Theses
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Browsing Theses by Discipline "Biological and Agricultural Engineering"
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- The Accuracy of Bioretention Cell Installations per North Carolina Design Standards and the Efficacy of Permeable Pavement with Internal Water Storage for Thermal Mitigation.(2012-03-09) Wardynski, Bradley; William Hunt, Chair; Gregory Jennings, Member; Michael Vepraskas, Minor
- Advanced Oxidation of Toluene using Ni-olivine Catalysts.(2011-06-17) Mbaneme, Veronica; Praveen Kolar, Chair; Charles Smith, Minor; Michael Boyette, Member; Mari Chinn, Minor
- Agricultural Robotics Using Absolute Position Sensors on a Zero Turning Radius Platform(2007-05-04) Powell, Nathaniel B; Gary Roberson, Committee Member; Mike Boyette, Committee Chair; Larry Stikeleather, Committee Member; Doug Barlage, Committee MemberAutonomous field equipment which can successfully replace human operators on tractors and other equipment may revolutionize agriculture. Replacing current field equipment such as large tractors with autonomous machines designed so that one person can supervise multiple machines will make it possible to use more machines without increasing the number of human operators needed. This makes it feasible to use smaller machines, which have benefits for cultivation, safety and the cost of purchasing and maintaining the equipment. This research is a step in the process of developing autonomous equipment. Using a zero turning radius vehicle, a prototype autonomous vehicle was constructed which measures position with a differential global positioning system (DGPS) receiver. A real time kinematic GPS (RTK-GPS) receiver was used for development and testing to obtain the most accurate results available. This work built upon previous autonomous navigation work using different sensors including a laser positioning system and a machine vision system. In addition to the GPS receiver an electronic compass was used to aid with turning behavior. These sensors were coordinated using inexpensive microcontrollers as input processors and a third microcontroller to coordinate the inputs and control the machine by controlling electronic actuators installed on the steering mechanisms. A simple control algorithm was implemented by combining the crosstrack and angular deviations from the reference path and applying a control input to the actuators based on that combined or "aggregate" error. The control input was calculated using a the traditional Proportional-Integral-Derivative controller. The system was developed and tested on a flat grassy lawn bordered by trees and buildings which provided an ideal simulation of a landscape management application. A straight line path 45 meters in length was set up for testing the machine. The machine started at one end of this path and navigated to the other end. The performance was measured by recording the position reported by the RTK-GPS on a handheld computer and calculating the crosstrack error between the recorded position and the straight line path. The results demonstrated that the autonomous navigation system was able to navigate the machine from point to point. The performance did not meet the desired standards of precision and was characterized by oscillations which were of higher amplitude and higher frequency than is acceptable for agricultural machines. Limitations in the microcontrollers' ability to store and manipulate the position data were a major factor. However, the potential of small zero turning radius platforms for agricultural robotics is significant and the simplicity of controlling such vehicles is a great advantage over traditional tractors.
