This document specifies the requirements for chemical treatment of wastewater by precipitation/flocculation for removal of phosphorus and suspended solids. The application of polymers is not described in this document. Differences in wastewater treatment throughout Europe have led to a variety of practices being developed. This document gives fundamental information about the practices; this standard has not attempted to specify all available practices. NOTE Chemical treatment can be performed in combination with primary and more commonly with secondary treatment, but it can also be performed as separate tertiary treatment, usually in combination with filtration (see EN 12255-16). Chemical treatment can provide a potential contribution to the circular economy through the recovery of materials, such as phosphorus, from wastewater or sludge.