page_title: Anaerobic lagoon
section_title: Description
hierarchical_section_title: Anaerobic lagoon / Design / Description
caption_attribution_description: English: View of the anaerobic lagoon at the dairy at California Polytechnic State University, San Luis Obispo. The dairy can be seen in the background and the 25-kW power plant fired using the biogas is on the right.
context_page_description: 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. 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 intermediate 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: a solid or sludge layer and a 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.
  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.
context_section_description: Anaerobic lagoons are earthen basins with a usual depth of 8 feet (2.4 metres), though greater depths are more beneficial to digestion as they minimize oxygen diffusion from the surface. To minimize leakage of animal waste into the ground water, newer lagoons are generally lined with clay Studies have shown that in fact the lagoons typically leak at a rate of approximately 1 millimetre (0.04 inches) per day, with or without a clay liner, because it is the sludge deposited at the base of the lagoon that limits the leakage rate, not the clay liner or underlying native soil. Anaerobic lagoons are not heated, aerated or mixed. Anaerobic lagoons are most effective in warmer temperatures; anaerobic bacteria are ineffective below 15 degrees Celsius (59 degrees Fahrenheit) Lagoons must be separated from other structures by a certain distance to prevent contamination. States regulate this separation distance. The overall size of the lagoon is determined by addition of four components: minimum design volume, volume of manure storage between periods of disposal, dilution volume and the volume of sludge accumulation between periods of sludge removal.
caption: Anaerobic treatment lagoon at the Cal Poly Dairy
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