Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: July 15, 1996
Publication Date: N/A
Technical Abstract: Nitrification is a very limiting process in waste animal treatment, but a necessary condition for nitrogen removal in the form of N2. With wastes rich in carbonaceous materials, such as swine wastewater, the nitrifying bacteria compete poorly with heterotrophic microorganisms. Nitrifiers need oxygen, lower carbon, a surface area, and a growth phase before sufficient numbers are present for effective nitrification. These conditions can be provided by immobilization. The nitrifiers are entrapped in 2 to 3 mm pellets made of polymers that are permeable to ammonia, oxygen and CO2 resulting in a fast and efficient removal of ammonia-N, a shorter (1/3) retention time than conventional processes, and smaller reactors. Typical materials are polyethylene glycol (PEG) and polyvinyl alcohol (PVA) polymers. Wastewater is treated in a nitrification tank equipped with a screen to retain the pellets and an aeration system for appropriate fluidization. The rate of nitrification with PEG pellets is about 250 mg of ammonia-N per L per day at a 7.5% pellet to total volume ratio. A small reactor with 12.8 m3 volume is required to nitrify the lagoon effluent from 1000 hog operation (3.2 kg N/day).