Phosphorus is an essential element for all life on earth. However, natural phosphorus resources (phosphate rock) are depleting. This paper describes the current situation and a forecast for future phosphate production and reserves. The current depletion of phosphate reserves and the increasingly stringent discharge regulations have led to the development of various phosphorus (P) recovery techniques from wastewater. Existing full-scale P-recovery techniques from the liquid phase, from the sludge phase and from sludge ash are reviewed. Although the full-scale P-recovery techniques have been shown to be technologically feasible, the economical feasibility, legislation and national policies are the major reasons why these techniques are not yet operational worldwide.

Municipal solid waste incinerator (MSWI) bottom ash (BA) was converted to zeolitic-type adsorbent materials by hydrothermal conversion under strongly alkaline conditions. The conversion product was determined to be a mixture of sodium aluminum silicate hydrate (SASH) and tobermorite (Ca 5 Si 6 O 16 (OH) 2 •4H 2 O). The BET specific surface area was 22.1 m 2 /g, which represented a significant gain compared to the BA (4.6 m 2 /g) due to the formation of micropores and mesopores. The converted BA demonstrated promising performance for application as a sorbent towards several heavy metals (oxyanions of As(V), and Cd 2+ , Co 2+ , Ni 2+ , Pb 2+ , and Zn 2+ ). Its performance was found to be generally superior to that of a mainly-clinoptilolite natural zeolite, achieving greater sorption extents and better stabilizing capability of contaminated sediments. At a lower dosage rate (50 mg sorbent per gram sediment) to that of natural zeolite, converted BA achieved greater than 80% reduction of cationic heavy metal concentrations in sediment porewater. These results suggest a promising route for reutilization of MSWI-BA, which can greatly enhance the sustainability of waste incineration technology.

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