- Alkaline Pretreatment of Coastal Bermudagrass for Bioethanol Production(2009-03-19) Wang, Ziyu; Ratna R. Sharma, Committee Member; Steven W. Peretti, Committee Member; Jay J. Cheng, Committee ChairSodium hydroxide and lime pretreatments of coastal bermudagrass for enhanced reducing sugars recovery were investigated in this study. In the study of sodium hydroxide pretreatment, coastal bermudagrass was pretreated with 0.5% to 3% (w/v) NaOH solutions for 15 min to 90 min at 121°C. For lime pretreatment, a variety of temperatures (room temperature to 121°C) at a range of residence times with different lime loadings (0.02 to 0.20 g/g dry biomass) were examined. Sodium hydroxide pretreatment at 121°C was more effective than lime pretreatment with regard to lignin removal with an average difference of 55%. After enzymatic hydrolysis with excessive cellulases and cellobiase, the best total reducing sugars yield for lime pretreatment was 78% of the theoretical maximum which is comparable to 77% for NaOH pretreatment at 121°C. The optimal conditions for NaOH pretreatment at 121°C are 15 min and 0.75% NaOH under which glucan and xylan conversion rates were approximately 91% and 65% respectively. As for lime pretreatment, the best condition is 100°C for 15 min with a lime loading of 0.1 g/g dry biomass under which 87% of glucan and 68% of xylan were converted to glucose and xylose respectively. The coastal bermudagrass pretreated under the recommended conditions with NaOH and lime was hydrolyzated with different enzyme loadings (cellulases: 0 to 40 FPU (FPU, filter paper unit, expressed as µmol of glucose produced per minute with filter paper as a substrate) /g dry biomass; cellobiase: 0 to 70 CBU (CBU, cellobiase unit, expressed as µmol of cellobiose that is converted into glucose per minute with cellobiose as a substrate)/g dry biomass). A cellulases loading of 20 FPU/g was required to improve sugar recovery for lime-pretreated biomass, while 15 FPU/g was sufficient for enhanced sugar yield for NaOH-pretreated biomass. The optimal cellobiase loading was found to be 10 CBU/g for the two types of pretreated biomass. The supplementation of xylanase during hydrolysis was not beneficial to higher sugar recovery for both pretreatment methods. More than 99% of glucose in the hydrolyzate was utilized by the yeast strain for ethanol production with 95% of the theoretical maximum yield for the hydrolyzate and 83% of the theoretical yield for the raw biomass. There was no significant difference in ethanol yield between NaOH and lime-pretreated coastal bermudagrass.
- Ammonia Emission from Stored Broiler Cake(2009-08-10) Yao, Haiyan; Dan H. Willits, Committee Member; Philip W. Westerman, Committee Member; Jason A. Osborne, Committee Member; Sanjay B. Shah, Committee Chair; Wayne P. Robarge, Committee Member; Lingjuan Wang, Committee MemberAmmonia emission from animal feeding operations has potential negative impacts on the environment and public health and it also reduces the nutrient value of animal waste. When conditions are not suitable for land application, broiler cake (or litter) may be stored in stockpiles which may contribute to ammonia emission. In this study, summer and winter ammonia emission factors from broiler cake stockpiles stored in a naturally ventilated shed were developed. The lab experiment measured relative ammonia emissions as affected by type of cover and depth of cake. Scrubbers were used to measure ammonia concentration both in the field and lab studies. In the field, the integrated horizontal flux (IHF) method and Fick’s law of diffusion were used to determine ammonia emissions due to forced and natural convections, respectively. The ammonia emission due to natural convection was <0.01% of total emission. However, it may be necessary to calculate emissions based on concentrations measured only during conditions of forced convection. In summer, the estimated total ammonia-N loss was 0.8 % of total N. In winter, the total ammonia loss was 1.4 % of total N during the first 7 d and 2.5 % for the whole 15-d period. The estimated average daily ammonia emission factor in summer (7 d) was 24.5 g NH3-N/m3-d of cake or 7.0 g NH3-N/AU (500 kg LW)-d. The estimated daily ammonia emission factor for the first 7 d in winter was 35.6 g NH3-N/m3–d or 42.5 g NH3-N/AU-d. The total ammonia lost during the 15-d winter study was 33.8 g NH3-N/m3-d or 40.2 g NH3-N/ AU-d. Ammonia losses from the tarp covered cake were significantly lower than the control and double depth treatments by 45% and 49%, respectively, at the end of study. Ammonia losses (g/m3) are lower from stockpiles with lower surface area per unit volume.
