Developing a Sustainable Biosolids Management Program for Pasco County, Florida

Authors: Hahn, Thomas; Cruz, Luis; Kenty, Kerstin; Forbes, Bob

Source: Proceedings of the Water Environment Federation, Residuals and Biosolids 2010 , pp. 1344-1369(26)

Publisher: Water Environment Federation

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Abstract:

In response to increasing costs associated with biosolids management and recent County strategic initiatives, the Pasco County Utilities Services Branch (PCUSB) in Pasco County, Florida, evaluated alternative biosolids disposal strategies to identify the most cost-effective and sustainable long-term solution. The County focused particularly on beneficial reuse alternatives due to recent County strategic vision initiatives. The referenced evaluation and associated results comprise a Biosolids Master Plan (BMP).

Handling, transporting, and disposing of dewatered biosolids from PCUSB's wastewater treatment facilities continually increase in cost. While the County no longer anticipates its population and economic growth to continue at the pace of the past decade, growth in the community will continue due to its proximity to the Tampa-St. Petersburg metropolitan area, driving the costs of Pasco County's biosolids management practices upward if the current practices continue. Some factors contributing to these increased costs include rising energy and transportation costs, increased landfill tipping fees, and increased volume of biosolids production.

During the initial phase of the PCUSB Biosolids Study, the project team identified and formulated a number of alternatives for managing and providing beneficial reuse of the biosolids. PCUSB currently dewaters all of its biosolids using belt filter presses (BFPs). Historical flow data and biosolids production data were provided by Pasco County. Based on these data, wastewater flow predictions were developed for the next 20 years, through 2028.

PCUSB stipulated that alternatives evaluated must be capable of compliance with both US EPA Class A pathogen-reduction and vector-attraction reduction criteria, as defined in 40 CFR Part 503 Sewage Sludge Rule (enforced by the US EPA), and Class AA standards imposed by the State of Florida. As part of the alternatives evaluation, it was recommended that PCUSB submit biosolids samples for analysis of pollutants regulated by US EPA to determine compliance with pollutant limits specified in Tables 1 and 3 of the 40 CFR Part 503 Sewage Sludge Rule. Compliance with Table 3 of the 503 Rule would demonstrate that PCUSB's biosolids are capable of meeting State of Florida Class AA standards, the highest regulatory standard attainable for biosolids.

With the regulatory requirements in mind, alternatives for long-term biosolids management were selected and developed in concert with input from PCUSB staff. While driven by necessity of meeting federal and state regulatory requirements, PCUSB also voiced nonmonetary drivers for the ideal solution, such as sustainability, promoting green practices, the desire to provide something positive for the rate payers (if possible), and a strong preference for a simple and elegant solution that worked. Bringing all of this together, the following alternatives were developed and will be described in detail in the manuscript.

Alternative 1, Dewater Biosolids at Shady Hills and Wesley Center WWTFs and Haul to Landfill for Disposal (current status quo, carried into the future)


Alternative 2, Centralized Composting Facility at Shady Hills WWTF/County Landfill


Alternative 3, Composting Facilities at Shady Hills WWTF and Wesley Center WWTF


Alternative 4, Centralized Heat Drying Facility at Shady Hills WWTF


Alternative 5, Heat Drying Facility at Shady Hills WWTF, Composting Facility at Wesley Center WWTF


Both non-cost criteria scores (benefits) and planning-level cost estimates were used during the project's biosolids management alternatives evaluation, with combined benefit-cost scores determined for each alternative. Details of the alternatives evaluation process, results, and conclusions will be presented. The presenter will also identify solids handling improvements at County facilities that do not have dewatering processes onsite, and how these improvements will integrate into and compliment a sustainable, long-term biosolids management program for Pasco County.

The analyses revealed that combined cost-benefit scores for the alternatives were within about 14 percent of each other, with the exception of Alternative 1 (future status quo), which was around 19 percent more expensive over the project life than the next closest alternative. After holding a workshop to present the results of the analyses to PCUSB, the County reiterated the desire for a solution that would meet all of the desired non-monetary wishes, the applicable regulatory requirements, and would be able to leverage existing staff expertise and availability. The recommended alternative is Alternative 3 - separate composting facilities at the County's two largest WWTFs, which met all of the stated criteria. The County accepted this solution, choosing to move forward with a phased implementation. This allows the County to control capital costs at start up and also, should fiscal and other drivers dictate it, the option to expand using a heat-drying facility rather than composting in the second phase.

The recommended facilities and operations are expected to establish a sound and sustainable biosolids-management program, which will allow PCUSB the flexibility to meet evolving biosolids management needs and preferences for many years into the future.

Keywords: BMP; Biosolids Master Plan; benefit-cost analysis; composting; heat drying

Document Type: Research Article

DOI: http://dx.doi.org/10.2175/193864710802767524

Publication date: January 1, 2010

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