APES Unit 2

Water Pollution/ Freshwater (Chapter 1/9/14)

water pollution

Any changes in the chemical, physical, or biological properties of water due to human activities

• point/nonpoint

• visible/nonvisible

point pollution

Discrete locations (can point to it)

examples:

• agriculture → animal feeding plants (manure via pipes),

• industry → sewage from treatment plants, factories, and disposal sites

• residential → wastewater treatment plant (pipe into lake)

nonpoint pollution

Widely distributed areas (cannot point to one source)

Examples:

• agriculture → farm fields, fertilizer runoff, overgrazed land

• industry → construction sites, oil/grease/debris runoff into storm drains

• residential → roads, residential neighborhoods, pet waste runoff

What problems does wastewater from humans and livestock pose to the environment?

changes to the dissolved oxygen and oxygen demand in the water due to the growth of decomposing aerobic microbes which feed of organic compounds in human/animal waste;

• oxygen demand

• nutrient release

• disease-causing organisms

Eutrophication Process

1. wastewater (contains human/animals waste) enter lake → increase phosphorus and nitrogen in water

2. decomposing aerobic microbes feed on organic compounds in wastewater

3. excessive/quick microbe growth and excessive nutrients in water leads to algal blooms which coat the surface of the water and prevent sun from reaching past water surface

4. subsurface plants die and decompose

5. decomposing microbes consume dead fish and nutrients decreasing DO and increasing BOD in water → no oxygen for fish/invertebrates

6. microbes decompose all dead organisms in the lake water for oxygen and fuels more decomposition!

dead zones

result of a high BOD; an area with extremely low oxygen concentration and very little life

Oxygen Sag Curve

• clean zone

  • High DO, low BOD

• decomposition zone

  • DO lowers, BOD spikes

• septic zone

  • Low DO, high BOD

• recovery zone

  • DO increases, BOD decreases

• clean zone

  • High DO, low BOD

disease-causing organisms (pathogens)

The same water used for drinking, bathing, and sewage can carry a variety of pathogens

(Biological pollution causes more health problems than any other type of water pollution)

examples:

• cholera

• dysentery

• typhoid fever

• stomach flu

• diarrhea

• hepatitis

Tests for disease-causing organisms

• presence of indicator species may suggest the presence of a pathogen

• ex. Fecal coliform bacteria are a group of usually harmless microorganisms found in human intestines → detection of them in a body of water indicates potential sewage contamination

types of water pollutants (8)

1. sediment

2. solid waste

3. thermal pollution

4. noise pollution

5. synthetic compounds

6. oil

7. heavy metals

8. biological pollutants

biological pollution

• Includes pathogenic microorganisms (bacteria, protists) which originate primarily from human/animal waste

• Pathogens can contaminate surface water AND groundwater

  • Overflowing of CAFOs (concentrated animal feeding operations) manure lagoons (ponds lined with rubber to store and decompose manure) which may contain pathogens/hormones/antibiotics, can bring pollutants to waterways

Heavy Metal Pollution

All heavy metals are neurotoxins that affect nervous system function/development

includes;

• lead → neurotoxin harmful to children’s developing brains

• arsenic → carcinogen, linked to bladder/lung/skin cancers

• mercury → damages the CNS and PNS (nervous systems), causing neurological issues like tremors or memory loss

How does lead enter the ecosystem

found in pipes and other materials in older construction → pollutes drinking water/lead water pipes when the rubber that protects them erodes

How does arsenic enter the ecosystem?

the heavy metal occurs naturally and through human activity such as mining and industry

How does mercury enter the ecosystem?

the heavy metal occurs naturally and through human activity, primarily burning coal

Clean zone

High DO

low BOD

Decomposition Zone

lowering DO

spiking BOD

septic zone

low DO

high BOD

recovery zone

increasing DO

decreasing BOD

what are CAFOs?

Concentrated Animal Feeding Operations produce large, lined manure lagoons or ponds filled with animal manure, which may contain pathogens as well as hormones and antibiotics used to treat animals during their mass growth in confined places.

