O φωσφόρος είναι ένα χημικό στοιχείο με πολλές λειτουργικότητες. Μία από τις βασικές χρήσεις του είναι ότι αποτελεί αναντικατάστατο λίπασμα ενώ επιπλέον είναι βασικό συστατικό του γενετικού υλικού, των κυτταρικών μεμβρανών, των οστών και των δοντιών, απαραίτητο στοιχείο της διατροφής ανθρώπων και ζώων κλπ. Η παρουσία υψηλών συγκεντρώσεων φωσφόρου στα υδάτινα οικοσυστήματα είναι ιδιαιτέρως βλαβερή καθώς αποτελεί την κύρια αιτία του ευτροφισμού. Αυξημένες ποσότητες φωσφόρου υπάρχουν στα αστικά υγρά απόβλητα, γεγονός που καθιστά αναγκαία την επεξεργασία τους για την απομάκρυνση του, πριν την τελική διάθεση τους στους υδάτινους αποδέκτες. Δεδομένου του ότι, ο φώσφορος προέρχεται από ορυκτά αποθέματα, τα οποία δεν είναι ανεξάντλητα, είναι επιβεβλημένη η ανάκτησή του, η οποία αποτελεί συμβολή στην αειφορία. Μία από τις μεθόδους ανάκτησης του φωσφόρου η οποία κερδίζει όλο και περισσότερο ερευνητικό ενδιαφέρον τα τελευταία χρόνια, είναι η καταβύθιση του με την μορφή στρουβίτη. Ο στρουβίτης, (MgΝΗ4PO4.6H2O) είναι ένα λευκό κρυσταλλικό στερεό το οποίο μπορεί να χρησιμοποιηθεί ως βραδέως αποδεσμευόμενο λίπασμα, εμπλουτίζοντας τις καλλιέργειες με τρία από πιο βασικά θρεπτικά συστατικά. Στην παρούσα εργασία μελετήθηκε η καταβύθιση στρουβίτη από υπέρκορα διαλύματα, η σύσταση των οποίων, προσομοιώνει την αντίστοιχη των αστικών υδατικών λυμάτων ως προς την περιεκτικότητα σε φωσφόρο και αμμωνία, σε αντιδραστήρα συνεχούς λειτουργίας του 1L. Η κινητική της καταβύθισης μελετήθηκε σε συνθήκες σταθερού υπερκορεσμού, pH 9.00 στους 25οC. Τα πειράματα πραγματοποιήθηκαν σε διαλύματα υπέρκορα ως προς στρουβίτη, στα οποία η στοιχειομετρική αναλογία των πλεγματικών ιόντων, ήταν 1:1:1 και 1:1:3 ως προς οποιοδήποτε από τα τρία ιόντα. Επίσης, μελετήθηκε καταβύθιση του στρουβίτη σε υπέρκορα διαλύματα παρουσία Na¬2SO4 και με διαβίβαση αέρα μέσω των διαλυμάτων. Τα αποτελέσματα των πειραμάτων έδειξαν, ότι ο ρυθμός καταβύθισης του στρουβίτη στα υπέρκορα διαλύματά του, εξαρτάται κυρίως από τον αντίστοιχο υπερκορεσμό, ο οποίος αποτελεί και την κινούσα δύναμη. Η ανάλυση των αποτελεσμάτων έγινε με την βοήθεια της κλασσικής θεωρίας πυρηνογένεσης. Η εξάρτηση του χρόνου επαγωγής, ο οποίος μεσολαβούσε μεταξύ της παρασκευής των υπέρκορων διαλυμάτων και της ανίχνευσης των πρώτων υπερκρίσιμων πυρήνων, από τον υπερκορεσμό, έδωσε τιμές για την επιφανειακή ενέργεια της σχηματιζόμενης φάσης ίσης με 15mJ/m2, ενώ ο αριθμός των δομικών μονάδων οι οποίες συγκροτούν τον κρίσιμο πυρήνα, βρέθηκε ίσος με 9. Επίσης, ο ρυθμός, φάνηκε να επηρεάζεται σε μικρό βαθμό από την σχετική αναλογία των πλεγματικών ιόντων. Συγκεκριμένα, όταν η αναλογία των ιόντων Mg :NH3 :P ήταν 3:1:1 ή 1:1:3, οι ρυθμοί οι οποίοι μετρήθηκαν ήταν μεγαλύτεροι σε σύγκριση με τους αντίστοιχους σε διαλύματα με αναλογία 1:1:1. Σε όλες τις περιπτώσεις, το βραδύ στάδιο στον μηχανισμό της καταβύθισης ήταν η επιφανειακή διάχυση των δομικών μονάδων στους υπερκρίσιμους πυρήνες. Το αποτέλεσμα αυτό είναι σε συμφωνία με τα αντίστοιχα σε διαφορετικές τιμές pH, και υποδηλώνει και στην περίπτωση αυτή, τον καθοριστικό ρόλο της επιφάνειας στην οποία λαμβάνει χώρα η πυρηνογένεση. Η παρουσία άλλων ουσιών στο διάλυμα, όπως το Na¬2SO4, είχε ως αποτέλεσμα την αύξηση του ρυθμού αυθόρμητης καταβύθισης του στρουβίτη στα υπέρκορα διαλύματά του. Η διαβίβαση αέρα μέσα από τα υπέρκορα διαλύματα, είχε ως αποτέλεσμα την επιτάχυνση του ρυθμού καταβύθισης σε βαθμό ανάλογο με τον αντίστοιχο παρουσία Na¬2SO4. / Phosphorus is a multifunctional chemical element. One of it’s significant uses is that it consists a non substituted fertilizer, moreover it is one of the basic components of DNA, of cell membranes, bones, teeth, an essential element in human and animal nutrition etc. Increased phosphorous concentration in water systems can be particularly damaging since it is the main cause of eutrophication. Increased amounts of phosphorous have been demonstrated in municipal wastewaters, so processing is required in order to remove phosphorous before final disposal to aquatic systems. Taking into consideration that phosphorus comes from mineral deposits that are not infinite, recovery is demanded, offering a contribution to sustainability. One of the recovery methods that is attracting more and more researcher’s interest over the past years is phosphorous precipitation as struvite. Struvite (MgΝΗ4PO4.6H2O) is a white mineral that can be used as a slow-release fertilizer, enriching agricultures with three of the basic nutrients. In the present study was investigated struvite precipitation in supersaturated solutions, with composition similar to that of municipal wastewaters in phosphorous and ammonia, in 1L continuously operated reactor. The kinetics of spontaneous precipitation was studied at constant solution supersaturation, pH 9.00 and 25οC. The experiments were carried out in supersaturated solutions with stoichiometric molar ratio of the ions 1:1:1 and 1:1:3 for any of the three ions. Struvite precipitation in supersaturated solutions was also studied in the presence of Na¬2SO4 and transmission of air in the solutions. The results