Browsing by Author "Detlef Knappe, Committee Member"

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Aerosolization and Quantification of Surrogate Biological Warfare Agents under Simulated Landfill Gas Conditions.
(2010-08-17) Prevost, Rossana; Morton Barlaz, Committee Chair; Francis Lajara De Los Reyes, Committee Member; Detlef Knappe, Committee Member
Assessment of Microbial UV Fluence-response using a Novel UV-LED Collimated Beam Apparatus.
(2010-06-28) Bowker, Colleen; Joel Ducoste, Committee Chair; Francis Lajara De Los Reyes, Committee Member; Detlef Knappe, Committee Member
Drinking Water Quality Assessment and Analysis of Centralized and Decentralized Wastewater Treatment Systems in the Philippines
(2009-08-10) Wellborn, Lauren Susan; Joel Ducoste, Committee Member; Detlef Knappe, Committee Member; Francis de los Reyes III, Committee Chair
The Philippines is a nation in Southeast Asia seeking to move forward in its development. The centralized and decentralized water and sanitation industries are growing, and a nongovernmental organization, Gawad Kalinga (GK), has taken a leading role to address issues of homelessness and poverty, significant problems throughout the country. This project had two main goals: to assess the effectiveness and sustainability of water and sanitation systems installed in villages built by Gawad Kalinga to help ensure systems installed in future villages are reliable; and to assess the microbial populations in three of the wastewater treatment plants (WWTPs) operated in Metro Manila, with the goal of identifying organisms present in the treatment plants to allow for improved design and operation of future WWTPs. Water quality was measured at 27 GK sites (from 43 sources) using Hach portable laboratory equipment and 3M coliform petri plates. The following parameters were measured: pathogens, total coliforms and thermotolerant bacteria (E. coli), acidity, alkalinity, arsenic, carbon dioxide, chloride, chlorine dioxide, free and total chlorine, color, total dissolved solids, copper, hardness, iron, manganese, nitrate, nitrite, ammonia, pH, dissolved oxygen, phosphate, sulfate, sulfide, suspended solids, temperature and turbidity. Results show that 95% of the sites visited tested positive for pathogens, as indicated by the Hach PathoScreen test. Many wells (52%) tested positive for total coliforms. E. coli was found in several of the wells (16%), but was not found in any municipally provided water source. Nitrate levels above the WHO and Philippine national standard of 35 mg/L were found in 30% of sources measured, and arsenic levels at or above the WHO standard of 50 ppb was found in one site. Interviews with 154 beneficiaries indicated that GK was responsible for a net improvement in water availability and sanitation access for 28% of its residents after they moved to GK villages. Three WWTPs were sampled for molecular analysis: University of the Philippines (UP), PhilAm, and Makati South. These three plants serve different communities and are designed slightly differently. Terminal restriction fragment length polymorphism (T-RFLP) was performed on samples taken from each of the plants in February, 2008 and again in March (UP) or June (PhilAm, Makati South) to determine changes in the microbial communities over time. Results indicate that though there was a change over time (most significantly for the UP treatment plant), most of the terminal restriction fragments do not match with known fragments, indicating most of the species in the samples are not in the T-RFLP database. Cloning results confirm the presence of potentially novel species, and approximately 64% of species cloned did not match 98% identity with known sequences. Results that were able to be matched with known species via phylogeny indicate that ÃŽÂ²-Proteobacteria comprise the largest fraction of microorganisms in the sampled WWTPs, followed by Firmicutes. The Makati South WWTP had lowest levels of diversity and richness among the three plants, but Manila Water Services, Inc reports that Makati South is the most reliable WWTP among those sampled for effluent water quality.
Evaluation of Computational Fluid Dynamics (CFD) for Modeling UV-Initiated Advanced Oxidation Processes
(2009-01-30) Alpert, Scott Michael; Karl Linden, Committee Member; David Ollis, Committee Member; Detlef Knappe, Committee Member; Joel Ducoste, Committee Chair
The use of ultraviolet-initiated (UV-initiated) advanced oxidation processes (AOP) is rapidly becoming an attractive alternative for the degradation of emerging organic contaminants that are not easily removed using conventional water treatment processes. Design and optimization of UV/H2O2 systems must incorporate both reactor design (hydrodynamics, lamp orientation) and chemical kinetics (reaction mechanisms, kinetic rate constants). This research lays the groundwork for a protocol for using CFD models to simulate UV-initiated AOPs and, in doing so, provides the start for an improved design process to meet the needs of the water treatment community. In this CFD model, the combination of turbulence sub-models, fluence rate sub-models, and kinetic rate equations results in a comprehensive and flexible design tool for predicting the effluent chemical composition from a UV-initiated AOP reactor. To validate the CFD simulation, the results of the model under various operating conditions were compared to pilot reactor trials for the target contaminants of an organic dye (methylene blue) and an antibiotic (sulfamethoxazole). The CFD model tends to under-predict the percent removal of methylene blue within the reactor. In addition, the percent difference between the pilot and the CFD results increases with increasing flow rates. Similar to the methylene blue trials, the CFD simulations for sulfamethoxazole degradation under-predict the percent removals measured in the pilot reactors. The sensitivity to model parameters was evaluated. The MSSS sub-model predicted higher fluence rate values than that of the RAD-LSI sub-model. This increase in fluence rate translates to higher contaminant removal percentages predicted for both methylene blue and SMX. The turbulence sub-model selection for this reactor configuration was found to not significantly impact the predicted removal for methylene blue. As expected, the overall degradation of methylene blue was a strong function of the value of the second-order kinetic rate constant describing the reaction between methylene blue and the hydroxyl radical. Further, the overall removal of methylene blue was shown to be sensitive to the concentration of the radical scavenger dissolved organic carbon in the water matrix.
