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At least 127 records · Page 7Linked to original sources
PubMed1996

Anaerobic degradation of phthalic acid esters during digestion of municipal solid waste under landfilling conditions.

Anaerobic microorganisms in municipal solid waste samples from laboratory-scale landfill reactors and a pilot-plant biogas digestor were investigated with the aim of assessing their ability to transform four commercially used phthalic acid esters (PAEs) and phthalic acid (PA). The PAEs studied were diethyl phthalate (DEP), butylbenzyl phthalate (BBP), dibutyl phthalate (DBP) and bis(2-ethylhexyl) phthalate (DEHP). No biological transformation of DEHP could be detected in any of the experiments. Together with waste samples from the simulated landfilling conditions, the PAEs (except DEHP) were hydrolytically transformed to their corresponding monoesters. These accumulated as end products, and in most cases they were not further degraded. During incubation with waste from the biogas digestor, the PAEs (except DEHP) were completely degraded to methane and carbon dioxide. The influence of the landfill development phase on the transformations was investigated utilizing PA and DEP as model substances. We found that during both the intense and stable methanogenic (but not the acidogenic) phases, the microorganisms in the samples had the potential to transform PA. A shorter lag phase was observed for the PA transformation in the samples from the stable methanogenic phase as compared with earlier phases. This indicates an increased capacity to degrade PA during the aging phases of the municipal solid waste in landfills. No enhancement of the DEP transformation could be observed as conditions in the methanogenic landfill model changed over a year's time. The results indicate that microorganisms developing in a methanogenic landfill environment have a substantially lower potential to degrade compared with those developing in a biogas reactor.

Anaerobiosis↗
PubMed1975

Studies on the survival and fate of enteroviruses in an experimental model of a municipal solid waste landfill and leachate.

In laboratory scale municipal solid waste lysimeters containing simulated refuse, and seeded with either laboratory or field strains of poliovirus type 1 and echovirus type 7, viruses were not detected in the lysimeter leachate produced over a 4-month period. In addition, viruses were detected in the lysimeter refuse contents after termination of lysimeter operation. These results appeared to be due to virus retention in the lysimeter caused by virus adsorption and virus inactivation. Evidence for virus inactivation was provided by the results of experiments on virus inactivation in composite leachate samples. Evidence for virus adsorption was supported by the rapid adsorption of viruses to various municipal solid waste components in the presence of a salt similar in composition to the major inorganic salts of leachates.

Adsorption↗
PubMed2002

A comparative analysis of a balance between the rates of polymer hydrolysis and acetoclastic methanogenesis during anaerobic digestion of solid waste.

A distributed model of anaerobic digestion of solid waste was developed. Waste, volatile fatty acids (VFA), methanogenic biomass and methane concentrations were the model variables. A system of parabolic partial differential equations in the one space variable and time with slab, cylindrical or spherical symmetry of the problem was solved numerically. Diffusion of VFA inhibiting both polymer hydrolysis and acetoclastic methanogenesis was taken into account. The model showed that concentration waves of methanogenic biomass and VFA propagated over reaction space. Diffusion-based "acceleration" of methane production in the reactor was possible when intensity of VFA utilisation in the methanogenic area was sufficient for complete digestion of incoming VFA. Otherwise, methanogenic area propagation would be suppressed. Optimum conditions for the solid waste digestion can be reached at low mass transfer at the beginning and at high mass transfer when methanogenic population increases. If the initial methanogenic biomass was localised at the centre of the reactor, the total reaction time was shorter as compared to the case when the initial biomass was uniformly distributed over the reactor volume. In the last case, there was no concentration wave propagation.

Bacteria, Anaerobic↗
PubMed2002

Effect of mass transfer on concentration wave propagation during anaerobic digestion of solid waste.

