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Optimization of Glycerol or Biodiesel Waste Prefermentation to Improve EBPR
Title
Optimization of Glycerol or Biodiesel Waste Prefermentation to Improve EBPR.
Creator
Ghasemi, Marzieh, Randall, Andrew, Duranceau, Steven, Lee, Woo Hyoung, Jimenez, Jose, University of Central Florida
Abstract / Description
The enhanced biological phosphorus removal (EBPR) process efficiency relies on different operational and process conditions especially the type of carbon source available in the wastewater. Acetic acid and propionic acid are the two major volatile fatty acids (VFAs) found in domestic wastewater which can drive biological phosphorus (P) removal to the desired level. However, often domestic wastewater does not have a sufficient amount of VFAs. Due to high acetate and propionate production-cost,...
Show moreThe enhanced biological phosphorus removal (EBPR) process efficiency relies on different operational and process conditions especially the type of carbon source available in the wastewater. Acetic acid and propionic acid are the two major volatile fatty acids (VFAs) found in domestic wastewater which can drive biological phosphorus (P) removal to the desired level. However, often domestic wastewater does not have a sufficient amount of VFAs. Due to high acetate and propionate production-cost, it is not economic to add acetate and propionate directly in full-scale wastewater treatment plants. This brought up the idea of using external carbon sources (e. g. molasses has been used successfully) in EBPR systems that can be converted to VFAs through a fermentation process. On the other hand, biodiesel fuels have been produced increasingly over the last decade. Crude glycerol is a biodiesel production major by-product that can be used as an external carbon source in wastewater treatment plant. Therefore, the main objective of this research is to optimize the glycerol/biodiesel waste fermentation process' operational conditions in pursuit of producing more favorable fermentation end-products (i. e. a mixture of acetic acid and propionic acid) by adding glycerol to a prefermenter versus direct addition to the anaerobic zone or fermentation with waste activated sludge. For this reason, different prefermenter parameters namely: mixing intensity, pH, temperature and solids retention time (SRT), were studied in a small scale fermentation media (serum bottles) and bench scale semi-continuous batch prefermenters. Experimental results revealed that glycerol/biodiesel waste fermentation resulted in a significant amount of VFAs production with propionic acid as the superior end-product followed by acetic acid and butyric acid. The VFA production was at its highest level when the initial pH was adjusted to 7 and 8.5. However, the optimum pH with respect to propionic acid production was 7. Increasing the temperature in serum bottles favored the total VFA production, specifically in the form of propionic acid. Regarding the mixing energy inconsistent results were obtained in the serum bottles compared to the bench scale prefermenters. The VFA production in mixed serum bottles at 200 rpm was higher than that of un-mixed ones. On the other hand, the unmixed or slowly mixed bench scale prefermenters showed higher VFA production than the mixed reactors. However, the serum bottles did not operate long enough to account for biomass acclimation and other long-term effects that the prefermenter experiments could account for. As a consequence one of the most important and consistently results was that VFA production was significantly enhanced by reducing mixing intensity from 100 rpm to 7 rpm and even ceasing mixing all together. This was true both for primary solids and glycerol. In addition propionate content was high under both high and low intensity, and adding glycerol also increased the fraction of primary solids that formed propionic acid instead of acetic acid. Increasing the SRT from 2 to 4 days increased the VFA production about 12% on average. In order to investigate the effect of glycerol on EBPR process efficiency two identical A2/O systems were monitored for 3 months. Experimental results suggested that glycerol addition could increase the P removal efficiency significantly. Adding glycerol to the prefermenter rather than the anaerobic zone resulted in a lower effluent soluble ortho phosphorus (SOP) (0.4 mg-P/L vs. 0.6 mg-P/L) but the difference was apparently statistically significant. Future experimentation should be done to determine if this effect is consistent, especially in carbon poor wastewaters. Also it would be desirable to conduct a longer pilot study or a full scale study to determine if this improvement in effluent SOP remains true over a range of temperature and changing influent conditions.
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Date Issued
2015
Identifier
CFE0006310, ucf:51612
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0006310
Sustainability Assessment of Wind Energy for Buildings
Title
Sustainability Assessment of Wind Energy for Buildings.
Creator
Noori, Mehdi, Tatari, Mehmet, Oloufa, Amr, Nam, Boo Hyun, University of Central Florida
Abstract / Description
Due to increasing concerns for global climate change, onshore and offshore wind energy technologies have stimulated a tremendous interest worldwide, and are considered as a viable solution to mitigate the environmental impacts related to electricity generation. Although wind energy technologies have been considered as one of the cleanest energy sources, they have a wide range of direct and indirect environmental impacts when the whole supply chain is considered. This study aims to quantify...