• May use manure byproducts (treated with decomposing bacteria) as fertilizer (act as runoff into waterways)

• Manure lagoons may overflow/flood during storms and run off into waterways

How do pathogens enter waterways?

Examples;

• dumped sewage

• treatment plants overflow

• farming runoff (animal manure)

• failed septic tanks/industrial facilities

Oil Pollution

petroleum products are highly toxic to many marine organisms

ex. birds, mammals, fish, algae, microorganisms (most/all parts of food chain)

sources of oil pollution

• drilling for undersea oil on offshore platforms (Deepwater Horizon)

• oil spills from tankers

• some occurs naturally (oil seeps)

remediation of oil pollution (how to fix it)

containment → booms keep the floating oil from spreading, then boats equipped with giant oil vacuums suck up as much oil as they can

Dispersants → chemicals break up the oil on the surface, helping it dissolve before it reaches shore

bacteria → scientists are trying to optimize oil-degrading bacteria to break down spilled oil (bioremediation → less impact on environment)

synthetic compound pollution

most commonly from industrial point sources or nonpoint sources when applied over large areas like farmland

ex. pesticides, pharmaceuticals

• can be toxic, persistent, cause genetic defects, and interfere with growth and sexual development

physical water pollutants

• sediment

• solid waste

• thermal pollution

• noise pollution

chemical water pollutants

• synthetic compounds

• oil

• heavy metals

• biological pollutants

Sediment pollution

refers to soil particles in bodies of water

• blocks sunlight penetration, reducing productivity of algae/plants and visibility of predators in ecosystem

• clogs animals’ gills, preventing aquatic organisms from obtaining oxygen

how does sediment pollution occur?

70% from human activities;

• clear-cutting → mining and clearing land (deforestation) for development increased rates of erosion creating sediment pollution by runoff

Solid waste pollution

Garbage thrown away by people (plastic pollution)

ex.; Litter that reaches aquatic ecosystems → unsightly and creates intestinal blockage and choking hazards for wildlife + toxic substances in the food chain

• US stopped dumping garbage into the ocean in the early 1980s

• Dumping problem remains in many developing countries

Thermal Pollution

Occurs when human activities cause a substantial change in the temperature of water

• Can cause thermal shock → when water temperature increases while the solubility of oxygen in the water decreases

• Thermal shock is fatal to organisms

what causes thermal pollution

ex.;

• Use of river water as coolant for factories or power plants

• Deforestation near water removes shade, which increases temperature

noise pollution

sounds emitted by ships and submarines can interfere with animal communication

ex.; loud sonar affects whales who rely on low-frequency, long-distance communication

possible solution to noise pollution

engineering ships with quieter propellers

how are DO and thermal pollution linked?

increase in the temp. of water (thermal pollution) → decreases solubility of oxygen in the water → decreases dissolved oxygen in the water

what types of pollution would result from increased erosion rates due to deforestation?

Deforestation (increased erosion of mountains) causes;

• Mainly sediment pollution (silt, clay, sand) in waterways from runoff

• Potentially biological pollution or fertilizer in water from runoff which would have been hidden by trees were it not for deforestation

Steps for drinking water treatment

1. coagulation

2. sedimentation

3. filtration

4. disinfection

coagulation (water treatment)

clump up particulate matter (small particles—pollen, silt, cell debris)

sedimentation (water treatment)

allow clumps to settle (sink to bottom)

filtration (water treatment)

filter out larger particles (sand, gravel, charcoal)

disinfection (water treatment)

kill the microbes (pathogenic) in remaining water using chlorine gas or UV

methods to treat wastewater

• septic system

• wetlands

septic system

a relatively small and simple sewage treatment system, made up of a spetic tank and a leach field, often used for homes in more rural areas

parts of a septic tank

• scum → waste that floats (scrap, oil)

• septage → fairly clear wastewater which drains to leach field

• sludge → solid waste (poopoo)

leach field

underground perforated pipes allow the septage from septic tank to drain into soil (directly connected to septage in septic tank)

how does a septic tank work?

