One of several gas vents at Nantmel landfill

Nantmel Landfill Site, 52°16′57″N 3°26′25″W / 52.282586, -3.440309 is a closed waste-disposal site situated outside the community of Nantmel, Llandrindod Wells, Powys. Llandrindod Wells (Llandrindod known locally as "Llandod" is a Town in Powys, Wales. This article is about the county of Wales For the ancient kingdom see Kingdom of Powys. It operated from 1960 to 1990, accepting domestic, commercial, non-hazardous industrial, inert and asbestos waste. Asbestos is a group of Minerals with long thin fibrous Crystals The word "asbestos" (῾ἀσβεστος is derived from a Greek adjective It was one of 80 municipal landfill sites in Powys, of which all have now closed. Three privately owned sites still operate within the county. ^[1] The site still produces significant pollutants, in the form of gas and leachate from landfill decomposition, and is currently undergoing rehabilitation. See also Natural gas, Biofuel Biogas typically refers to a Gas produced by the biological breakdown of Organic matter in the Leachate is the liquid that drains or 'leaches' from a Landfill; it varies widely in composition regarding the age of the landfill and the type of Waste that Decomposition (or spoilage) refers to the break down of tissue of a formerly living Organism into simpler forms of matter Land rehabilitation is the process of returning the land in a given area to some degree of its former state after some process ( Industry, Natural disasters etc ^[2]

Structure

The 8. 5ha site was constructed in a valley, with the stream piped underneath and the waste lain on top, forming the present day dome shape, characteristic of many landfills. Explanation The hectare is commonly used in most countries around the world especially in domains concerned with land planning and management such as Agriculture, For other uses see Water treatment and Land reclamation. A landfill, also known as a dump (and historically as Unlike modern landfills, which are impermeably sealed with geomembranes, Nantmel was engineered without effective base and cap layers, for instance subsoil from a local road-widening scheme was used instead of a liner. Geomembranes are a kind of Geosynthetic material They are impermeable membranes used widely as cut-offs and liners Intended to be reclaimed for pastoral purposes, the site was fenced, but the availability of higher quality pasture in the surrounding fields led to little interest from farmers. Pastoral, as an adjective refers to the lifestyle of Shepherds and Pastoralists moving livestock around larger areas of land according to seasons and availability Without the compaction and grazing by farm animals, the plants and topsoil became low quality, and the intention now appears to leave the site for conservation purposes. Topsoil is the upper outermost layer of soil usually the top 2 to 8 inches

Leachate treatment

Students from Aberystwyth University view the leachate lagoon (Photo from top of Nitrification tower)

Initially the leachate was managed to the 'dilute and disperse principle', producing up to 600 tonnes of leachate a day. Aberystwyth University (Prifysgol Aberystwyth sometimes called "Aber" or "the College by the Sea" is a university located in Aberystwyth, Wales Dilute is an Indie rock band from Fremont, California. They formed in 1996. Disperse is a Christian Rock band from Southern Indiana. History The band consist of Guitarists Chris Billings and Andy Higham his brother This article is about the tonne or metric ton For other tons see Ton. This cost the council £330,000 per annum to remove in tankers to Hereford. P Q R Hereford ( ˈhɛrɨfəd is a city, Civil parish and County town of Herefordshire, England. ^[3] In 1996 the installation of an on-site treatment system means costs are now just £65,000 per annum, a move commended by the Environment Agency. The Environment Agency (Asiantaeth yr Amgylchedd is a Non-Departmental Public Body of the Department for Environment Food and Rural Affairs and an Assembly ^[3]