showed that the rate of struvite precipitation in supersaturated solutions mainly depends on the supersaturation in respect to the precipitating solid, which is the driving force. Results analysis was performed in accordance to the classical nucleation theory. The dependence of the induction time, the period of time between the achievement of supersaturation and the formation of the first critical nucleus, from supersaturation, lead to surface energy for the newly formed phase 15mJ/m2, and the number of molecules in a critical nucleus was calculated p=9. The rate of struvite precipitation proved to have a minor dependence on the ratio of the ions. More specifically, when stoichiometric molar ratio of the ions Mg :NH3 :P was 3:1:1 or 1:1:3, the calculated rates were a bit higher compared to the ratios in supersaturated solutions with stoichiometric molar ratio 1:1:1. In all the cases the slow step in the mechanism of precipitation was surface diffusion of the solute molecules on the critical nuclei surface. The results are in accordance with those under different pH values and suggest the importance of the surface where nuclei formation takes place. The presence of other substances in the solution, such as Na¬2SO4, resulted in an increased rate of struvite spontaneous precipitation in supersaturated solutions. The transmission of air through the supersaturated solutions also increased the rate of precipitation in a way similar to that under the presence of Na2SO4.

Magnesium oxide (MgO) is a cost-effective and environmentally sustainable alternative to magnesium chloride (MgCl2) and sodium hydroxide (NaOH) used for sidestream struvite recovery from anaerobically digested supernatant (centrate) through the Pearl® process. MgO is produced from magnesite (MgCO3) calcination, and different calcination conditions can alter the quality and characteristics of the MgO product. It was hypothesized that the insolubility of MgO could provide a "slowly available" form of Mg2+ in the reactor and consequently allow the reactor to be operated beyond design phosphorus (P) reactor loading. MgO has been utilized in other P recovery technologies, e.g. the Phospaq™ Process, but operation and performance of MgO using a full-scale Pearl® 500 fluidized bed reactor was investigated. Performance at rated reactor loading utilizing MgO was initially comparable to baseline conventional MgCl2 reactor operation, ≥50% struvite yield (P recovered/theoretical P recovery) and ≥70% total phosphorus (TP) removal. However, the pilot reactor operated at 2X reactor loading showed comparable results to baseline performance at 1.5X reactor loading. During the full-scale pilot, optimization of the reactor utilizing MgO was limited by the struvite product size that the struvite post-processing equipment could effectively harvest. Additionally, the MgO characteristics due to calcination conditions were hypothesized to affect struvite precipitation kinetics. In struvite precipitation jar testing, MgO products were used to analyze the saturation index, measure precipitation kinetics, and understand the effect that MgO hydration and reactivity had on struvite precipitation. Jar testing showed that initial P removal increased with increasing MgO product reactivity. The most reactive MgO used, Timab AK98, showed 1-40% P removal and substantial decrease in solution saturation index immediately after dosing MgO to centrate. The slower P removal and decrease in saturation index observed with the less reactive material suggests that MgO can provide a "slowly available" Mg2+ reserve throughout the struvite precipitation reaction. / Master of Science / Phosphorus is an essential element for human, plant and animal health. Necessary bodily functions cannot be performed without inputting phosphorus to cell metabolic pathways, such as cell repair and formation of nucleic acids, bone mineral and stored energy. Phosphates are the most common form of phosphorus found in the environment and are a component of many common substances, such as detergents, fertilizers, food and urine. Due to the increasing population and food demand the need for phosphorus-based fertilizers has soared since the 1940s. In 2018, 240 megatons of phosphate rock were mined, and 17 megatons of phosphorus were extracted from mined ore. 15 megatons of the extracted phosphorus were used in fertilizer production. Because of phosphorus loss from the soil and inefficient agro-practices, only 20% of the extracted phosphorus is consumed by humans and animals from food and little is then recycled from our waste systems. There is a major gap in the agricultural phosphorus cycle that is necessary to address with sustainable practices (Oster, M. et al. 2018). Phosphorus can be recovered from wastewater in the form of struvite, which is a mineral that can be utilized a slow-release fertilizer. Conventional methods of phosphorus recovery from wastewater have the potential to be costly. By utilizing an alternative chemical, struvite recovery can be more cost-effective and environmentally sustainable.

