Environmental Geology Spring
2010 – Text Notes
Water Contamination
Biological, chemical and physical degradation of water quality that is related
to the intended use.
Point Source Contamination – identifiable confined location represented
by a single point on a map.
• Industrial effluents
• Municipal sewage effluent
• Leaking underground storage tanks
• Deep well injection of waste
• Leaking landfills
• Animal feed yards
Non-point Source Contamination – not at discrete location, covers a broad
area
• Urban runoff, parking lots, golf courses, lawns, industrial
complexes
• Agricultural runoff, both row crop and pasture land
• Atmospheric fallout
Examples:
Pesticide and nitrate contamination resulting from agricultural production in
Northeastern Nebraska. Looked at slide of spring flush of pesticides
including Atrazine and its daughter products.
Also looked at impact of nitrogen based fertilizers on shallow ground water.
Parts per million – ppm, approximately
equivalent to 1 mg/L
Parts per billion – ppb, approximately equivalent to 1 microgram/L
Analytical instruments are now capable of detecting many contaminants in the
sub-ppb range. The detection limit for the atrazine
from the example sites was 0.02 ppb. The safe drinking water standard for
atrazine has been set at 3.0 ppb by the U.S. EPA.
Consumption of water above this level on a regular basis will likely result in
adverse health problems in a certain percentage of the population.
Looked at example of Atrazine in the Platte River and
its impact on the municipal water supply for the cities of Lincoln and Omaha,
Nebraska.
Nutrient Loading of Surface Water and Groundwater in Arkansas
Nutrients of concern are nitrate-nitrogen and phosphorus
Primary sources:
Lawns, golf courses, agricultural fertilizers, applied animal manures, animal
feed yards, septic effluent
Problem:
Eutrophication: Rapid increase in plant life (algal
blooms in water bodies); plants die, sink and decay; decay process uses up
oxygen in the water and the fish and other aquatic animals die or move out of
the area. Stressed algae can also give off toxins that can impart taste
and odor to the water and in some cases can be toxic to humans and other
animals. This is what causes the water in Fayetteville to taste and smell
during the fall of the year (the phenomenon is more pronounced in some years
than in others).
Drinking water standards:
• Established to protect public health
• Relate to water provided for public consumption
• Establish a Maximum Contaminant Level (MCL) –
This is an enforceable level that public water supply systems must meet for
their delivered water.
• Establishes a Maximum Contaminant Level Goal (MCLG)
– this is a goal that is set to begin action if contaminant approach or
exceed this level.
For a full listing of primary and secondary drinking water standards go to
www.epa.gov and follow the links through the office of water to drinking water
standards.
Pathogens: (primarily bacteria and viruses)
• Difficult to monitor for each individual pathogen
• Use an indicator organism: presence of this organism
indicates the system has been impacted by outside sources and is therefore
vulnerable to impact by other more serious pathogens. We use fecal coliform bacteria as a primary indicator organism.
Milwaukee, WI – 1993 – Outbreak of severe gastrointestinal problems
related to runoff of dairy manures into lake Michigan. The manures
contained cryptosporidium, a microorganism that was not as easily killed as
other pathogens. Treatment process did not kill the cryptosporidium resulting
in about 400,000 people developing severe gastrointestinal problems.
Several people died as a result of this incident (mostly very young, very old,
or those with compromised immune systems).
Guinea Worm Disease: Impacts large segments of population in Africa,
India, Bangladesh, etc.; results only from drinking unfiltered water.
People collect water from shallow wells; open pits, ponds, and streams with
little to no treatment. The Cyclops stage of this organism lives in the
water and is consumed by those drinking the untreated water. About 1-year
after ingestion a worm forms and emerges from the body, usually through the
lower extremities (the worms can be up to 3 feet long). This is extremely
painful and eaves a nasty wound subject to secondary infection. Bathing
the wound in water often makes it feel better but when afflicted people do this
the worm releases more Cyclops into the water supply and the cycle starts
over. This has been a major thrust of the World Health Organization
(supply clean drinking water sources to these areas in hopes of eliminating
this problem). It is easily treated with minimal filtration of the water.