A distributed model of anaerobic digestion of solid waste was developed to study effects of mass transfer on the rate of propagation of initiation methanogenic area. The diffusion and advection of volatile fatty acids (VFA) and methanogenic biomass were taken into account in the model of a one-dimensional (ID) reactor. It was considered that VFA inhibits both polymer hydrolysis and acetoclastic methanogenesis. This approach allows to view the bioreactor as an active medium that provokes concentration waves from some area of methanogenic initiation (local VFA depression) to the total reactor volume. The model shows that mass transfer-based acceleration of methane production in the reactor is possible when the intensity of VFA utilization in the methanogenic area is sufficient for a complete digestion of the incoming VFA. Otherwise, initiation methanogenic area will be suppressed by increasing concentration of VFA. The obtained results emphasize the importance of considering spatial heterogeneity of the reaction for the analysis of solid anaerobic digestion in bioreactors and landfills. The digestion of solid waste can be optimized by setting the low rate of mass transfer (mixing or leachate recirculation) during lag-phase of the reaction with subsequent increase in the mass transfer rate in parallel with the propagation of methanogenic population. In this case, the rate of concentration waves substantially increases.

Biomass↗
PubMed2006

[Ecoefficiency: a tool to reduce solid waste production and waste of materials in health care units].

The main goal of health care units is patient care. During this process, water, energy, and different materials are used, generating liquid effluents and solid waste that require adequate treatment. Although medical waste management demands increasing attention by health care units, reduction in the generation of medical solid waste has still not been set as a priority. Using ecoefficiency techniques, it is possible to demonstrate whether a company is meeting it standards for quality, procedures, environmental control, and economic efficiency. Therefore, ecoefficient companies realize both economic and environmental benefits through progressive reduction in solid waste, liquid effluents, and air emissions. This new concept requires further dissemination among health care units, since many are making efforts to improve quality of services, but still overlook the issue of waste and generate an increasing amount of solid waste. This leads not only to waste of raw materials but also additional costs for proper waste management.

Efficiency, Organizational↗
PubMed1999

Bioconversion of mixed solids waste to ethanol.

A mixed solids waste (MSW) feedstock, comprising construction lumber waste (35% oven-dry basis), almond tree prunings (20%), wheat straw (20%), office waste paper (12.5%), and newsprint (12.5%), was converted to ethanol via dilute-acid pretreatment followed by enzymatic hydrolysis and yeast fermentation. The MSW was pretreated with dilute sulfuric acid (0.4% w/w) at 210 degrees C for 3 min in a 4-L steam explosion reactor, then washed with water to recover the solubilized hemicellulose. The digestibility of water-washed, pretreated MSW was 90% in batch enzymatic hydrolysis at 66 FPU/g cellulose. Using an enzyme-recycle bioreactor system, greater than 90% cellulose hydrolysis was achieved at a net enzyme loading of about 10 FPU/g cellulose. Enzyme recycling using membrane filtration and a fed-batch fermentation technique is a promising option for significantly reducing the cost of enzyme in cellulose hydrolysis. The hexose sugars were readily fermentable using a Saccharomyces cerevisiae yeast strain that was adapted to the hydrolysate. Solid residue after enzyme digestion was subjected to various furnace experiments designed to assess the fouling and slagging characteristics. Results of these analyses suggest the residue to be of a low to moderate slagging and fouling type if burned by itself.

Biodegradation, Environmental↗
PubMed2003

Characterization of the solid waste stream of the Tohono O'odham nation.

The Tohono O'odham Nation's Solid Waste Management Program (SWMP) and the Sonora Environmental Research Institute, Inc. (SERI) completed a waste characterization study for the Tohono O'odham Nation (the Nation) to aid in the development of an effective waste management plan. The Nation has recently switched from open dumping and burning of waste to collection in dumpsters and transportation to regulated landfills. The study indicated that members of the Nation produce approximately one-third of the average amount of municipal solid waste produced per person per day in the United States. Far fewer hazardous materials and yard trimmings are found in the waste stream than is the U.S. average. Source reduction options are limited because much of the residential waste comes from packaging materials. Recycling opportunities exist but are hampered by the long distance to markets, which forces the Nation to look at innovative ways of utilizing materials on site. An education program focusing on the traditional O'odham lifestyle has been implemented to help reduce solid waste generation while improving people's health and the environment.

