A Bigger-Picture Look at Florida's Nutrient-Loading and the Relative Insignificance of Biosolids-Derived Products

The State of Florida suffers from location-specific, surface-water eutrophication that has been principally attributed to excess nutrient loading. The Saint John's River basin and Lake Okeechobee have been noted among others, as problem areas. Excessive nutrient loading to the everglades and seasonal toxic red tides are related problems. In response to these challenges, the Florida Department of Environmental Protection (FDEP) has proposed new Class-B land application rules (FDEP, 2019a) restricting application to below agronomic loading rates for phosphorus (P) and prohibiting application to sites where the water tables encroaches within 15 centimeters of the surface on a seasonal basis. In FDEP's own analysis (FDEP, 2019b) they estimate that between 4 and 10 times more land would be needed to handle the State's current Class-B biosolids production. This paper will provide nutrient accounting for significant sources of nutrients within agricultural and urban settings. These sources include Class-B biosolids land application; Class-AA biosolids (the State of Florida's term for Class-A biosolids that also meet the State's more-restrictive-than-Part-503 metals requirements) that have been registered as 'fertilizers'; other fertilizers; agricultural manures; water resource recovery facilities' (WRRF) surface-water discharges; and WRRF effluent used as reuse water. County-based nutrient loads by source are compared with nutrient removal rates by harvested crops and net over and under loads are identified geographically using color-indexed maps. These combined data suggest that additional regulatory targets will be required if Florida is to solve its surface-water impairment issues, since contributions of nutrients from the regulated sources, namely Class-B biosolids and POTW surface-water discharges represent only 5 to 10% of the total relative Nitrogen (N) and P loads. Finally, while this paper is Florida-specific, many observations are not unique to that state and will have relevant analogs in other geographies. Figure 2 shows an FDEP map (FDEP, 2020) of the state's nutrient impaired waters. Impairment sources shown include nitrogen (N), P, algal mats, and chlorophyll. Highlighted locations include areas immediately offshore from major metropolitan centers, Lake Okeechobee and its surroundings, the gulf offshore from the Everglades, and the Georgia-fed Suwanee and Ochlockonee watersheds, among others. The nutrient sources included in this analysis include the following, in order of decreasing relative significance: 1) Chemical Fertilizers; 2) Carbon-Based Fertilizers, which include Class-AA biosolids; 3) Recovered Manures; 4) Reuse Water; 5) Legume-Fixed Nitrogen; 6) Class-B Biosolids; and 7) Surface Water Discharges & with only some of these covered in this abstract. These nutrient sources and their relative impacts will be detailed in the full paper. For this abstract, the following are of note: 1. Fertilizers. Fertilizer manufacturers are required to report sales of fertilizer to the Florida Department of Agriculture and Consumer Services' (FDACS). Individual manufacturer reports are consolidated by FDACS into a statewide Tonnage Report, by county; data in Table 1 summarize 2018 fertilizer sales. Figures 3A and 3B show a map of Florida with chemical fertilizer purchases by county using the resulting chemical fertilizer loading for N and P, respectively in 2018. The Figure-3 maps are typical of Figures 3 and 4. Each map uses the same color-weighting for each county's annual N loading: ranging from white (representing 0), through yellow (at 6 million pounds per year, 'Mppy'), to red (at 12 Mppy). Similarly, each county's annual P loading is scaled from white (for 0), through yellow (3 Mppy), to red (6 Mppy). The maps further differentiate between predominantly urban counties (those with heavier-weight borders). These 9 most populous counties represent over 58% of the state's population and include: Miami-Dade (2,761,581); Broward (1,951,260); Palm Beach (1,485,941); Hillsborough (1,436,888); Orange (1,380,645); Pinellas (975,280); Duval (950,181); Lee (754,610); and Polk (708,009). 2. Class-AA Biosolids Fertilizers. In the State, Class-A products are registered as fertilizers with FDACS and are no longer subject to FDEP regulation and included in the Tonnage Report. FDCAS rules run contrary to FDEP water-quality objectives however; with requirements that fertilizer N and P labeling amount to 'guaranteed minimums' (that are subject to fines if and only if actual concentrations are found to be below labeled concentrations). As such, FDCAS rules encourage nutrient-loading under-reporting for Class-AA biosolids; and every fertilizer listed in the Tonnage Reports. 3. Class-B Biosolids. Figure 3 shows the loading from Class B biosolids which are centered in two counties immediately south of Orlando & while land application is of little significance elsewhere. These two heavily loaded counties do contribute to Lake Okeechobee's impairment. Class-B biosolids, however, only represent roughly 1/3 of the N and 1/2 of the P applied locally, so that there is more demand than what is met by biosolids alone. 4. WRRF Surface-Water Discharges. Figure 4 shows N and P loads attributable to effluent discharge. As shown by the white maps, it is apparent that the state's nearly uniform 5, 5, 3, and 1 mg/L effluent limits for TSS, BOD, TN, and P, respectively have made this category insignificant with respect to nutrient loading. There are two exceptions to the limits: one in Tampa (for P) and another in Jacksonville (for P and N). 5. State Total Nutrient Loading, Uptake, and Net Loading. Figures 5, 6, and 7 all have different scales than the earlier maps (as shown on each). Figure 4 shows the total nutrient loading from all sources while Figure 5 shows the estimated, potentially-offsetting total crop nutrient uptake. Figure 6 shows the net nutrient overloads (red) or underloading (blue) for each county. SUMMARY This assessment shows how an overall and complete inventory of nutrient loads, while rarely undertaken, can provide insight into the almost certain causes of surface water impairment. It also suggests that geography-specific regulation; and more specifically that stricter regulation of farm entities is warranted, especially for nutrient-overloaded jurisdictions. From the nutrient accounting performed, the wastewater treatment industry is only responsible for 12 to 13% of Florida's N and between 9 and 10% of the State's P, in the forms of surface-water discharges, Reuse Water, Class-B Biosolids and Class-AA Biosolids-Derived Fertilizers. The industry has been highly regulated for decades and has performed very well. Finally, to truly address eutrophication and impaired waters in Florida, it is suggested that the commercial fertilizer and farm industries be monitored closely and potentially regulated to ensure that their contributions to nutrient loading are better understood and then almost certainly curtailed on specific sites, as warranted. Additionally, between one quarter and one third of chemical fertilizer use occurs in Florida's 9 most-populous urban counties (although there is considerable agricultural activity in some of these counties that would reduce the loading attributable to the 'general public'). Creative options are similarly warranted to limit what the general public can buy and apply in specific geographies where runoff contributes to surface-water impairment. The paper discusses these and other issues within Florida. Opportunities for improving the State's surface water quality and regulatory framework are also discussed.