Browsing by Author "Francis de los Reyes, Committee Member"

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Analysis of Grease Abatement Devices and the Measurement of Fat, Oil, and Grease in Food Service Establishment Waste Streams
(2010-02-16) Aziz, Tarek N; Kevin Keener, Committee Member; George Roberts, Committee Member; Francis de los Reyes, Committee Member; Joel Ducoste, Committee Chair
The release of fat, oil, and grease (FOG) into collection systems ultimately results in the blockage of pipes and subsequent sanitary sewer overflows (SSOs). SSOs are a risk to public health and the environment as they release untreated sewage laden with high nutrient and pathogen loading. Currently, municipalities whose function it is to maintain these collection systems are at a loss as there is a substantial lack of scientifically-based guidance regarding the effective abatement and measurement of FOG. This research aims to examine the performance of grease abatement devices and to investigate the measurement of FOG in food-laden waste streams. Grease abatement devices (GAD) are commonly large, below ground tanks which act to provide adequate hydraulic retention time (HRT) for the separation of light FOG material from influent wastewater. Common designs for GAD require the use of dual compartments and sizing for an approximate 30 min HRT. 24 hour monitoring of 24 field GADs indicated highly intermittent systems with the vast majority experience HRTs far greater than design. Average HRT for most GADs was greater than 2 hrs with peak discharges 3-7 times the average flow rate. Chemical characterization of GADs indicated the presence of anaerobic microbial activity. Spatial and temporal observation of FOG and food solids profiles in a field GAD indicated what appeared to be the channeling of food solids into the second compartment for a straight pipe and no-inlet configured GAD. Observation of a distributive inlet showed an elimination of this channeling effect and significant reduction in second compartment food solid accumulation. As a result of this improved solids sedimentation, it was hypothesized that distributive configurations may also provide improvements in separation of FOG materials by making more efficient use of the GAD cross-sectional area. Lab-scale and computational fluid dynamics (CFD) modeling of GADs was performed to evaluate a commonly observed submerged inlet pipe configurations and develop design improvements to enhance FOG removal efficiency. Lab-scale results indicated that enhanced FOG removal performance was obtained by tripling the HRT from 20 minutes to 1 hr, however, performance values close to the performance of the 1 hr HRT were obtained with a 20 minute HRT by modifying the internal configuration. As hypothesized from observations of the field GADs, it is believed that the use of distributive inlet configurations may act to reduce short-circuiting effects in GADs. Results indicated lab-scale GAD improvement through the use of distributive configurations. The removal of the baffle wall was also explored in the present study. When the wall was removed with a shortened submerged pipe, GAD performance improved from the standard configuration. When an inverted-inlet tee was used without compartmentalization, however, lab-scale results indicated a poorer performance than the standard configuration. Investigation into CFD simulations of GAD configurations followed performance trends established in the lab-scale experiments except in conditions featuring the inverted tee inlet. It is hypothesized that the exclusion of droplet coalescence and breakup in the CFD simulation resulted in these discrepancies. Investigation into the LLE of edible- FOG in synthetic food-laden waste streams indicated substantial interference in the presence of wheat flour and whey proteins. Other comparisons with sucrose, corn starch, and a surrogate fiber indicated no interference with FOG recovery. LLE of various free-fatty acids and FOG types of varying levels of saturation indicated no significant difference in recovery performance. Investigation of an EPA defined standard material (hexadecane) indicated that the volatile nature of the compound lead to its substantially poorer recovery than food-based standards which indicated no volatilization during testing. All sample recovery was slightly low indicating the persistent adhesion of samples to lab-ware.
Biodegradability of Wood Products under Simulated Landfill Conditions
(2009-12-03) Padgett, Jennifer Margaret; Morton A. Barlaz, Committee Chair; Francis de los Reyes, Committee Member; Ilona Peszlen, Committee Member
Landfills are the highest source of anthropogenic methane in the United States. Although it is known that methane and carbon dioxide are common products of anaerobic degradation, the amount of methane and carbon dioxide produced is not known for some individual components of municipal solid waste (MSW). Accordingly, there is no data on methane yield or the amount of carbon sequestered during the anaerobic degradation of wood, a common component of MSW. It is important to obtain these data to estimate landfill methane yields and the role of wood in methane emissions. The objective of this research was to develop data to predict the rate and extent of wood decomposition in landfills. The decomposition of wood products was analyzed in reactors filled with a hardwood, a softwood and four engineered woods (plywood, oriented strand board, particleboard and medium-density fiberboard). They are the dominant types of wood products produced in the United States according to the United States Department of Agriculture (USDA). Experiments were conducted in triplicate in 8-L reactors containing the shredded wood and seeded with well decomposed refuse. To promote optimal biodegradation, reactors were maintained in a room at 35Ã‚Â°C and operated with leachate recirculation and neutralization. Nitrogen and phosphorus were added to ensure that their availability did not limit the extent of degradation. Methane yields of 29.93, 7.40, 6.23, 66.55, 5.31, 4.59 ml of CH4/ dry gram of wood, were measured for hardwood, softwood, plywood, oriented strand board, particleboard and medium-density fiberboard, respectively. Natural extractives in the hardwood and softwood tested, did not have an effect on methane yield while the synthetic resins used in engineered woods contributed to the measured methane yields.