- Assessment of Bioenergy Crop Production Feasibility along North Carolina Department of Transportation Highway Rights-of-Way.(2011-10-31) Mayer, Michelle; Matthew Veal, Chair; Gary Roberson, Minor; Michael Boyette, Member
- Assessment of GreenSeeker in Peanut Disease Detection.(2012-03-23) Isaev, Davron; Gary Roberson, Chair; Michael Boyette, Member; David Jordan, Member
- An Assessment of the Dilute Acid Pretreatment of Coastal Bermudagrass for Bioethanol Production(2009-11-30) Redding, Arthur Philip; Steven W. Peretti, Committee Member; Ratna R. Sharma-Shivappa, Committee Member; Jay J. Cheng, Committee ChairThere is a clear interest domestically to examine alternative liquid fuels which are more sustainable and environmentally friendly than gasoline. Bioethanol is a leading candidate for this replacement, but limitations exist on current starch based production. As a result, lignocellulosics are being examined. Lignocellulosics require a pretreatment step to degrade the biomass enough to allow enzymes to access to the carbohydrates. Dilute acid pretreatment has been demonstrated across many lignocellulosic feedstocks as a leading method compared to other pretreatment options. Coastal bermudagrass was identified as a promising lignocellulosic feedstock for bioethanol production. It is well suited for the Southeastern United States where it is currently grown for nutrient management in concentrated animal farming operations and as a source of hay. In a full factorial experimental design, dilute sulfuric acid pretreatment was used to pretreat coastal bermudagrass at 120, 140, 160, and 180ºC using 0.3, 0.6, 0.9, and 1.2% w/w sulfuric acid over residence times of 5, 15, 30, and 60 minutes. After enzymatic hydrolysis, the highest yield of total sugars (combined xylose and glucose) was 97%, which was shared by the pretreatment condition combinations of 0.9% acid at 160ºC for 15 minutes and 1.2% acid at 160ºC for 5 minutes. The prehydrolyzate liquor was analyzed for inhibitory compounds (furfural, hydroxymethylfurfural (HMF)) in order to assess potential risk for inhibition during fermentation. Accounting for the inhibitory compounds, a pretreatment with 1.2% acid at 140ºC for 30 minutes with a total sugar yield of 94% o r0.9% acid at 160 ºC for five minutes with a total sugar yield of 91% may be more favorable for fermentation because furfural levels remain under the inhibitory threshold concentration of 1 g/L. Additionally, due to significant interactions between factors, there are likely optimal pretreatment condition combinations possible other than those found experimentally. Both kinetic and multiple linear regression (MLR) models have been developed in other studies to describe dilute acid pretreatment, however no study has yet applied an artificial neural network (ANN). In this study, the utility of an ANN was assessed for modeling the dilute acid pretreatment of coastal bermudagrass using statistics that quantified the error between the predicted data and actual data and through a comparison with an MLR model. The statistics used were the coefficient of determination (R2), the root mean squared error (RMSE), and the root percent deviation (RPD). A standard 2nd-order polynomial multiple linear regression (MLR) model was developed for comparison with the ANN model. Time (minutes), acid concentration (% w/w), and temperature (ºC) were input into the models to generate xylose in the prehydrolyzate (PreH), glucose in the PreH, furfural in the PreH, HMF in the PreH, xylose in the enzymatic hydrolyzate (EH), and glucose in the EH. It was found that the two types of models predicted most of the outputs closely with the exception of the xylose in the PreH, which the ANN predicted more accurately. An ANN model with six hidden layer neurons was found to be the best overall model and confirmed the utility of utilizing ANN modeling in the area of biomass pretreatment.
