Extraction of phosphorus from sewage sludge ash and sewage sludge – problem analysis

Abstract

Phosphorus as an essential element for agricultural production becomes scarcer and scarcer due to the depletion of phosphate rocks. It seems necessary to implement the cheap and effective recovery methods of this element from all kinds of waste. A particularly valuable source of phosphorus are the ashes from thermal incineration of sewage sludge and dry sewage sludge. Optimization of sequential extraction of phosphorus contained in the ash from the thermal treatment of sewage sludge and dry sewage sludge allows for the selection of an efficient and technologically uncomplicated method of phosphorus recovery, while maintaining the low content of heavy metals, which are one of the main reasons for the limitations in the use of sludge and sludge ash in agriculture. The effectiveness of these processes, combined with the amount of sewage sludge in Poland, will allow for the calculation of the recoverable amount of phosphorus which can go back into biological circle, thus reducing the consumption of the natural phosphorus resources.