Facing the pressure of population growth and global warming, this dissertation provided an array of innovative carbon-efficient wastewater treatment technologies for resource recovery, process intensification, and anammox featured next generation biological nutrient removal (BNR) technologies. These technologies aim to supplant traditional carbon-intensive treatment processes with more sustainable alternatives. To this end, the dissertation first comprehensively reviewed what resources can be recovered from wastewater, and how these valuable resources can contribute to the carbon neutrality in water resource reclamation facilities (WRRFs) and help achieve sustainable society development. Then, the effect of mixed liquor recycle (MLR) configurations on the process intensification through continuous-flow aerobic granulation was explored in plug flow reactors. The results demonstrated that MLR configuration could hinder the sludge granulation, but the hindrance could be alleviated to some extent by its location change. In order to eliminate the energy consuming MLR, endogenous denitrification was taken advantage through a synergistic integration with partial nitrification, partial denitrification anammox (PdNA), and enhanced biological phosphorus removal (EBPR). This idea was tested in a pilot setup treating real primary effluent under highly variable influent conditions and low temperatures. The results showcased substantial carbon savings while meeting the stringent effluent requirements. To take a deeper dive into the PdNA performance and the underlying mechanisms, two parallel pilot-scale moving bed biofilm reactor (MBBR) treatment trains fed with methanol and glycerol, respectively, were operated in a local WRRF. Their efficacies in achieving stringent nutrient removal targets and carbon savings were compared. The impacts of operational conditions on the mechanisms and performance were elucidated. In the culmination of this dissertation, a sidestream process intensification and resource recovery technique, namely thermal hydrolysis pretreatment (THP) enhanced anaerobic digestion (AD), was experimented to compare the efficiencies between thermophilic and mesophilic AD when integrated with THP. To sum up, this dissertation not only advanced our understanding of carbon-efficient wastewater treatment processes but also laid the groundwork for their practical implementation, contributing to the global effort towards sustainability. / Doctor of Philosophy / Wastewater treatment consumes 3-4% of the energy produced in the U.S. and contributes to approximately 1.6% global greenhouse gas emissions. This dissertation aims to advance a series of carbon-efficient technologies specifically tailored for sustainable wastewater treatment. To this end, a variety of valuable resources that can be recovered or reused in wastewater treatment plants was firstly reviewed. Then, an advanced technology that can turn dispersed bacteria into bacteria aggregates was tested with real wastewater in a local wastewater treatment plant. Although these bacteria aggregates allow more wastewater to be treated with less small footprint, which was great, it was realized from this study that the formation of these bacteria aggregates was hindered by the nitrate water recycle which has been commonly practiced for using influent carbon for nitrogen removal. This nitrate water recycle consumed excessive energy for its high flow rate. To save this energy, a novel bioprocessing design was developed to eliminate the need for this nitrate water recycle by using carbon stored in bacterial cells. This new design also incorporated phosphorus recovery capacity and a low carbon nitrogen removal technique into one consolidated system to create an all-in-one solution to meet the stringent wastewater treatment requirement. This low carbon nitrogen removal technique harnessed a special group of bacteria that can use ammonia to reduce nitrite to nitrogen gas. Hence, only minor carbon source needs to be provided to reduce nitrate to nitrite for these bacteria to utilize. Two types of carbon sources, namely methanol and glycerol, were compared in a pilot-scale study to understand their efficiencies in generating nitrite. Results indicated that although both types of carbon sources can work, methanol is better suited for low strength wastewater treatment. These results provided an engineering basis for the full-scale application of the technology in the same wastewater treatment plant where the pilot study was performed. Besides liquid treatment, a carbon efficient solid treatment technology was also studied. The bottleneck constraining the rate of sewage sludge conversion to flammable menthane gas was identified, which provided engineering guidance for the design of the solid treatment process that can destroy more sewage sludge within smaller reactor spaces. In essence, this dissertation offers promising solutions for modern wastewater treatment plants to achieve low carbon wastewater treatment without compromising the treatment performance.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/119139 |
| Date | 28 May 2024 |
| Creators | Wang, Jiefu |
| Contributors | Civil and Environmental Engineering, Wang, Zhiwu, Novak, John Thomas, Pruden-Bagchi, Amy Jill, Wilson, Christopher Allen |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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