3. Biosolids Disposal

Introduction

Treatment of domestic wastewater produces two principal byproducts: effluent (see Chapter 1) and biosolids or “sewage sludge.” Biosolids are solid or semisolid organic matter recovered from the sewage treatment process. They can be disposed of in landfills, incinerated to produce energy, or processed and used as fertilizer or compost. When applied to farms, ranches, forest lands, and public parks, their use is regulated by the Florida Department of Environmental Protection (FDEP) (Chapter 62-640, F.A.C.). Biosolids are classified into Class B, Class A, or Class AA, based on their level of treatment, with Class AA representing the highest level of pathogen and heavy metal reduction.

In addition to meeting specific sanitary requirements under the federal Clean Water Act, Class AA biosolids must meet stringent heavy metal limits. Products meeting these standards and licensed as fertilizer with the Florida Department of Agriculture and Consumer Services (FDACS) avoid additional regulations on compost distribution and marketing. Biosolids are about $60 per acre cheaper than synthetic fertilizer (FDEP 2019b). Once meeting Class AA standards, composted biosolids are essentially unregulated, allowing broad commercial and retail usage. However, there are emerging concerns about the potential spread of untreated biosolids contaminants such as PFAS, pharmaceuticals, and microplastics across the landscape, raising new questions about long-term environmental and health impacts.

Florida’s wastewater treatment facilities produce about 350,000 dry tons of biosolids annually. Approximately 25% is disposed of in landfills. About 30%—or 90,000 tons—of Class B biosolids are spread at approximately 140 permitted sites, primarily on pastures and hayfields. Class B biosolids still contain some bacteria and heavy metals, and local governments may ban their application.

Figure 3.1. Biosolids produced as a byproduct of wastewater treatment in Florida are disposed in landfills or dried and processed into Class B or Class AA products.

The remaining 45%—about 150,000 tons—are processed in 39 permitted Class AA facilities across Florida before distribution as commercial fertilizer and compost products. The distribution and use of Class AA biosolids are not tracked, and local governments cannot ban their use. An additional 9,000 dry tons of Class AA pellets are imported from out-of-state facilities.

Biosolids from the major wastewater treatment facilities (WWTFs) in Sarasota County are disposed of at a facility in Charlotte County. The only biosolids currently disposed of in Sarasota County are those purchased from a commercial Class AA composting operation, such as Synagro, for use as a soil amendment.