Short-term sludge fermentation was explored as a means of solubilizing phosphorus from different types of undigested sludge to facilitate nutrient recovery and generate volatile fatty acids (VFA) for enhanced nutrient removal. Phosphorus solubilization and VFA production was compared from the fermentation of primary sludge (PS), waste activated sludge (WAS), and from co-fermenting primary and waste activated sludge from wastewater treatment plants that do not practice biological nutrient removal. Co-fermented sludge resulted in the best combination of nutrient release and VFA production compared to separate fermentation of PS and WAS. After 4 days of fermentation, co-fermented sludge contained 48% of TP as dissolved phosphorus, and produced 1624 mg l-1 of VFA-COD which corresponds to a VFA-COD production rate of 0.139 mg mg-1 VS. In terms of total sludge management, co-fermentation resulted in greater overall VFA production and phosphorus solubilization than individual sludge fermentation.

Phosphorus is an essential source with significance use in agriculture. Phosphorus is lost in the human intensified global cycle and it is important to remove phosphorus from water body. However, important and potential sources for phosphorus product which is suitable and effective for fertilizer use may be ignored due to over emphasize on the pollution prevention. This work aims to identify the potential of phosphorus recovery from solid organic waste in Sweden. Based on the result of Material Flow Analysis of phosphorus, solid food waste is identified the main solid waste fractions containing phosphorus substances of phosphorus in Sweden. From the case study and comparison of three alternatives, the possibility of recovery of phosphorus from household solid food waste is analyzed. A SWOT analyst is applied to provide a best solution for phosphorus recovery from food waste. The key drivers, the system boundaries for the phosphorus recovery and collection, storage, transport and use of the phosphorus are also discussed.

Phosphorus (P) is one of the fundamental chemical elements and one of the building blocks of life. In nature, there are two major P flows. One P flow is natural, where P over thousands and millions of years gets mobilised from P rock and circulates, “changing hands” many times before it gets deposited and biologically unavailable. The second is the anthropogenic flow, three times larger than the natural P cycle. To feed the anthropogenic flow, P is mined from the P rock and processed towards the final product - phosphoric acid. From here, P is used in chemical industry, food and beverage industry, pharmacy, but mostly in agriculture as a fertiliser. Because fertilisers are applied on farmlands on a yearly basis, the turnover of P in agriculture, the largest consumer of the man-made P circle, occurs only once, therefore, it can be considered a primarily linear flow. From the man-made P flow, P leaches into the natural cycle. The consequence of this can be seen in the environment through eutrophication, and the formation of dead zones in lakes and the ocean, causing environmental damage. The importance of P and the danger it poses for the environment were recognised in EU regulations as well as in member states laws. Today, P is classified as a critical raw material at the EU level, and legal incentives are in place on both levels to reduce P emissions into the environment and to begin recovering P from human-made waste streams. There are several possible sources of P in human waste streams, including agricultural runoff, animal manures, food and food processing waste, wastewater and wastewater sludge, sewage sludge ash, but also already existing, immobilised, and unavailable P in the soil. This research focuses on wastewater and wastewater sludge for P recovery. It is estimated that if all the P in wastewater were recovered, this would cover 20% of the world's annual fertiliser needs. In wastewater treatment plants (WWTP), P recovery is usually done using chemically based P recovery technologies. The application of biologically based technologies from the wastewater focuses solely on P removal. Biological P recovery technologies are currently demonstrated only on a laboratory-scale. Here, a research gap was recognised. Based on available laboratory-scale work regarding P recovery using brewer's yeast, a new pilot-scale process was proposed for biological P recovery (BioP-Rec module) from WWTP process streams. A BioP-Rec module was installed in the full-scale WWTP, where successful biological P recovery was demonstrated with three different process stages. In stage 1, in anaerobic conditions, a free P-rich substrate was created using return sludge. In stage 2, starved brewer's yeast was used to recover the P by its accumulation in the cells. In stage 3, yeast was filtered to produce yeast sludge as a fertiliser. While working with the BioP-Rec module, an effort was made to work within or above the free P concentration of 0.05 kg/m3, which is considered economically feasible for P recovery. In addition, an effort was made for the BioP-Rec module to be compliant with the German Sewage Sludge Ordinance (GSSO) P content in dry matter (DM) threshold of 20 gP/kgDM in biosolids. From 2029, the GSSO will demand that WWTP with P content in DM above previously stated, in Germany, will need to mandatory recover the P in their process. If the BioP-Rec module as a technology can already demonstrate that it can fulfil defined thresholds, this would be a strong argument for its future