Recycling phosphorus from wastewater: Plant availability of phosphorus from sewage sludge and related products
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Recycling phosphorus from wastewater : Plant availability of phosphorus from sewage sludge and related products. / Lemming, Camilla Kjærulff.
Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, 2017.Research output: Book/Report › Ph.D. thesis
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TY - BOOK
T1 - Recycling phosphorus from wastewater
T2 - Plant availability of phosphorus from sewage sludge and related products
AU - Lemming, Camilla Kjærulff
PY - 2017
Y1 - 2017
N2 - Phosphorus (P) is an essential plant nutrient and a non-renewable resource of which the futuresupply to agriculture is challenged by limited and geopolitical unevenly distributed mineral Preserves. Recycling of P from waste is an important mean to minimise the dependence on thelimited mineral P reserves. Wastewater represents the largest urban flow of P in waste. Hence,knowledge about plant P availability of products from the wastewater treatment system, and alsocomparison to other waste P sources and mineral P is essential to obtain an efficient recyclingand to prioritise between different P recycling options.The work of this PhD focused on the plant P availability of sewage sludge, a P-rich residue fromwastewater treatment which is commonly applied to agricultural soil in Denmark. The overallobjective of the PhD work was to evaluate the plant availability of P in sewage sludge and otherwastewater-derived products, and to relate this to the availability from other P-containing wasteproducts and mineral P fertiliser. This included aspects of development over time and soilaccumulation, as well as effects of soil pH and the spatial distribution in soil.The P sources applied in this PhD work included anaerobically digested and dewatered sewagesludges from six different wastewater treatment plants, thermally dried sewage sludge, foursewage sludge incineration ashes, thermochemically treated sewage sludge ash, struvite, tworejectwater evaporation products, composted household waste, cattle manure and mineral Pfertiliser. The applied methods consisted predominantly of pot studies and soil incubation studieswith focus on describing and evaluating the plant P availability of the P sources against eachother. In addition, rhizobox studies for root observations and characterisation of soil from a longtermfield experiment were included in combination with 33P isotope techniques.In particular sewage sludges, but also sewage sludge incineration ashes, from differentwastewater treatment plants varied substantially in P availability. The variation between differentsludges could be partly related to the use of precipitation chemicals during the wastewatertreatment; thus, precipitation with Al (compared to Fe) and increased (Fe+Al)/P molar ratio wereindicated to have a negative impact on P availability. The sludge treatment options thermaldrying and in particular incineration was found to clearly reduce P availability compared to theundried/un-incinerated sewage sludge. However, as opposed to an often stated view, the asheswere shown to have some degree of P fertilisation value, with a tendency to increase inavailability over time. Soil pH was found to have a clear effect on sewage sludge P availability,but not on ash P availability. Furthermore, it was demonstrated that products from alternativerecovery treatment, e.g. struvite and thermochemically treated ash, do not necessarily implyhigher P availability than sewage sludge.Compared to mineral P fertiliser (TSP, triple super phosphate), sewage sludges generally showedlower availability of P. Thus, average relative fertiliser efficiencies ranged from 51-77% whenadded to a moderately acidic soil, and 20-37 % when added to moderately alkaline soil, for foursludges derived from wastewater treatment plants using combined Fe-precipitation andbiological P removal (the common approach for wastewater P removal in Denmark). However,the difference between TSP and sludges decreased over time (examined for up to 197 days),indicating more stable and slow-release properties from the sewage sludge compared to TSP.Compared to composted household waste, sewage sludge showed higher P availability in both ashort-term and a long-term perspective. Following long-term excess waste P applications to soil,the availability of accumulated residual P was higher when applied with sewage sludge than withcomposted household waste, but lower than when applied with cattle manure.Localised application of sewage sludge to maize resulted in increased root proliferation in andaround the sludge patch (similar to localised TSP). However, P uptake from the sludge was notenhanced compared to a situation with homogenous distribution; rather it was slightly reduced(contrary to TSP). Localised application of sewage sludge ash did not imply any root responsesand the plants did not take up P from the localised ash. In contrast, homogenously distributed ashresulted in a well-developed root system and a substantial uptake of P from the ash. Based onthese results, localised applications of sewage sludge and sewage sludge ashes cannot berecommended.Methodological considerations included an evaluation of the WEP (water extractable P) methodused in most of the experiments to describe P availability after application to soil, was evaluated.This suggested that the simple WEP method can be a useful alternative to more expensive andadvanced methods in terms of ranking the P availability from different P sources.Overall, the research conducted within the present PhD work contributes to a betterunderstanding of P availability from sewage sludge and related products, and it can potentiallyserve as input for prioritisation of waste management strategies with focus on potential changesin wastewater and sludge management to enhance efficient P recycling from wastewater. Thismay be particularly relevant for wastewater treatment plants in areas where increased recyclingof wastewater P is targeted. In Denmark, this may apply to the Sjælland area (RegionHovedstaden + Region Sjælland) where recycling of P from wastewater is low compared to otherparts of the country due to a high degree of incineration in the Copenhagen area. Finally, in thiscontext, tentative recommendations and specific suggestions for future research objectives areprovided.
