Lecture 38

Sources of Ground-Water

Contamination

Fetter 11

(I) Sources Designed to discharge substances

Septic Tanks / Cesspools

        Transform nitrogen to less hazardous forms, do not remove N.

Injection Wells

        Brine, Hazardous Waste

Land application

       Sludge- heavy metals, dioxins

(II) Source Designed to Store, Treat, Dispose

	Landfill ® Regulated ~ 12,000 in U.S ~ 2,500 open dumps Leachate generated
	Surface Impoundments Pits, Lagoons ® evaporate
	Mine Wastes Often inorganic
	Animal Burials Radioactive carcasses and other radioactive tracers
	Storage Tanks Above / Below ground ® 2.5 million in U.S
	Radioactive Waste Disposal Yucca Mountain

(III) Retain substances during Transport

	Pipeline-Bemidji
	Transfer stations.

(IV) Discharge as Result of other Activities

	Irrigation Selenium, salts
	Pesticides
	Fertilizer - natural/ anthropogenic
	Road Salt
	Urban Runoff
	Water Softeners

(V) Sources as conduits to aquifers

	Production wells Poor construction can cause introduction of contaminants.
	Excavation

(VI) Naturally Occurring that is aided by Humans

Saltwater intrusions aided by ground-water withdrawals

Coal mines

Threats to Water Quality

* Uranium from All Department of Education sites are long-term contamination.

Water Quality Standards

-Regulations on limits of constituents in water.

Safe Drinking Water Act - and amendments passed by Congress

	Environment Protection Agency - Regulatory Agency - developed drinking water standards
	MCL- Maximum contaminant level (enforced)
	MCLG - goals (guidelines for MCL) Selection criteria include: (1) Detection (2) Potential health risk (3) Occurrence or potential for occurrence
	We are not a zero tolerance society.

Risk 1 death per 1,000,000

Cancer - assume - lifetime Health Advisory level

Person weighs 70 kilograms and drinking 2 liters of water per day.

* feed to rats to see if toxic

Total Dissolved Solids-

-Total amount of solids (mg/L) that remain in a sample that is evaporated to dryness.

Contaminant - makes unfit for use through contact or addition.

Pollute - complete decay through contamination.

-Many types of contaminants occur naturally, many do not.

-Many contaminants can not be tasted.-Radon, As, Cu.

Major Constituents in water are:

Calcium, Magnesium, Sodium, Potassium, Chloride, Sulfide, Carbonate

Bicarbonate, Silicate.

Trace elements- a few mg/L

Dissolved gases- Oxygen, carbondioxide, nitrogen, methane

Important in surface water.

ENV 302 - Lectures