• All household wastewater will flow from a main pipe into the septic tank

• Septic tanks separate wastewater into scum, septage, and sludge, therefore naturally filtering the water

• The tank is on a natural decline (angle) so that septage and wastewater will naturally flow into the leach field and disperse into the soil

• The cleaned water will eventually return to groundwater from the soil

preliminary treatment (wastewater treatment)

remove all large objects from incoming wastewater

• uses a bar screen

primary treatment (wastewater treatment)

similar to a septic tank;

• physical separation of the parts of wastewater based on how they settle by density

uses:

• primary clarifier

Secondary treatment (wastewater treatment)

Similar to a leach field;

• biological separation of remaining wastewater

uses:

• bacteria to break down organic materials

• aeration tank (oxygen for bacteria to live)

• secondary clarifier (to allow for more settling of particles in water)

sludge treatment

Goal:

• Reduce the volume of sludge (dehydrate, allow for anaerobic decomposition)

steps:

1. digestion

2. dewatering

3. land application

result:

• fertilizer

• landfill

• burned

Final treatment (wastwater treatment)

Goal:

• Kill harmful microbes and pathogens so that wastewater can be used again and/or put back into the environment

uses:

• UV light

• chlorine gas

• ozone

Wetlands (as wastewater treatment)

Primary- and secondary-treated wastewater will be pumped into a wetland where microbes will decompose the remaining pollutants (which are…)

• Wetland-treated water can naturally percolate into groundwater, replenishing aquifers

• An alternative solution to treating wastewater, rather than treatment plants

Clean Water Act (CWA)

• 1977

• set standards for contaminant levels in surface waters

• funded construction of wastewater treatment plants

• Does not address groundwater

Goal:

• keep freshwater ecosystems clean (lakes, rivers, wetlands)

Methods:

• mandates that industrial dischargers of toxic pollutants use best available technology (BAT) to control pollution, with strict enforcement

• New treatment standard for conventional pollutants called best conventional technology (BCT) to develop area-wide treatment management planning

Safe Drinking Water Act (SDWA)

• 1974

• Established MCLs (Maximum Contaminate Levels) ~90 chemicals

• Sources of drinking water, so MCLs for surface and groundwater

Goal:

• Keep water safe (not clean) for human consumption (aquifers, lakes, reservoir)

compare the relative ease of remediating contaminated groundwater vs contaminated surface water

surface water:

• better accessibility, higher flow rates, simpler monitoring → easier and faster

• Months/years to remediate

groundwater:

• low accessibility, slower flow rates, complex monitoring → costly, harder, slower

• Years/decades to remediate

Maximum contaminant Level (MCL)

The standard for safe drinking water established by the EPA under the Safe drinking Water Act

Where is Freshwater on Earth

2.5% of all water

• 79% ice caps/glaciers

• 20% groundwater

• 1% surface (lakes, soil)

runoff

water that falls from the sky or melts from snow or a glacier that flows over a land surface

where does runoff end up?

converges in low-lying areas → forms streams → forms rivers → reach ocean/lakes

how does groundwater become surface water

groundwater (from an aquifer) becomes surface water through springs, keeping rivers flowing and wetlands moist even in dry conditions

floodplain

the areas near a river’s course that are flooded periodically (normally in the spring)

levees

an enlarged bank built up on each side of a river to protect against flooding

traits of a floodplain

• frequently flood

• fertile soil

• damage nearby properties

• good for agriculture

watersheds

the area of land drained by a river system and all of its tributaries

characters of a watershed

area (how much water collects/fast it drains)

length (longer for water to travel down)

slope (how fast runoff drains/infiltration rates)

soil (permeability of water)

vegetation types (runoff due to leaf/plant cover)

divides with adjoining watershed (defines where precip. will flow)

freshwater biomes

Lakes and ponds (interchangeably)

wetlands

• marshes, swamps, bogs, vernal pools

Littoral zone

shallow areas along the edges where aquatic plants can grow, surface of water

limnetic zone

upper layer of water that is shallow enough to recieve sunlight and allow for photosynthesis by phytoplankton

profundal zone

no sunlight reaches here, lacks photosynthesis

• b/w limnetic and benthic

benthic zone

extends along the bottom of the lake/pond, no sunlight

wetlands

systems where the soil is saturated with water, often containing standing shallow water

