Conditions influencing the removal of phosphate from synthetic wastewater: influence of the ionic composition

Large quantities of phosphate present in wastewater are one of the main causes of eutrophication that negatively affects many natural water bodies, both fresh and marine. It is desirable that water treatment facilities remove phosphorus from the wastewater before it is returned to the environment. The aim of this paper was to investigate the feasibility of phosphate removal from synthetic wastewater by calcium chloride addition in order to determine optimal operating conditions (pH and Ca/P molar ratios) and to study the influence of the ionic composition of a synthetic solution on calcium phosphate precipitation. It was shown that the optimum Ca/P ratio is 1.5 and the nitrate ions have no effect on phosphorus removal. In the case where ammonium or hydrocarbonate ions are present in significant amounts, the phosphorus removal will increase by 7% at pH = 8 and 9.