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Erscheinungsjahr
- 2017 (3) (entfernen)
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- Englisch (3)
Schlagworte
- Low-temperature-conversion (2)
- P-fractionation (2)
- P-plant-availability (2)
- P-recovery (2)
- Sewage sludge (2)
- Thermochemical treatment (2)
- Chemical extraction tests (1)
- Phosphate recovery (1)
- Plant growth experiments (1)
- Recycling (1)
The plant-availability of phosphorus (P) in fertilizers and soil can strongly influence the yield of agricultural crops. However, there are no methods to efficiently and satisfactorily analyze the plant-availability of P in sewage sludge-based P fertilizers except by undertaking time-consuming and complex pot or field experiments. We employed the diffusive gradients in thin films (DGT) technique to quantify the plant P availability of various types of P fertilizers with a novel focus on sewage sludge-based P fertilizers. Mixtures of fertilizer and soil were incubated for 3 weeks at 60% water holding capacity. DGT devices were deployed at the beginning of the incubation and again after 1, 2, and 3 weeks. Two weeks of incubation were sufficient for the formation of plant-available P in the fertilizer/soil mixtures. In a pot experiment, the DGT technique predicted maize (Zea mays L.) biomass yield and P uptake significantly more accurately than standard chemical extraction tests for P fertilizers (e.g., water, citric acid, and neutral ammonium citrate). Therefore, the DGT technique can be recommended as a reliable and robust method to screen the performance of different types of sewage sludge-based P fertilizers for maize cultivation minimizing the need for time-consuming and costly pot or field experiments.
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.
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.