• heavily impacted by human activities (draining and filling for agriculture, withdrawing water for irrigation, construction of dams → cannot recharge aquifers, stop/slow water flow)

marshes

consist of cattails and bulrushes that grow above the waters’ surface, can lead to ponds

swamps

contain standing water and in forested areas, covered in all sides by forests

bogs

ponds covered in thick floating mats of vegetation, low standing water

vernal pools

seasonal; form in snowmelt (early spring) and dry up in late summer

water specific examples of ecosystem services

slowing runoff, reducing flooding, recharging aquifers, filtering pollutants

surface water alteration

The excessive withdrawal and diversion of surface water has led to many world rivers running dry before reaching the sea → alters ecology of river and delta

Aral Sea

over years went basically dry due to surface water alteration (dams/agriculture/draining for water)

Dams

any obstruction placed in a river or stream to block its floww

what do dams create?

reservoirs

reservoirs

artificial lakes, created by dams, that store water for human use (dug by humans)

pros of dams

reliable drinking water (if protected watershed)

reliable farming irrigation

less carbon emissions compared to fossil fuels

renewable energy

flood control by storing seasonal surges

potential new recreational opportunities on reservoir side

cons of dams

• 40-80 million people displaced

• buildup of sediment behind dams

• risk of catastrophic failure

• habitat alteration (both up and downstream)

• lost recreational opportunities of the riverside

• disruption of flooding that builds topsoil

• fisheries decline from thermal pollution and blockage of fish migration

Three Gorges Dam on China’s Yangtze River

• Cost $39 billion to build

• reservoir flooded 22 cities, farmland, and habitat

• Displaced 1.24 million people (Sichuan province, China)

• provides energy for 5.4 million households per month

why are some dams being removed?

• restore riparian ecosystems

• re-establish fisheries

• revive river recreation, such as fly-fishing and rafting

• return of shellfish and fish habitats near the mouths of rivers disrupted by the dam

groundwater

water beneath the surface that resides within pores in soil or rock

• water that does not evaporate, flow into waterways, or get taken up by organisms will infiltrate into groundwater

infiltrate

seep into pores of rock/soil/ground

water to groundwater

water table

the upper border of the layer completely filled with water of an aquifer

aquifers

contains groundwater in porous and spongelike formations of rock or sand, can contain water for thousands of years at a time

recharge zone

any area where water can infiltrate through the surface and reach an aquifer

confined aquifer

trapped by impermeable clay

• little/no recharge area

• slow/no recharge rate

• older

• artesian well

• less prone to pollution

• 
  

unconfined aquifer

not trapped by clay, open to recharge area

• large recharge area

• faster recharge rate

• younger

• normal well

• more prone to pollution via runoff

Ogallala Aquifer

the largest known aquifer located under the Great Plains of the US, very old confined aquifer

cone of depression

when a deep well extracts water from an aquifer, a cone forms in water table and shallow wells can go dry

sinkholes

as aquifers lose water, they become less able to support overlying strata, causing land surface to subside (collapse)

saltwater intrusion

wells drained in coastal aquifer decreases the water table, reduces water pressure, and allows salt water to move into aquifer and contaminate well water with salt

Total per capita water use per day

the total water use per person for agriculture, industry, and households varies tremendously per country

freshwater uses from largest to smallest

agriculture (70%)

industry (20%)

residential (10%)

Types of irrigation from lowest efficiency to highest efficiency

furrow, flood, spray, drip

furrow

a trench that is flooded with water

least efficient (highest evaporation)