Looked at examples of bacterial loading of springs in northwest Arkansas that
suggest our system can potentially be impacted by pathogenic organisms.
Biochemical Oxygen Demand (BOD): Amount of oxygen used for bacterial
decomposition
Sources of organic matter to streams include: agricultural runoff and municipal
sewage effluent
Dissolved Oxygen concentration of less than 5 mg/L is not good. Aquatic
fauna need 5 mg/L or greater to remain viable.
Organic loading causes BOD to increase; same as eutrophication
process.
As BOD increases DO decreases because it is being consumed by the organisms
that are facilitating the decay process.
Goal of clean water act is to assure that our loading does not adversely impact
the entire aquatic system. While the solution to pollution is dilution,
if the entire aquatic system is impacted beyond limits then the entire
ecosystem collapses. TMDL’s (total maximum
daily loads are being established for selected water bodies to address this
problem). The TMDL establishes the total load the water body can
assimilate and still remain a viable ecosystem. All point and nonpoint sources of contamination must be considered when
calculating the TMDL value for a water body.
Waste Water Treatment: Oh What Fun We Had at the Sewer Plant!!!
Basics:
• Primary Treatment: screening, sedimentation –
to form sludge; sludge to digester; wastewater to secondary treatment
• Secondary treatment: activated sludge: aeration tank
– aerobic bacterial digestion; sedimentation; anaerobic digestion
• After secondary treatment about 90% of contaminants
have been removed; except nitrate, phosphorus, metals, some solvents and
pesticides
• Disinfect and discharge to receiving water
• Tertiary treatment removes almost all contaminants
(considered to be reclaimed water)
Other Contaminants:
Thermal Contamination (Includes both hot and cold)
Examples: Warm water discharge by Arkansas One into Lake Dardenelle
(great winter fishing spot); cold water discharge below Beaver Lake Dam and
other White River reservoirs that have created a habitat suitable for a world
class trout fishery (eliminated habitat as a small mouth bass fishery which was
the natural condition of the stream prior to the reservoirs).
Metals and other Toxins:
Showed example list of industries producing a myriad of waste metals
Metals and other toxins:
Examples: mercury, lead, cadmium, dioxin
Often accumulate in bodies of organisms that consume the metals – Metals
concentrate in fatty tissues and organs such as the liver. As higher
order predators consume lower order species the metals become further
concentrated because they are not easily expelled from the body (they
accumulate over time). This process is called bioaccumulation.
Examples in Arkansas include mercury in bottom sediments of some lakes from
both naturally occurring and industrial sources, and dioxin contamination in
Bayou Meto, the Arkansas River near Pine Bluff, and
the Red River near Ashdown. Fish consumption advisories have been issued
for many of these areas.
Acid mine drainage: Surface water or groundwater picks up sulfide
minerals (pyrite, galena): forms sulfuric acid; this puts metals in solution
until the water becomes oxygenated or the pH is buffered. Then the metals
precipitate in the environment.
One of the worst areas in the U.S. is the Tri-State mining district
Arkansas-Oklahoma-Missouri. Lead/Zinc mines operated until the
1960’s; after closure the mines flooded and overflowed to Tar
Creek. In addition, runoff from mine tailings piles also provided acid
drainage to Tar Creek. Designated as superfund site, still not cleaned
up.
Examples of Organic Contaminants:
Light Non-Aqueous Phase Liquids (LNAPL): Example: gasoline; floats on water
Dense Non-Aqueous Phase Liquids (DNAPL): Example Perchlorethylene;
used in dry cleaning industry; sinks to bottom of aquifer; flows along top of
low permeability units and may flow against groundwater flow if low
permeability units are dipping upgradient.
Salt Water Intrusion due to heavy groundwater withdrawal along our populated
coastal areas.