development. In addition, economics of the current pilot-scale BioP-Rec process is explored, and further ideas were given towards its upgrade and possible further adoption. This work can be used as a stepping stone in the further development of environmentally friendly, biologically based P recovery processes towards further scale-up.:Content Summary 8 Zusammenfassung 10 1 Introduction 13 1.1 Phosphorus (P) 13 1.2 Wastewater P sources, P removal and recovery 16 1.2.1 Wastewater P sources 16 1.2.2 Wastewater P removal and recovery 19 1.2.2.1 Biological P removal 20 1.2.2.2 Chemical P removal 23 1.2.2.3 Biological P recovery 25 1.2.2.4 Biological P recovery with yeast 26 1.2.2.5 Chemical P recovery 31 1.3 Economically feasible P recovery 33 1.4 Legal framework for P recovery 34 1.5 Aim of this study 37 2 Publications 41 2.1 List of publications 41 2.2 Published articles 43 2.2.1 New developments in biological phosphorus accessibility and recovery approaches from soil and waste streams 45 2.2.2 A framework for P-cycle assessment in wastewater treatment plants 57 2.2.3 Biological recovery of phosphorus (BioP-Rec) from wastewater streams using brewer's yeast on pilot-scale 71 3 Discussion 91 3.1 WWTP P balance for P recovery 91 3.2 WWTP design impacting free P availability 93 3.3 Free P hot spots for biological P recovery 95 3.4 BioP-Rec module P recovery 97 3.4.1 BioP-Rec module version 1 97 3.4.2 BioP-Rec module development concept 98 3.4.3 BioP-Rec module work concept 100 3.4.3.1 Stage 1 101 3.4.3.2 Stage 2 104 3.4.3.3 Stage 3 108 3.4.4 P enriched yeast as a fertiliser 108 3.5 Process economics 110 3.6 Steps to consider towards optimisation of the process economics 112 3.6.1 Process parameter optimisation 114 3.6.1.1 Different acid for higher free P release in stage 1 114 3.6.1.2 Different flocculant 115 3.6.1.3 Sucrose to yeast ration for stage 2a (starvation) and stage 2b (free P uptake) 115 3.6.1.4 Reuse some of the BioP-Rec module waste streams 117 3.6.1.5 Process aeration optimisation 117 3.6.2 Technology optimisation 117 3.6.3 Possible positive effects of the optimisation steps 118 3.6.4 Secondary value adding effects that can offset development costs 119 3.6.5 Directions for future BioP-Rec development 120 3.7 Future prospects and conclusion 123 3.7.1 Future prospects of the BioP-Rec module application 123 3.7.2 Further yeasts P uptake research 123 4 References 125 Declaration of authorship and independent work 147 Curriculum vitae 151 List of publications and conference contributions 153 5 Appendix 5-1 5.1 Supplementary information on Publication 2 5-3 5.2 Supplementary information on Publication 3 5-23 5.3. Unpublished data connected to Publication 3: Original brewer's yeast phosphorus uptake without and with sucrose as a carbon source 5-45 6 Acknowledgements 6-54 / Phosphor (P) ist eines der grundlegenden chemischen Elemente und einer der Bausteine des Lebens. In der Natur gibt es zwei große P-Ströme. Ein P-Strom ist natürlich, wenn P über Tausende und Millionen von Jahren aus P-Gestein mobilisiert und zirkuliert, dabei „durch mehrere Hände wandert“, bevor es abgelagert und biologisch unverfügbar wird. Der zweite ist der anthropogene Strom, der dreimal größer ist als der natürliche P-Kreislauf. Um den anthropogenen Strom zu speisen, wird P aus dem P-Gestein abgebaut und zum Endprodukt - Phosphorsäure - verarbeitet. Dieser P wird in der chemischen, in der Lebensmittel- und Getränkeindustrie, in der Medizin, aber hauptsächlich in der Landwirtschaft als Düngemittel verwendet. Da Düngemittel jährlich auf landwirtschaftlichen Flächen ausgebracht wird, findet der Umsatz von P in der Landwirtschaft, nur einmal statt und kann daher als überwiegend linearer Fluss betrachtet werden. Aus dem anthropogenen P-Fluss gelangt P in den natürlichen Kreislauf. Die Folgen davon sind in der Umwelt durch Eutrophierung und die Bildung von Todeszonen in Seen und im Ozean zu sehen, was Umweltschäden zur Folge hat. Die Bedeutung von P und die Gefahr, die es für die Umwelt darstellt, wurden in EU-Verordnungen sowie in den Gesetzen der Mitgliedstaaten anerkannt. Heute ist P auf EU-Ebene als kritischer Rohstoff eingestuft und es bestehen rechtliche Anreize auf beiden Ebenen, um die P-Emissionen in die Umwelt zu reduzieren und die Rückgewinnung von P aus anthropogenen Abfallströmen zu beginnen. Es gibt mehrere mögliche Quellen von P in anthropogenen Abfallströmen, einschließlich landwirtschaftlicher Abflüsse, tierischer Exkremente, Lebensmittel- und Lebensmittelverarbeitungsabfälle, Abwasser und Klärschlamm, Klärschlammasche, aber auch bereits vorhandenes, immobilisiertes und nicht verfügbares P im Boden. Diese Forschung konzentriert sich auf die P-Rückgewinnung aus Abwasser und Abwasserschlamm. Schätzungen ergaben, dass eine erfolgreiche P-Rückgewinnung aus dem Abwasser 20% des jährlichen weltweiten Düngerbedarfs decken würde. In Kläranlagen (KA) erfolgt die P-Rückgewinnung in der Regel mit chemischen P-Rückgewinnungstechnologien. Der Einsatz von biologischen Technologien konzentriert sich ausschließlich auf die P-Entfernung aus dem Abwasser und nicht auf die P-Rückgewinnung. Biologische P-Rückgewinnungstechnologien werden derzeit nur im Labormaßstab demonstriert. Hier wurde eine Forschungslücke erkannt. Basierend auf den verfügbaren Laborarbeiten zur P-Rückgewinnung mit Brauereihefe wurde ein neuer Pilotmaßstab-Prozess für die biologische P-Rückgewinnung (BioP-Rec-Modul) aus KA-Prozessströmen vorgeschlagen. Ein BioP-Rec-Modul wurde auf einer kommunalen KA installiert, wo die erfolgreiche biologische