Browsing by Author "Dr. Morton A. Barlaz, Committee Chair"

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Effect of Aging on the Bioavailability of Toluene Sorbed to Municipal Solid Waste Components
(2003-09-03) Chen, Ye; Dr. Francis L. de los Reyes III, Committee Member; Dr. Detlef R. U. Knappe, Committee Co-Chair; Dr. Morton A. Barlaz, Committee Chair; Dr. Michael R. Hyman, Committee Member
The bioavailability of toluene sorbed to individual municipal solid waste (MSW) component [office paper, newsprint, model food and yard waste, high density polyethylene (HDPE) and poly(vinyl chloride)(PVC)] was evaluated. Effects of sorbent decomposition on toluene bioavailability were studied by evaluating biodegradable sorbents in both fresh and anaerobically decomposed form. To determine the effect of aging on toluene bioavailability, bioavailability tests were performed for MSW components that were in contact with toluene for 1, 30, and 180 days. At the termination of bioavailability test, sequential organic solvent extraction, alkali extraction, and combustion were used to determine the fate of toluene that was not available to bacteria. Lignocellulosic waste (fresh and degraded office paper, newsprint) was subjected to enzymatic hydrolysis and acid hydrolysis to determine the effect of individual biopolymers in paper on the sorption and bioavailability of toluene. The bioavailability of toluene sorbed to MSW components was highest in HDPE, a rubbery polymer, followed by the biopolymers and finally PVC, a glassy polymer. Except for HDPE, aging significantly reduced the bioavailability of toluene sorbed to MSW components. Relative to the 1-day aging time, the bioavailability of toluene sorbed to biopolymers was reduced by 11-22% and 12-29% after 30 and 180 days of aging, respectively. For fresh and degraded office paper, the reduced bioavailability was a combination effect of aging and pH increase. Analysis of solid phase at the termination of bioavailability tests indicated that the remaining 14C in sorbents was sequestered within and/or covalently bound to sorbent organic matter. Stronger association between sorbent organic matter and 14C was observed during aging as less 14C was recovered by organic solvent extraction and more 14C was detected in the humic substances when aging time increased. Large molecular weight substances in the humic matter may form covalent binding with toluene and/or intermediates of toluene biodegradation. Humic acid had 3.7-24.3 times higher affinity for toluene than fulvic acid. Enzymatic hydrolysis and bioavailability tests were conducted to identify the effect of individual biopolymers in paper on toluene sorption. Toluene release from cellulose and hemicellulose was not enhanced after enzyme addition, indicating that cellulose and hemicellulose exhibited limited sorptive capacity for toluene. Lignin controlled toluene sorption and bioavailability for both fresh and degraded newsprint. Bioavailability tests showed no significant difference between toluene sorbed to biopolymer composite (fresh and degraded newsprint) and their isolated lignins. However, the presence of lignin could explain only 54% of the sorption capacity of degraded office paper. Bioavailability of toluene sorbed to degraded office paper lignin showed a higher initial biodegradation rate and mineralization extent than toluene sorbed to degraded office paper composite. Crude protein and lipophilic extractives were likely to contribute to the higher sorptive capacity of biopolymer composite. Lipophilic extractives provided highly hydrophobic environment for toluene uptake and caused the declined toluene bioavailability.
