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An anaerobic lagoon or manure lagoon is a man-made outdoor earthen basin filled with animal waste that undergoes anaerobic respiration as part of a system designed to manage and treat refuse created by Concentrated Animal Feeding Operations (CAFOs). Anaerobic lagoons are created from a manure slurry, which is washed out from underneath the animal pens and then piped into the lagoon. Sometimes the slurry is placed in an intermediary holding tank under or next to the barns before it is deposited in a lagoon. Once in the lagoon, the manure settles into two layers: solid, or sludge, layer and the liquid layer. The manure then undergoes the process of anaerobic respiration, whereby the volatile organic compounds are converted into carbon dioxide and methane. Anaerobic lagoons are usually used to pretreat high strength industrial wastewaters, and municipal wastewaters. This allows for preliminary sedimentation of suspended solids as a pretreatment process. 〔(【引用サイトリンク】url=http://water.epa.gov/scitech/wastetech/upload/2002_10_15_mtb_alagoons.pdf )〕 Anaerobic lagoons have been shown to harbor and emit substances which can cause adverse environmental and health effects. These substances are emitted through two main pathways: gas emissions and lagoon overflow. Gas emissions are continuous (though the amount may vary based on the season) and are a product of the manure slurry itself. The most prevalent gasses emitted by the lagoon are: ammonia, hydrogen sulfide, methane, and carbon dioxide. Lagoon overflow is caused by faulty lagoons, such as cracks or improper construction, or adverse weather conditions, such as increased rainfall or strong winds. These overflows release harmful substances into the surrounding land and water such as: antibiotics, estrogens, bacteria, pesticides, heavy metals, and protozoa. In response to environmental and health concerns, the Environmental Protection Agency (EPA) has tightened regulation of the CAFO under the Clean Water Act (CWA). Some states have imposed their own regulation as well. Due to repeated overflows and resultant health concerns, North Carolina banned the construction of new anaerobic lagoons in 1999. There has also been a significant push for the research, development and implementation of environmentally sound technologies (ESTs) which would allow for safer containment and recycling of CAFO waste. == Background == Beginning in the 1950s with poultry and then later in the 1970s and 1980s with cattle and swine, meat producers in the United States have turned to the Concentrated Animal Feeding Operation as a way to more efficiently produce large quantities of meat. This switch has benefited the United States consumer by increasing the amount of meat that can be grown thereby decreasing the price of meat. However, the increase in livestock has generated an increase in manure. In 2006, for example, livestock operations in the United States produced 133 million tons of manure.〔 Unlike manure produced in a conventional farm, CAFO manure cannot all be used as direct fertilizer on agricultural land due to the poor quality of the manure. Moreover, CAFOs produce a high volume of manure. A feeding operation with 800,000 pigs could produce over 1.6 million tons of waste a year.〔 The high quantity of manure produced by a CAFO must be dealt with in some way, as improper manure management can result in water, air and soil damage.〔 As a result, manure collection and disposal has become an increasing problem.〔(【引用サイトリンク】url=http://www.nrdc.org/water/pollution/nspills.asp )〕 In order to manage their waste, CAFOs have developed Agricultural wastewater treatment plans. To save on manual labor, many CAFOs handle manure waste as a liquid. In this system, the animals are kept in pens with grated floors so the waste and spray water can be drained from underfloor gutters and piped to storage tanks or anaerobic lagoons.〔 Once at a lagoon, the purpose is to treat the waste and make it suitable for spreading on agricultural fields.〔 There are three main types of lagoon: anaerobic, which is inhibited by oxygen; aerobic, which requires oxygen; and facultative, which is maintained with or without oxygen.〔 Aerobic lagoons provide a higher degree of treatment with less odor production, though they require a significant amount of space and maintenance. Because of this demand, almost all livestock lagoons are anaerobic lagoons.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Anaerobic lagoon」の詳細全文を読む スポンサード リンク
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