A covered in-ground lagoon ...

A covered in-ground lagoon system. In this sealed system, bacteria digest the animal waste anaerobically, creating biogas that is used to power an electricity generator. Heat from the generator is then utilized to heat a hog farrowing house. Treated water from the digester unit is transported to a second earthen unit, from which it is used to flush waste out of livestock buildings and into the digester system. The effluent is irrigated seasonally onto Bermuda grass to remove excess nutrients. Plans are to use the effluent in the future for aquaculture and/or greenhouse plant production.

Aerobic upflow fixed-media biofiltration/solids separation/solids coating. This system flushes pre-screened liquid manure through two biofilters containing plastic media, on which a film of bacteria is cultivated. The bacteria convert almost all the harmful ammonia in the wastewater into nitrates and nitrites, and reduce the concentration of odor-causing compounds. The system results in liquid effluent and solids that can be used as fertilizer.

Sequencing batch reactor. This technology -- which has been used to treat wastewater from small communities for many years -- treats swine manure in a three-step sequence. The waste is transported to a containment vessel and subjected to an aeration cycle before solids are allowed to settle out for disposal. The process reduces organic carbon and phosphorus in the treated effluent. It also converts ammonia to nitrate and then turns the nitrate into nitrogen gas that can be released safely into the atmosphere.

Constructed wetlands system. This system uses natural wetland plants to remove nitrogen from treated swine wastewater, therefore preventing the overloading of nutrients on agricultural land to which the effluent is applied. The plants are arranged in a series of free-surface-flow constructed wetland cells. The waste water is pre-treated by a solids-separation and aeration process before the wetland treatment, removing excess nutrients, odor-causing compounds, and converting ammonia into nitrate. As a result, harmless nitrogen gas rather than ammonia is released into the wetlands system.

High temperature anaerobic digestion and solids composting. In this system, the manure is anaerobically digested in an enclosed and heated tank. The resulting biogas is used to produce electricity. Partially digested solids are combined with composted material; the resulting high-nutrient compost can be used for greenhouse crop production.

In addition to addressing environmental concerns, Williams says, all five of the technologies significantly reduce odors usually associated with hog waste treatment systems.

The stored manure is sometimes treated, either before or during storage.The reasons for treatment include:

1.Odour control

2. Energy recovery

3. Reduction of manure volume—especially where extended transportation is necessary

4. Reduction of nutrient content—in some circumstances where insufficient land is available to receive the manure

5. Enhance (speed up) the decomposition of manure

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