (algal blooms). This process can be natural but is often accelerated by human activities (cultural eutrophication).

Process of Eutrophication

1. Nutrient Enrichment: Excess nutrients, primarily nitrates (NO₃^-) and phosphates (PO₄^3-), enter the water body, typically from agricultural runoff, sewage discharge, and industrial waste.
Algal Bloom: The abundant nutrients stimulate rapid growth of algae and other aquatic plants on the water's surface, forming a dense