P-Rückgewinnung mit drei verschiedenen Prozessstufen demonstriert wurde. In der Stufe 1 wurde unter anaeroben Bedingungen ein freies P-reiches Substrat mit Rücklaufschlamm erzeugt. In Stufe 2 wurden ausgehungerter Brauereihefen eingesetzt, um das P durch Akkumulation in den Zellen zurückzugewinnen. In Stufe 3 wurde die Hefe filtriert, um Hefeschlamm als Dünger zu produzieren. Bei der Arbeit mit dem BioP-Rec-Modul wurde versucht, innerhalb oder oberhalb der freien P-Konzentration von 0,05 kg/m3 zu arbeiten, die als wirtschaftlich rentabel für die P-Rückgewinnung betrachtet wird. Außerdem wurde darauf geachtet, dass das BioP-Rec-Modul den Grenzwert, festgelegt in der deutschen Klärschlammverordnung (AbfKlärV), für den P-Gehalt in der Trockensubstanz (DM) von 20 gP/kgDM in Klärschlämmen einhält. Ab 2029 wird die AbfKlärV in Deutschland fordern, dass Kläranlagen mit einem P-Gehalt in DM, der über den zuvor genannten Werten liegt, zwingend den P in ihrem Prozess zurückgewinnen müssen. Wenn das BioP-Rec-Modul als Technologie bereits demonstrieren kann, dass es die definierten Grenzwerte erfüllen kann, wäre das ein starkes Argument für seine zukünftige Entwicklung. Darüber hinaus wird die Wirtschaftlichkeit des derzeitigen BioP-Rec-Verfahrens im Pilotmaßstab untersucht, und es werden weitere Ideen zu seiner Verbesserung und möglichen weiteren Einführung vorgestellt. Diese Arbeit kann als Sprungbrett für die weitere Entwicklung von umweltfreundlichen, biologisch basierten P-Rückgewinnungsprozessen in größerem Maßstab genutzt werden.:Content Summary 8 Zusammenfassung 10 1 Introduction 13 1.1 Phosphorus (P) 13 1.2 Wastewater P sources, P removal and recovery 16 1.2.1 Wastewater P sources 16 1.2.2 Wastewater P removal and recovery 19 1.2.2.1 Biological P removal 20 1.2.2.2 Chemical P removal 23 1.2.2.3 Biological P recovery 25 1.2.2.4 Biological P recovery with yeast 26 1.2.2.5 Chemical P recovery 31 1.3 Economically feasible P recovery 33 1.4 Legal framework for P recovery 34 1.5 Aim of this study 37 2 Publications 41 2.1 List of publications 41 2.2 Published articles 43 2.2.1 New developments in biological phosphorus accessibility and recovery approaches from soil and waste streams 45 2.2.2 A framework for P-cycle assessment in wastewater treatment plants 57 2.2.3 Biological recovery of phosphorus (BioP-Rec) from wastewater streams using brewer's yeast on pilot-scale 71 3 Discussion 91 3.1 WWTP P balance for P recovery 91 3.2 WWTP design impacting free P availability 93 3.3 Free P hot spots for biological P recovery 95 3.4 BioP-Rec module P recovery 97 3.4.1 BioP-Rec module version 1 97 3.4.2 BioP-Rec module development concept 98 3.4.3 BioP-Rec module work concept 100 3.4.3.1 Stage 1 101 3.4.3.2 Stage 2 104 3.4.3.3 Stage 3 108 3.4.4 P enriched yeast as a fertiliser 108 3.5 Process economics 110 3.6 Steps to consider towards optimisation of the process economics 112 3.6.1 Process parameter optimisation 114 3.6.1.1 Different acid for higher free P release in stage 1 114 3.6.1.2 Different flocculant 115 3.6.1.3 Sucrose to yeast ration for stage 2a (starvation) and stage 2b (free P uptake) 115 3.6.1.4 Reuse some of the BioP-Rec module waste streams 117 3.6.1.5 Process aeration optimisation 117 3.6.2 Technology optimisation 117 3.6.3 Possible positive effects of the optimisation steps 118 3.6.4 Secondary value adding effects that can offset development costs 119 3.6.5 Directions for future BioP-Rec development 120 3.7 Future prospects and conclusion 123 3.7.1 Future prospects of the BioP-Rec module application 123 3.7.2 Further yeasts P uptake research 123 4 References 125 Declaration of authorship and independent work 147 Curriculum vitae 151 List of publications and conference contributions 153 5 Appendix 5-1 5.1 Supplementary information on Publication 2 5-3 5.2 Supplementary information on Publication 3 5-23 5.3. Unpublished data connected to Publication 3: Original brewer's yeast phosphorus uptake without and with sucrose as a carbon source 5-45 6 Acknowledgements 6-54

In the efforts to create sustainable production of heat and power and to reduce the net CO2 emissions to the atmosphere, alternative fuels are today being utilised. These fuels are, for example, biofuels and waste derived fuels such as different residues from the agricultural sector and the pulp and paper industry, municipal sewage sludge and municipal sorted solid waste. These fuels put new demands on the combustion facilities due to their chemical composition and this in turn calls for methods of prediction for the evaluation of their combustion behaviour. Most significant for the majority of these fuels are the high alkali and chlorine concentrations which cause bed agglomeration, deposit formation and corrosion on heat transfer surfaces. These problems can be solved if sufficient knowledge is obtained of the specific fuel or fuel mix. In this work, chemical fractionation, a step by step leaching method, was used on fuels, fuel mixes and fly ashes from co-combustion in a fluidised bed combustor. In addition, XRD and SEM-EDX were used for the fuel and fly ash characterisation. Different alkali chloride reducing additives i.e. kaolin, zeolites and sulphur were investigated as was the influence of various bed materials: silica sand, olivine sand and blast furnace slag (BFS). Some of the new, alternative fuels, such as municipal sewage sludge and meat and bone meal (MBM) contain high concentrations of phosphorus which is a very important nutrient essential in many biological processes. Phosphorus rock used as raw material in