Septage includes liquids, solids, concentrated BOD, nutrients, toxics, inorganic materials (such as sand) pathogens, oil, grease, hair, debris, and odorous materials which have accumulated over a period of time and have been pumped out of septic tanks and cesspools to be treated and for eventual appropriate disposal. This can be accomplished through either surface or subsurface land application, or added upstream to a sewage treatment plant at a sewer manhole or at the beginning of the process. Surface application can be accomplished through spreading the material on the ground or using spray irrigation. Subsurface application can occur through plowing the septage into furrows or injecting it below the surface. It can also be buried in sanitary landfills. Surface disposal can result in odor problems, and fly and mosquito problems, and provide an opportunity for aerosols to be created containing viruses and bacteria.
Best Practices for Septage Treatment/Disposal: Land Application
• The septage should be removed from the septic tanks’ or cesspools by licensed trained sewage haulers who must remove it in a safe and effective manner and take it to the point of disposal.
• Buffers should be provided and setbacks observed between the areas of application of the septage and any water sources. The slope of the area, type of soil, climate, weather conditions, and application rates are very significant. Food used for human consumption should not be grown in this area.
• Stabilization of the septage or pretreatment should be done if feasible prior to the land application. This can be accomplished by using stabilization lagoons, chlorine oxidation, aerobic digestion, and biological and chemical treatment.
• In the spray irrigation process, the septage must be screened and pretreated and applied to the ground at a rate of 80-100 pounds per square inch through nozzles. The material can also be spread out in furrows and on the land in thin layers. This is then covered up by a plow.
• Septage or sludge must never be applied to frozen agricultural land.
• Use alternate means of disposal, if available, such as taking the septage to a sewage treatment plant for processing which is preferable if the septage is properly controlled and released into the treatment process without affecting what is occurring.