Effect of various types of thermochemical processing of sewage sludges on phosphorus speciation, solubility, and fertilization performance. (April 2017)

• Record Type: Journal Article
• Authors: Steckenmesser, Daniel; Vogel, Christian; Adam, Christian; Steffens, Diedrich
• Is Part Of: Waste management. Volume 62(2017)
• Page Start: 194
• Page End: 203
• Publication Date: 2017-04
• Subjects: P-recovery -- Low-temperature-conversion -- Thermochemical treatment -- P-fractionation -- P-plant-availability -- Sewage sludge; Hazardous wastes -- Periodicals; Refuse and refuse disposal -- Periodicals; 363.728
• DOI: 10.1016/j.wasman.2017.02.019
• Languages: English
• ISSNs: 0956-053X

Abstract

Highlights: Ca/P and Na/P ratios are important parameters for P-recycling. Sewage sludge from different waste water treatment have to be treated differently. Formic acid adequately estimates P-availability of products from thermal P-recycling. Abstract: Sewage sludge has one of the highest phosphorus (P) recovery potentials of all waste materials. Therefore, P-recycling from sewage sludge could contribute to closing the P-cycle. Recently, various thermal processes for P-recovery have been developed, but there is still a demand for information on the effect of different process parameters (e.g. additives and temperature) on P-speciation and especially on the fertilization performance. In the present study, two common methods (low-temperature conversion at 400–500 °C and thermochemical treatment at 950 °C) were investigated and combined to produce highly bioavailable P-fertilizers from two different types of sewage sludge based on chemical phosphorus precipitation (Chem-P) and enhanced biological phosphorus removal (Bio-P). The results of P-fractionation, X-ray diffraction analysis, and pot experiments with maize showed that Bio-P sludges attain high P-plant-availability after treatment at low temperatures (400 °C). In contrast, Chem-P sludges can adequately be treated at higher temperatures under reductive conditions with sodium additives to form highly bioavailable calcium-sodium-phosphate. Additionally, also highly heavy-metal contaminated sludges can be thermochemically treated at high temperatures to achieve the legal requirements for fertilizers.