Development of a Decision Support Methodology for the Design of Animal Waste Management Strategies to Achieve Regional Environmental Objectives
(2003-03-03) Anastasiou, Christos Charalambou; S. Ranji Ranjithan, Committee Chair; Sarah K. Liehr, Committee Co-Chair; John J. Classen, Committee Member; E. Downey Brill, Committee Member; Francis de los Reyes, Committee Member
Management of waste from confined animal feeding operations is becoming increasingly important. While anaerobic lagoons and sprayfields are currently used for treatment, recent administrative initiatives call for their replacement. This decision has increased the need for characterization of the cost and treatment effectiveness of alternative technologies. However, due to variations in farm characteristics (e.g., size, location), identification of the most cost-effective combination of treatment technologies to achieve collective environmental goals requires an integrated approach (i.e. all combinations of treatment technology alternatives at all farms in a region must be considered simultaneously). The objective of this research was to develop a regional management decision-support framework to assist policy-makers, planners, and farmers in making cost effective lagoon replacement decisions to achieve desired treatment and public protection goals. A major component of the framework is a cost and treatment efficiency assessment tool to evaluate alternative animal waste treatment technologies for individual farms. Outputs from the assessment tool, together with geospatial data, feed into the regional management component of the framework, which consists of several formal optimization techniques that assist in the search for good decisions. Among these techniques are an optimization engine (integer programming) that can be used to find management strategies that meet cost and environmental targets, and a method for efficiently generating alternatives (Modeling to Generate Alternatives (MGA)). The management alternatives have similar cost and environmental performance but may behave differently for unmodeled objectives (e.g., risk or equity). Finally, the regional management framework includes an uncertainty analysis component that allows the evaluation of alternatives while taking into consideration the uncertainty in model inputs. The decision-support framework was demonstrated through an illustrative example; the regional waste management of swine farms in the Lower Neuse River watershed in eastern North Carolina to achieve a 30% reduction in nitrogen loading. Results show that 1) a regional management approach is essential for achieving cost savings, 2) there is significant flexibility in meeting the nitrogen reduction and cost targets, 3) consideration of uncertainty may lead to the selection of a different solution, 4) the decision support framework can be used successfully to address a range of concerns, including but not limited to cost, risk, equity, and uncertainty.
Evaluating Sequential Disinfection in a Water Treatment System Using a Non-biological Surrogate.
(2005-01-11) Richards, Brannon Heath; Detlef R. U. Knappe, Committee Member; Francis de los Reyes, Committee Member; Joel Ducoste, Committee Chair
Fluorescent YG-microspheres (Polysciences Inc.) were evaluated to simulate Cryptosporidium inactivation in a flow-through system that utilizes multiple disinfectants. Experiments were performed in a disinfection process consisting of an ozone primary stage and a secondary free chlorine treatment stage. Impacts of the chemical disinfectant exposure were calculated by tracking the changes in fluorescence distribution with a flow cytometer. Microspheres were initially pretreated to reduce their fluorescence intensity to a level that would allow them to closely mimic Cryptosporidium. Microsphere survival ratios (N/No) were calculated by replicating the inactivation of Cryptosporidium observed by Driedger et al. [6] and selecting an appropriate fluorescence intensity threshold in a histogram analysis. The results from these flow-through experiments suggest that the fluorescence decay of YG-fluorescent microspheres does display synergistic effects when free chlorine is used sequentially with ozone. This study also included the use of numerical models to simulate sequential disinfection processes. Femlab 3.0a and the Segregated Flow Reactor method were used to evaluate sequential disinfection processes. These numerical models were set up to mimic the experimental conditions observed in this research. The sequential disinfection inactivation predicted in these models was similar to the experimental fluorescence decay of the microspheres. However, the models were not effective at predicting fluorescent intensity changes at different intermediate points within the disinfection process stream.
Laboratory Studies in Chlorinated Solvents and Hydrocarbon Bioremediation
(2008-04-24) Tillotson, Jason Matthew; Robert C. Borden, Committee Chair; Morton A. Barlaz, Committee Member; Francis de los Reyes, Committee Member
Swine Wastewater Treatment in an Integrated System of Anaerobig Digestion and Duckweed Nutrient Removal: Pilot Study
(2005-04-13) Lyerly, Courtney Neil; Sarah Liehr, Committee Member; Jiayang Cheng, Committee Chair; Francis de los Reyes, Committee Member
Organics destruction and nutrient uptake in an integrated pilot system of anaerobic digestion and duckweed nutrient removal for swine wastewater treatment were monitored under field conditions. Raw swine wastewater of 100 gallons/day was first treated in a 1,000-gallon anaerobic digester with floating ballast rings. Organic compounds in the wastewater were digested to produce biogas. Many nutrients including nitrogen and phosphorus remain in the effluent of the anaerobic digester. Three duckweeds (Lemna gibba 8678, Lemna minor 8627, and Spirodela, punctata 7776) were grown in three 1,000- gallon tanks to recover nutrients from the anaerobic effluent. The duckweed was periodically harvested and can be used as animal, poultry, and fish feed. The Three species were compared for growth and nutrient removal characteristics. This research provides an initial understanding of the attached-growth anaerobic digester and the characteristics exhibited by duckweed in the treatment of swine wastewater under conditions similar to those found in North Carolina. Both the anaerobic digester and the duckweed tanks were run as completely mixed systems. The performance of the system was monitored by measuring chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN), ammonia nitrogen, total phosphorus (TP), ortho-phosphate-phosphorus, and pH in the influent and effluent of each treatment unit.