- Catchment-scale Evaluation of the Hydrologic and Water Quality Impacts of Residential Stormwater Street Retrofits in Wilmington, North Carolina.(2013-03-25) Page, Jonathan Lewis; William Hunt, Chair; Gregory Jennings, Member; Richard McLaughlin, Minor
- Characterization of Nutrient and Sediment Transport in a Restored Agricultural Stream(2007-03-26) Spangler, Justin Thomas; Dr. Gregory D. Jennings, Committee Chair; Dr. Deanna L. Osmond, Committee Member; Dr. Garry L. Grabow, Committee MemberThe Purlear Creek restoration project is a restored agricultural stream located in Wilkes County, North Carolina. The project site consists of 3,755 linear meters of restored stream located in a pastured beef operation. Restoration activities included the return of dimension, pattern and profile as well as reestablishing a reliable floodplain connection. Permanent fencing was installed to protect a 7.6 m vegetated buffer on either side of the stream and prevent cattle from damaging the riparian area. Load calculations indicate a 36% (0.16 kg N⁄day⁄100m) decrease in mass of total nitrogen (TN) between the inflow and outflow stations located at the boundaries of the restored reach. Nitrate nitrogen (NO3-N) increased by 29%, but the corresponding decrease in total nitrogen indicates the presence of transformation processes within the project site. The mean TKN concentrations throughout the site were higher than other streams within the same Ecoregion as reported by the EPA. The loading calculations indicate a 19% reduction in both TP and O-PO4-P as the load from the inflow tributaries pass through the restored site. The mean TP concentration for all the sampling stations throughout the study site were well above the TP concentration observed at other streams in the Ecoregion. The TSS concentration exhibited a significant reduction in both concentration and load as the inflow surface water passed through the restored site. The inflow load was reduced by 82% (6.74 kg⁄day⁄100m) over the course of the study period. Permanent cross sections along the tributary below the unrestricted cattle access confirm the deposition of material along the channel and indicate a decrease in cross sectional area over the course of the study. Of the inflow tributaries, the tributary flowing from a pasture with unrestricted cattle access to the stream repeatedly returns markedly higher concentrations of constituents such as TN, Organic N, total ammonium nitrogen (NH3-N), total phosphorus (TP), orthophosphate phosphorus (O-PO4-P), total suspended solids (TSS) and Escherichia coli. The Nitrogen Loss Estimation Worksheet (NLEW) and Phosphorus Loss Assessment Tool (PLAT) programs were used to quantify the anticipated nitrogen and phosphorus losses from within the pasture. These tools indicate an estimated field loss of 4,394 kg N⁄yr and 214 kg of P⁄yr when fertilizer application rates similar to the actual application rates were used for the study period. Overall, the combination of the stream restoration and the implementation of a vegetated riparian buffer indicate an improvement in water quality within this agricultural headwater restoration. Conditions favor nutrient cycling which decreases the quantity of N. Sedimentation within the restored site decreases the quantity of TSS and TP transported through the site. Benthic macroinvertebrate collected post restoration does not indicate a favorable ecological response to the restoration efforts.
- CO2 Enrichment and Hot Water Heat in a Greenhouse as a Mean of Recovering Bioresources From Swine Waste(2001-08-23) Marbis, Juan Manuel; Dan Willits, Chair; Mary Peet, Co-Chair; Jiayang Cheng, Co-ChairPredictions of heating and cooling requirements of a greenhouse located at the Barham Farm, Zebulon, N.C. were made via computer simulation. Kimball's Modular Energy Balance Model (MEB) was used to simulate thermal behavior of the greenhouse. The weather inputs to the model were provided by data collected at the greenhouse and a Typical Meteorological Year (TMY2) data file for Raleigh, NC. Greenhouse air temperature (Tai), inside CO2 concentration (CO2) and inside relative humidity (RH) levels were used to validate the accuracy of the model. Absolute percentage differences ranging from 5.92% to 10.67% for Tai were observed. CO2 levels showed the biggest differences between observed and predicted data, from 14.93% to 42.33%, and RH showed a difference of 9.79% to 19.41%. Heating times were under-predicted, showing percentage difference between observed and predicted periods from -3.01% to -34.87%. On the other hand, cooling periods were over-predicted. With the exception of the month of February were cooling periods were under-predicted. Percentage difference for cooling periods ranged from -3.59% to 27.80%. The use of supplemental heat using a 10,000 gallon hot water tank serving as a waste heat collector was simulated. No data was available on its operation. Based on specific operating assumptions, it is expected that heat from the hot water will supply approximately 35% of the total energy demand of the greenhouse in a typical meteorological year. It was observed that the use of supplemental heat is most sensitive to its initial water temperature and the cutoff temperature. Outside weather conditions to which the use of hot water is most sensitive are solar radiation and wind speed.
