Partial denitrification anammox (PdNA) is an emerging wastewater treatment technology with the potential to increase process capacity and save on energy and carbon. PdNA circumvents potential issues with stability of the more familiar mainstream partial nitritation anammox (PNA) process. The PdNA process can be used to effectively remove ammonia, nitrate, and nitrite from mainstream municipal waste streams. To retain slow growing anammox, some sort of retention system is needed with media being a common solution to this problem. PdNA has been successfully implemented in mainstream full-scale systems in sand filters and with moving media. The goal of this study was to assess the denitrifying capabilities, anammox treatment capacity, and effective surface area to volume of two types of fixed media. A nitrifying pilot was set up to assess the effective surface area to volume. To assess the nitrifying and anammox ammonia removal capabilities of the fixed media, a fixed media PdNA system was installed in the second anoxic zone of a full-scale municipal wastewater treatment plant. The fixed media system consisted of three modules of sheets modified to mimic a plug flow system. After accounting for the estimated nitrate removal from mixed liquor, denitrification rates normalized to media surface area were 0.52 +/- 1.9 g/m2-day in the first module, 0.62 +/- 0.91 g/m2-day for the second module, and 0.56 +/- 0.90 g/m2-day for the third module. In ex situ batch testing it was found that maximum ex-situ anammox ammonia removal rates for the / Master of Science / Urban population growth has created a two-pronged problem for wastewater treatment plants. Plants in populated areas are seeing increases in flow along with growing space restrictions that limit new infrastructure construction. Additionally, rising environmental awareness from the public has spurred regulatory agencies to impose tighter limits on the quality of water leaving plants and entering sensitive watersheds. These factors have driven a need for treatment techniques that allow plants to operate better with their existing equipment.
Overall, this concept is known as process intensification. One such method that treatment plants are using to intensify wastewater treatment is the addition of plastic media into their existing tanks. This media provides additional surfaces for the microorganisms that biodegrade the pollutants in the wastewater to grow and allows waste to be treated faster in the same area. It also allows slow growing organisms to be retained in the system that would otherwise not have time to grow. Such slow-growing microbes are especially critical for the removal of ammonia, a toxic form of nitrogen that occurs in high concentrations in wastewater.
The partial denitrification-anammox process is an intensification process that leverages microbial metabolisms to convert nitrate to nitrite instead of denitrifying the nitrate all the way to nitrogen gas. Plants then let more ammonia pass through the aeration zone, where ammonia is converted to nitrate. The bleed through ammonia and the nitrite generated from partial denitrification is used by microbes called anammox, which denitrify without the addition of carbon. The full denitrification process requires externally added carbon, which is energy intensive to produce and expensive, and aeration requires energy to run the aeration blowers. Bypassing the full denitrification process using PdNA results in two-fold cost and energy savings.
The plastic media help slow-growing anammox bacteria attach and grow to achieve this aim. Most of the plants that use plastic media use media that is free floating in the tank. However, certain plants cannot use this floating plastic media because it can either plug up the system, or flow to the end of the treatment tank and have no way to get back to the front. In instances such as these it could be beneficial to use a type of media that is fixed in place.
One potential use of fixed media that has never been tried before is with partial denitrification with anammox. This research sets out to evaluate the effectiveness of fixed media with use in a partial denitrification anammox process and compare it to a treatment tank of moving media that is present at the same plant to find out whether it may be a viable option for retrofitting plants that cannot use moving media.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/118637 |
| Date | 18 April 2024 |
| Creators | Wieczorek, Nathan Vincent |
| Contributors | Civil and Environmental Engineering, Pruden-Bagchi, Amy Jill, Bott, Charles B., Knocke, William R. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Rights | Creative Commons Attribution 4.0 International, http://creativecommons.org/licenses/by/4.0/ |
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