A Method to Quantify In-Situ Growth Rates of a Filament and a Floc-former Using Real-time Quantitative PCR
(2007-12-23) Nguyen, Vivi Le; Detlef Knappe, Committee Member; Morton Barlaz, Committee Member; Francis de los Reyes, Committee Chair
Microbial ecology of intermittently aerated reactors treating swine wastewater: molecular approaches for identifying key nitrogen-removing bacteria
(2007-08-10) Mota, Cesar Rossas; Jiayang Cheng, Committee Member; Michael Hyman, Committee Member; Detlef Knappe, Committee Member; Morton Barlaz, Committee Member; Francis L. de los Reyes III, Committee Chair
Modeling Chloramines Formation in Turbulent Flow
(2004-12-03) Liu, Yanjin; Joel J. Ducoste, Committee Chair; George Roberts, Committee Member; Ranji Ranjithan, Committee Member; Detlef Knappe, Committee Member
A study was performed to investigate the use of Computational Fluid Dynamics (CFD) for the analysis of ammonia injection methods to produce chloramines. Three types of ammonia diffusers were simulated and tested in the present work. In this study, CFD fluid flow and turbulence models were combined with chloramines kinetic models to predict downstream spatial distribution of residual free chlorine. As part of this study, two chemical species transport models, single fluid model (SFM) and multi-fluid model (MFM), were evaluated. In addition, several turbulence models were combined with the MFM approach to investigate the impact of turbulent model selection on the free chlorine residual. The turbulence models examined in this study include the standard k-e, RNG k-e, and k-ω models. All model predictions were compared with experimental measurements of the free chlorine residual at different upstream and downstream locations from the ammonia injection point. The experimental tests include the placement of a perforated baffle to investigate the impact of background turbulence on the overall mixing process. A simple flow visualization experiment using an inert tracer was also performed to qualitatively evaluate the fluid flow pattern in the vicinity of the ammonia injection point. Furthermore, a sensitivity analysis was performed to investigate the impact of several turbulent mixing time scales (eddy-dissipation time scale, Kolmogorov time scale, and Corrsin time scale) on the residual free chlorine concentration. Results showed that the flow field with the standard turbulence model and RNG turbulence model reasonably matched the fluid flow pattern characterized by the flow visualization test. The CFD/MFM modeling approach was found to better predict the free chlorine spatial distribution than the CFD/SFM approach. Moreover, results showed that the CFD chloramines model with the standard or RNG turbulence model was able to predict the downstream chloramines formation for a cone-shape diffuser and a three-bar diffuser. Results also showed that the CFD chloramines model with the EDT or KOLM time scale was able to predict the downstream chloramines formation for the cone-shape diffuser and the three-bar diffuser. However, the CFD chloramines model with different turbulence models consistently over-predicted the residual free chlorine for a T-bar diffuser. This could be explained by the complex turbulent structure, produced by a strong inlet jet, was not properly characterized using these two-equation turbulence models. The CFD/MFM chloramines model was found to improve the prediction of the free chlorine spatial distribution for the T-bar diffuser when the Corrsin time scale was used. In addition, a baffle, placed upstream from the injection point to reduce the strong inlet jet, was found to have significant impact on the mixing and chloramines formation for the T-bar diffuser mixer case. Overall, the CFD/MFM chloramines models of the baffle configuration better predicted residual free chlorine for all three diffuser configurations than the un-baffled reactor cases.
