Frequently
Asked
Questions
[ The FAQ's ]

Frequently Asked Biosolids Questions
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1. What are Biosolids?
   Biosolids are nutrient-rich organic materials resulting from the treatment of municipal sewage in a treatment facility. When quality controlled, monitored and processed, these residuals can be recycled and applied as fertilizer to improve and maintain productive soils and stimulate plant growth.
   
   
2. What Is The Difference Between Biosolids And Sludge?
   Biosolids are processed municipal sewage sludge that meet specific quality control standards. Biosolids are extensively treated, carefully monitored and must be used in accordance with regulatory requirements. Sludge is not subject to quality controls and is not allowed to be recycled without further processing and extensive monitoring.
   
   
3. Why Do We Have Biosolids?
   We have biosolids because of the wastewater treatment process. Water treatment technology has made our water safer for drinking, recreation and seafood harvesting. Thirty years ago, thousands of American cities dumped their raw sewage directly into the nation's rivers, lakes, and bays. Now, Federal and state regulations require local governments to treat wastewater and to make the decision whether to recycle biosolids as fertilizer, incinerate it, or bury it in a landfill.
   
   
4. How Are Biosolids Generated And Processed?
   Biosolids are created through the treatment of wastewater generated from municipal sewage treatment facilities. The treatment of biosolids can actually begin before the wastewater reaches the sewage treatment plant. In larger wastewater treatment systems, pre-treatment regulations require that industrial facilities process their wastewater to remove hazardous contaminants before it is sent to a wastewater treatment plant. Wastewater treatment facilities monitor incoming wastewater streams to ensure their recyclability and compatibility with the treatment plant process.
   
   Once the wastewater reaches the plant, the sewage goes through physical and biological processes that clean the wastewater and remove the solids. The Philadelphia Water Department has Anaerobic digesters to significantly reduce pathogens (disease-causing organisms, such as certain bacteria, viruses and parasites) and other organisms capable of transporting disease. Anaerobic digestion is a natural process that heats the biosolids for 15 days or more and reduces pathogens by 99.99%. This process also stabilizes the biosolids making it non-putrescible and reduces odors.
   
   
5. How Are Biosolids Used?
   After treatment and processing, biosolids can be recycled and applied as fertilizer to improve and maintain productive soils and stimulate plant growth. At mine reclamation sites, the ground is first leveled or returned to original contour. Lime is added to the soil surface to raise the ph to 6.5 (ideal for grasses and legumes.) Biosolids is applied to the surface about 2 inches deep (60 dry tons per acre.) Large farm equipment, a disc, is used to blend the biosolids into the top 8 inches of soil. This step is also effective in reducing odors. Next, the area is seeded using a mixture of grass and legume seeds, water and mulch. The land application of biosolids completes a natural cycle in the environment. By treating sewage sludge, it becomes biosolids that can be used as valuable fertilizer, instead of taking up space in a landfill or other disposal facility.

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