Simulation of the behavior of a refuse landfill on a laboratory scale.

The characteristics and properties of waste in a landfill, and its evolution over time, are difficult to estimate because of the heterogeneity of materials, biomass degradation, density, cover material, and infiltration of water. In this work, a lysimeter was used to simulate how refuse from mechanical-biological treatment (MBT) plants evolved in a landfill over a 45-day period. Water was added as a way to imitate the effects produced during rainy seasons. Field capacity and changes in the physical and chemical properties (volatile solids, biomass, and heating value) were analyzed. The results of this research show that the percentage of biomass lowers, and the heating value increases, after bringing about infiltration and percolation of water in the waste mass. Therefore in order to stabilize waste in a landfill, employing irrigation or leachate recirculation could be advisable. As the heating value increases after percolation, it could also be a good idea to recover the fuel material after stabilization.

Application of inert wastes in the construction, operation and closure of landfills: Calculation tool.

Waste from construction and demolition activities represents one of the highest volumes of waste in Europe. 500 million tonnes are produced throughout the whole EU every year. In some EU members like Spain, approximately 83 per cent of such waste is disposed in landfills. The remaining part is classified and processed in treatment facilities so that it can later be used as recycled aggregates in the construction sector (sand, gravel, aggregates, etc.) but without much commercial success. The aim of this study is to use recycled aggregates from inert wastes (IW) in the different phases of a landfill (construction, operation and closure) with the aid of a new computer tool called LABWASTE.14. This tool incorporates the mathematical relationship among the activities of the landfill and provides as a result the economic viability of using recycled aggregates compared to aggregates from quarries. Therefore, knowing the needs of aggregates in landfills (dams, drainage layers, covering layers, collection wells, etc.) may determine the amount of IW that could be recovered. These calculations can be obtained from some of the data that is introduced (population, land physiography, etc.). Furthermore, the use of LABWASTE.14 makes it possible to reduce the demand for aggregates from quarries.

Environmental risk index: a tool to assess the safety of dams for leachate.

Dams for leachate store very toxic substances that contain a large amount of organic material and, probably, heavy metals; they therefore constitute an important threat to the environment. Existing models of environmental risk assessment for landfills do not take into consideration the specific risk that leachate dams may represent for the environment. In this paper a methodology to improve the environmental safety is presented according to the parameters used in their construction and management. In order to do that, the following characteristics of the dam must be known: (1) geotechnical stability, (2) erosion of downstream slope, (3) type of sealing of the dam, (4) overtopping probability, (5) volume of leachate stored inside the dam and (6) pollution load of leachate. Once these parameters have been calculated, they are transformed by means of rating curves into homogeneous units, so as to make it possible to operate between them. From the study and analysis of these parameters an environmental risk index for a dam for leachate can be calculated. If the environmental risk index exceeds an established value then it involves a dam for leachate with high environmental risk, therefore preventive measures in its design, construction and management would be necessary.

Design of a model to assess the environmental risk of leachate dams.

Leachate dams store very toxic liquids, leachate, that contain a large amount of pollutant substances. Most of them are located in gullies or ravines, so if a dam breaks, leachate would advance downstream provoking an important environmental impact. In order to assess this environmental risk, the following procedure has been established: firstly, rating curves have been set up which relate characteristics of the dam with the environmental risk, secondly, a weight has been assigned to each parameter, and thirdly, the environmental elements which could be affected by the leachate have been assessed. Relating the risk generated by the characteristics of the dam with the environmental elements located in the risk area, the environmental risk index of a leachate dam can be calculated. If the environmental risk index exceeds a certain value, then it is a dam with a high environmental risk. A high value can be due to low geotechnical stability, to very sensitive environmental elements, or both.