Description
Wastewater treatment is needed so rivers and streams are suitable for fishing, swimming and drinking water. For the first half of the 20th century, pollution in the Nation’s urban waterways resulted in frequent occurrences of low dissolved oxygen, fish kills, algal blooms and bacterial contamination. Early efforts in water pollution control prevented human waste from reaching water supplies or reduced floating debris that obstructed shipping. Pollution problems and their control were primarily localnot national, concerns. Since then, population and industrial growth have increased demands on our natural resources, altering the situation dramatically.