| PB recently conducted a 26-month-long reclaimed water pilot test for Orange County, Florida, to look at one of many innovative strategies aimed at using reclaimed water to meet increasing water demands in central Florida. The pilot facility, which we designed (Figure 1), went into operation in February 2004 and included ultrafiltration (UF), nanofiltration (NF), and ultraviolet (UV) disinfection processes.
Acronyms/
Abbreviations |
| EPA: |
U.S. Environmental Protection Agency |
| FDEP: |
Florida Department of Environmental Protection |
| NF: |
Nanofiltration |
| UF: |
Ultrafiltration |
| UV: |
Ultraviolet
disinfection |
In coordination with the Florida Department of Environmental Protection (FDEP), we compiled and analyzed water samples for all "full treatment" requirements (Chapter 62-610, Florida Administrative Code) including:
Primary and secondary drinking water standards, with primary being EPA enforceable standards for health and secondary being EPA aesthetic standards
Mutagenicity (the capacity to induce mutations)
Total organic carbon
Total organic halogen.
We used the pilot study to analyze an array of other drinking water constituents, including:
- Bacteria
- Viruses
- Protozoans
- Trihalomethane (THM) precursors
- Microconstituents (e.g., hormones and pharmaceuticals).
Quantitative analysis of many of these constituents fell outside the capabilities of most analytical labs, so we and Orange County teamed with the U.S. Geological Survey, Florida International University and the University of South Florida to make use of the highly specialized analytical capabilities of their various research laboratories.
Through this pilot, we along with the client and FDEP are on the forefront of research into the effectiveness of membrane technologies to treat reclaimed water, or recycled wastewater, for possible reintroduction into water supply sources.
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Figure 1: Orange County, Florida’s reclaimed water pilot test facility, outside (top) and inside (bottom) views.
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Interim Results were Successful
The pilot test began as a UF-NF system with a plan to add a UV system for final disinfection after sufficient data on the UF-NF process were collected. The UF and NF membranes were chosen for their ability to reduce total organic carbon and pass total dissolved solids and chloride. These features make it possible to meet FDEP standards, but also leave a less-aggressive concentrate stream that can be easily treated in a typical wastewater treatment facility.
In August of 2004, with six full months of data available, the UV system was added. At that time, coliform levels were not being met, and the UV was expected to provide the necessary disinfection. The process proved to reduce bacteria and other microorganisms in two challenge tests conducted by Orange County Utilities. These challenge tests introduced three types of surrogate microbial pathogens and bacteria of varying size upstream of the NF and upstream of the UV. The surrogate materials were injected and measured before and after the NF and UV to determine the integrity of the NF membranes and of the UV unit after extended use. Results showed that the NF removed the surrogate pathogens at a rate of more than 99 percent and the UV unit reduced the surrogates at a range of from 66 percent to more than 99 percent.
In July of 2005 the pilot facility was relocated to a second Orange County water reclamation facility to show that results could be repeated. The pilot process exhibited similar removal rates at the new location, showing that the plant was versatile and could be put into service in various locations of Orange County.
Chlorination
The pilot effluent met all requirements of the full treatment rule with the exception of nitrite and infrequent coliform detection. In addition, although the challenge tests proved that UV was reducing microorganisms in the water, daily sampling indicated that it was unable to destroy the colonies of regrowth that would occasionally slough off of the membranes and downstream piping. To correct this challenge, oxidize the nitrite, and meet potential disinfection requirements, a chlorination step was added to the process in December of 2004. This additional step was studied for its effectiveness and continued until the end of the pilot study in April of 2006. Though results of daily samples were inconclusive, additional focus studies showed that biogrowth and nitrite could be controlled with constant chlorine monitoring and feed rate adjustment.
Mutagenicity Test
In addition to the water quality parameters mentioned above, the full treatment rule requires that a pilot test show the "results of a biological testing procedure approved by the FDEP to determine the mutagenicity of the reclaimed water." The Orange County Utilities Laboratory, in conjunction with the University of South Florida, devised a mutagenicity testing protocol, which, if approved, would be the first of its kind in the State of Florida and would set a precedent for future pilot projects. In September of 2005, the FDEP began the approval process for this testing protocol. As of August 2006, results were pending.
Final Results
Orange County and PB operated the Reclaimed Water Pilot Test until April 28, 2006. It was agreed that the project had provided sufficient data to be considered for a full scale operation. |
