Search results for "waste disposal"
showing 10 items of 246 documents
Water retention behaviour and microstructural evolution of MX-80 bentonite during wetting and drying cycles
2014
MX-80 bentonite used in engineered barrier systems would be subjected to wetting and drying cycles. To assess the response of the material under such circumstances, a comprehensive experimental characterisation of the water retention behaviour of compacted MX-80 granular bentonite was performed in this study. A new methodology is proposed to investigate this behaviour under a constant volume condition for specimens prepared at different dry densities. The material was subjected to different hydraulic paths, including cyclic variations of the water content. As a result, an irreversible modification of the retention behaviour was observed when the material approached a fully saturated state …
Microfungal Alkylation and Volatilization of Selenium Adsorbed by Goethite
2009
Selenium adsorbed in the oxyanionic form by Fe-oxides like goethite is considered of benefit for long-term stabilization of (79)Se under near field conditions of radionuclide waste disposal sites. However, microbe-mediated volatilization of the uranium fission product (79)Se has not yet been considered for risk assessment based on the use of the water-solid distribution coefficient K(D). We have performed incubation experiments in a ternary system selenium-microbe-goethite and show that mycobiota including the common black microfungi genera Alternaria alternata are capable of volatilizing the Se even if immobilized by goethite. The microfungi were incubated in a standardized nutrient broth …
Effect of C/N shock variation on the performances of a moving bed membrane bioreactor.
2015
Abstract The effect of a sharp variation of C/N ratio in a moving bed membrane bioreactor (MB-MBR) pilot plant treating high strength wastewater has been investigated. The experimental campaign was divided into two periods, each characterized by a different C/N ratio (namely, 2.5 and 15, Period 1 and Period 2, respectively). The MB-MBR system was analyzed in terms of organic carbon removal, nitrification efficiency, biokinetic activity and fouling behavior. The results showed that the nitrification process was severely affected by lower C/N value and by high concentration of ammonia. It was noticed an extensive stress effect on the autotrophic bacteria. Furthermore, it was observed an incre…
Performance and convergence in municipal waste treatment in the European Union.
2019
This paper assesses performance and convergence in the treatment of municipal waste by the members of the European Union-27 (EU-27) during the period 1995-2016. First, a composite indicator of performance -including landfill, incineration, recycling, and composting and digestion as treatment operations- is computed with Data Envelopment Analysis and Multi-Criteria-Decision-Making techniques at country and year levels. Then, convergence is assessed using the techniques proposed by Phillips and Sul (2007, 2009) and, more recently, by Kong et al. (2017). The best performers are Central and Northern European countries such as Denmark, Austria and Germany, whereas the worst are some Eastern Euro…
Biogas from municipal solid waste landfills: A simplified mathematical model
2018
AbstractMunicipal solid waste (MSW) landfills now represent one of the most important issues related to the waste management cycle. Knowledge of biogas production is a key aspect for the proper exploitation of this energy source, even in the post-closure period. In the present study, a simple mathematical model was proposed for the simulation of biogas production. The model is based on first-order biodegradation kinetics and also takes into account the temperature variation in time and depth as well as landfill settlement. The model was applied to an operating landfill located in Sicily, in Italy, and the first results obtained are promising. Indeed, the results showed a good fit between me…
The influence of solid retention time on IFAS-MBR systems: analysis of system behavior.
2018
A University of Cape Town Integrated Fixed-Film Activated Sludge Membrane Bioreactor (UCT-IFAS-MBR) pilot plant was operated at different values of the sludge retention time (SRT). Three SRTs were investigated at different durations: indefinitely, 30 and 15 days. The organic carbon, nitrogen and phosphorus removal, kinetic/stoichiometric parameters, membrane fouling tendency and sludge filtration properties were assessed. The findings showed that by decreasing the SRT, the pilot plant could maintain excellent carbon removal efficiencies throughout the experiments. In contrast, the biological carbon removal showed a slight nitrification and was slightly affected by the decrease of the SRT, s…
Bedrock Characterisation of Four Candidate Repository Sites in Finland As Determined by He-Gas Methods
1999
AbstractAt the end of the year 2000, one of four sites will be chosen as the final repository site in Finland. Therefore accurate and comprehensive statistics of the bedrock characteristics such as porosity [% ] and effective diffusion coefficient [m2/s ] of these sites are of importance. Altogether 115 rock samples from the four sites were measured by different He-gas methods to achieve this goal.The results obtained indicate that the average bedrock properties at these sites are quite similar. Variations among individual samples and different rock types within one repository site were larger than variations among the averaged values of the four sites. Some indication of increased microfra…
Optimum design and operation of primary sludge fermentation schemes for volatile fatty acids production.
2003
This paper presents a model-knowledge based algorithm for optimising the primary sludge fermentation process design and operation. This is a recently used method to obtain the volatile fatty acids (VFA), needed to improve biological nutrient removal processes, directly from the raw wastewater. The proposed algorithm consists in a heuristic reasoning algorithm based on the expert knowledge of the process. Only effluent VFA and the sludge blanket height (SBH) have to be set as design criteria, and the optimisation algorithm obtains the minimum return sludge and waste sludge flow rates which fulfil those design criteria. A pilot plant fed with municipal raw wastewater was operated in order to …
Trends of organochlorine compounds in Finnish inland waters
2001
Caged common lake mussels (Anodonta piscinalis) have been used in the monitoring of organochlorine compounds in pulp and paper mill recipient watercourses of Finland annually from 1984 to 1998. Statistically significant decreasing trends of chlorophenols and chloroguaiacols originating from chlorobleaching were observed in all recipients in parallel with the decreasing discharges from the mills. Metabolites of chlorophenols, chloroanisoles and chloroveratroles had no or slightly increasing trends. Elevated PCB concentrations were measured in four watercourses. In two areas, PCBs were found to be significantly increasing, in two other cases they showed no trend. A mill producing recycled pap…
Refractory organic pollutants and toxicity in pulp and paper mill wastewaters
2015
This review describes medium and high molecular weight organic material found in wastewaters from pulp and paper industry. The aim is to review the versatile pollutants and the analysis methods for their determination. Among other pollutants, biocides, extractives, and lignin-derived compounds are major contributors to harmful effects, such as toxicity, of industrial wastewaters. Toxicity of wastewaters from pulp and paper mills is briefly evaluated including the methods for toxicity analyses. Traditionally, wastewater purification includes mechanical treatment followed by chemical and/or biological treatment processes. A variety of methods are available for the purification of industrial w…