A review of phosphorus recovery methods at various steps of wastewater treatment and sewage sludge management. The concept of “no solid waste generation” and analytical methods

Abstract

Phosphorus deposits around the world are rapidly depleting, therefore phosphorus recovery methods are gaining more and more interest both in science and industry. This article presents the main methods of phosphorus recovery from sewage sludge. The described approaches are divided in two groups: phosphorus recovery from sewage sludge and leachate, and recovery of phosphorus from sewage sludge ashes. The latter seems to have more advantages connected with both ecological and economical aspects. The need for development of “no solid waste generation” strategy is becoming more and more urgent. The concept of comprehensive management of all solid residues after what is currently considered the most ecological process of sewage sludge incineration connected with phosphorus recovery based on acidic extraction, is described in the article. Solid residues after phosphorus recovery from sewage sludge ashes by means of acidic extraction can be stabilized with solid residues after sewage sludge incineration exhaust gas treatment. Such an approach may enable production of phosphoric raw material together with stabilized construction material. Advantages and disadvantages of the discussed approaches are given. An analysis of the composition of ashes produced in different sewage sludge treatment plants indicates that the proposed technology could be successfully applied in most of such units, especially because the concentrations of elements such as K, Mg, Na, P are sufficiently high, respectively 1.5–12.1 g/kg; 9.9–14.9 g/kg; 3.6–13,3 g/kg and 27,4–99,0 g/kg. However, a phosphorus recovery method should be developed separately for each treatment plant. Only then all comprehensive management methods will be ecologically and economically justified. Analytical methods which could be of use at every step of designing a proper phosphorus recovery process are described.