The technology that you are likely referring to is struvite crystallization. This is a chemical process that occurs naturally in small amounts in wastewater systems. By providing the appropriate conditions, this reaction can occur at levels sufficient to remove a large portion of the phosphorus from liquid manure or digester effluent.
In some areas, fields near livestock operations have received enough manure, over time, to raise soil phosphorus to levels that pose potential risks to water quality. Raw manure and digester effluent contain large amounts of water, which makes it bulky and expensive to transport to fields farther away from the livestock. Technologies, such as struvite crystallization, that process manure nutrients into forms that are economically viable to transport are receiving a great deal of attention.
In terms of using this process on animal manure, it appears that laboratory-scale evaluation began in earnest in the late 1990s. The process has progressed to the point where farm-scale (full-scale) systems are being evaluated. A description of the technology:
Research Summary: Phosphorus Removal. A newsletter article with a photo of a pilot scale system is at: April 2007 Newsletter.
Struvite formation has also been used to reduce phosphorus in various animal manure slurries, but recovery of the struvite is more difficult from slurries.
Author: Jill Heemstra, University of Nebraska
