Water Pollution

1. Water Pollution Part 2

2. Cultural Eutrophication • Process by which human activity increases the amount of nutrients entering surface waters • Nitrates (NO3-) – water soluble, poison water supply, reduce effectiveness of hemoglobin, contribute to acid rain, may be related to decline of amphibians • Phosphates (PO43-) – not water soluble, up 75% from preindustrial levels • Lead to algae blooms

3. Steps of an Algal bloom • Increased algae due to increased nitrate and/or phosphate concentrations  decreased light penetration  deeper plants die off  less oxygen released into the water • Increased material for decomposers  decrease in oxygen concentrations • Lower oxygen concentrations  aquatic organisms die off  water contamination • Decaying fish, algae, and other organisms add toxins to the water.

4. Algal Blooms

5. Algal Blooms

6. How to control for eutrophication • Plant vegetation along streambeds • Slows erosion • Absorbs some nutrients • Control application and timing of fertilizer run off • Control run off from feed lots • Use biological controls • Denitrifying bacteria

7. Ground water Pollution • 50% of the people in the US depend on groundwater for their water supplies • Some countries 95% • EPA estimates 4.5 trillion liters of water seep into ground water supplies each day • 34 billion liters per year of the most dangerous liquid wastes are injected into the ground below the water table • Water in aquifers remain there about 1,400 years • Cleaning up contaminated ground water is almost impossible and very expensive – could cost $1 trillion per year

8. Maintaining Water Quality and Water Purification

9. Drinking water treatment Methods • Adsorption – contaminants stick to surface of granular or powders activated charcoal • Disinfection – chlorine, chloramines, chlorine dioxide, ozone, and UV radiation • Filtration – removes clay, slits, natural organic matter, and precipitants form the treatment process • Flocculation-Sedimentation – process that combines small particles into larger particles and then settle out of the water as sediment, uses alum, iron salts or synthetic organic polymers • Ion Exchange – removes inorganic constituents, can removes arsenic, chromium, excess fluoride, nitrates, radium, and uranium

10. Water treatment remediation technologies • Adsorption/absorption – solutes concentrate at the surface of a sorbent (absorbing surface), thereby reducing contamination • Aeration – bubbling air through water increases rates of oxidation • Air stripping – VOCs are separated from groundwater by exposing water to air (VOCs evaporate due to their high vapor pressure) • Bioreactors – groundwater is acted upon by microorganisms • Constructed Wetland – uses natural geochemical and biological process that parallel natural wetlands (living machines)

11. Water treatment remediation technologies • Deep-well injection – uses injection wells to place treated or untreated liquid wastes into geological formations that do not pose a potential risk to groundwater • Enhanced bioremediation – the natural rate of bioremediation is enhanced by adding oxygen and nutrients into groundwater • Fluid-vapor extraction – a vacuum system is applied to low-permeable soil to remove liquids and gases • Granulated activated carbon (GAC) – ground water is pumped through a series of columns containing activated carbon

12. Water treatment remediation technologies • Hot water or steam flushing – steam or hot water is forced into an aquifer to vaporize volatile contaminants and is then treated through fluid-vapor extraction • In-well air stripping – air is injected into wells, the air picks up various contaminants (VOCs) the vapors are then drawn off by vapor extraction • Ion exchange– involves exchanging one ion for another • Phytoremediation – uses plants to remove contamination • UV oxidation – uses UV light, ozone, or hydrogen peroxide to destroy microbiological contaminants

13. Sewage Treatment/ Septic Systems Incorporates physical, chemical, and biological processes to remove contaminants

14. Septic Systems • Have tank and drain field • Steps: • Waste water enters the tank • solids settle out • Anaerobic digestion using bacteria treats settled solids, reducing their volume • Excess liquid leaves the tank and moves through a pipe with holes to a leach field where water percolates into the soil • Some pollutants (ex. Nitrogen) do not decompose and can contaminate ground water • About 25% of Americans rely on septic systems

15. Septic System

16. Sewage Treatment • Primary Treatment – Separation of Solids - Physical • Reduces oils, grease, fats, sands, grit, and coarse solids • Uses sand catchers, screens, and sedimentation • Secondary Treatment – Breakdown by bacteria - biological • Degrade the biological content from food waste, human waste, soaps, and detergents • Uses filters, activated sludge, oxidizing beds, trickle filter beds, secondary sedimentation

17. Sewage Treatment • Tertiary Treatment – Disinfection – chemical • Treats water before discharge to the environment • Uses sand filtration, lagooning, constructed wetlands, nutrient removal via biological or chemical precipitation, denitrification and phosphorus removal using bacteria, microfiltration, disinfection with UV light, chlorine, or ozone • Quaternary Treatment – Ultrapure water • Treats water for groundwater recharge and industrial use • Uses membrane filtration, reverse osmosis

18. Sewage Treatment

19. Relevant Laws • Clean Water Act (1972): • Established basic structure for regulating discharge of pollutants into US waters • Gave EPA authority to implement pollution control programs • Continued requirements to set standards for all contaminants of surface water • Made it unlawful to discharge into navigable waters without a permit • Funded construction of sewage treatment plants

20. Relevant Laws • Safe Drinking Water Act (1974): established standards for safe drinking water in the US • Ocean Dumping Ban Act (1988): made it unlawful to dump, or transport for dumping, sewage, sludge, or industrial wastes into the ocean • Oil Spill Prevention and Liability Act (1990): strengthened EPAs ability to prevent and respond to catastrophic oil spills