The current system (detailed in^[2]) consists of an S3 Environmental Solutions Ltd nitrification tower^[4] (a trickling filter also known as an aeration or biofilm tower) through which the leachate is circulated over a biofilm supported on a plastic media. Nitrification is the biological oxidation of Ammonia with oxygen into Nitrite followed by the oxidation of these nitrites into Nitrates Degradation A trickling filter consists of a fixed bed of rocks Gravel, Slag, Polyurethane Foam, sphagnum Peat moss, or plastic media Aeration is the Process by which Air is circulated through mixed with or dissolved in a Liquid or substance A biofilm is a structured community of Microorganisms encapsulated within a self-developed polymeric matrix and adherent to a living or inert surface A biofilm is a structured community of Microorganisms encapsulated within a self-developed polymeric matrix and adherent to a living or inert surface The partially-treated leachate then leaves behind iron-rich sludge in the leachate lagoon (visibly stained orange; see photo to the left and satellite images) and is polished in a series of reed and gravel filter beds and a wetland system. Iron (ˈаɪɚn is a Chemical element with the symbol Fe (ferrum and Atomic number 26 Gravel is rock that is of a specific Particle size range In Geology, gravel is any loose rock that is larger than two millimeters (2mm A wetland is an area of Land consisting of Soil that is Saturated with Moisture, such as a Swamp, Marsh, or Bog ^[2] By this point the leachate meets water quality levels, and so can be released into the river system. ^[2]

The tower maintains aerobic conditions, favourable for the biofilm within, which allows:

• the degradation of organic components,
• metallic ions to be oxidised to insoluble forms (e. Redox (shorthand for reduction-oxidation reaction describes all Chemical reactions in which atoms have their Oxidation number ( Oxidation state Solubility is the characteristic Physical property referring to the ability of a given substance the Solute, to dissolve in a Solvent. g. ferrous iron to ferric iron),
• ammonia to be oxidised (via nitrite) to nitrate,
• remaining metals to precipitate into the lagoon sludge with ferric hydroxides. Iron(II oxide, also known as ferrous oxide, iron oxide/oxidized iron or more commonly rusted Ferric is a term that means containing or having to do with Iron, derived from the Latin word ferrum, meaning "iron" Ammonia is a compound with the formula N[[hydrogen H3]] It is normally encountered as a Gas with a characteristic pungent Odor The nitrite Ion is NO2− The anion is bent being Isoelectronic with O3. In Inorganic chemistry, a nitrate is a salt of Nitric acid with an Ion composed of one Nitrogen and three Oxygen atoms In Chemistry, hydroxide is the most common name for the diatomic Anion OH− consisting of Oxygen and Hydrogen

Among other pollutants, this system removes the leachate's high Biological Oxygen Demand, the ammoniacal nitrogen and ferrous iron contents. Biochemical Oxygen Demand or Biological Oxygen Demand (BOD is a chemical procedure for determining how fast biological organisms use up oxygen in a body of water Ammonia is a compound with the formula N[[hydrogen H3]] It is normally encountered as a Gas with a characteristic pungent Odor Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 ^[2]

Gas management

Landfill contents quickly degrade through the aerobic stage (1 week), and the acetogenic stages (approximately 1 month), and so Nantmel is now in the methanogenic stage (20-40 years), producing large amounts of methane, a potent greenhouse gas. Acetogenesis is a process through which Acetate is produced by Anaerobic bacteria from a variety of energy (for example Hydrogen) and carbon (for example Methanogenesis or biomethanation is the formation of Methane by Microbes known as Methanogens Organisms capable of producing methane have been Methane is a Chemical compound with the molecular formula. It is the simplest Alkane, and the principal component of Natural gas. Greenhouse gases are gaseous constituents of the atmosphere bothnatural and anthropogenic that absorb and emit radiation at specific wavelengths within the spectrum of thermal infrared At other larger sites this gas is captured and burnt for energy (see Biogas), but at Nantmel it is passively vented into the atmosphere (see top photo). See also Natural gas, Biofuel Biogas typically refers to a Gas produced by the biological breakdown of Organic matter in the In densely populated areas this would be impossible due to the asphyxiation risk. As the waste stabilises, methane production will reduce.

References