- Combined Alkaline Pretreatment of Wheat Straw for Fermentable Sugar Production: Optimization through Response Surface Methodology.(2012-12-18) Pandey, Pankaj; Jay Cheng, Chair; Ratna Sharma, Member; Praveen Kolar, Member
- Comparing Digital Image Analysis and Other Turf Quality Measurements in the Evaluation of Smart Irrigation Technologies.(2010-11-05) Ghali, Ihab; Garry Grabow, Committee Chair; Rodney Huffman, Committee Chair; Grady Miller, Committee Member
- A Comparison of Chemical Pretreatment Methods for Converting Cotton Stalks to Ethanol(2005-05-02) Silverstein, Rebecca Anne; Ratna Sharma, Committee ChairThe objective of this study was to investigate the effectiveness of sulfuric acid, sodium hydroxide, hydrogen peroxide, and ozone pretreatments for conversion of cotton stalks to ethanol. Sulfuric acid, sodium hydroxide, and hydrogen peroxide at concentrations of 0.5, 1, and 2% (w/v) were used to pretreat ground cotton stalk samples at a solid loading of 10% (w/v). Treatment temperatures of 90 degrees Celsius and 121 degrees Celsius at 15 psi were investigated for residence times of 30, 60, and 90 minutes. Ozone pretreatment was performed in the liquid phase at 4 degrees Celsius with constant sparging. Lignin, carbohydrate, and moisture content analyses were performed on the pretreated solids. The pretreated solids from sulfuric acid, sodium hydroxide, and hydrogen peroxide pretreatment (at 2%, 60 min, 121C/15psi) showed significant lignin degradation and/or high sugar availability and hence were hydrolyzed by cellulases from Trichoderma reesei and β-glucosidase at 50 degrees Celsius. The results showed that time, temperature and concentration were all significant (p is less than or equal to 0.05) factors in delignification for NaOH and xylan removal for H2SO4. Sulfuric acid pretreatment resulted in the highest xylan reduction (95.23% for 2% acid, 90 min, 121C/15psi) during pretreatment and the lowest cellulose to glucose conversion during hydrolysis (23.85%). Sodium hydroxide pretreatment resulted in the highest level of delignification (65.63% for 2% NaOH, 90 min, 121C/15psi) and the highest cellulose conversion (60.8%). Hydrogen peroxide pretreatment resulted in significantly lower (p is less than or equal to 0.05) delignification (maximum of 29.51% with 2%, 30 min, 121C/15psi) and cellulose conversion (49.8%) than sodium hydroxide pretreatment, but had a higher (p is less than or equal to 0.05) conversion than sulfuric acid pretreatment. Ozone pretreatment showed no significant changes in lignin, xylan, or glucan contents with increasing time. Quadratic models using time, temperature, and concentration as numeric variables were developed to predict xylan reduction for H2SO4 pretreatment and lignin reduction for NaOH pretreatment. In addition, linear models relating a modified severity parameter (log Mo) combining the pretreatment parameters with xylan or lignin reduction were developed and resulted in R-squared values of 0.89 and 0.78, respectively.
- A Comparison of Runoff Quality and Quantity from an Innovative Underground Low Impact Development and a Conventional Development.(2013-04-22) Wilson, Corinne Eileen; William Hunt, Chair; Gregory Jennings, Member; Andrew Fox, Minor
- Constructed Wetlands as Remediation Tools for Shallow Groundwater Contaminated by Swine Lagoon Seepage(2005-02-04) Hathaway, Jon Michael; Robert O. Evans, Committee Chair; Michael R. Burchell II, Committee Member; Stephen W. Broome, Committee MemberSwine waste is typically flushed from beneath confinement houses into anaerobic lagoons for temporary storage and partial treatment. When improperly constructed, studies have shown that there is potential for the high strength wastewater to leak from the lagoon into the surrounding groundwater. Constructed wetlands have been implemented as treatment systems for wastewater. Biogeochemical reactions in wetlands make them viable options for wastewater treatment. Wetlands may remove pollutants such as nutrients through adsorption, nitrification, denitrification, and plant uptake. Studies have shown that constructed wetlands are able to attenuate substantial amounts of nitrogen and phosphorous from wastewater. Denitrification is the primary mechanism by which nitrogen is removed from wastewater in constructed wetlands. Research has shown that nitrification of ammonium nitrogen to nitrate may indirectly limit denitrification. One practice that may increase the nitrogen assimilation in a constructed wetland is the use of a nitrification pretreatment system such as a trickling filter. A trickling filter contains media on which nitrifying bacteria can attach, and provides an aerobic environment in which the nitrification process can take place. This study evaluated a site where a swine lagoon had leaked into the surrounding groundwater. The swine lagoon was eventually closed-out and a plan to pump out the contaminated groundwater was initiated. The goal was to pump at a rate that would change the subsurface gradient causing the contaminated water to stop flowing towards a nearby stream. The water was pumped