Groundwater Pollution

Groundwater Pollution

• Groundwater provides about one-fourth of the freshwater used in the United States.
• Groundwater is typically of excellent quality due to natural soil filtration.
• Pollutant travel distance depends on soil and pollutant type.
• Soluble pollutants bypass soil filtering.

Sources of Contamination

• Groundwater is generally free of turbidity due to natural filtration, but it usually contains dissolved minerals.
• Groundwater is usually harder than surface water.
• Natural contaminants in groundwater usually pose no threat to public health.
• Main sources of groundwater pollution include waste disposal, accidental spills of hazardous substances, petroleum leaks from old underground storage tanks, and hydraulic fracturing.
• Industrial chemical waste disposal via land is the least expensive method, though it is prone to leaks.
• Contaminated liquids from unlined sources percolate through soil into aquifers.
• Liquid from solid waste landfills is called leachate.
• Industrial wastes are sometimes injected into the ground through deep wells.
• Groundwater is often saline (high salt concentrations) beyond 300 m (1000 ft) of depth.
• Improper deep well injection may lead to accidental water supply contamination.

Subsurface Sewage Disposal Systems

• The most common subsurface sewage disposal systems are septic tanks and leaching fields.
• Septic tanks trap solids and allow liquid effluent to flow into buried perforated pipes.
• The pipes create a leaching or absorption field, allowing sewage effluent to seep into the soil to degrade naturally.
• Septic systems can be sources of fecal bacteria and viral contamination in private wells.
• Septic systems inadequate design, poor construction, or lack of maintenance prevent proper function of septic systems.

Municipal Landfills

• Burial on the ground is a common method for disposing of municipal refuse.
• High levels of BOD, chloride, nitrate, organics, heavy metals, and other contaminants can easily reach groundwater.
• Entering underlying aquifers occurs from municipal landfills
• Modern solid waste is put in landfills rather than dumps.
• Proper placement and bottom liners can protect groundwater quality.

Mining, Petroleum, and Agriculture

• Surface water near mines becomes polluted with dissolved metals, solids, acidity, and radioactive materials.
• Petroleum products are also groundwater pollutants.
• Fertilizers and pesticides pollute water.
• Nitrates are a health concern in drinking water.
• This is due to the health problem that it presents known as blue baby.

Urban Areas and Saltwater Intrusion

• Road salt increases chloride and TDS concentrations in groundwater.
• Saltwater intrusion is the flow of seawater into wells.
• Coastal areas have a boundary line between fresh groundwater and saline water.
• Salty wells from seawater intrusion are abandoned as drinking water sources.
• A "groundwater barrier," can prevent saltwater intrusion.

Ocean Pollution

• Ocean water is naturally saline, so it is not considered "polluted" due to its mineral content, mostly sodium chloride.
• Ocean water's inorganic minerals, especially sodium chloride, prevents it from being seen as polluted.
• Ocean water is generally unsuitable for human use unless desalinated but serves as a convenient receptacle for many wastes.
• Sewage effluent, discharged into waterways or underground, eventually reaches the ocean.
• Ocean dumping of sludge results in high levels of bacteria and toxic metals.
• Oil spills from tankers and offshore wells are an issue.
• Physical barriers and mechanical collection can control oil spills.
• Prevention is key to addressing oil spills.
• Floating plastic trash can kill marine life by ingestion.
• Chemicals in plastic pose adverse health effects in fish and humans.
• Estuaries are natural transition zones between fresh and saline waters.
• Estuaries are biologically productive, being critical to both terrestrial and marine organisms.
• Pollution and poor land-use management threaten estuaries.
• Treated sewage effluent from coastal cities is discharged into the ocean via outfalls.

Water Quality Standards

• Water quality standards are the amount of impurities allowed in water used for particular purpose.
• These are legally enforceable by government agencies.
• The standards include rules for sampling, testing, and reporting to the public.
• Three types of water quality standards exist: stream, effluent, and drinking water standards.
• The ultimate goal is the protection of both public health and environmental quality.
• The EPA and state agencies enforce water quality standards.
• These standards encompass stream, surface water, drinking water, pollutants, and wastewater.

Stream Standards

• The Water Quality Act (CWA, 1965) was amended, and strengthened it by the Federal Water Pollution Control Act Amendments (FWPCA, 1972).
• The FWPCA created a national permit system for point source dischargers impacting stream standards and regulating pollutants.
• States must classify surface waters based on "maximum beneficial use" with water quality standards.
• Specific pollutant criteria must limit the number of pollutants allowed for surface water classifications.
• Classifications and criteria are known as stream standards.
• These standards have been created for lakes and coastal waters as well.
• Four classes of surface waters are generally identified.
• Class A water is suitable for swimming, and Class B water is suitable for maintenance of fish, secondary recreations.
• Class C water is for public supply after treatment and purification, and Class D water is for agricultural and industrial use.
• Water quality criteria include limits on dissolved oxygen, coliforms, solids, turbidity, pH, and toxic wastes.
• A minimum DO of 5 mg/L maintains fish life, but only 3 mg/L is needed for Class D waters to maintain aerobic conditions.

Watershed and Indicators

• Nonpoint runoff from urban and agricultural lands is now the primary source of water pollution.
• A watershed management approach is key to controlling pollution from urban and agricultural lands.
• Water quality control activities are integrated within hydrologic drainage basins.
• The Clean Water Action Plan: Restoring and Protecting America's Waters was initiated in 1998.
• Reduction of polluted runoff is a goal.
• The CWA also protects drinking water sources and natural resources.
• A watershed focus implements cost-effective pollution control strategies.
• The EPA has produced the index of watershed indicators (IWI) on a watershed scale.
• The IWI organizes indicators of a watershed in order to assess the condition of watersheds.
• The factors in the IWI include conventional water quality, sediment contamination, fish consumption advisories, wetlands loss rates, and soil loss.

Total Maximum Daily Load Program

• A total maximum daily load (TMDL) specifies the maximum amount of a specific pollutant that a water body can receive while still meeting water quality standards.
• TMDLs allocate pollutant loads among both point and nonpoint sources.
• States must develop a list of impaired water bodies under the CWA.
• These lists of impaired water bodies are updated every 2 years.