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- Phosphorus (15) (entfernen)
Organisationseinheit der BAM
Phosphorus (P) resource availability and quality is declining and recycling P-fertilizers from waste materials are becoming increasingly important. One important secondary P resource is sewage sludge (SSL) where P is often bound as aluminum phosphate (Al-P), iron phosphate (Fe-P) and polyphosphate (poly-P), respectively. Thermal treatment in different ways is a promising way in P recycling to produce highly plant-available P-fertilizers. To investigate mechanisms behind transformation of hardly available P-species toward plant-available P forms we treated a model SSL containing different kinds of defined P sources by low-temperature conversion (LTC) at 500 °C and subsequent thermochemical treatment of the LTC product with Na additives (TCT) at 950 °C, respectively. Pot experiments with ryegrass were carried out to determine the plant availability of P of the different treatments. The poly-P (here pyrophosphates) based fertilizers had a very high plant availability after both thermal treatments. During LTC treatment the plant availability of the Fe-P and Al-P variants increased because of the Formation of Fe(II) phosphates and/or pyro-/polyphosphates. Especially the formation of Al-polyphosphate shows a high plant availability. The subsequent TCT further increased strongly the plant availability of the Fe-P variants because of the formation of highly plant-available CaNaPO4. Thus, a direct TCT without prior LTC probably also produce CaNaPO4 and is recommended for Fe-P based SSL. However, a molar Ca/P ratio of 1 in the fertilizer is favorable for CaNaPO4 formation. Thus, the knowledge on the source of primary P in SSL is essential for choosing the accurate thermal treatment method to produce highly plant-available P-fertilizers from SSL.
There is a growing concern of the direct use of contaminated sewage sludge in agriculture due possible environmental and health hazards. Thus, incineration of the sludge and thus increasing amounts of sewage sludge ashes (SSA) are to be expected in the future. SSA contains considerable amounts of phosphorus (P) and technology metals that might be recovered as secondary raw materials. Since the EU for instance depends completely on the import of rock phosphate needed for fertilizer production, alternative sources for P are in order. Furthermore, rock phosphate is often contaminated with heavy metals like Cd and U, leading to health and environmental hazards. P recovered from SSA might diminish these problems. To determine the possible recovery potential of P and technology metals from SSA, we conducted a survey of German mono incineration facilities and analyzed the respective SSA for their elemental composition. More than 95% of the emerging SSA was monitored. Results indicate a P recovery potential of 18,000 t/a (up to 13% of the annual P demands for fertilizer production). The concentrations of Cd and U in SSA are one to two Orders of magnitude lower than in rock phosphate and could help to reduce possible hazards.
Phosphorus (P) is an essential element for all forms of life and is applied as fertilizer in agriculture. The P availability for plants may be highly dependent on the chemical state of P in fertilizers and soils; however, the nature of this dependence remains obscure due to the limitations of generally applied wet chemical and instrumental analytical approaches. This paper focuses on recently developed infrared, Raman, ultraviolet and X-ray microspectroscopic techniques for the characterization of P in soil. Microspectroscopic techniques have the advantage that discrete P phases can be distinguished and characterized even if their mass fractions are very low. However, only small volumes of soil can be analyzed by microspectroscopic methods hence a combination of macro- and microspectroscopic techniques is a promising concept.
Incineration of sewage sludge is expected to increase in the future due to growing concerns about the direct use of sludge in agriculture. Sewage sludge is the pollutant sink of wastewater treatment and thus loaded with contaminants that might pose environmental hazards. Incineration degrades organic pollutants efficiently, but since the ash is currently mostly disposed of, all valuable component like phosphorus (P) and technologically relevant metals present in the sewage sludge ash (SSA) are removed from the economic cycle entirely. We conducted a complete survey of SSA from German mono-incineration facilities and determined the theoretical recovery potential of 57 elements. German SSA contains up to 19,000 t/a P which equals approximately 13% of phosphorus applied in the German agriculture in form of phosphate rock based mineral fertilizers. Thus, SSA is an important secondary resource of P. However, its P-solubility in ammonium citrate solution, an indicator for the bioavailability, is only about 26%. Treatment of SSA is recommended to enhance P bioavailability and remove heavy metals before it is applied as fertilizer. The recovery potential for technologically relevant metals is generally low, but some of these elements might be recovered efficiently in the course of P recovery exploiting synergies.
