m50.    What other types of pollutants are there? 

Thermal pollution is caused by power plants. They are only 32-32% efficient; therefore they give off thermal pollution. Warmer water lowers dissolved oxygen content by decreasing the solubility of water. This means that fish cannot survive in the oxygen-poor environment. About 44% of the river pollutants are from society, deposition from the atmosphere accounts for 33%, deliberate dumping adds 10%, and oil and gas production contribute 1%. In the US, 35% of all municipal sewage ends up virtually untreated in marine waters.

Annually, ¹/₃ of the US costal waters are closed to shellfish harvests because of pollution. Dumping of industrial wastes off the US coasts has stopped. Barges and ships legally dump large quantities of dredge spoils (contain toxic metals). Ships dump large amounts of garbage at sea because of cost. The US is responsible for about ¹/₃ of all the trash thrown or washed into the world's oceans.  Each year, wildlife die from ingesting plastic cups, bags, 6-pack yokes or getting tangled in drift nets or other debris; 2 million sea birds and 100,000 marine mammals and sea turtles are affected. Great Britain and Pakistan dispose of low-level radioactive wastes in coastal areas. Soviet Union dumps large quantities of low and high level radioactive wastes into the Arctic Ocean and into rivers that run into this ocean. Washing out tankers and releasing ballast release more oil than from oil spills. Half the oil reaching the oceans is waste from city sewers.

Groundwater contamination can be considered permanent. In 1982, 45% of large public water systems were contaminated with organic chemicals, most commonly pesticides and nitrates. By 1990, the drinking water of 4.5 million Americans was contaminated with nitrates. Groundwater can be contaminated by leakage from underground storage tanks, landfills, and hazardous waste dumps. No soil is effective in filtering out viruses or many synthetic organic chemicals. Non-point source pollution is lead by agriculture, although folks putting fertilizer and pesticides dump more of these pollutants, percentage wise, than do farmers.

Point source pollution generally comes from sewage. Primary sewage treatment uses screens to filter out large debris such as sticks, and rags. Secondary sewage treatment uses aerobic bacteria to remove up to 90% of biodegradable, oxygen-demanding wastes. Advanced sewage treatment is a series of chemical and physical processes to remove specific pollutants left in the water. Sewage treatment produces a gooey sludge that must be disposed of or recycled as fertilizer.  About 54% is used as fertilizer. Water for drinking is usually run through sand filters then through activated charcoal and then disinfected.

e18.    Does water recover from pollution?

e19.    What materials can cause water pollution?  

e20.    What are environmental hazards and risks?

e21.    What are chemical hazards?

e23.    How is soil important to plants?

g19.    Where do you find air pollution?