6 Water Resources- Water Pollution- Wastewater TreatmentEnvironmet_ Water_Workbook

Chapter 4: Water Resources (pages 83 – 103)

4.1: The Hydrologic Cycle

  • Key Process: One-fourth of the sun's energy facilitates water evaporation, driving the hydrologic cycle.

  • Evapotranspiration: Water evaporates from wet surfaces and is released by plants through transpiration, combining to move water into the atmosphere.

  • Purification Process: As water evaporates, impurities (like DDT) remain behind, purifying water.

  • Water Distribution:

    • World's Water: 94.2% in oceans, 1.65% in ice caps/glaciers.

4.2: U.S. Water Resources and Uses

  • Average annual rainfall: ~30 inches, resulting in 4200 billion gallons of daily precipitation.

  • Evapotranspiration Loss: 70% of rainfall (300 bgd) is lost to evapo-transpiration; 1200 bgd available for daily runoff.

  • Water Usage Breakdown in 1970:

    • Agriculture: 41% of withdrawals, 84% of consumption.

    • Thermal Pollution: steam-electric plants withdraw fresh/saline water mainly for cooling, returning almost all water, albeit heated.

4.3: Groundwater

  • Significance: Groundwater supplies 22% of current water withdrawals in the U.S.

  • Water Table Definition: Water percolates through soil to an impermeable layer, filling pores and crevices until it reaches the water table.

  • Groundwater Issues:

    • Subsidence: Caused by water table drops, leading to ground level sinking.

    • Overexploitation: Unsustainable depletion can make groundwater extraction economically unfeasible.

    • Coastal Intrusion: Excessive freshwater pumping causes saline intrusion, contaminating wells.

4.7: Conclusions

  • Focus on distribution and water quality is crucial. Despite adequate water quantity, challenges exist in maintaining quality.

  • Addressing shortages in southwestern U.S. requires strategies such as water importation, strict conservation, and enhanced desalination efforts.

  • Overexploited rivers impact relations with Mexico due to degraded water quality.

Chapter 5: Water Pollutants (pages 105 – 122)

5.1: Types of Pollutants

  • Oxygen-demanding wastes: Biodegradable organics causing oxygen depletion, impacting aquatic life.

  • Disease-causing agents: Pathogens from sewage harming human health.

  • Synthetic organics: Toxic compounds like detergents and pesticides.

  • Nutrients: Excess nitrogen and phosphorus from runoff lead to algae growth (eutrophication).

  • Inorganic chemicals: Heavy metals and acids from mining operations.

  • Sediments: Erosion from land impacting aquatic environments.

  • Radioactive substances: Contaminants from mining and industrial activities.

  • Thermal discharges: Elevated temperatures from power plants affecting ecosystems.

5.3: Dissolved Oxygen (DO)

  • Importance of DO: Critical for aquatic life, varies by fish species and conditions.

  • Oxygen Transfer Processes:

    • Reaeration: Entry of oxygen from atmosphere to water.

    • Photosynthesis & Respiration: Affect DO levels in diurnal cycles.

5.4: Decomposition

  • Aerobic vs Anaerobic Decomposition: Influences oxygen removal from water; excessive organic matter can lead to anaerobic conditions, producing toxins.

5.5: Biochemical Oxygen Demand (BOD)

  • BOD Measurement: Indicates pollution potential; essential for water quality management.

  • Rate of oxygen demand: Important for predicting ecosystem health based on organic waste decomposition.

5.6: The Oxygen Sag Curve

  • Interaction of deoxygenation and reaeration creates the oxygen sag curve, illustrating how waste impacts dissolved oxygen levels downstream.

5.9: Conclusions

  • Organic wastes need regulation to prevent overloads that lead to anaerobic decomposition, shifting aquatic ecosystems adversely.

Chapter 7: The Treatment of Water and Wastes (pages 143 – 168)

7.1: Biological Health Hazards

  • Key Waterborne Diseases: Related to sewage contamination include cholera, typhoid fever, dysentery.

  • Control through sanitation measures and proper waste treatment.

7.2: Urban Water and Sewage Systems

  • Safe drinking water treatment and sewage systems correlate with reduced disease incidence.

  • Sewage Treatment Overview:

    • Raw sewage processed typically in primary, secondary, or tertiary systems to enhance quality.

7.3: Water Quality Criteria

  • Criteria vary based on intended use (e.g., recreation vs. drinking).

  • Coliform bacteria testing is key for determining pathogen presence in water supplies.

7.4: Water Treatment Fundamentals

  • Steps: Mixing, coagulation, settling, filtration, and chlorination ensure raw water meets drinking standards.

7.5: Desalination

  • Technologies: Necessary for areas with high TDS levels, particularly reverse osmosis and distillation, though energy-consuming.

7.6: Sewage Treatment Fundamentals

  • Sewage Composition & Treatment Types: Overview of primary, secondary, and tertiary processes, focusing on nutrient removal and environmental impact.

7.9: The Cost of Water Pollution Control

  • Economic considerations for implementing effective pollution control measures, with large capital and O&M costs highlighted.