Arizona↗
PubMed2003

Distributed model of solid waste anaerobic digestion: effects of leachate recirculation and pH adjustment.

A distributed model of solid waste digestion in a 1-D bioreactor with leachate recirculation and pH adjustment was developed to analyze the balance between the rates of polymer hydrolysis/acidogenesis and methanogenesis during the anaerobic digestion of municipal solid waste (MSW). The model was calibrated on previously published experimental data generated in 2-L reactors filled with shredded refuse and operated with leachate recirculation and neutralization. Based on model simulations, both waste degradation and methane production were stimulated when inhibition was prevented rapidly from the start, throughout the reactor volume, by leachate recirculation and neutralization. An optimal strategy to reduce the time needed for solid waste digestion is discussed.

Anaerobiosis↗
PubMed2004

Effect of alkalinity on the performance of a simulated landfill bioreactor digesting organic solid wastes.

This study investigated the effects of alkalinity on the anaerobic treatment of the organic solid wastes collected from the kitchen of Engineering Faculty in Dokuz Eylul University, Izmir, Turkey and the leachate characteristics treated in three simulated landfill anaerobic bioreactors. All of the reactors were operated with leachate recirculation. One reactor was operated without alkalinity addition. The second reactor was operated by the addition of 3 g l-1 d-1 of NaHCO3 alkalinity to the leachate and the third reactor was operated by the addition of 6 g l-1 d-1 NaHCO3 alkalinity to the leachate. After 65 d of anaerobic incubation, it was observed that the chemical oxygen demand (COD), volatile fatty acids (VFA) concentrations, and biochemical oxygen demand to chemical oxygen demand (BOD5/COD) ratios in the leachate samples produced from the alkalinity added reactors were lower than the control reactor while the pH values were higher than the control reactor. The COD values were measured as 18900, 3800 and 2900 mg l-1 while the VFA concentrations were 6900, 1400 and 1290 mg l-1, respectively, in the leachate samples of the control, and reactors containing 3 g l-1 NaHCO3 and 6 g l-1 NaHCO3 after 65 d of anaerobic incubation. The total nitrogen (TN), total phosphorus (TP) and ammonium nitrogen (NH4-N) concentrations in organic solid waste (OSW) significantly reduced in the reactor containing 6 g l-1 NaHCO3 by d 65. The values of pH were 6.54, 7.19 and 7.31, after 65 d of anaerobic incubation, respectively, in the aforementioned reactors results in neutral environmental conditions in alkalinity added reactors. Methane percentage of the control, reactors containing 3 g l-1 NaHCO3 and 6 g l-1 NaHCO3 were 37%, 64% and 65%, respectively, after 65 d of incubation. BOD5/COD ratios of 0.27 and 0.25 were achieved in the 3 and 6 g l-1 NaHCO3 containing reactors, indicating a better OSW stabilization. Alkalinity addition reduced the waste quantity, the organic content of the solid waste and the biodegradation time.

Bacteria, Anaerobic↗
PubMed1993

Variability over time in the mutagenicity of ashes from municipal solid-waste incinerators.

Incineration of municipal solid waste as an alternative to its disposal in landfills has advantages such as volume reduction and generation of energy. However, both air emissions and the residual ash may pose environmental and human health hazards. The Ames mutagenicity assay was used to determine the mutagenicity of fly and bottom ash from two incinerators over time. This assay is an alternative to costly and time-consuming chemical analyses and is more realistic for the assessment of the best disposition of the ash i.e. whether it could pose a risk to handlers of the ash, whether it can be used in cement or as a fertilizer or whether it should be relegated to a landfill. The mutagenic potency of fly and bottom ash on a per g weight basis of material is similar. Furthermore, the variability over time in mutagenicity indicates that constant monitoring of incineration products and byproducts is essential.

Humans↗
PubMed2001

Cellulolytic activity in leachate during leach-bed anaerobic digestion of municipal solid waste.