into a constructed wetland where nutrients could be removed. After three years of pumping the contaminated groundwater, a trickling filter was implemented to nitrify the wastewater before it was discharged into the wetland. Over the course of the study, the average NH4-N concentration in wells located down gradient of the former lagoon decreased by more than 60%, and the hydraulic gradient between the former lagoon and the nearby stream was reduced by greater than 65%. The constructed wetland assimilated greater than 76% of the total nitrogen and more than 22% of the total phosphorous that it received, resulting in the assimilation greater than 915 kg of total nitrogen and more than 145 kg of total phosphorous. The nitrification pretreatment system converted 20% of the NH4-N it received to NO3-N on a mass basis. In the samples taken from the trickling filter, the arithmetic average amount of NH4-N that was converted to NO3-N was 37%. Although the nitrification pretreatment system was functional, there was no identified increase in total nitrogen assimilation within the constructed wetland. This may have been due to influent ammonium nitrogen concentrations becoming too low for the trickling filter to function at maximum efficiency by the time it was incorporated into the system.
- Conversion of Industrial Sweetpotatoes for the Production of Ethanol(2008-12-07) Duvernay, William Hauser; Mari S. Chinn, Committee Chair; Ratna R. Sharma-Shivappa, Committee Member; G. Craig Yencho, Committee MemberStarch is a renewable resource which is currently being used to produce ethanol from corn. Although corn starch to ethanol is a mature conversion process, corn production is not feasible for every region of the United States. Sweet potatoes (Ipomoea batatas, Morning Glory Family) are a low-impact starch crop grown primarily in the southeast region of the U.S. and offer a viable, alternative starchy raw material that can be converted to useful sugar feedstocks needed for production of ethanol and other value added products. The process of converting sweetpotato starch into ethanol can be described in three basic steps: liquefaction using α-amylase or some other liquefying agent to gelatinize available starch, saccharification using at least one saccharifying enzyme to convert gelatinized starch into fermentable sugars, and fermentation of the sugars into ethanol. The overall goal of this project was to effectively generate the information necessary to define an environmentally friendly process for conversion of industrial sweetpotato varieties into simple sugars and ethanol. Specific objectives included: 1) Examining liquefaction, saccharification, and fermentation of FTA-94 industrial sweetpotatoes (ISP) using α-amylase and glucoamylase for the production of ethanol, and 2) Examining the enzymatic hydrolysis and fermentation of industrial sweetpotatoes with the addition of pullulanase for ethanol production. The significance of enzyme loading rate, incubation time, and temperature on changes in starch content, soluble sugar concentrations and ethanol yield (when appropriate) during each conversion step was measured. One α-amylase (Liquozyme SC) and three glucoamylases (Spirizyme Fuel, Spirizyme Plus Tech, and Spirizyme Ultra) were tested during liquefaction and saccharification at 85 and 65˚C, respectively, over time. Results showed that the majority of the available starch, 47.7 and 65.4%, was converted during liquefaction of flour and fresh sweetpotato preparations, respectively, with the addition of 0.45 KNU-S/g dry ISP of Liquozyme SC after 2 hours of incubation (66.4 and 80.1% initial starch contents). Saccharification was generally able to increase the breakdown of starch, but it main purpose was to convert the susceptible starch to fermentable sugars. The addition of 5.0 AGU/g of Spirizyme Ultra after 48 hours of incubation was able to produce 862.2 and 743.9 mg of simple sugars/g of starch with flour and fresh preparations, respectively. Fermentation with Ethanol Red Yeast of these appropriate loadings tested ethanol generation over time with and without the addition of salt niturients and was able to generate 62.6 and 33.6 g/L of ethanol for flour (25% w/v substrate loading) and fresh (12.5% w/v) ISP, respectively, after 48 hours of fermentation without salts. The addition of pullulanase during 48 hours of saccharification with 5.0 AGU/g Spirizyme Ultra at 45, 55, and 65ºC showed no consistent increase in the change in starch content. Adding 0.5 NPUN/g of Promozyme during saccharification at 55ºC slightly increased the amount of recovered glucose, producing 828.7 and 869.7 mg/g starch of glucose only for flour and fresh ISP. Fermentation of these treatment combinations yielded ethanol values of 310.7 and 333.3 mg/g dry ISP for flour and fresh preparations. Results of these experiments show that sweetpotatoes offer a viable alternative starch source for ethanol production. If implemented in the southeastern region of the United States, it wouild be possible to generate at least 700 gallon of ethanol per acre of industrial sweetpotatoes.
