Water Pollution Part 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

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.

Algal Blooms

Algal Blooms

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

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

Maintaining Water Quality and Water Purification

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

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)

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

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

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

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

Septic System

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

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

Sewage Treatment

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

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