Numerical Simulation of UV Disinfection Reators: Impact of Fluence Rate Distribution and Turbulence Modeling
(2004-12-30) Liu, Dong; David Ollis, Committee Member; Francis de los Reyes III, Committee Member; Detlef Knappe, Committee Member; Joel. J. Ducoste, Committee Chair
This study investigated two most important parts for numerical simulation of UV disinfection reactors: fluence rate distribution and turbulence modeling. In the first part, the evaluation of alternative fluence rate distribution models, including Multiple Point Source Summation (MPSS), Multiple Segment Source Summation (MSSS), Line Source Integration (LSI), Modified LSI (RAD-LSI), Discrete Ordinate (DO) and View Factor models, has been performed. As part of the evaluation, a complete MSSS model, which accounts for the quartz sleeve thickness while calculating refraction angles, was developed. In addition, a simple attenuation factor approach was introduced to integrate the physics of reflection, refraction, and absorption effects into the LSI model. In the second part, six turbulence models, including standard k-e, k-e RNG, k-w(88), revised k-w(98), Reynolds Stress Transport (RST), and Two-Fluid (TF), were investigated and applied to the flow field simulation of a closed conduit polychromatic UV reactor. Predicted flow field, kinetic turbulence energy, and turbulence energy dissipation rate were compared with the experimental data from a Particle Image Velocimetry (PIV) analysis at four locations close to the UV lamps. All of the predicted flow fields were combined with a MSSS fluence rate model and three different microbial inactivation kinetic models to simulate the disinfection process at two UV lamp power conditions. Microbial transport was simulated using the Lagrangian based particle tracking method. As part of the turbulence model analysis, the fluence distribution and the effluent microbial inactivation predicted by all turbulence models were reported. In the fluence rate distribution study, the results showed that models, neglecting the effects of refraction, deviated significantly from the experimental data. In addition, the MSSS approach or models that incorporated the MSSS concept were found to agree well with the experimentally measured fluence rate distribution. Moreover, little difference was found between the results of the MSSS model with quartz sleeve thickness and UVCalc_3D, which does not model the quartz sleeve thickness in the refraction angle calculation but uses a factor to account for the effects of the quartz sleeve on the fluence rate. The attenuation factor combined with LSI model was found to match the MSSS model predictions, while reducing the computational cost. The results show that the fluence distributions and the effluent inactivation level were sensitive to the turbulence model selection. The level of sensitivity was a function of the operating conditions and the UV response kinetics of the microorganisms. In the turbulence model study, the results show that operating conditions that produce higher log inactivation or microorganisms with higher sensitivity to UV will show greater sensitivity to the turbulence model selection. In addition, a broader fluence distribution was found with turbulence models that predicted a larger wake region behind the lamps and greater turbulent mixing characteristics. Overall, the results of this study suggest that numerical simulations of UV processes using CFD should be initially validated with experimental bioassay tests prior to its use as a tool for understanding and evaluating the UV disinfection performance for a specific reactor design and target microorganism.
Performance of an Onsite Wastewater Treatment System and Analysis of the Microbial Populations in the Wastewater.
(2010-06-30) Vazquez Pineiro, Mariann; Francis Lajara De Los Reyes, Committee Chair; Detlef Knappe, Committee Member; Sanmugavadivel Ranjithan, Committee Member
Performance of Grease Abatement Systems.
(2010-07-22) Gallimore, Erin; Joel Ducoste, Committee Chair; Francis Lajara De Los Reyes, Committee Member; Detlef Knappe, Committee Member
Production of Co-Siderophore Complexes by Ligand-Promoted Dissolution
(2009-07-13) Bi, Yuqiang; Owen Duckworth, Committee Chair; Dean Hesterberg, Committee Member; Detlef Knappe, Committee Member
Recent research indicates that siderophores, a class of biogenic ligands with known exceptional affinity for Fe(III), can also strongly complex Co(III), an element essential to normal metabolic function of microbes and animals. This study was conducted to examine the siderophore-promoted dissolution rates and mechanisms of Co from model synthetic Co-bearing minerals to elucidate the role of siderophores in biogeochemical processes of Co. Dissolution of heterogenite (CoOOH) and four Co-goethites (Co-FeOOH) with different levels of Co substitution were investigated in the presence of a trihydroxamate siderophore, desferrioxamine B (DFOB), using batch and flow-through experiments, respectively. By measuring the complex and total metal concentrations in dissolution products, dissolution rates via multiple pathways were measured as a function of pH. Results showed that DFOB promoted dissolution of Co from Co-bearing minerals via pH-dependent mechanisms. For heterogenite, ligand-promoted dissolution was the dominant pathway at neutral to alkaline pH, while reductive dissolution became dominant for pH < 6. Cobalt substitution in Co-goethite resulted in increased total dissolution rates of both Co and Fe, but ligand-promoted and reductive Co dissolution pathways were difficult to examine due to the slow dissolution rates. The fast dissolution rate of heterogenite, coupled with the high affinity of Co(III) for DFOB, suggests that siderophore-promoted dissolution of Co(III) oxides is a biogeochemically favorable process. Although the association of Co with Fe oxide mineral may limit the Co dissolution rate, siderophore-promoted Co dissolution may still be an effective enough way to increase Co bioavailability. The results also suggest the possibility of radionuclide 60Co by siderophores from recalcitrant Fe oxide phases, which may be important to the fate and transport of 60Co in contaminated environments.
Remediation of Soil - Sorbed Cesium Through the Process of Clay Fines Dispersion and Piping
(2008-08-03) Kunberger, Tanya Marie King; Roy Borden, Committee Member; Detlef Knappe, Committee Member; Mohammed Gabr, Committee Chair; Dean Hesterberg, Committee Co-Chair