Substrate-Driven Phosphorus Bioavailability Dynamics of Novel Inorganic and Organic Fertilizing Products Recovered from Municipal Wastewater—Tests with Ryegrass

Abstract

Municipal wastewater is a valuable source of phosphorus (P) for the production of fertilizing products, such as microalgae (MA), crab carapace material (CCM), P salt produced by chemical leaching of sludge (P salt CL), and sewage sludge ash produced by pyrolysis and the incineration of sludge (SSA PI). This study compares the P availability of these fertilizing products in three planting substrates (S1, S2, and S3) during a four-month growth period of perennial ryegrass. The unfertilized control in substrate S3 had a high and available P that masked the effect of the added fertilizing products. The P salt CL fertilizer exhibited the lowest shoot dry matter in the alkaline S2 substrate. Still, it can be used as a good source of P in both acidic and alkaline substrates, given that its shoot P content was among the highest in all substrates tested. The organic-rich fertilizing products, MA and CCM, are better suited for acidic substrates since a pronounced reduction in the shoot yield and P content was seen in the alkaline S2 substrate. In contrast, for the SSA PI fertilizer, the very small differences in shoot dry matter and P content in S1 compared to S2 indicated that it is suitable for both acidic and alkaline substrates. Four months were needed to observe the maximum shoot yields treated with these P fertilizing products. Considering that the substrate solution P (using Rhizons) for the P salt CL and MA fertilizers proved to be similar to shoot P uptake, Rhizon extraction could be used for assessing P bioavailability. The chemical composition of novel products indicated their potential to deliver not only P, but also other nutrients to plants. However, concentrations of inorganic contaminants in all products, except CCM, pointed out a possibility to pollute the environment by applying these fertilizers.

Phosphorus Release Dynamics from Ashes during a Soil Incubation Study: Effect of Feedstock Characteristics and Combustion Conditions

“…In our results, the Pearson correlation demonstrated a high association between P release and water-soluble P (see Table 4). These results align with the results reported by Bodgan et al [28] who highlighted that the soluble-water P extraction method aligned with the available P fraction in recycled P fertilisers during the initial four months of plant growth. In contrast, Duboc et al [29] examined four extraction methods across 70 fertilizers and concluded that H20 extraction was not an appropriate predictor of P availability and shoot biomass due to the lowest regression values.…”

“…Apatite phosphate minerals, characterised by the chemical formula Ca 5 (PO 4 ) 3 (OH,F,Cl), exhibit ions that confer characteristic hardness and stability. Additionally, Wang et al [28] reported that higher temperatures stimulated the formation of Ca 3 (PO 4 ) 2 during sewage sludge incineration; hydroxyapatite (Ca 5 (PO 4 ) 3 (OH)) and calcium pyrophosphate (Ca 2 P 2 O 7 ) were also detected.…”

Pilot-scale phosphate recovery from wastewater to create a fertiliser product: An integrated assessment of adsorbent performance and quality

“…Phosphorus uptake efficiency/availability (PUE, %) using the CCM, after four months of ryegrass growth with two substrates was 10 ± 2% (river sand substrate) and 1.1 ± 0.4% (alkali -artificial mineral substrate). Time had a pronounced effect on P release from the CCM, which indicated the slow-release characteristics of the CCM (Bogdan et al, 2022).…”

“…Using the methods described in Bogdan et al (2022), a pot trial was established to assess the P availability (to plants) of the CCM product. TSP was utilised as a positive control, while the omission of any fertilising product (Zero P) was used as a negative control.…”

“…In terms of organic compounds present, very low concentrations of several organic contaminants (e.g., o, p'-DDE, p, p'-DDE and DDX), polychlorinated biphenyls -PCBs (e.g., PCB 28 and PCB 52) and pharmaceuticals (e.g., paracetamol) were detected, at the low µg/kg level and far below current legislative limits for organo-mineral products as listed in the legislative limit for WHO toxicity equivalents kg − 1 dm of PCDD/F13. More information about organic pollutants in CCM can be found in Bogdan et al (2022).…”