industrial wastes (2) sewage (3) agricultural chemicals and wastesSewage consists of human wastes, garbage, and water that has been used for laundering or bathing. In many countries in the world, including our own, raw sewage is piped right into river, lakes, and oceans. Most of the sewage in the United States goes through treatment plants that remove solids and such dissolved substances as the nutrients nitrogen and phosphorus. Grey water, the water we use to bathe ourselves, and the water that we wash our dishes with, can create potentially large problems for plants and animals. About 25 percent of the households of the United States use SEPTIC TANK systems, which pass the sewage through tanks and filter it through leaching fields into the land. Some sewage in the United States still goes untreated directly into waterways or the ocean. However, government regulations control the amount and the quality of the discharge.
đang được dịch, vui lòng đợi..
