The plant availability of phosphorus from thermo-chemically treated sewage sludge ashes as studied by 33P labeling techniques

Abstract

Phosphorus resources have to be managed sustainably and therefore the recycling of P from waste streams is essential. A thermo-chemical recycling process has been developed to produce a P fertilizer from sewage sludge ash (SSA) but its plant availability is unknown. Methods Two SSA products prepared with either CaCl 2 (SSACa) or MgCl 2 (SSAMg) as chemical reactant during the thermal treatment were mixed with three soils previously labeled with 33 P. Reference treatments with water-soluble P added at equal amounts of total P were included. The transfer of P from SSACa and SSAMg to Lolium multiflorum or P pools of sequentially extracted soil-fertilizer incubations were quantified. Results The shoot P uptake from SSAMg was higher than from SSACa. For SSAMg the relative effectiveness compared to a water-soluble P fertilizer was 88 % on an acidic and 71 % on a neutral soil but only 4 % on an alkaline soil. The proportion of P derived from the fertilizer in the plant and in the first two extraction pools of soil-fertilizer incubations were strongly correlated, suggesting that it is sufficient to conduct an incubation study to obtain robust information on plant P availability. Conclusions We conclude that under acidic to neutral conditions SSAMg presents an appropriate alternative to conventional P fertilizers and the dissolution of P from SSAMg seems to be governed by protons and cations in the soil solution.

Phosphorus effects of recycled products from municipal wastewater on crops in a field experiment

“…Over time, Mg-P reacts in soil to the plant available trimagnesium phosphate, while Ca-P converts to the plant unavailable hydroxyapatite (Vogel et al 2013). In addition, the chlorine donor (CaCl 2 ) used during thermochemical treatment of the Ca-SSA resulted in the formation of poor soluble P compounds, which were not completely decomposed by the partial H 2 SO 4 treatment (Nanzer et al 2014). This was visible in the low concentration of citric acid soluble P (plant-available proportions of P t ) of the Ca-SSA (Table 1).…”

New perspectives for the design of sustainable bioprocesses for phosphorus recovery from waste

“…by 32P-or 33P-labeled fertiliser, to measure the nutrient uptake from the fertiliser directly (Achat et al, 2014). By comparing the specific activity (SA, ratio of the radioisotope and the stable isotope) in the plant to the SA of the labeled fertiliser, the amount of P derived from the fertiliser taken up by the plant can be assessed (Nanzer et al, 2014). For complex fertilisers containing multiple P species, an indirect labelling approach, where plant available soil P is labeled, can be used.…”

“…For complex fertilisers containing multiple P species, an indirect labelling approach, where plant available soil P is labeled, can be used. The indirect labeling method is based on the plant available soil P can be labeled homogeneously and that any dilution of the SA comes from the (unlabeled) P fertiliser (Nanzer et al, 2014). In this case, P derived from the fertiliser is assessed by comparing the SA of a fertilized plant to the SA of an unfertilized plant grown on the same soil (Fardeau et al, 1996).…”

Appraisal of changes in sewage sludge management

“…Faster release of easily biodegradable organic matter means savings from mass and volume reduction (Maroušek 2013) and represents new financial opportunities linked with easier dewatering (Ruiz-Hernando et al 2013), stabilization and byproduct recycling (Strong et al 2011). In particular, reuse of phosphorus (Nanzer et al 2014) is the main reason why fermentation residues from sewage sludge are still used for agronomical purposes in some developing countries. In developed countries, due to higher concentrations of microorganisms and harmful substances, such as heavy metals, poorly biodegradable organic compounds, bacteria, viruses, pharmaceuticals, hormones and dioxins, the sewage sludge fermentation residues are routinely processed by combustion or pyrolysis (Magdziarz and Werle 2014).…”