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Groundwater pollution and protection
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Pollution of ground water (chemicals from agriculture, salt extrusion,
underground storage tanks, biological contamination).
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Law of contaminated land, in which owner is responsible on damage occur
from his land (Comprehensive Environmental Superfund Legislation, more
formally known as the compensation and liability Act 1981).
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Impose a levy on all disposers of toxic waste into site that could result in
long-term groundwater pollution.
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Because many sited are abandoned, superfund was used for clean-up and
risk assessment (ranking of hazards and priorities list formed).
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En Europe the probability of a European community directive on the civil
liability of wastes. Thus directive will impose a statutory responsibility on
the land water to clean up and site that is contaminated, or pay for any
consequences arising from the site in the future.
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Cambridge
water
company
vs.
Eastern
countries
leather
case
(tetrachloroethane or perchloroethane) acceptable by EU 1µg/L, found 70170 µg/1) case settled in 1993 in the house of lord. They found that is
unreasonable to hold Eastern Countries liable for activities undertaken so
long ago.
Sources of ground water pollution
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Change of groundwater quality may result from the direct or indirect
influence of anthropogenic activities.
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Direct (introduction of natural or artificial)
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Indirect (changes of quality as result of interference with hydrogeology,
physical and biochemical processes but without the addition of substances.
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Contaminants includes:
toxic chemicals, heavy metals, organic solvent,
mineral oils, pesticides and fertilizers, and microbiological contaminant such
as faecal bacteria and viruses.
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Contaminated ground water: groundwater that has been affected by human
activities to the extent that it has higher concentration of dissolved or
suspended constituents than the maximum admissible concentrations
formulated by national or international standards for drinking, industrial or
agricultural purposes.
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The risk of groundwater pollution depends on
1. Accessibility of the saturated zone.
2. physical and biochemical attenuation capacity of contaminant within the
geological strata overly the water table.
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The behavior of toxic chemicals in ground water is complicated by the
physical and chemical characteristics of contaminants involved (Box. 13.3
and 13.4).
Groundwater contamination cases:
1. Nasau County, NY.
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Infiltration of metal plating waste through disposal basins.
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Contamination occur in early 1940’s, with plume contain chromium and
cadmium.
1.
The upper glacial aquifer of late Pleistocene age
2. The maggoty aquifer of late Cretaceous age.
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Pollution plumes are formed (Box 13.2, 13.3)
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2. Nitrate contamination of the Jersey bedrock aquifer (Island)
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Pollution by nitrogen fertilizer from agriculture, with estimated leaching
losses of up to 100 kg N/ha.
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Ground water resources are affected by both exploitation and surface
pollution, as main water supply is from surface water storage.
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Geology (formed of Precambrian crystalline rock)
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Regional distribution of nitrate concentration (Fig 13.4 as nitrate decrease in
a coastal direction.
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The EU commission maximum admissible concentration for nitrate in
drinking water of 50 mg/L.
3. Jet Fuel Clean-up at Heathrow Airport
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Hydrocarbon contamination by Jet Fuel resulted from cracked Fuel pipe
(Kerosene) over a number of years.
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Geology (Heathrow is built on top low Terrance adjacent to river Thames
flood plain, 4.5 m of coarse clean gravel overlying low-permeability clay).
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Remediation include large-diameter wells lined with perforated concrete
rings about 1.5 M in diameter. The kerosene was removed by floating oilskimmer pumps. Surface-mounted centrifugal pump installed with their
intakes in the two wells, were also used to lower water table and encourage
the kerosene to move toward the recovery wells.
4. Organic solvent contamination at an industrial site.
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Organic solvent contamination at an industrial site.
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Soil permeability is high (soil gas concentration)
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Bore hold techniques
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Ground water protection Policies in industrised countries
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The science of contaminant hydrogeology is driven by:
1. Development in analytical procedure for identification of pollutants.
2. Need to formulate water quality standards and aquifer protection policies.
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In the US, the concern triggers the introduction in 1980 of the
comprehensive Environmental Response, Compensation and liability Act:
“Superfund” legislation.
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Environmental Protection Agency used Methodology designed to permit
systematic evaluation of the ground water pollution. The system has two
components.
1. The designation of mappable units, termed hydro geological setting.
2. The superposition of a relative rating system having the acronym
DRASTIC.
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Each hydro geological setting have physical characteristic that affect
groundwater pollution potential. Most important factors are:
Depth (D), net recharge ®, aquifer media (A), soil media (S) topography
slop (T), impact of vadose zone (I) and hydraulic conductivity of the a quifer
(C).
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In Europe, the European Community has enacted controlling legislation
(Council of European Communities 1980a, 1980b, and 1991, Section 84),
responsible to protect ground water quality.
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Policy towards mapping regional ground water vulnerability and also
defining groundwater sources protection zones (National Rivers Authority,
1992). Based on hydro geological principles (Box 13.5).
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In Netherlands, Zoning system includes a first zone based on a delay time of
50 days to protect against pathogens and viruses. A delay of 10 year is need,
however 10-25 years protection zones is extended to about 800 and 1200 M
from borehole.
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Ground water pollution and protection in developed countries.
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Scheme consists of large number of boreholes.
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Shallow dug wells, better-yield boreholes (10-100 L/S) are quite widely
developed.
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Sewage and pour-flush pit latrines are source of pollution
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Organic nitrogen source is common source.
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Inorganic fertilizer and pesticides.
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Small scale industry.
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Protection of ground water supply sources requires a broad-based pollution
control policy comprising:
1.
Minimum separation, depending on the hydro geological environment,
between ground water supply source and excreta disposal unit for
microbiological protection.
2.
Dilution Zones of modified land used to alleviate the impact of polluting
land-use activities.
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