the phosphate industry is a depleting natural resource estimated to last for only 30-200 years according to different sources. The combustion of municipal sewage sludge enriches the phosphorus in the ashes while hazardous components such as pathogens and organic pollutants are rendered harmless after combustion. However, toxic heavy metals are also enriched in the ashes. One aim of the work was to find a sufficiently effective and low cost method for phosphorus extraction from fly ashes derived from municipal sewage sludge combustion. Two types of municipal sewage sludges were investigated using different chemicals for the phosphorus cleaning step in the waste water treatment plants. The first sewage sludge derived from a plant using iron sulphate as flocculant to precipitate phosphorus as iron phosphate. The second sludge meanwhile came from a plant using aluminium sulphate as flocculant to precipitate phosphorus as aluminium phosphate. Both sewage sludges were dewatered prior to combustion and co-combusted with wood pellets. At pH 1 nearly all the phosphorus was released from the fly ash derived from the sewage sludge where aluminium sulphate was used as a phosphorus precipitation agent. Iron sulphate as precipitant inhibited the phosphorus extraction from the ashes, resulting in only 50-80% of the phosphorus being released. Furthermore, the mobility of heavy metals to the leachates was investigated to establish whether the leachates were suitable as fertilisers. Only minor fractions of Pd, Hg, Cr, Cu, Mn, Co, Ni, As, Sb, V and Zn were found in the leachates, all well within the legislated limitations for fertilisers. However, one exception was Cd that was nearly totally dissolved in the leachate. Thus a decadmiation of the leachate is necessary prior to any utilisation of the ashes and reuse of phosphorus as fertiliser. / <p>Akademisk avhandling för avläggande av teknologie doktorsexamen vid Chalmers tekniska högskola försvaras vid offentlig disputation den 15 oktober 2008</p>

With a growing population but scarce primary phosphorus sources, recycling of the vital element has become an important research area throughout the last decades. Several streams in society are potential resources for recirculation but municipal sewage is considered one of the most available materials. With current technologies in wastewater treatment, over 95 % of the influent phosphorus is captured in the sludge along with a variety of other nutrients. However, due to increasing fractions of pharmaceutical residues and heavy metals also following the sludge, direct use as fertiliser is being phased out in most European countries in favour of extraction methods. Extraction of nutrients from the sludge is problematic mainly because of dewaterability difficulties. Thus, pretreatment of the material is required to access the desired components at a reasonable cost and energy consumption. Hydrothermal carbonisation (HTC) is a technology showing high potential for treatment of wet carbonaceous material without necessity of prior drying. The resulting product is hygenised, essentially free from pharmaceuticals and easily dewatered. In this Master’s thesis principal conditions for release of phosphorus from HTC converted digested sludge under acid leaching have been experimentally investigated. Dependence of time, temperature, dry solids (DS) content of HTC sludge and pH have been studied. Also, differences arising from acid type have been considered by comparing acidulation with sulphuric acid and hydrochloric acid. A short investigation of the recovery of the dissolved phosphorus from leachate by precipitation was also performed where calcium ions were added to both sulphuric and hydrochloric acid leachates. Extraction of phosphorus from HTC converted sludge has shown to be easier than from pure metal phosphates under comparable leaching conditions and pH values. Also, the dissolved phosphorus concentrations obtained in the presence of HTC converted sludge was higher than for theoretical equilibrium concentrations where all phosphorus is in the form of iron(III) or aluminium(III) phosphate. A maximum leachate phosphorus concentration was around 2500 mg/L, recorded in leaching experiments performed at a dry HTC product concentration of 10 % (w/w) in an extraction solution of water acidified with sulphuric acid. Leaching procedures performed at pH values between 2 and 1 with 1 and 5 % DS HTC product resulted in dissolution of 90 % of ingoing phosphorus at an acid charge of 0.5 kg H2SO4/kg DS HTC product. At this chemical charge, release of phosphorus from converted sludge is fast. Similar amounts of dissolved phosphorus were recorded after 15 min as after 16 h retention time. Possibly, time dependence becomes relevant at lower charges. The dissolution of phosphorus is negatively affected by temperature increases at moderate acid loads, and by possibly by hydrochloric acid at pH values below 2. Addition of calcium gave a dissolved phosphorus reduction of 99.9 % in both the sulphuric acid and hydrochloric acid leachates. Gypsum, CaSO4, also precipitates from the sulphuric acid leachate resulting in 67 % more dry mass. Due to high release of metals during acidulation, the precipitate was also contaminated with large fractions of metals in addition to calcium. In summary, this investigation has demonstrated that up to 90 % of the phosphorus content of the HTC converted sludge can be released by acid leaching, and almost 100 % of the phosphorus can be recovered from the leachate by precipitation with calcium ions.

