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Summary• Available freshwater is in limited supply• Groundwater is being withdrawn from aquifers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 TechniquesChemical 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