Type of Document Thesis Author Smith, Leland A. URN etd-12222008-112912 Title Promising Approaches to Nitrogen Removal from Septic Effluent Using Nitrification and Denitrification Filters Degree Master of Science Department Civil and Environmental Engineering, Department of Advisory Committee
Advisor Name Title Amy Chan Hilton Committee Chair Gang Chen Committee Member Wenrui Huang Committee Member Keywords
- Floridan Aquifer
- Water Resources
Date of Defense 2008-12-16 Availability unrestricted AbstractResidential wastewater management in urban fringe and rural areas in northwest and north central Florida is commonly accomplished using on-site wastewater treatment systems (OWTSs), typically consisting of septic tank and drainfield combinations, with each residence typically being served by an OWTS that is owned and operated by the individual homeowner. Known and/or potential environmental impacts to ground and surface waters, attributed to use of septic tank and drainfield systems, are currently receiving significant attention from scientific and regulatory communities, in Florida and elsewhere. Effluent nitrogen concentration is typically the main concern because of the tendency of nitrate nitrogen to migrate rapidly in groundwater, and the association of nitrate nitrogen with both human health and environmental effects.
Septic effluent nitrification and/or denitrification filters can be equipped with a variety of filter media and can be configured in a variety of different ways to provide better nitrogen removal than is typically achieved by a conventional septic tank and drainfield system alone. There are, however, many variations on this idea, some producing better nitrogen removal results than others.
A literature review was conducted to collect information regarding the nitrogen removal performance, operation and maintenance considerations and permitting constraints of septic effluent nitrification and/or denitrification filters in various operating configurations. The results gained in several different studies were reviewed and key design elements were identified. Research into the performance of these filter systems included consideration of filters operating in single pass and recirculating configurations, and combinations thereof. Major septic effluent filter studies that were reviewed for this thesis include:
1. Pulsed Recirculating Sand Filter Systems (Lamb et al., 1987)
2. Anne Arundel County, MD System 1 (Piluk and Hao, 1989; Piluk and Byers, 2001)
3. Anne Arundel County, MD System 2 (Piluk and Byers, 2001)
4. Modified Recirculating Sand Filter (RSF2) system (Sandy et al., 1987)
5. RUCK System (Laak, 1981; Lamb et al., 1987)
6. Non Woven Textile Fabric (NWTF) Filter System (Leverenz et al., 2001)
7. Passive Nitrogen Removal Systems (Smith et al., 2008)
Statistical information on permits issued for innovative OWTSs and testing data on nitrogen removal performance of performance-based treatment systems were obtained from the Florida Department of Health (FDOH), and were reviewed for information of relevance to the research objective. The FDOH statistical information reviewed did not indicate numbers of alternative systems permitted, but did include numbers of performance-based treatment systems (PBTSs) and aerobic treatment units (ATUs) permitted. FDOH statistics show that ATUs have been implemented widely, including in many parts of north central and northwest Florida, most notably in Franklin County. PBTSs, however, have not been implemented to a significant degree.
Conclusions were drawn relative to specific nitrogen removal technologies and operating configurations that seem promising for potential broad based, near term implementation in septic effluent filter systems in decentralized wastewater management scenarios that are commonly encountered in rural and urban fringe development projects in north central and northwest Florida. Along those lines, the following types of systems were identified as seeming to be particularly promising:
1. Recirculating sand filter (RSF) system equipped with an upflow anoxic filter; and
2. RSF system with quiescent recirculation to an anoxic pump tank.
Other technologies and configurations that seem promising but likely in need of testing and evaluation for potential FDOH approval include the following:
1. Passive nitrogen removal systems (PNRSs), as explored by Smith et al. (2008).
2. RSFs in combination with drip irrigation.
3. RSFs in combination with drip irrigation and denitrification enhancement through the use of alternative trench bedding, in order to maintain an abundant supply of carbon in locations where organic carbon supply is poor.
Based on a review of the state regulations governing the use of septic tank and drainfield systems and other on-site wastewater treatment systems, the importance of regulatory agency pre-application meetings was stressed as a way to improve the odds of success for a project that may potentially involve the use of an alternative or innovative system.
The findings of this thesis support the implementation of septic effluent nitrification and denitrification filter systems in decentralized wastewater management scenarios in rural and urban fringe development projects in north central and northwest Florida, and the expansion of the variety of treatment technologies and configurations that are approved as “alternative systems” under the FDOH Chapter 64E-6, F.A.C. regulations.
Finally, FDOH-compiled permitting statistics and performance data suggest that further exploration of unit processes within commercially available PBTSs utilizing packed bed media filters may reveal opportunities for further enhancement of selected systems through application of conclusions drawn from the literature review.
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