Transcript Water Resources and Pollution

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• Groundwater is being withdrawn from aquifers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