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Water Resources and Pollution Summary • Available freshwater is in limited supply • Groundwater is being withdrawn from aquifers faster than it can be recharged • Dams provide freshwater reservoirs and hydroelectric power but disrupt ecosystems, displace people and valuable arable land • Human activities (like agricultural runoff, industrial discharge, mining practices) pollute aquatic ecosystems and groundwater • Sewage treatment plants help reduce water pollution Strategies to Protect Groundwater • Increase price of water to discourage waste • Reduce use of crops that need excessive watering • Reduce use of fertilizers, pesticides and industrial chemicals • Implement water conservation practices in homes • Gov’t susidies or tax breaks for water conservation Improving Irrigation Methods • 40% of the freshwater used in U.S. goes to irrigation of crops using flood irrigation • Drip irrigation or micro-irrigation is more efficient (95%) because water is delivered slowly directly to roots = no evaporation or runoff – ALSO INCREASES CROP YIELDS BY 20-90%!!!!!! • Center pivot – increases water use efficiency to 80% Industrial and Residential Water Conservation • Introduce grey water systems where water that is not contaminated by residential sewage or industrial chemicals is diverted and collected for use on lawns, washing cars, flushing toilets • Use low-flow showerheads and low-volume toilets • Recycle industrial-use water within the factory Water Testing Techniques Physical water Quality • Temperature – affects DO (dissolved oxygen) levels and reproductive cycles • River/Stream Flow Velocity • Turbidity – measures cloudiness of water due to suspended solids. Water clarity is important to photosynthesis in aquatic systems! Water Testing Techniques Chemical Water Quality • pH – most organisms require pH of 6-9 • DO – dissolved oxygen must be at least 5ppm or organisms become stressed = unhealthy ecosystem – Highest in cold, fast-moving water – If DO is low, may indicate cultural eutrophication (excess fertilizer), sewage or thermal pollution (artificially warm water from electrical power plants) • Nitrates/Nitrites & Phosphates lead to eutrophication usually from fertilizer runoff, sewage, septic tank leaks, animal waste from factory farming • Hardness – presence of metals in water which may increase due to acid rain (causing increased solubility & loss of ability to buffer the pH of aquatic systems) Water Testing Techniques Biological Water Quality • Fecal Coliform – indicates fecal contamination from sewage, septic tank leaks, animals waste from factory farming • Biological Indicators – monitoring of organisms to measure ecosystem health over time – Benthic macroinvertebrates: aquatic insects and their larvae, crustaceans. E.g., stonefly, mayfly, caddisfly. – Fish species: sensitive to DO concentrations, temp & pH Groundwater Pollution • Nondegradable wastes (arsenic, lead, fluoride) can remain permanently • Slowly degradable wastes (DDT and other pesticides, herbicides, fungicides) can persist for tens – thousands of years • Prevention & Remediation (cleanup) – Prevention more cost effective! – Remediation methods include injecting microorganisms into aquifers to degrade pollutants or water pumped to surface to be cleaned and returned to aquifer – ALL VERY EXPENSIVE! Preventing Groundwater Pollution • Protect natural water filtration systems (wetlands and river buffer zones) • Use alternative energy sources to reduce mercury emissions from coal-burning power plants • Sustainable Agriculture not factory farming – Reduce soil erosion by keeping land covered with vegetation (called no-till agriculture) – Reduce fertilizer use to bare minimum or farm organically – Use integrated pest management (IPM) not pesticides – Limit or eliminate large animal feedlots/factory farms Sewage Treatment • Primary – physical process using screens and grit tank to remove large debris – Solids settle out as sludge • Secondary – biological process where aerobic bacteria breakdown wastes in aeration tanks – Additional solids settle out as sludge – Water then treated with chlorine (can react becoming chlorinated hydrocarbons linked to human endocrine and nervous system damage – Safer alternatives to chlorination are ozone or ultraviolet light • Advanced or tertiary treatment – used to remove excess nitrates from fertilizer-contaminated water Diagram showing Primary, Secondary & Tertiary Treatment Secondary Treatment – Aeration Tank with aerobic bacteria hard at work “activated sludge” Additional Sewage Treatment Options – use natural ecosystem services as a model! • Sludge from sewage treatment facilities can be incinerated or treated for harmful bacteria, toxic metals and then can be applied as fertilizer • Require industries to remove toxic and hazardous waste before reaching municiapl sewage treatment plant (E’town requires this) • Use natural and artificial wetland systems to treat sewage: water pumped into oxidation ponds where bacteria break down organic waste for 30 days, then pumped into marsh where plants and bacteria filter and clean water Water Quality Legislation