- Denitrification of Aquaculture Wastewater using Agricultural by-products as Biofilter Media(2005-07-27) Saliling, Willie Jones Bayotlang; Dr. Philip W. Westerman, Committee Co-Chair; Dr. Francis L. de los Reyes III, Committee Member; Dr. Thomas M. Losordo, Committee Co-ChairThis research evaluated wood chips and wheat straw as inexpensive and readily available biofilter media for denitrification as alternatives to commonly used plastic media. Nine 3.6-L laboratory scale reactors (40 cm packed height x 10 cm dia) were built to evaluate performance of wood chips, wheat straw, and Kaldnes plastic media to reduce nitrate from synthetic and real aquaculture wastewater. The upflow bioreactors were loaded at a constant flow rate and three influent concentrations of 50, 120, and 200 mg NO₃-N/L each for at least four weeks, in sequence. Experiments showed that both wood chips and wheat straw are comparable to Kaldnes plastic media in terms of reducing nitrate. As high as 99% of nitrate (as high as 200 mg NO₃-N/L) were reduced. Pseudo-steady state denitrification rates at 200 mg NO₃-N/L influent averaged 1365 ± 39 g NO3-N/m³/day for wood chips, 1361 ± 80 g NO₃-N/m³/day for wheat straw, and 1326 ± 74 g NO₃-N /m³/day for Kaldnes. These values were not even the maximum potential since nitrate profile along reactors showed substantial reduction in the lower half of the reactors with rates more than double than what was estimated for the whole reactor. Treatment of real wastewater also showed comparable performance with that at the 50 mg NO₃-N /L synthetic experiments. COD consumption per NO₃-N removed was highest in Kaldnes media (3.41 to 3.95) compared to wood chips (3.34 to 3.64) and wheat straw (3.26 to 3.46). COD/NO₃-N ratios for the real wastewater were low (<2.0). Effluent ammonia concentrations were close to zero while nitrites were around 2.0 mg NO₂-N/L for all reactor types. There was alkalinity production and pH increased corresponding to NO₃-N removed. On the other hand, the oxidation-reduction potential also decreased with nitrate removal. Wood chips and wheat straw lost 16.2% and 37.7% of their masses, respectively over 140 days. There were physical signs of degradation like discoloration and structural transformation. Carbon/Nitrogen (C/N) ratio and lignin mass of the media also decreased. Considerable amount of microbial biomass also developed inside the reactors decreasing porosity. By Polymerase Chain Reaction —Denaturing Gradient Gel Electrophoresis (PCR-DGGE) analysis, it was shown that the bacterial populations differed among reactor types and with column height.
- Design and Operation of a Biofilter for Treatment of Swine House Pit Ventilation Exhaust.(2011-05-27) Hood, Matthew; Sanjay Shah, Chair; Larry Stikeleather, Member; Lingjuan Wang, Member; Praveen Kolar, Member
- Design of a Pneumatic Baling System for Burley and Flue-cured Tobacco.(2008-06-11) Boaz, Robert Dale; Dr. W. David Smith, Committee Member; Dr. Larry F. Stikeleather, Committee Member; Dr. Michael D. Boyette, Committee Chair