The Effect of Special Wastes on Refuse Decomposition and Phosphorus Cycling in Lab-Scale Municipal Solid Waste Reactors
(2007-09-16) Sadri, Ahmad; Dr. Morton A. Barlaz, Committee Chair; Dr. Detlef R. Knappe, Committee Member; Dr. Francis L. de los Reyes, Committee Member
In this research, the use of laboratory-scale tests to evaluate the effect of various non-hazardous wastes on refuse decomposition is demonstrated. Non-hazardous wastes are receiving increased interest from landfill owners especially with respect to bioreactor operation. These wastes could benefit bioreactors in that they represent sources of liquid, nutrients, and/or substrate. However, landfill operators should exercise caution in accepting these wastes, as some could have detrimental effects on refuse decomposition. Three wastes were evaluated including (1) aerobically digested wastewater treatment plant biosolids which represent a nutrient source, (2) burnt sugar, which is a viscous glucose/lactic acid mixture from an agricultural process and represents a high carbon, acidic substrate, and wastes from the production of fabric softener and detergent. As each waste had unique properties, testing protocols were adapted to address the specific concerns surrounding each material. Biosolids were compatible with refuse decomposition but they did not increase maximum methane production rates and yields or reduce lag times to the onset of methane production. There is some evidence that biosolids increased ammonia and phosphorus, but these were not found to be limiting. Burnt sugar experiments suggested that actively decomposing refuse has the potential to attenuate relatively high loading of a highly degradable and low pH substrate. Detergent experiments demonstrated significant inhibition of refuse decomposition at low waste additions.
A Life-Cycle Analysis of Alternatives for the Management of Waste Hot-Mix Asphalt, Commercial Food Waste, and Construction and Demolition Waste.
(2008-12-03) Levis, James William; Dr. Ranji S. Ranjithan, Committee Co-Chair; Dr. E. Downey Brill, Committee Member; Dr. Morton A. Barlaz, Committee Chair
Effective management of commercially generated food waste presents an opportunity for avoided global warming potential, renewable energy production, and renewable agrochemical production. The vast majority of food waste is landfilled, but source separated collection of the organic fraction of municipal waste is becoming more common. Currently in the US, food waste that is not buried in a landfill is aerobically composted and the end product has the potential to be used as a soil amendment that can replace mineral fertilizers or other agrochemicals. In Europe, anaerobic digestion (AD) of organic wastes is more common. AD facilities produce methane that can be used as an energy source. The residual from AD can also be used as a soil amendment similar to what is produced at composting facilities. An LCI was performed for food waste processed through several aerobic composting systems, an AD facility, and a landfill with and without energy recovery. The functional unit was one ton of food waste plus 0.6 tons of yard waste. The yard waste was considered because it is used as a bulking agent in food waste composting processes. The AD alternative was superior in every category due to the efficient collection of the methane generated and its conversion to energy. The two landfilling alternatives resulted in the highest GWP although the landfill with energy recovery alternative had the second lowest emissions and energy use. The composting alternatives were superior relative to the landfilling without energy recovery alternative. C&D waste is solid waste generated during the construction, renovation, or demolition of buildings and other structures. A life-cycle model was developed to evaluate two alternatives for the management of C&D waste; (1) recycling (2) and landfill disposal. The C&D waste LCI considered the recovery of ten materials present in a mixed C&D waste stream. All of the materials except for wallboard and miscellaneous materials are recovered for beneficial use. All of the recovered materials except for wood are assumed to replace virgin materials. Wood is assumed to be burned in a co-fired coal plant to produce electricity. The results of this analysis indicate that recovering mixed C&D leads to significant reductions in emissions, energy use, and GWP when compared to landfill disposal of mixed C&D waste.
