Designing a new manure-handling facility is sometimes easier than improving an existing nutrient management facility, but there are some basic components that need to be included in any good manure-handling system. The operation and maintenance of the system needs to be considered at the time of design.
Animal feeding operations that have daily discharge of liquid waste and that plan on storing wastewater should have a gravity or mechanical separator to treat wastewater before it enters a lagoon. Using a separator lengthens the interval between sludge management required for lagoon maintenance. For example, a lagoon with a properly functioning separator may need to have sludge removed every 10 years, compared to a lagoon without a separator, which will need to be cleaned every five years or less.
The next component needed is a storage lagoon for wastewater. Although many different styles have been designed, I prefer to have a deep lagoon about 16 feet, if that is possible at your farm site. When properly sized, started and maintained, a lagoon that is both anaerobic and aerobic will have minimal odor. Any water pulled out of the lagoon should be taken off the top to reduce offensive odors.
It is beneficial to have a second lagoon that acts as a polishing pond. It is best to plumb the lagoon so that when the first lagoon fills, the overflow goes into the second lagoon. Always maintain a full level in the first lagoon, since its primary function is treatment. The primary purpose for the second lagoon is polishing and storage of the wastewater. The second lagoon should be almost empty going into the winter to maximize storage capacity.
A relatively new concept developed at Iowa State University and researched in Clay Center, Nebraska, is the use of a vegetation treatment system (VTS) for containment of wastewater. At the Animal Research Center in Clay Center, Nebraska, a low-maintenance, low-cost VTS was installed eight years ago.
The system consists of an earthen settling basin just below the feedlot which settles out the solids. The liquids that remain go out on a field via 8-inch PVC pipe (gated pipe is preferable). The wastewater then goes out on a grass field. The grass then uses the wastewater for nutrients and moisture as it develops. The crop, which in this case is brome, is then harvested and hauled off to be fed to livestock.
An interesting finding from research at Clay Center was there was not a build-up of nutrients in the soil, which some may suspect. This is due to the nutrient uptake rate from the brome grass, which is eventually hauled away to be fed. Thus, the nutrients are being exported in the feed.
Pastures adjacent to the VTS and grazed by livestock have more nutrients in the soil than where the VTS is. A VTS is great for operations that have wastewater on a periodic basis or for those wishing to expand their present system.
A successful waste management system is designed with the operation and operator in mind. ANM
Dallen R. Smith, Agriculture Water Quality Project Coordinator, Utah State University for Ag Nutrient Management