Show moreDue to increasing concerns for global climate change, onshore and offshore wind energy technologies have stimulated a tremendous interest worldwide, and are considered as a viable solution to mitigate the environmental impacts related to electricity generation. Although wind energy technologies have been considered as one of the cleanest energy sources, they have a wide range of direct and indirect environmental impacts when the whole supply chain is considered. This study aims to quantify the direct and indirect environmental impacts of onshore and offshore wind power technologies by tracing all of the economy-wide supply chain requirements. To accomplish this goal, we developed a comprehensive hybrid life cycle assessment (LCA) model in which process-based LCA model is combined with the economic input-output (EIO) analysis. The analysis results show that on average, concrete and steel and their supply chains are responsible for 37% and 24% of carbon footprint, consequently. On average, offshore wind turbines produce 48% less greenhouse gas emissions per kWh produced electricity than onshore wind turbines. For the onshore wind turbines, concrete, aggregates, and crushed stone approximately consume 95% of total water in this construction phase. On the other hand, concrete, lead, copper, and aggregate are responsible for around 90% of total water for the offshore wind turbines. It is also found that the more capacity the wind turbine has, the less environmental impact the wind turbine generates per kWh electricity. Moreover, based on the economic and environmental impacts of studied wind turbines and also three more nonrenewable energy sources, this study develops a decision making framework to understand the best energy source mix for a building in the state of Florida. This framework accounts for the uncertainty in the input material by deploying a Monte Carlo simulation approach. The results of decision making framework show that natural gas is a better option among nonrenewable sources. On the other hand, V90-3.0 MW offshore wind turbine is the best source of energy among renewable energy sources for a building.The findings of this research are critical for policy makers to understand the direct and indirect environmental impacts of different onshore and offshore wind energy systems. Also this study furnishes the decision maker with a range of possible energy mixes based on different economic and environmental weights.
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Date Issued
2013
Identifier
CFE0005038, ucf:50017
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0005038
Biological Nutrient Removal (BNR) Process Optimization and Recovery of Embedded Energy Using Biodiesel By-product
Title
Biological Nutrient Removal (BNR) Process Optimization and Recovery of Embedded Energy Using Biodiesel By-product.
Creator
Salamah, Sultan, Randall, Andrew, Duranceau, Steven, Chopra, Manoj, University of Central Florida
Abstract / Description
Enhanced biological phosphorus removal (EBPR) as well as biological nitrogen removal require a carbon source to be carried out. Volatile fatty acid (VFAs) (mainly acetic and propionic acids) are the major driving force for EBPR. Many domestic wastewaters have an insufficient amount of VFAs. However, carbon sources such as acetic and propionic acids can be produced using primary solids fermentation process. Due to the cost of VFA production, an external carbon source can be added to the...
Show moreEnhanced biological phosphorus removal (EBPR) as well as biological nitrogen removal require a carbon source to be carried out. Volatile fatty acid (VFAs) (mainly acetic and propionic acids) are the major driving force for EBPR. Many domestic wastewaters have an insufficient amount of VFAs. However, carbon sources such as acetic and propionic acids can be produced using primary solids fermentation process. Due to the cost of VFA production, an external carbon source can be added to the biological nutrient removal (BNR) system that can be fermented to provide the desired VFAs. Glycerol (biodiesel by-product) offers a solution to reduce carbon addition cost if can be fermented to acetic and propionic acid or can be used directly as an external carbon substrate for EBPR and denitrification. Using glycerol in wastewater treatment can also offset the biodiesel plant disposal cost and reduce the BNR chemical cost. The main objective of this study was to optimize the prefermentation process and optimize the BNR system using glycerol as an external carbon source. In this work, Optimization of the prefermentation process using glycerol, mixing, and hydrogen gas addition was evaluated. EBPR performance within an A2O-BNR system was evaluated using either a direct glycerol method to the anaerobic zone or by co-fermentation with primary solids. Also, optimization of the nitrogen removal (specifically denitrification) efficiency of a 5-stage BardenphoTM BNR system using either a direct glycerol method to the second anoxic zone or by co-fermentation with primary solids was evaluated. It was found in this study that glycerol was an efficient external carbon substrate for EBPR as well as biological nitrogen removal. The prefermentation experiment showed that glycerol co-fermentation with primary solids produced significantly higher (p(<)0.05) VFAs than primary solids fermentation alone, even more than the possible value from the added glycerol (427 mg-COD/L). The increased VFAs imply that the glycerol addition stimulated additional fermentation of primary solids. Lowering the prefermenter mixing energy (50 to 7 rpm) resulted in a significant increase in VFAs production (80%). Also, purging the headspace of the prefermenter with hydrogen gas did not lead to more VFAs, but significantly (p(<)0.05) increased the propionic acid to acetic acid ratio by 41%. In the A2O-BNR pilot plant experiment, it was found that glycerol is a suitable renewable external substrate to drive enhanced EBPR as well as denitrification. The results from both locations of glycerol addition (direct vs. fermented) were beneficial to the BNR system. Both systems had similar effluent quality and achieved total nitrogen (TN) and total phosphorus (TP) removals up to 86% and 92% respectively. The 5-stage BardenphoTM BNR experiment investigated the location of glycerol addition (direct vs. fermented) on the performance of denitrification in the second anoxic zone and the overall performance. The results from both systems were that glycerol was beneficial to the BNR system and had virtually similar effluent quality. Both systems achieve complete denitrification and excellent removal of TN and TP up to 95% and 89% respectively. Also, the pilot that received fermented glycerol had significantly higher VFAs loading and lower observed yield. The side-stream prefermenter effluent flowing to the second anoxic reactor did not cause high effluent ammonia (NH3) concentration. In summary, the location at which glycerol was added did not affect effluent quality for nitrogen and phosphorus. However, glycerol addition and mixing energy did impact prefermenter performance and effluent quality.
