Embed Size (px)
Citation preview
2-‐4-‐3: Water Pollution
A"er this lecture, you should be able to: Iden6fy the various types of pollu6on (Unit 2-‐3) and describe their poten6al
sources and effects with respect to water.
Explain how dissolved oxygen measurements can be used to assess overall water quality in an ecosystem.
Explain how nutrients, such as nitrogen and phosphorus, which are essen6al to living organisms, can nega6vely impact aqua6c ecosystems.
Explain how sedimenta6on effects both aqua6c and terrestrial ecosystems.
Evaluate the different variables that affect surface water and ground water.
Water Pollution Degrada6on of water quality
Based on: Intended use of the water How far the water departs
from the norm It’s effects on public health It’s ecological impacts
Primary water pollu6on problem is the lack of clean, disease free drinking water Outbreaks of waterborne
disease affects several billion people worldwide
All segments of society may contribute to water pollu6on
Increasing popula6on may cause: Introduc6on of more pollutants Increased demands on finite
water resources
Water pollutants include Heavy metals Sediment Certain radioac6ve isotopes Heat Fecal coliform bacteria Phosphorus Nitrogen Sodium, and other useful (even
necessary) elements Pathogenic bacteria and viruses
Water Pollution Standards
EPA sets thresholds and limits on some but not all pollutants 700 iden6fied drinking
water contaminants
Waterborne Diseases Primary water pollu6on
problem globally Effects vary from an upset
stomach to death Example cholera
Early 1990s -‐ widespread suffering and death in South America
North America is not immune to outbreaks of waterborne disease Fecal coliform bacteria used
as indicator of disease Escherichia coli (E. coli) is
deadly to humans -‐ outbreaks result from ea6ng contaminated meat
US EPA thresholds levels: 200 cells/100 ml water for
swimming 0 cells/100ml water for
drinking water
Dissolved Oxygen Bacteria in stream decompose
organic maYer Decomposi6on requires oxygen More bacteria decomposi6on =
less oxygen in the water available to fish and other organisms
Oxygen can be decreased to point where aqua6c organisms die off
A stream with an low dissolved oxygen (DO) is considered polluted
BOD (Biological Oxygen Demand) Amount of oxygen required for
biochemical decomposi6on Measure of the amount of oxygen
consumed by microorganisms as they break down organic maYer
Rou6nely measured as part of water quality at waste water treatment plants
Source of organic maYer include: Natural sources Agricultural runoff Urban sewage
US EPA defines the threshold for water pollu6on alert as DO levels of less than 5 mg/L
Biochemical Oxygen Demand (BOD) Three zones are iden6fied a"er a spill
Pollu6on zone High BOD
Ac6ve decomposi6on zone Dissolved oxygen content reaches a minimum
Recovery zone Dissolved oxygen increases and the BOD is reduced
Eutrophication Two important nutrients that cause water
pollu6on are phosphorous and nitrogen Highest levels found in agricultural
areas
Process by which a body of water develops a high concentra6on of nutrients Nutrients cause a large growth in
aqua6c plants and photosynthe6c bacteria and algae Use up dissolved oxygen
High popula6ons of bacteria and algae naturally die off Input of organic maYer into water-‐ more
nutrients
Oxygen content lowered to point where aqua6c organisms die
Eutrophication
Oligotrophic lake Lake with rela6vely low
concentra6on of nutrients required by life
Clear water Low abundance of aqua6c
life
Eutrophic lake Lake with high
concentra6on of nutrients O"en with mats of algae
and murky water Abundance of life
Cultural eutrophica6on Human processes that add
nutrients to water
Solu6on -‐ ensure that high concentra6ons of nutrients do not enter water use phosphate-‐free
detergents control nitrogen runoff dispose or reuse treated
wastewater advanced water treatment
methods
Sediment Sediment consis6ng of rock and
mineral fragments Ranging in size from gravel
(>2mm) to finer sand, silt and clay to even finer par6cles
Cause sediment pollu6on By volume and mass,
greatest water pollutant
Two fold problem Erosion Reduces the quality of water
resource it enters
Land use effects erosion and sedimenta6on Forested areas more stable Agricultural prac6ces can
lead to large soil loss Large quan66es of sediment
lost during construc6on phase of urbaniza6on
Surface Water Pollution Too much of an undesirable or harmful substance
flows into a body of water
Substance exceeds the natural ability of that water body to:
Remove the undesirable material
Dilute it to a harmless concentra6on Convert it to a harmless form
Point source Pollutant Dis6nct and confined Pipes from municipal or industrial sites that
empty into a stream or river
Nonpoint source Diffused and intermiYent Ex: runoff Influenced by land use, climate, hydrology,
topography, na6ve vegeta6on, and geology Difficult to monitor and control
Two tradi6onal approaches to dealing with surface water pollu6on are To reduce the sources To treat the water to remove pollutants or
convert them to forms that can be disposed of safely
Two new approaches are Nanotechnology
Uses extremely small par6cles to “capture” heavy metals in water
Urban run-‐off naturaliza6on
Groundwater Pollution ~Half of all people in US depend
on groundwater for drinking Long believed to be pure and
safe to drink Can be contaminated from a
number of sources May become worse as human
popula6on pressures increase
The hazard presented by a par6cular groundwater pollutant depends on: Concentra6on or toxicity of the
pollutant Degree or exposure of people or
other organisms to the pollutant
Pollu6on leaking from buried gasoline tanks from service sta6ons Wide spread problem Thousands of old tanks removed and
surrounding groundwater and soil treated Disposal of soil,
Vapor extrac6on of water
Use of microorganisms (bioremedia6on)
Principles of Groundwater Pollution Important points about groundwater pollutants:
Some pollutants, such as gasoline, are lighter than water and float on the groundwater
Some pollutants have mul6ple phases: liquid, vapor, and dissolved
Some pollutants are heavier than water and sink or move downward through groundwater
Method used to treat must take into account the physical and chemical proper6es of the pollutant and how these interact with water
Emphasis should be on preven6ng pollutants from entering groundwater in the first place
End-‐of-‐Lecture Objectives
Iden6fy the various types of pollu6on (Unit 2-‐3) and describe their poten6al sources and effects with respect to water.
Explain how dissolved oxygen measurements can be used to assess overall water quality in an ecosystem.
Explain how nutrients, such as nitrogen and phosphorus, which are essen6al to living organisms, can nega6vely impact aqua6c ecosystems.
Explain how sedimenta6on effects both aqua6c and terrestrial ecosystems.
Evaluate the different variables that affect surface water and ground water.
