Biological phosphorus removal, its role in phosphorus recycling

At present the main types of phosphorus removal from wastewater effluents are chemical precipitation using alum or lime and biological removal. These methods of removal do not recycle phosphorus as a truly sustainable product because ii is removed along with various other waste products. The development of phosphorus removal by crystallisation has provided a way of removing phosphorus in a form that has potential to be a raw material for the phosphate industry such as struvite and hydroxyapatite. Through combining biological phosphorus removal and crystallisation a number of benefits in terms of process economics can be made. By treating the effluent initially with a biological process a concentrated phosphorus effluent stream is produced. This concentration of phosphorus will significantly reduce the volume of effluent that needs to be treated which means that the crystallisation reactor size can be greatly reduced. This review describes the main types of commercial biological phosphorus removal technologies such as the Phostrip, the modified Bardenpho and Rotanox processes along with a comprehensive examination of current crystallisation processes. Together with an examination of the potential benefits of using biological removal and crystallisation in combination as a method of removing phosphorus so that it can be recycled.