O ciclo aberto que o fósforo percorre na sociedade contemporânea pode ser visto como uma das maiores falhas da sua sustentabilidade. Sendo este um elemento básico para qualquer ser vivo, é realmente incômodo pensar que todo o fósforo que percorre as diversas instâncias da sociedade (como agricultura, alimentos ou consumo humano) provém direta ou indiretamente da mineração, portanto, de uma fonte esgotável. Se algumas estimativas da duração de toda a reserva de rochas fosfatadas do planeta não estivessem beirando a casa de um século, esse tema, acerca da geração de uma fonte renovável e sustentável de P, não teria o mesmo peso. A presente pesquisa, realizada com uma visão multidisciplinar levando em conta estudos mineralógicos; agrícolas; de crescimento de cristais; formação de carapaça de crustáceos marinhos; tratamento de esgoto; termodinâmica e cinética de precipitações químicas traz à luz da realidade nacional uma discussão acerca dos parâmetros que possibilitam a recuperação do fósforo (e do nitrogênio) diretamente do esgoto. Nos últimos anos, diversas tentativas de precipitação de estruvita no Brasil não foram bem sucedidas. Por esse motivo, essa dissertação foi desenvolvida com o intuito de contribuir com uma melhor compreensão a respeito dos fenômenos envolvidos na formação e crescimento desses cristais. Para isso, foram realizados ensaios com amostras de água ultrapura; efluente do reator anaeróbio de fluxo ascendente com manto de lodo da estação de tratamento de esgoto (ETE) Anhumas; urina pura e efluente dos processos de desaguamento do lodo da ETE Franca (um sistema de lodos ativados convencionais). Este último apresentou altas concentrações de cálcio, o maior interveniente na formação de estruvita, devido ao recebimento de lodo de estação de tratamento de água. A investigação experimental foi dividida em três etapas: (1) Primeiramente, as principais variáveis da reação de cristalização foram avaliadas e percebeu-se que, o que a rege é o quanto o meio se encontra supersaturado com relação aos sais de estruvita. Portanto, as variáveis que influenciam na supersaturação (como pH e concentração de reagentes) podem ser manipuladas para que a reação ocorra da maneira que for desejável. (2) Quando a água residuária contém cálcio, forma-se uma fase amorfa de carbonato de cálcio, que é muito reativa e bastante metaestável (que nesse caso acaba sendo estabilizada), na qual o fósforo e o magnésio adsorvem, podendo inclusive causar uma falsa impressão de que se formou estruvita, devido ao consumo dos reagentes. Deste entendimento, foi possível uma proposta bastante simples de solução para o problema: semeadura com cristais de estruvita. (3) A última etapa da dissertação explica o porquê da dificuldade de encontrar os picos de estruvita nos difratogramas de raios-x, tanto em algumas pesquisas nacionais quanto no começo do presente estudo. Esta dificuldade está relacionada às mudanças de fases do cristal quando exposto a altas temperaturas, isto é, durante o processo de secagem em estufa. / The opened cycle in which the phosphorus flows within the contemporary society is one of the biggest lack on its sustainability. Being this element so primary for the life of any being, it is really uncomfortable to think that all phosphorus that runs through all instances of our society (as agriculture, foods or human consumption) comes directly or indirectly from mining, thus a non-renewable source. By means of a multidisciplinary vision taking into account mineralogical, agriculture, crystal growth, marine crustaceous, wastewater treatment, chemical kinetics and thermodynamic studies the parameters which govern this crystallization reaction were brought to light, in order to make possible the recovery of phosphorus directly from sewage. For this reason, the development of this research was to create a better comprehension around the phenomena of formation and growth of struvite crystals. The crystallization media used were ultrapure water, effluent from an upflow anaerobic sludge bed reactor also treating domestic sewage in real scale, urine, and effluent of the dewatering processes of the sludge from a conventional activated sludge system (anaerobically digested) treating domestic sewage in real scale (because this WWTP receives WTP sludge with a high content of calcium, the major interfering ion on struvite formation). This study was made in three steps: (1) At first, the main parameters (usually controlled) of this crystallization reaction were evaluated. It was concluded that what controls the reaction is how much the crystallization media is supersaturated of the struvite salts. Thus, all parameters which have an influence on that (as pH and reagents concentration) can be manipulated for the reaction to occur in the desirable way. (2) The ion which interfere the most on the formation of struvite (calcium) was also studied, and the conclusion was that an amorphous calcium carbonate phase, was formed, which is a very metastable morphology of this salt, and thus it is not found in other conditions which are not as specific as those. With this theory, a proposal of a simple solution for this problem was formulated: struvite seeding. (3) The last step of this research explains why the characteristic peaks of struvite crystals were so difficult to be found on the x-ray diffractograms on the beginning of this study and by other Brazilian researchers. This difficult is related to the phase transitions due to the exposition of the crystals to higher temperatures.

