: Introduction

I. " Brush your teeth with the best toothpaste. Then rinse your mouth with industrial waste.'
Tom Lehrer

Water pollution is a historical problem:
A 4000 BC palace at Knossos in Crete featured 8 drainage system all which emptied into the sea.
Romans built aquifers that dumped their wastes into the Tiber River
During the Middle Ages, Paris and London had waste disposal systems that functioned as both dump and water source resulting in many cases of typhoid dysentery etc.

Today water pollution continues as a major problem in spite of the Clean Water Act of 25 years ago as evidenced by the following :

Thirty-seven percent of assessed estuaries today are classified as impaired, with urban runoff, municipal point sources and agriculture identified as the leading sources of pollution. Nutrients and bacteria lead the list of causes of pollution.

Nationwide the number of fish consumption advisories rose by 26 percent from 1995 to 1996 to a total of 2,193. Since 1993, there has been a 72 percent increase. The four toxics responsible for over 90 percent of all the nation's advisories were mercury, PCBs, dioxins,and DDT. EPA estimates that 160,000 factories dump 57,000 tons of toxic organic chemicals and 68,000 tons of toxic metals into the U.S. coastal waters each year. In the U.S., sewage treatment plants dump 5.9 trillion gallons of wastewater into coastal waters each year.

Not all of the toxins that continue to poison public waters are discharged directly into the water either. For example, in the Great Lakes, 58 to 89 percent of the PCBs and 95 percent of the lead in the upper lakes (Superior, Michigan and Huron) come from the atmosphere. Air deposition accounted for up to 82 percent of the PCBs entering Massachusetts Bay, and 80 percent of the mercury and 34 percent of the PCBs entering Delaware Bay

The Clean Water Act of 1972 has never adequately addressed the problem of polluted runoff ( relative to point sources) , now the number-one cause of pollution in the nation's waters. Each time it rains, water runs off the land and picks up toxic pesticides and fertilizers from farm fields and lawns, heavy metals and oils from cars and trucks, manure and microbes from animal feedlots, poisonous chemicals and metals from mining sites, and sediment from construction sites, farms and timber operations. Three and a quarter million tons of oil enter the oceans of the world each year.
For the Chesapeake Bay, the urban, agricultural and animal manure runoff translates into a nutrient load of 438,000 pounds a day of nitrogen and phosphorus, most of it from Maryland, Pennsylvania and Virginia, says the Chesapeake Bay Foundation.

II. The major water pollutants as you might surmise from the material above includes:

Sediments

Inorganic chemicals: heavy metals, salts, acid deposition

Disease vectors: virus through algae

Excess plant nutrients leading to eutrophication

Organics: pesticides, oils through plastics

Oxygen-demanding wastes

Radioactivity from mining & nuclear waste disposal sites and Thermal loads from hot waters from cooling reactor plants

Follow each of the above linked headings for a primer on the many faces of water pollution!