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Water Pollution Big Idea The LARGER the population GROWS the greater the pollution will FLOW and the negative effects we’ll KNOW. http://www.epa.gov/owow/tmdl/overviewfs.html Point Source Pollution vs. Nonpoint Source Pollution What’s the difference? Point Source Pollution comes from a specific source, like a pipe factories, industry, municipal treatment plants can be monitored and controlled by a permit system What is nonpoint source pollution? Nonpoint Source (NPS) Pollution is pollution associated with stormwater or runoff NPS pollution cannot be traced to a direct discharge point such as a wastewater treatment facility Examples of NPS oil & grease from cars fertilizers animal waste grass clippings septic systems sewage & cleaners from boats household cleaning products litter Pollutant Transport Mechanisms • NPS pollutants build up on land surfaces during dry weather Atmospheric deposition Fertilizer applications Animal waste Automotive exhaust/fluid leaks • Pollutants are washed off land surfaces during precipitation events (stormwater runoff) • Stormwater runoff will flow to lakes and streams Point or Non-Point Source? Eroding soil from construction sites Leachate from landfill Overflowing hog lagoon Pesticides Septic tank leak Storm water run-off from city streets Point or Non-Point Source? Eroding soil from construction sites NON-POINT Leachate from landfill POINT Overflowing hog lagoon POINT Pesticides NON-POINT Septic tank leak POINT Storm water run-off from city streets NON-POINT Pollutant build-up and wash off are affected by land use. Imperviousness increases runoff Land use changes impact build up Linking Land Use to Water Quality More Imperviousness = More Water What is impervious cover? roads, rooftops, parking lots, and other hard surfaces that do not allow stormwater to soak into the ground “predominant American vegetation” Impervious Cover • provides a surface for accumulation of pollutants • leads to increased polluted runoff and flooding • inhibits recharge of groundwater Impact of Nonpoint Source Pollution fish and wildlife recreational water activities commercial fishing tourism drinking water quality Pollutants Found in Runoff Sediment Soil particles transported from their source Biochemical Oxygen Demand (BOD) ● Oxygen depleting material Leaves Organic material Toxics ● Pesticides Herbicides Fungicides Insecticides ● Metals (naturally occurring in soil, automotive emissions/ tires) Lead Zinc Mercury ● Petroleum Hydrocarbons (automotive exhaust and fuel/oil) Debris Litter and illegal dumping Nutrients ● Various types of materials that become dissolved and suspended in water (commonly found in fertilizer and plant material): Nitrogen (N) Phosphorus (P) Bacteria/ Pathogens Originating from: ● Pets ● Waterfowl ● Failing septic systems Thermal Stress Heated runoff, removal of streamside vegetation Potential Sources of Pollutants Found in Residential Areas Nutrients: Fertilizers and septic systems Pathogens: Pet waste and septic systems Sediment: Construction, road sand, soil erosion Toxic: Pesticides, household products Debris: Litter and illegal dumping Thermal: heated runoff, removal of streamside vegetation Pollutants from Agriculture Sediment Nutrients Pathogens Pesticides Why are these pollutants important? Sediment reduces light penetration in stream, clogs gills of fish and aquatic invertebrates. Nutrients act as fertilizer for algae & aquatic plants which can cause highly varying dissolved oxygen levels. At low DO levels, the aquatic life has the potential to be harmed. Toxics can impact life and contaminate drinking water supplies. Bacteria/Pathogens are an indicator of possible viruses present in the system. Inefficient Irrigation Worldwide, the amount of land under irrigation has been increasing. Whether from aquifers or surface bodies of water, the majority of the freshwater we use for irrigation is lost before it ever reaches the crops. Figure 14-15 Inefficient Irrigation Flood and Furrow Irrigation Inefficient “flood and furrow” irrigation, in which fields are liberally flooded with water that may evaporate from shallow standing pools, accounts for 90% of irrigation worldwide. Over-irrigation leads to waterlogging and salinization, which affects 1/5 of farmland today and reduces world farming income by $11 billion. Unfortunately, huge amounts of groundwater are being used up for little gain; because of the dry climate and inefficient irrigation methods. We Can Cut Water Waste in Irrigation Flood irrigation Wasteful Center pivot, low pressure sprinkler Low-energy, precision application sprinklers Drip or trickle irrigation, microirrigation Costly; less water waste Center pivot (efficiency 80% with low-pressure sprinkler and 90–95% with LEPA Drip irrigation sprinkler) Gravity flow Water usually pumped from (efficiency 90–95%) (efficiency 60% and 80% with surge valves) Above- or below-ground underground and sprayed Water usually comes from an from mobile boom with pipes or tubes deliver water aqueduct system or a nearby river. sprinklers. to individual plant roots. Fig. 13-20, p. 335 Solutions: Reducing Irrigation Water Waste Eutrophication Most nutrients in water come from organic matter (leaves, waste, etc.) Nutrients are an essential part of any aquatic ecosystem, but when slow-moving waters contain too much, they are eutrophic. Eutrophication Eutrophication= build-up of organic matter in water causing algal blooms Outcomes: • Decreased sunlight • Decaying matter uses oxygen • Suffocation/Fish Kills Artificial Eutrophication Humans act as a catalyst by adding excess nutrients to the soil Main culprits= phosphates from fertilizers and cleaning agents Human activity can also cause thermal pollution POLLUTION OF GROUNDWATER It can take hundreds to thousand of years for contaminated groundwater to cleanse itself of degradable wastes. Nondegradable wastes (toxic lead, arsenic, flouride) are there permanently. Slowly degradable wastes (such as DDT) are there for decades. Groundwater has low flow rates, few bacteria, & cold temps - all slow down recovery time Avg. recycling time for groundwater = 1400 years Leaking tank Water table Groundwater flow Free gasoline dissolves in Gasoline leakage plumegroundwater (liquid phase) (dissolved phase) Migrating vapor phase Contaminant plume movesWater well with the groundwater Fig. 21-8, p. 502 Surface water vs. Groundwater Which is generally more polluted? ~ Surface Water Which is harder to clean up? ~ Groundwater Groundwater pollution sticks around... Very cold, no bacterial breakdown Very slow water movement: recharge can take 100’s or 1000’s of years Pollutants can stick to rocks in aquifer and pollute new water What Pollutes Groundwater? Sources of Groundwater pollution... landfills leaky underground storage tanks mines septic tanks hazardous waste - deep well injection any pollutant in runoff that percolates Laws Clean Water Act – surface water 1972 – make water swimmable and fishable by regulating point sources 1977 and 1987 – storm water runoff Section 404 – requires permit for draining, dredging, filling wetlands Mitigation banking Safe Drinking Water Act (1974) – monitors levels of contaminants in groundwater
