Fosnrs 1: The Florida Onsite Sewage Nitrogen Reduction Strategies (FOSNRS) Study, Project Overview.

Onsite Wastewater Systems (OWS) serve approximately one-third of all households in Florida.  The relative impact of OWS on total nitrogen loading varies from watershed to watershed with estimates ranging from below five to more than 20 percent.  Regardless of the source, excessive nitrogen has negative effects on public health and the environment.  There is widespread interest in the management of OWS and the nitrogen impacts in Florida and the nation.  For these reasons the State has initiated the Florida Onsite Sewage Nitrogen Reduction Strategies (FOSNRS) Project, the subject of this series of presentations.

A technological approach to this issue consists of requiring better treatment from onsite systems.  This approach has some history in Florida, where OWS are regulated by the Florida Department of Health (FDOH) and some form of better or advanced treatment has been required in several areas of the state for over a decade.  Permitting categories for advanced systems are usually aerobic treatment units (ATU) certified to ANSI/NSF-Standard 40 and sometimes engineer-designed performance-based treatment systems (PBTS).  These advanced systems require more maintenance and management than a conventional OWS.  Florida law currently requires the following basic requirements for advanced systems: biennial operating permit issued by FDOH, current maintenance contract with a maintenance entity (ME), annual inspection by FDOH, and two annual maintenance inspections by the ME. 

FDOH recently completed a comprehensive evaluation of both the operation and management of existing advanced systems in Florida.  This study was mostly funded through EPA’s Nonpoint Source Pollution Section 319(h) grant program.  The data collected during this project addressed an administrative perspective (completeness of paperwork), included an assessment of user group perceptions, and assessed operation and treatment performance in the field.  Overwhelmingly, existing advanced treatment systems in Florida utilize an extended aeration approach, which contrasts with the passive approach of the FOSNRS study.  Among the findings of the study was a quantification of the frequency of various operational issues under the existing management approach.  Treatment systems often had issues related to mechanical aeration, e.g., systems that were turned off or the aerator was not working.  Analysis of sampling results confirmed that such mechanical aeration issues had a direct effect on the nitrogen and cBOD5 removal performance levels of advanced systems. The study results provide a point of comparison for results from the currently ongoing FOSNRS study.

In discussions of the role of OWS in watershed protection, frequent questions concern the attenuation of nitrogen after discharge to a drainfield and the effectiveness, costs, and reliability of existing treatment technologies.  The Florida Legislature tasked FDOH in 2008 to conduct a multi-faceted study of nitrogen from OWS, and to develop cost-effective, passive strategies for nitrogen reduction for OWS in Florida.  The significance of this FOSNRS Project is that it evaluates and develops strategies to reduce nitrogen impacts from OWS regulated by FDOH.  The goal is to further evaluate the transport of nitrogen from OWS and to develop onsite nitrogen reduction systems that complement the use of conventional OWS, are cost effective and ecologically protective, and have reduced operation and maintenance costs.  The project includes the following major tasks:

Task A – Technology Evaluation for Field Testing: Review, Prioritization, and Development:  This task includes a literature review, technology evaluation, prioritization of technologies to be examined during field testing, and further experimentation with approaches tested in a previous DOH passive nitrogen removal study.  Objectives of this task were to perform controlled testing at a unique test facility to develop design criteria for new passive nitrogen reduction systems for testing at actual home sites.

Task B – Field Testing of Technologies and Cost Documentation:  This task includes installation of top-ranked nitrogen reduction technologies at actual homes, with documentation of their performance and cost.  Cost documentation for the systems will be broken down by permitting, design, materials and construction, and operation and maintenance.

Task C – Evaluation of Nitrogen Reduction Provided by Soils and Shallow Groundwater:  This task includes several field evaluations of nitrogen reduction in Florida soils and shallow groundwater and also will provide data for the development of a simple planning model in Task D.

Task D – Nitrogen Fate and Transport Modeling:  The objective of this task is to develop a simple fate and transport model of nitrogen from OWS that can be used for assessment, planning, and siting of OWS.

The results of the legislatively mandated FOSNRS project will ultimately benefit Florida’s approximately 2.7 million OWS owners by finding cost-effective nitrogen reduction strategies that will improve environmental and public health protection.  The other presentations proposed for this session will focus on task specific aspects of this study and other closely related work.