The degradation of municipal solid waste (MSW) under mesophilic conditions can be enhanced by exchanging leachate between fresh waste and stabilised waste. The optimum point in time when leachate from an anaerobically digesting waste bed can be used to initiate degradation of another waste bed might occur when the leachate of the digesting waste bed is highly active with cellulolytic and methanogenic bacteria. In this study, the cellulolytic activity of the leachate was measured using the cellulose-azure assay. As products of hydrolysis are soluble compounds, the rate of generation of these compounds was estimated based on a soluble chemical oxygen demand (SCOD) balance around the fresh waste bed. It was found that once the readily soluble material present in MSW was washed out there was very little generation of SCOD without the production of methane, indicating that flushing leachate from a stabilised waste bed resulted in a balanced inoculation of the fresh waste bed. With the onset of sustained methanogenesis, the rate of SCOD generation equalled the SCOD released from the digester as methane. The experimental findings also showed that cellulolytic activities of the leachate samples closely followed the trend of SCOD generation. reserved.

Biodegradation, Environmental↗
PubMed2002

Using multiple criteria decision analysis for supporting decisions of solid waste management.

Design of solid-waste management systems requires consideration of multiple alternative solutions and evaluation criteria because the systems can have complex and conflicting impacts on different stakeholders. Multiple criteria decision analysis (MCDA) has been found to be a fruitful approach to solve this design problem. In this paper, the MCDA approach is applied to solve the landfill selection problem in Regina of Saskatchewan Canada. The systematic approach of MCDA helps decision makers select the most preferable decision and provides the basis of a decision support system. The techniques that are used in this study include: 1) Simple Weighted Addition method, 2) Weighted Product method, 3) TOPSIS, 4) cooperative game theory, and 5) ELECTRE. The results generated with these methods are compared and ranked so that the most preferable solution is identified.

Decision Support Techniques↗
PubMed2004

Enhancement of carbon and nitrogen transformations during composting of municipal solid waste.

Appropriate management of municipal solid waste (MSW) is viewed as an integrated system encompassing waste minimization, recycling, and resource recovery. This has increased the interest in the composting process, in which the biodegradable portion of MSW is biologically converted into a valuable product that can be utilized as a soil conditioner or fertilizer. Effective operation of the composting process can be achieved by determining the optimal conditions for the controlling parameters in order to enhance the biological reactions during composting. Information on biodegradation rates are also essential for process design. Therefore, this study was conducted in order to examine the factors affecting process performance and transformation of essential elements of MSW such as carbon and nitrogen. A pilot study of in-vessel aerobic composting of MSW was carried out and the operating parameters, which affect biodegradation of carbonaceous and nitrogenous matter were studied using a specially designed rotating drum and a carbon-rich MSW. The effects of temperature, moisture content, and air flow rate were examined. The performance of the composting process was evaluated by measuring the carbon and nitrogen content during experiments, each of which lasted for 30 days. The study showed that enhanced transformations of carbon and nitrogen occur at 55 degrees C for temperature, 60% for moisture content, and 10L/kgh for air flow rate using the food-rich MSW generated in the Gulf countries.

Bacteria, Aerobic↗
PubMed2001

Analysis of ingredient and heating value of municipal solid waste.

Great differences between municipal solid wastes (MSW) produced at different places and different times in terms of such parameters as physical ingredient and heating value lead to difficulty in effective handling of MSW. In this paper, ingredient, heating value and their temporal varying trends of typical MSW in Beijing were continuously measured and analyzed. With consideration of the process in pyrolysis and incineration, correlation between physical ingredients and heating values was induced, favorable for evaluation of heating value needed in handling of MSW from simple analysis of physical ingredients of it.

China↗
PubMed2004

Risk of congenital anomalies in the vicinity of municipal solid waste incinerators.

