Legislation such as the CWA represents one method of preventing and controlling water pollution. Many other methods exist, some dealing with nonpoint sources of pollution and others with point sources. Some approaches are more effective than others, but all can contribute to the fight against water pollution.
Nonpoint Pollution Control
Most nonpoint water pollution results from the runoff of agricultural products such as fertilizer (see also eutrophication). The following is a list of strategies that can control nonpoint water pollution:
- Reduce the need for fertilizer by planting crops that absorb nitrogen from the atmosphere. Legumes such as soybeans contain specialized bacteria that "fix" atmospheric nitrogen, converting it into usable nitrates. These legumes can be planted alternately with normal crops.
- Plant buffer zones between agricultural fields and nearby surface water. These zones prevent fertilizer from entering the water and causing eutrophication.
- Reduce harmful pesticide runoff by applying pesticides as sparingly as possible.
- Control runoff of animal wastes by locating grazing areas on flat land that is removed from surface water and flood zones.
- Reduce soil erosion and flooding through reforestation of watersheds (see also erosion).
Point Pollution Control
Two major sources of point pollution in water are oil spills and sewage disposal. Oil spills can be cleaned up through mechanical, chemical, and natural methods. Mechanical methods include using small boats to vacuum up oil off the surface of the water and using large absorbent pads to soak up oil on beaches. Chemical methods involve dispersing agents that make slicks of oil less concentrated, or congealing agents that do just the opposite, clumping oil together so that it sinks to the bottom and does less harm. Over time, natural forces such as winds and waves mix the oil together with water, and some bacteria are able to decompose it. Overall, however, these methods remove only part of the oil, usually only 12-15% of what was originally spilled. The best way to protect water from oil spills is to prevent the spills from ever occurring in the first place. This can be done by requiring double hulls for all oil tankers and by protecting sensitive coastal areas from oil drilling and shipping.
In urban areas, sewage flows through a network of pipes to wastewater treatment facilities. When rain causes these sewer systems to overflow, untreated sewage is discharged directly into surface waters. The best way to control this type of pollution may be to prevent toxic wastes from ever reaching sewage plants at all. This can be accomplished through the following methods:
- Requiring industries to remove all hazardous wastes from water sent to sewage treatment plants.
- Encourage industries to reduce toxic chemical use and waste through cleaner production.
- Encourage the use of less harmful household chemicals.