Oxidation of Methane in Landfill Covers: A Strategy to Maximize Energy Revenue
(2008-08-14) Azam, Hossain Mohammad Muyeed-Ul-; Dr. Morton A. Barlaz, Committee Chair
Yolo County, CA is planning to optimize landfill gas collection by collecting gas during times of peak power demand and storing gas in the landfill during off peak periods by reducing the vacuum on the gas collection system. The objective of this research was to evaluate the efficacy of this approach by evaluating whether gas emissions would increase at low vacuum. Biologically active covers composed of compost⁄wood chips (80⁄20), pure compost, or green waste at thicknesses of 0.31 to 0.9 m were tested using static chambers to measure methane emissions and oxidation potential during rainy and dry season. In addition, laboratory column tests were conducted with two year old green waste to evaluate the effects of pressure gradient, moisture addition to simulate the dry and rainy seasons in California, and continuous vs. intermittent methane feed. The effect of climate was significant. In the field, the highest CH4 emission was 20.85 gm CH4⁄m2-d in 0.91 m compost + wood chips and 5.255 gm CH4⁄m2-d in 0.31 m soil during the rainy and dry seasons, respectively. When CH4 oxidation was measured using stable isotopes, it varied from 5 to over 99%. In the rainy season tests, there was a statistically significant decrease in CH4 emissions when the gas system vacuum was increased for the covers with the highest emissions (0.91 m compost + wood chips, 0.31 m compost, soil). In contrast, there was not an increase in CH4 emissions associated with reduced gas collection system vacuum during the dry season tests. The average flux rate in dry season was below 5.255 gm CH4⁄m2-d in all the covers both for low and high vacuum. While there were many confounding issues, emissions at low vacuum during the rainy season were the highest. Overall, all covers tested were effective in controlling gas release. The emissions data are consistent with the soil gas profile data where CH4 concentrations for the dry season were in the ppmv range while the corresponding concentrations were in the % range for the rainy season tests. Laboratory columns were filled with 2 year old green waste that is used at the Yolo County landfill as a daily cover. In most cases, methane oxidation decreased as the flux or pressure gradient increased. The addition of moisture inhibited methane oxidation by restricting O2 diffusion in the green waste as evidenced by the reduced O2 concentrations at depth in the water addition columns. The inhibitory effect of water addition on methane oxidation was most apparent at the end of the experiment at the CH4 feed rate of 147.2 gm⁄m2-day. Moreover, the average CH4 uptake data do not suggest any effect associated with pulsed flow in CH4 oxidation. The maximum oxidation rate measured in this study was 664.2 gm CH4⁄m2-d but was only measured in one of the eight columns. Both the field and laboratory results indicate that high moisture can inhibit methane oxidation. It is encouraging to note that during the dry season, there was no increase in emissions during periods when the gas collection system vacuum was reduced. There was an increase in CH4 emissions at low vacuum during the rainy season. However, this may not be critical as the hottest temperatures and associated highest demand for electricity are likely to occur during the dry season. Except for the soil and 0.31 m green waste, all covers of different thicknesses performed well. Therefore, the cover type to be used in the field should be based on availability of the material and cost.
Production of Non Methane Organic Compounds During the Decomposition of Refuse and Individual Waste Components and Under Different Operating Conditions
(2002-09-04) Ihnatolya, John Charles; Dr. Morton A. Barlaz, Committee Chair
There has been an increased interest in the emissions of non-methane organic compounds (NMOCs) during refuse decomposition. In addition to the New Performance Standards in the Clean Air Act, many state regulatory agencies require estimates of NMOC emissions as part of the landfill permitting process. The objectives of this new project are to measure NMOC yields for specific waste components entering landfills and the effect of alternate oxidation-reduction potentials (O2, NO3, CH4) on NMOC production. The experimental design consists of 8 treatments conducted in triplicate 7-l reactors. Four of the 8 treatments consist of shredded residential municipal solid waste (MSW), in which, the residential MSW was decomposed under aerobic conditions for 30 days followed by methanogenic conditions, decomposed under nitrate-reducing conditions, spiked with selected HHW plus methanogenic leachate initially, and decomposed under methanogenic conditions methanogenic leachate. The other four treatments were food waste; a mixture of grass; leaves and branches; a mixture of the dominant paper types present in MSW; and a leachate control. The results are preliminary though day 73. The average NMOC yields for the aerobic, mixed paper, yard waste, MSW, MSW plus HHW, nitrate, food waste and leachate controls were as follows: 2.28*10-1; 7.44*10-3; 1.45*10-2; 6.97*10-2; 5.84*10-2; 3.08*10-2; 2.93*10-1 mg-C/dry g; and 6.85*10-4 mg-C/mL, respectively.
