Fort Walton Beach Council agenda — 12-24-2010 Regular — reading text

5 TSS, mg /L 20 -30 5 d TN, m / L No limit 3 0. 82- 1. 73 TP, mg /L No limit 1 0. 069 — 0. 415 Notes: 1. Nationwide technology based standards required by the Clean Water Act for all wastewater treatment plants. 2. Florida standards required by state law for discharge to specific nutrient sensitive water bodies. 3. Proposed in- stream water quality standards that would become end -of p- ipe limits unless a facility obtains a mixing zone or site - specific alternative criteria. Carollo Engineers 4 Packet Pg. 113  14. 1. c CURRENT NUTRIENT REMOVAL TECHNOLOGY Today more than 65 Florida plants with a total treatment capacity of over 500 million gallons per day (mgd) use various AWT technologies to produce high quality reclaimed water. However, these plants represent only a relatively small fraction of the plants in Florida. In order to achieve current AWT water quality limits, a plant generally must remove about 96% to 98% of TN and 85 to 88% of TP from raw sewage. At nearly all AWT plants in Florida, reclaimed water meeting AWT limits is achieved using a combination of a biological nutrient removal (BNR) treatment technology plus some form of filtration. BNR processes grow naturally occurring bacteria to remove the oxygen demanding organic pollutants, nitrogen, and phosphorus from raw sewage. Most of the nitrogen is released to the atmosphere as nitrogen gas while the phosphorus is Q CL removed with biosolids wasted from the plant. W c The TN in reclaimed water consists of inorganic nitrogen (ammonia and nitrates) and organic a nitrogen. The ammonia and nitrates can be removed down to low levels by conventional BNR processes — nitrification and denitrification with supplemental carbon (e. g. methanol) if U) 3 necessary. The presence in reclaimed water of soluble nitrogen and phosphorus compounds that c are not biodegradable ( also known as refractory compounds) ultimately sets the lowest concentrations possible at treatment plants that rely on biological treatment methods. Researchers call the refractory dissolved organic nitrogen ( RDON). RDON is present in many raw water supplies and thus is present in the influent to water reclamation facilities. RDON is CL also a byproduct of biological treatment and will be found in reclaimed water even if not found 0 in raw sewage. rn 0 The effluent TN and TP concentrations reported by Florida AWT plants are generally consistent 0 with the lowest effluent concentrations of TN and TP typically reported by researchers as a achievable with current BNR technologies. In other words, Florida AWT plants are already z removing nutrients as well or better than most BNR plants. z a ADDITIONAL TECHNOLOGIES TO MEET PROPOSED NUMERIC E NUTRIENT CRITERIA M a Water treatment technologies do exist to produce reclaimed water with any desired water quality such as the ultra pure water required for electronics manufacturing and high -pressure boiler feed water. Since most technologies that can achieve these limits are typically used for applications other than removing nutrients from reclaimed water, little data exists on their performance in removing nitrogen and phosphorus to meet NNC. The additional treatment technologies that might be used to meet numeric nutrient criteria include high -pressure membranes ( reverse osmosis and nano filtration), adsorption ( activated Carollo Engineers 5 Packet Pg. 114  74. 1. c carbon and reactive filtration), oxidation (ozone, UV, peroxide), chemical coagulation and precipitation, and ion exchange. Of the aforementioned additional treatment technologies, reverse osmosis ( RO) is a leading candidate technology when considering very low nutrient limits because of its ability remove nearly all constituents in the water to very low concentrations. In simple terms, RO is a selectively permeable barrier that rejects nearly all contaminants larger than a specific size, while letting water molecules through. A number of large water reclamation plants currently use RO to produce very high quality reclaimed water. These include the West Basin plant in El Segundo, California (22. 5 mg(i), the Scottsdale, Arizona Water Campus ( 14 mgd), the GWRS ( 70 mgd) plant in Orange County California, and four NEWater plants in Singapore ( Bedok, 8. 4 mgd; Kranji, 10. 6 mgd; Seletar, 5. 0 mgd; and Ulu Pandan, 39. 1 mgd) among others. All of these facilities have successfully used membrane technologies to produce exceptionally high quality water for other purposes than to remove nutrients. Specifically, the West Basin plant in El Segundo and the GWRS plant use; MF /RO treated reclaimed water to create saltwater intrusion barriers and for indirect potable reuse. The Scottsdale plant treats to drinking water standards and then injects MF /RO treated water into an aquifer to supplement drinking water supplies, and the four NEWater plants in Singapore; use MF /RO or UF/ RO to create high quality industrial water supplies for electronics manufacturing and to provide supplemental water to a reservoir used as a drinking water supply. Figure 1 provides a schematic representation of the sequence of treatment zones in the typical Florida water reclamation plant designed to meet AWT limits using BNR along with the selected additional technology of reverse osmosis membranes and associated concentrate disposal. 0 a a U Z Z C d E M U M 4. 0 Q Carollo Engineers 6 Packet Pg. 115  14. 1. c Advanced Wastewater Treatment AWT Anaerobic Anoxic Clarifier Disinfection L— Anoxic Aeration Aeration 0t Filters MF /RO Concentrate Treatment F Microfiltration MF) Reverse Osmosis ( RO) Product Water To AOP/ Stabilization Solids to Disposal Brine Crystallizer Concentrator Figure 1. Schematic illustration of the type of processes likely required for Florida wastewater plants to comply with the proposed numeric nutrient criteria. CHALLENGES ASSOCIATED WITH REVERSE OSMOSIS SYSTEMS