<p>This thesis focused on testing the suitability of reactive filter media used for phosphorus (P) removal from wastewater as fertilizers, thus recycling P to agriculture. The work compared the P sorption capacity of several materials in order to assess their suitability as a source of P for plants. The selected materials (Filtra P, Polonite and wollastonite) were saturated with P and used as soil amendments in a pot experiment. The amendments tended to improve the yield of barley and ryegrass compared with no P addition. The amendments also increased soil pH, P availability and cation exchange capacity in the studied soils. The substrates studied here can be of particular interest for acid soils. Of the materials studied, Polonite appears to be the most suitable substrate for the recycling of P from wastewater to agriculture</p>

This thesis focused on testing the suitability of reactive filter media used for phosphorus (P) removal from wastewater as fertilizers, thus recycling P to agriculture. The work compared the P sorption capacity of several materials in order to assess their suitability as a source of P for plants. The selected materials (Filtra P, Polonite and wollastonite) were saturated with P and used as soil amendments in a pot experiment. The amendments tended to improve the yield of barley and ryegrass compared with no P addition. The amendments also increased soil pH, P availability and cation exchange capacity in the studied soils. The substrates studied here can be of particular interest for acid soils. Of the materials studied, Polonite appears to be the most suitable substrate for the recycling of P from wastewater to agriculture / QC 20101103

This thesis studied the viability of recycling filter substrates as soil amendments after being used in on-site systems for phosphorus (P) removal from wastewater. Focus was put on the materials Filtra P and Polonite, which are commercial products used in compact filters in Sweden. A prerequisite for this choice was to review filter materials and P sorption capacity. The filter substrates (Filtra P, Polonite and wollastonite tailings) were recycled from laboratory infiltration columns as soil amendments to a neutral agricultural soil and to an acid meadow soil to study their impacts on soil properties and yield of barley and ryegrass. The amendments tended to improve the yield and showed a liming effect, significantly increasing soil pH and the availability of P. In another experiment, samples of Filtra P and Polonite were equilibrated in batch experiments with the two soils in order to study the P dynamics in the soil-substrate system.  Batch equilibrations confirmed the liming potential of Filtra P and Polonite and showed that improved P availability in soils was strongly dependent on substrate P concentration, phase of sorbed P, and soil type. Finally, samples of Polonite used for household wastewater treatment were recycled as soil amendments to a mountain meadow and to an agricultural field for wheat cropping. The liming effect of Polonite was confirmed under field conditions and the results were similar to those of lime for the mountain meadow soil. However, the results were quite different for the agricultural field, where Polonite did not affect soil pH or any other chemical and physical soil properties investigated and had no impact on wheat yield and quality. The results from field experiments suggested that Polonite can be safely recycled to meadows and cropping fields at rates of 5-10 ton ha-1 but long-term studies are needed to forecast the effects of accumulation. / QC 20100708