Sorption Behavior and Persistence of Organic Contaminants in Landfills
(2009-11-01) Saquing, Jovita Marquez; Dr. Morton A. Barlaz, Committee Chair; Dr. Detlef R.U. Knappe, Committee Co-Chair; Dr. Francis L. de los Reyes III, Committee Member; Dr. Neal E. Blair, Committee Member
Sorption and desorption are important processes governing the distribution and fate of hydrophobic organic contaminants (HOCs) in landfills. The principal objectives of this research were to evaluate factors that control the sorption and desorption of HOCs from municipal solid waste (MSW), and to develop quantitative descriptions of sorption and desorption that are sensitive to waste composition. Desorption rates of toluene, o-xylene and tetrachloroethene from individual MSW components [high-density polyethylene (HDPE); poly(vinyl chloride) (PVC); office paper (OP); newsprint (NP); and rabbit food (RF), a model food and yard waste] were determined. The effects of sorbent and sorbate properties, solvent composition (ultrapure water, acidogenic and methanogenic leachates), and contact time (Ã¢â‚¬Å“agingÃ¢â‚¬Â ) on desorption rates were evaluated. HOC desorption rates from plastics were rapid for HDPE (D = 10-10 cm2/s), a rubbery polymer, but slower for PVC (D = 10-13-10-14 cm2/s), a glassy polymer. For biopolymer composites, a large fraction (45-94%) of sorbed HOCs was rapidly released (Dr = 10-9-10-10 cm2/s) while the remaining fraction desorbed slowly (Ds = 10-11-10-16 cm2/s). The toluene desorption rate from PVC was one order of magnitude faster in acidogenic leachate than in either ultrapure water or methanogenic leachate, a result that was primarily attributed to the plasticizing effect of volatile fatty acids in acidogenic leachate. Solvent composition did not otherwise influence HOC desorption rates. For biopolymer composites, small increases in the slowly desorbing HOC fraction were observed with increased aging time. The impact of discarded plastic materials on the fate and transport of HOCs in landfills was also examined. Sorption affinity and (de)sorption rates of toluene were compared for individual MSW post-consumer plastics (drinking water container, prescription drug bottle, soda bottle, disposable cold cup, computer casing, carpet, formica sheet and vinyl flooring) and model polymers (HDPE, PVC) at dilute aqueous concentrations. The studied plastic materials and model polymers were characterized [X-ray diffractometry, differential scanning calorimetry, and C, H, and N analyses] to evaluate the effects of the amorphous fraction (famorphous) and the organic carbon fraction (foc) on toluene sorption, and to determine the rubbery and glassy behavior of post-consumer plastics. Generally, partition coefficients (Kp) of toluene in plastic materials were 1 to 2 orders of magnitude higher than in biopolymer composites such as OP and NP. The Kp of toluene in plastics was affected by famorphous but not foc. The diffusivity (D) of toluene in rubbery plastics (model HDPE, drinking water container, and prescription drug bottle) was similar (D = 10-10 cm2/s). Among glassy plastics (model PVC, soda bottle, computer casing, disposable cold cup), the diffusivity of toluene was also similar (D = 10-12 cm2/s) but two orders of magnitude smaller than for the rubbery plastics. To predict the solid-liquid partitioning of a range of HOCs, one-parameter linear free energy relationships (op-LFERs) between the organic-carbon-normalized partition coefficients (Koc) and the sorbate octanol-water partition coefficients (Kow) were developed for individual MSW components. Kp estimates for toluene sorption to two solid waste mixtures (i.e. one with and one without a glassy plastic) using the new op-LFERs for individual MSW components were in close agreement with experimentally determined Kp values. Discrepancies were larger when Kp values determined with established op-LFERs that had been derived for soil and sediment organic matter, and a MSW mixture. Correlations between HOC diffusion coefficients in rubbery and glassy plastics and HOC molecular size were also established and confirmed. The ability to predict contaminant sorption as a function of both MSW composition and sorbate properties represents a step forward in describing contaminant fate and transport in solid waste systems.