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Date Issued
2017
Identifier
CFE0006788, ucf:51826
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0006788
Nano-Particles in Multi-Scale Composites and Ballistic Applications
Title
Nano-Particles in Multi-Scale Composites and Ballistic Applications.
Creator
Gibson, Jason, Gou, Jihua, Raghavan, Seetha, Bai, Yuanli, Zhai, Lei, University of Central Florida
Abstract / Description
Carbon nanotubes, graphene and nano sized core shell rubber particles have all been extensively researched for their capability to improve mechanical properties of thermoset resins. However, there has been a lack of research on their evaluation for energy absorption in high velocity impact scenarios, and the fundamental mechanics of their failure mechanisms during highly dynamic stress transfer through the matrix. This fundamental research is essential for laying the foundation for...
Show moreCarbon nanotubes, graphene and nano sized core shell rubber particles have all been extensively researched for their capability to improve mechanical properties of thermoset resins. However, there has been a lack of research on their evaluation for energy absorption in high velocity impact scenarios, and the fundamental mechanics of their failure mechanisms during highly dynamic stress transfer through the matrix. This fundamental research is essential for laying the foundation for improvement in ballistic performance in composite armor. In hard armor applications, energy absorption is largely accomplished through delamination between plies of the composite laminate. This energy absorption is accomplished through two mechanisms. The first being the elongation of the fiber reinforcement contained in the resin matrix, and the second is the propagation of the crack in between the discreet fabric plies. This research aims to fundamentally study the energy absorption characteristics of various nano-particles as reinforcements in thermoset resin for high velocity impact applications. Multiple morphologies will be evaluated through use of platelet, tubular and spherical shaped nano-particles. Evaluations of the effect on stress transfer through the matrix due to the combination of nano sized and micro scale particles of milled fiber is conducted. Three different nano-particles are utilized, specifically, multi-walled carbon nanotubes, graphene, and core shell rubber particles. The difference in surface area, aspect ratio and molecular structure between the tube, platelet and spherical nano-particles causes energy absorption through different failure mechanisms. This changes the impact performance of composite panels enhanced with the nano-particle fillers. Composite panels made through the use of dispersing the various nano-particles in a non-contact planetary mixer, are evaluated through various dynamic and static testing, including unnotched cantilever beam impact, mixed mode fracture toughness, split-Hopkinson bar, and ballistic V50 testing.The unnotched cantilever beam testing showed that the addition of milled fiber degraded the impact resistance of the samples. Addition of graphene nano platelets unilaterally degraded impact resistance through the unnotched cantilever beam testing. 1.5% loading of MWCNT showed the greatest increase in impact resistance, with a 43% increase over baseline.Determining the critical load for mixed mode interlaminar shear testing can be difficult for composite panels that bend without breaking. An iterative technique of optimizing the coefficient of determination, R2, in linear regression is developed for objectively determining the point of non-linearity for critical load. This allows for a mathematical method of determination; thereby eliminating any subjective decision of choosing where the data becomes non-linear. The core shell rubber nano particles showed the greatest strain energy release rate with an exponential improvement over the baseline results.Synergistic effects between nano and micro sized particles in the resin matrix during transfer of the stress wave were created and evaluated. Loadings of 1% milled carbon fiber enhanced the V50 ballistic performance of both carbon nanotube and core shell rubber particles in the resin matrix. However, the addition of milled carbon fiber degrades the impact resistance of all nano-particle enhanced resin matrices. Therefore, benefits gained from the addition of micro-sized particles in combination with nano-sized particles, are only seen in high energy impact scenarios with micro second durations.Loadings of 1% core shell rubber particles and 1% milled carbon fiber have an improvement of 8% in V50 ballistic performance over the baseline epoxy sample for 44 mag single wad cutter gas check projectiles. Loadings of 1% multi-walled carbon nanotubes with 1% milled carbon fiber have an improvement of 7.3% in V50 ballistic performance over the baseline epoxy sample.The failure mechanism of the various nano-particle enhanced resin matrices during the ballistic event is discussed through the use of scanning electron microscope images and Raman spectroscopy of the panels after failure. The Raman spectroscopy data shows a Raman shift for the fibers that had an enhancement in the V50 performance through the use of nano-particles. The Raman band for Kevlar(&)#174; centered at 1,649 cm-1 stemming from the stretching of the C==O bond of the fiber shows to be more sensitive to the residual axial strain, while the Raman band centered at 1,611 cm-1 stemming from the C-C phenyl ring is minimally affected for the CSR enhanced panels due to the failure mechanism of the CSR particles during crack propagation.
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Date Issued
2013
Identifier
CFE0004849, ucf:49714
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0004849