ENVIRONMENTAL EDUCATION SERIES ENVIRONMENTAL QUALITY Agriculture & Natural Resources
EXTENSION ENVIRONMENTAL EDUCATION, AUBURN UNIVERSITY, AL 36849-5647

Advantages Of Using Sewage Sludge

 Growers who use sludge as a fertilizer have the following advantages: (1) they can use it alone or as a supplement to commercial fertilizers; (2) sludge can be obtained at little or no cost; and (3) most growers or farmers in Alabama live near small cities and municipalities; therefore, it can be easily obtained.

 Nutrient value of sludge may vary from source to source, based on factors such as treatment processes, origin, types, and quantities of wastewater treated. The sludge should be applied according to crop requirements. Consequently, soil should be tested to determine nutrient needs.

 Potential Problems

 Concerns about applying sludge to land include the potential for applying too much or too little of each nutrient; the presence of toxic constituents; and the possible detrimental effects on water quality from leaching, erosion, or runoff losses. Because of these potential problems, restrictions have been placed on land application of sludge. Steepness of slope and soil conditions may limit or prohibit application. There are restrictions on how close sludge can be applied to homes, wells, streams, roads, and property lines. EPA (Environmental Protection Agency) has also set application limits for five heavy metals (nickel, zinc, copper, lead, and cadmium) to a given area. After these limits have been reached, sludge application must cease, but the land can still be used for normal crop production. In addition to these restrictions, a permit is required by ADEM (Alabama Department of Environmental Management) before sludge can be applied to land. (For more information, contact ADEM at 1751 Federal Drive, Montgomery, AL 36130.) If sludge is applied in accordance with ADEM and EPA regulations, there will be few risks to the environment.

 Good Management Practices

 EPA recommendations for the use of sewage sludge are as follows:

1. Farmers should not accept sludge or apply it to land without a complete waste analysis.
2. The soil pH on sludge application sites should be maintained above 6.5 to lower plant uptake of heavy metals.
3. Sludge should be applied by directly injecting it in the soil or incorporating it into the soil within 24 hours to reduce the potential for odor and loss of nutrients in runoff.
4. For surface application, use only sludge that has been properly digested and stabilized at the treatment plant.
5. Do not apply sludge long before it will be utilized by the crop.
6. Keep accurate records of sludge applications. Sewage sludge containing heavy metals should be monitored to prevent contamination of soil or groundwater.
7. Excessive rates can contribute to leaching, erosion, and runoff losses; therefore, do not apply more than is needed.