BACKGROUND: Although municipal solid waste incineration (MSWI) has contributed to increase the overall environmental load of particulate matter containing dioxins and metals, evidence of health consequences to populations is sparse. AIMS: To assess at a regional level (in southeast France) the impact of these emissions on birth defect rates. METHODS: Communities with fewer than 50 000 inhabitants surrounding the 70 incinerators that operated at least one year from 1988 to 1997 were studied. Each exposed community (n = 194) was assigned an exposure index estimated from a Gaussian plume model. Poisson models and a reference population of the 2678 unexposed communities in the region were used to calculate relative risks for congenital malformations, adjusted for year of birth, maternal age, department of birth, population density, average family income, and when available, local road traffic. RESULTS: The rate of congenital anomalies was not significantly higher in exposed compared with unexposed communities. Some subgroups of major anomalies, specifically facial clefts and renal dysplasia, were more frequent in the exposed communities. Among exposed communities, a dose-response trend of risk with increasing exposure was observed for obstructive uropathies. Risks of cardiac anomalies, obstructive uropathies, and skin anomalies increased linearly with road traffic density. CONCLUSIONS: Although both incinerator emissions and road traffic may plausibly explain some of the excess risks observed, several alternative explanations, including exposure misclassification, ascertainment bias, and residual confounding cannot be excluded. Some of the effects observed, if real, might be attributable to old-technology MSWIs and the persistent pollution they have generated.

Abnormalities, Drug-Induced↗
PubMed2001

Synthetic fuel for imitation of municipal solid waste in experimental studies of waste incineration.

Synthetic fuel is prepared to imitate municipal solid waste (MSW) in experimental studies of incineration processes. The fuel is composed based on the Environmental Protection Agency reports on the materials contained in MSW. Uniform synthetic fuel pellets are prepared using available and inexpensive components including newsprint, hardwood mulch, low density polyethylene, iron, animal feed, sand, and water to imitate paperbound, wood, yard trimming, plastic, metal, food wastes, and other materials in MSW. The synthetic fuel preparation procedure enables one to reproduce and modify the fuel for a wide range of experiments in which the mechanisms of waste incineration are addressed. The fuel is characterized using standard ASTM tests and it is shown that its parameters, such as combustion enthalpy, density, as well as moisture, ash and fixed carbon contents are adequate for the representation of municipal solid waste. In addition, chlorine, nitrogen, and sulfur contents of the fuel are shown to be similar to those of MSW. Experiments are conducted in which the synthetic fuel is used for operation of a pilot-scale incinerator research facility. Steady-state temperature operation regimes are achieved and reproduced in these experiments. Thermodynamic equilibrium flame conditions are computed using an isentropic one-dimensional equilibrium code for a wide range of fuel/air ratios. The molecular species used to represent the fuel composition included cellulose, water, iron, polyethylene, methanamine, and silica. The predicted concentrations of carbon monoxide, nitric oxides, and oxygen in the combustion products are compared with the respective experimental concentrations in the pilot-scale incinerator exhaust.

Air Pollutants↗
PubMed2006

Composting of lead-contaminated solid waste with inocula of white-rot fungus.

The treatment of the simulated lead-contaminated solid waste by composting with white-rot fungus was studied at laboratory scale. The composting system without the inocula of white-rot fungus was prepared as control, and the composting of the uncontaminated solid waste with the inocula of white-rot fungus was carried out as the other control. The results indicated that the solid waste inoculated with white-rot fungus could be successfully processed. The final compost was mature with 70.5% of lead (Pb) in residual fraction and none in exchangeable fraction. Germination index reached 120%. All the results indicated that the bioavailability of Pb in compost was reduced and the potential harm of Pb in compost was alleviated by composting with the inocula of white-rot fungus.

Basidiomycota↗
PubMed2005

From dumping to sanitary landfills--solid waste management in Israel.

To address the problem of solid waste in Israel, the Ministry of the Environment has formulated a policy based on integrated waste management. The policy calls for reduction of waste at source, reuse, recycling (including composting), waste-to-energy technologies, and landfilling. Due to the implementation of this policy, all the large dumps were closed, state-of-the art landfills were built, and recovery rates have increased from 3% in the beginning of the 1990s to almost 20% in 2003. More than 95% of the municipal solid waste is disposed and treated in an environmentally sound manner - in comparison to a mere 10% just a decade ago. The policy was implemented utilizing both enforcement and financial support ("stick and carrot" approach).

Conservation of Natural Resources↗