O ciclo aberto que o fósforo percorre na sociedade contemporânea pode ser visto como uma das maiores falhas da sua sustentabilidade. Sendo este um elemento básico para qualquer ser vivo, é realmente incômodo pensar que todo o fósforo que percorre as diversas instâncias da sociedade (como agricultura, alimentos ou consumo humano) provém direta ou indiretamente da mineração, portanto, de uma fonte esgotável. Se algumas estimativas da duração de toda a reserva de rochas fosfatadas do planeta não estivessem beirando a casa de um século, esse tema, acerca da geração de uma fonte renovável e sustentável de P, não teria o mesmo peso. A presente pesquisa, realizada com uma visão multidisciplinar levando em conta estudos mineralógicos; agrícolas; de crescimento de cristais; formação de carapaça de crustáceos marinhos; tratamento de esgoto; termodinâmica e cinética de precipitações químicas traz à luz da realidade nacional uma discussão acerca dos parâmetros que possibilitam a recuperação do fósforo (e do nitrogênio) diretamente do esgoto. Nos últimos anos, diversas tentativas de precipitação de estruvita no Brasil não foram bem sucedidas. Por esse motivo, essa dissertação foi desenvolvida com o intuito de contribuir com uma melhor compreensão a respeito dos fenômenos envolvidos na formação e crescimento desses cristais. Para isso, foram realizados ensaios com amostras de água ultrapura; efluente do reator anaeróbio de fluxo ascendente com manto de lodo da estação de tratamento de esgoto (ETE) Anhumas; urina pura e efluente dos processos de desaguamento do lodo da ETE Franca (um sistema de lodos ativados convencionais). Este último apresentou altas concentrações de cálcio, o maior interveniente na formação de estruvita, devido ao recebimento de lodo de estação de tratamento de água. A investigação experimental foi dividida em três etapas: (1) Primeiramente, as principais variáveis da reação de cristalização foram avaliadas e percebeu-se que, o que a rege é o quanto o meio se encontra supersaturado com relação aos sais de estruvita. Portanto, as variáveis que influenciam na supersaturação (como pH e concentração de reagentes) podem ser manipuladas para que a reação ocorra da maneira que for desejável. (2) Quando a água residuária contém cálcio, forma-se uma fase amorfa de carbonato de cálcio, que é muito reativa e bastante metaestável (que nesse caso acaba sendo estabilizada), na qual o fósforo e o magnésio adsorvem, podendo inclusive causar uma falsa impressão de que se formou estruvita, devido ao consumo dos reagentes. Deste entendimento, foi possível uma proposta bastante simples de solução para o problema: semeadura com cristais de estruvita. (3) A última etapa da dissertação explica o porquê da dificuldade de encontrar os picos de estruvita nos difratogramas de raios-x, tanto em algumas pesquisas nacionais quanto no começo do presente estudo. Esta dificuldade está relacionada às mudanças de fases do cristal quando exposto a altas temperaturas, isto é, durante o processo de secagem em estufa. / The opened cycle in which the phosphorus flows within the contemporary society is one of the biggest lack on its sustainability. Being this element so primary for the life of any being, it is really uncomfortable to think that all phosphorus that runs through all instances of our society (as agriculture, foods or human consumption) comes directly or indirectly from mining, thus a non-renewable source. By means of a multidisciplinary vision taking into account mineralogical, agriculture, crystal growth, marine crustaceous, wastewater treatment, chemical kinetics and thermodynamic studies the parameters which govern this crystallization reaction were brought to light, in order to make possible the recovery of phosphorus directly from sewage. For this reason, the development of this research was to create a better comprehension around the phenomena of formation and growth of struvite crystals. The crystallization media used were ultrapure water, effluent from an upflow anaerobic sludge bed reactor also treating domestic sewage in real scale, urine, and effluent of the dewatering processes of the sludge from a conventional activated sludge system (anaerobically digested) treating domestic sewage in real scale (because this WWTP receives WTP sludge with a high content of calcium, the major interfering ion on struvite formation). This study was made in three steps: (1) At first, the main parameters (usually controlled) of this crystallization reaction were evaluated. It was concluded that what controls the reaction is how much the crystallization media is supersaturated of the struvite salts. Thus, all parameters which have an influence on that (as pH and reagents concentration) can be manipulated for the reaction to occur in the desirable way. (2) The ion which interfere the most on the formation of struvite (calcium) was also studied, and the conclusion was that an amorphous calcium carbonate phase, was formed, which is a very metastable morphology of this salt, and thus it is not found in other conditions which are not as specific as those. With this theory, a proposal of a simple solution for this problem was formulated: struvite seeding. (3) The last step of this research explains why the characteristic peaks of struvite crystals were so difficult to be found on the x-ray diffractograms on the beginning of this study and by other Brazilian researchers. This difficult is related to the phase transitions due to the exposition of the crystals to higher temperatures.

In working towards a sustainable society, recycling and recovery of products together with handling of scarce resources must be considered. The growing quantities of sludge from wastewater treatment plants and the increasingly stringent restrictions on landfilling and on agricultural use of sludge are promoting other disposal alternatives. Sludge fractionation, providing sludge volume reduction, product recovery and separation of toxic substances into a small stream, has gained particular interest. In this thesis, the potential for phosphate release and recovery from treated sewage sludge is investigated as an alternative for agricultural use in urban areas. Leaching and recovery experiments were performed on sludge residue from supercritical water oxidation, ash from incineration and dried sludge at different temperatures. Results showed that acid or alkaline leaching is a promising method to release phosphate from sewage sludge treated with supercritical water oxidation, incineration, or drying at 300°C. The leaching is affected by a number of factors, including how the sludge residue has been produced, the origin of the sludge residue, the quantity of chemicals added and the presence of ions in the leachate. The implementation of any particular sludge treatment technology would depend on cost, environmental regulations, and social aspects. The results of this thesis may be beneficial for minimizing the use and cost of chemicals, and give increased knowledge for further development of technology for phosphate recovery. / QC 20100930