AB - Phosphorus (P) is an essential plant nutrient and a non-renewable resource of which the futuresupply to agriculture is challenged by limited and geopolitical unevenly distributed mineral Preserves. Recycling of P from waste is an important mean to minimise the dependence on thelimited mineral P reserves. Wastewater represents the largest urban flow of P in waste. Hence,knowledge about plant P availability of products from the wastewater treatment system, and alsocomparison to other waste P sources and mineral P is essential to obtain an efficient recyclingand to prioritise between different P recycling options.The work of this PhD focused on the plant P availability of sewage sludge, a P-rich residue fromwastewater treatment which is commonly applied to agricultural soil in Denmark. The overallobjective of the PhD work was to evaluate the plant availability of P in sewage sludge and otherwastewater-derived products, and to relate this to the availability from other P-containing wasteproducts and mineral P fertiliser. This included aspects of development over time and soilaccumulation, as well as effects of soil pH and the spatial distribution in soil.The P sources applied in this PhD work included anaerobically digested and dewatered sewagesludges from six different wastewater treatment plants, thermally dried sewage sludge, foursewage sludge incineration ashes, thermochemically treated sewage sludge ash, struvite, tworejectwater evaporation products, composted household waste, cattle manure and mineral Pfertiliser. The applied methods consisted predominantly of pot studies and soil incubation studieswith focus on describing and evaluating the plant P availability of the P sources against eachother. In addition, rhizobox studies for root observations and characterisation of soil from a longtermfield experiment were included in combination with 33P isotope techniques.In particular sewage sludges, but also sewage sludge incineration ashes, from differentwastewater treatment plants varied substantially in P availability. The variation between differentsludges could be partly related to the use of precipitation chemicals during the wastewatertreatment; thus, precipitation with Al (compared to Fe) and increased (Fe+Al)/P molar ratio wereindicated to have a negative impact on P availability. The sludge treatment options thermaldrying and in particular incineration was found to clearly reduce P availability compared to theundried/un-incinerated sewage sludge. However, as opposed to an often stated view, the asheswere shown to have some degree of P fertilisation value, with a tendency to increase inavailability over time. Soil pH was found to have a clear effect on sewage sludge P availability,but not on ash P availability. Furthermore, it was demonstrated that products from alternativerecovery treatment, e.g. struvite and thermochemically treated ash, do not necessarily implyhigher P availability than sewage sludge.Compared to mineral P fertiliser (TSP, triple super phosphate), sewage sludges generally showedlower availability of P. Thus, average relative fertiliser efficiencies ranged from 51-77% whenadded to a moderately acidic soil, and 20-37 % when added to moderately alkaline soil, for foursludges derived from wastewater treatment plants using combined Fe-precipitation andbiological P removal (the common approach for wastewater P removal in Denmark). However,the difference between TSP and sludges decreased over time (examined for up to 197 days),indicating more stable and slow-release properties from the sewage sludge compared to TSP.Compared to composted household waste, sewage sludge showed higher P availability in both ashort-term and a long-term perspective. Following long-term excess waste P applications to soil,the availability of accumulated residual P was higher when applied with sewage sludge than withcomposted household waste, but lower than when applied with cattle manure.Localised application of sewage sludge to maize resulted in increased root proliferation in andaround the sludge patch (similar to localised TSP). However, P uptake from the sludge was notenhanced compared to a situation with homogenous distribution; rather it was slightly reduced(contrary to TSP). Localised application of sewage sludge ash did not imply any root responsesand the plants did not take up P from the localised ash. In contrast, homogenously distributed ashresulted in a well-developed root system and a substantial uptake of P from the ash. Based onthese results, localised applications of sewage sludge and sewage sludge ashes cannot berecommended.Methodological considerations included an evaluation of the WEP (water extractable P) methodused in most of the experiments to describe P availability after application to soil, was evaluated.This suggested that the simple WEP method can be a useful alternative to more expensive andadvanced methods in terms of ranking the P availability from different P sources.Overall, the research conducted within the present PhD work contributes to a betterunderstanding of P availability from sewage sludge and related products, and it can potentiallyserve as input for prioritisation of waste management strategies with focus on potential changesin wastewater and sludge management to enhance efficient P recycling from wastewater. Thismay be particularly relevant for wastewater treatment plants in areas where increased recyclingof wastewater P is targeted. In Denmark, this may apply to the Sjælland area (RegionHovedstaden + Region Sjælland) where recycling of P from wastewater is low compared to otherparts of the country due to a high degree of incineration in the Copenhagen area. Finally, in thiscontext, tentative recommendations and specific suggestions for future research objectives areprovided.
UR - https://soeg.kb.dk/permalink/45KBDK_KGL/fbp0ps/alma99122488121905763
M3 - Ph.D. thesis
BT - Recycling phosphorus from wastewater
PB - Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen
ER -
ID: 187014998