In the near future, phosphorus (P) recycling will gain importance in terms of decreasing primary resources. Sewage sludge (SSL) is an adequate secondary P-resource for P-fertilizer production but it is also a sink for heavy metals and organic pollutants. The present study is an investigation on thermochemical P-recycling of SSL. Various temperatures and amendments were tested regarding their performance to remove heavy metals and polycyclic aromatic hydrocarbons (PAH) and simultaneous increase of the plant-availability of P. The investigations were carried out on two types of SSL originating from wastewater treatment plants with chemical P-precipitation and enhanced biological P-removal, respectively. The results show that thermochemical treatment with chlorine donors is suitable to remove the majority of heavy metals and that a combination of a gaseous chlorine donor (HCl) and sodium additives leads to both high heavy metal removal and high plant availability of P. Furthermore, plant experiments Show that almost all investigated thermochemical treatments can significantly reduce the bioavailability and plant uptake of heavy metals. Furthermore, PAHs are secondarily formed during low-temperature treatments (400–500 ° ), but can be significantly reduced by using sodium carbonate as an additive.
Popioły pochodzące z instalacji do spalania komunalnych osadów ściekowych, znajdującej się na terytorium Polski, poddano procesom termochemicznego przekształcania, dzięki czemu otrzymano produkty nawozowe spełniające kryteria dopuszczające je do obrotu jako nawozy mineralne. Ponadto dokonano analizy możliwości wykorzystania popiołów na cele nawozowe zgodnie z obecnie przyjętymi dokumentami strategicznymi i planistycznymi dotyczącymi gospodarki odpadami na poziomie krajowym i europejskim.
This paper presents an inventory of sewage sludge ashes (SSA) generated in the mono-incineration plants for municipal sewage sludge in Poland. This research focused on the detailed study of mass flows, chemical composition, and phosphorus recovery potential. There are currently 11 sludge mono-incineration plants operated with a total capacity of 160,300 Mg dry weight (d.w.) of sludge annually. Recently, a significant increase in the amount of SSA generated in these plants has been observed, reaching 26,756 Mg in 2018. Chemical composition of SSA showed significant amounts of the main nutrients: calcium (~14%), phosphorus (~13%), magnesium (~3%), and potassium (~1%). Additional main elements were iron (~14.5%), silicon (~13%), and aluminium (~6%). The main trace elements in the SSA were zinc (~3750 mg/kg) and copper (~899 mg/kg). Pollutants, according to fertilizer regulations of different countries, present in Polish SSA were chromium(~703 mg/kg), nickel (~260 mg/kg), lead (~94 mg/kg), and Cadmium (~9 mg/kg). The radionuclides, uranium, and thorium often present in higher amounts in commercial phosphate rock-based fertilizers, were only detected in SSA t low levels of 4–9 mg/kg and 2–3 mg/kg, respectively. Theoretical phosphorus recovery potential from the SSA (from plants in Cracow, Lodz, Gdansk, Gdynia, Szczecin, and Kielce) was estimated at 1613.8 Mg, of which 33.9% is bioavailable. Currently, in Poland, the recommended approach is the production of fertilizers as a result of the extraction of phosphorus from the SSA with its use in the production of secondary mineral fertilizers.
Further research in this area is required considering Polish conditions and legislation.
Microspectroscopy reveals dust-derived apatite grains in acidic, highly-weathered Hawaiian soils
(2021)
Dust deposition is an important source of phosphorus (P) to many ecosystems. However, there is little evidence of dust-derived P-containing minerals in soils. Here we studied P forms along a well-described climatic Gradient on Hawaii, which is also a dust deposition gradient. Soil mineralogy and soil P forms from six sites along the climatic gradient were analyzed with bulk (X-ray diffraction and P K-edge X-ray absorption near edge structure) and microscale (X-ray fluorescence, P K-edge X-ray absorption near edge structure, and Raman) analysis methods. In the wettest soils, apatite grains ranging from 5 to 30 μm in size were co-located at the micro-scale with quartz, a known continental dust indicator suggesting recent atmospheric deposition. In addition to co-location with quartz, further evidence of dust-derived P included backward trajectory modeling indicating that dust particles could be brought to Hawaii from the major global dust-loading areas in central Asia and northern Africa. Although it is not certain whether the individual observed apatite grains were derived from long-distance transport of dust, or from local dust sources such as volcanic ash or windblown fertilizer, these observations offer direct evidence that P-containing minerals have reached surface layers of highly-weathered grassland soils through atmospheric deposition.