The technology of phosphorous removal and recovery from swine wastewater by struvite crystallization reaction

Abstract

Swine wastewater has a high potential for phosphorous recovery in Japan. The pH of swine wastewater increased up to approximately 8.5 with continuous aeration, and a large part of the soluble PO4-P, Mg and Ca was crystallized. A reactor for removing and recovering phosphorous from swine wastewater was designed with a dual function i.e., crystallization through aeration, and separation of formed struvite by settling. However, a dehydration, composting and characterization process was first needed before using sediment sludge, including struvite, on farmland, since it will settle along with huge amounts of other suspended solids (organic matter). For the recovery of pure struvite, an accumulation device was designed and its efficiency was examined. During submergence in the aeration column of the demonstration reactor, struvite cross-bridged and it accumulated on the face of the device. The struvite could be scraped off easily with only a light brushing, and was found to be approximately 95% pure. Because this device is made of a very simple structure, it should be acceptable to swine farmers.