Waste disposal deposits
Construction of a waste deposit in Tulcea.
Depending on the type of waste accepted, the deposits are classified into hazardous waste deposits (class a), non-hazardous waste deposits (class b), deposits for inert materials (class c) and landfills for only one type of waste (monodepony). Deposits must have guard systems, weighing equipment, analysis laboratories, gas recovery and leachate treatment plants, machinery (bulldozers, loaders, compactors, scrapers, excavators) and maintenance services for these machines.
Compaction of waste in a warehouse.
Currently, landfilling requires the closure of landfill (burial) and is a common practice in many countries. Such ramps are organized in quarries where the operation has ended or in abandoned mines. A properly constructed and operated waste ramp is a relatively inexpensive method that meets the ecological criteria for waste disposal. Old, unsuitable ramps have negative effects on the environment, such as littering, attracting pests (insects, rodents) and air, water and soil pollution. Air pollution occurs through miasma and by the release of gases resulting from fermentation, such as carbon dioxide and methane, which produce a greenhouse effect and contribute to global warming. The pollution of water and soil is done by leachate (the liquid leaked from biochemical processes), which, in the absence of an insulating layer, infiltrates the soil and pollutes the waters of the groundwater. These pollution can be so severe that it prevents the growth of plants above these ramps. Normally, on the ramp, the waste is compacted to increase their density and stability, and covered with foil and earth..
Ramps for organic waste have waste gas recovery facilities. The main components of this gas are methane (54%) and carbon dioxide (45%), plus small amounts of hydrogen sulphide, carbon monoxide, mercaptans, aldehydes, esters and other organic compounds. It can be recovered by burning. If there is no possibility of local recovery, it is recommended that it be burned at the light installation because the carbon dioxide resulting from combustion of methane has a lower greenhouse effect than the initial methane.
To prevent the leachate from seeping into the ground, modern ramps are provided with insulating layers, which may be clay (clay) or thick sheets of plastic (geomembrane) or textile (geotextile). Clay layer thickness must be greater than 1 m for inert or non-hazardous waste and greater than 5 m for hazardous waste.
Incineration for waste disposal
Spittelau incineration plant in Vienna.
Incineration is a method of waste disposal by burning them. It is one of the methods of heat treatment of waste. After incineration, heat, gas, steam and ash are obtained.
Lately, there has been talk of waste co-incineration. In this case the waste is burned in the outlets of the large energy boilers or in the cement kilns, in combination with their usual fuel. The share of waste in the fuel mixture is approx. 10%. The term "co-incineration" applies if the combustion of the fuel mixture containing and waste does not divert the combustion plant from its ordinary use. If in such an installation the main purpose becomes incineration of waste, the process will be considered incineration, not co-incineration, and the conditions for authorizing the operation in this case will be stricter, ie those for incinerators.
The international symbol of recycling.
Recovery means the extraction of waste resources that can be reused. Recovery can be done through recycling, reuse, regeneration or any other process of extraction of auxiliary raw materials. Both the material and the energetic part can be recovered. Materials can be reused to produce new goods, and energy can be converted into electricity. As with elimination, recovery must be done without endangering human health and using processes or methods that may be environmentally harmful.
Material recovery in waste disposal
Sorted and sorted steel waste for recycling at Central European Waste Management facility in Wels, Austria.
For a successful recycling, a sorting is required depending on the quality of the material, sorting that starts with their selective collection. They can also be separated into waste sorting facilities.
Common materials that can be recovered are aluminum from beer cans, steel from food packaging and sprays, high-density polyethylene and polyethylene terephthalate packaging, bottles and jars, paper from newspapers and magazines, cardboard from packaging. Plastics such as vinyl polychloride, low density polyethylene, polypropylene (PP) and polystyrene (PS) can be recovered, although they are not currently collected. Products made from such materials are usually homogeneous, containing a single component, which facilitates recycling. By comparison, recycling of electrical and electronic equipment is more difficult, as it requires technologies to separate the different materials that compose them.
In warehouses, recovery begins with sorting materials. For mixed waste, the first operation is shredding, which is operated in mills with hammers, drills, shredders, shreds. Next is the dimensional sorting in drum site, vibrating sieves, ballistic separators, densimetric sorting in cyclones, magnetic sorting of ferrous materials, optical sorting (for glass) and, eventually, manual sorting. Following purification operations by washing. The sorted and purified wastes are packed in the press, being ready for delivery to the beneficiary.
If the mixed waste contains biological components, they can be processed biologically, but the other recoverable materials should be separated as far as possible
Biological processing in waste disposal
Composting arrangement.
Organic waste, such as vegetable waste, food waste and paper, can be recycled by composting, which involves a process of decomposition of organic matter. The result is compost, an excellent agricultural fertilizer. During composting, biogas with a high content of methane is produced, which can be used as such, for example in stoves, or in power plants for the production of electricity. By composting in arranged plants the natural process of decomposition of organic matter is accelerated.
Composting can be carried out both in small individual installations in households and in large industrial installations (eg wastewater treatment plants). It can occur both by aerobic and anaerobic fermentation.
Another source of biogas is municipal sludge, resulting from municipal wastewater treatment plants or industrial wastewater treatment plants.
Combustible materials can be obtained both by biological processing and by high pressure pyrolysis and gasification processes in oxygen poor atmosphere. Advanced methods (plasma arc gasification) can produce a synthesis gas (syngas) with an even better composition, consisting of carbon monoxide and hydrogen.
Energy recovery from waste disposal
Wastes from which energy can be recovered are wood (wood waste from crops, waste from wood industry and demolition), storage gas and biogas. The wood has a calorific value of 14–17 MJ / kg, and the storage gas and biogas have similar compositions and calorific values of 20–25 MJ / m³N. As a result they can be burned in domestic installations, or in boilers for the production of heat or, with the help of turbines, the electric current.