Biofuels production and utilisation can reduce the emission of greenhouse gases, dependence on fossil fuels and also improve energy security. Ethanol is the most important biofuel in the transportation sector; however, its production from lignocelluloses faces some challenges. Conventionally, lignocellulosic hydrolysis and fermentation has mostly been performed by separate hydrolysis and fermentation (SHF) or simultaneous saccharification and fermentation (SSF). SHF results in product inhibition during enzymatic hydrolysis and increased contamination risk. During SSF, suboptimal conditions are used and the fermenting organism cannot be reused. Bacterial contamination is another major concern in ethanol production, which usually results in low ethanol yield. In these studies, the above-mentioned challenges have been addressed. A novel method for lignocellulosic ethanol production ‘Simultaneous saccharification filtration and fermentation (SSFF)’ was developed. It circumvents the disadvantages of SSF and SHF; specifically, it uses a membrane for filtration and allows both the hydrolysis and fermentation to be carried out at different optimum conditions. SSFF also offers the possibility of cell reuse for several cultivations. The method was initially applied to pretreated spruce, with a flocculating strain of yeast Saccharomyces cerevisiae. SSFF was further developed and applied to pretreated wheat straw, a xylose rich lignocellulosic material, using encapsulated xylose fermenting strain of S. cerevisiae. High solids loading of 12% suspended solids (SS) was used to combat bacterial contamination and improve ethanol yield. Oil palm empty fruit bunch (OPEFB) was pretreated with fungal and phosphoric acid in order to improve its ethanol yield. An evaluation of biofuel production in Nigeria was also carried out. SSFF resulted in ethanol yield of 85% of the theoretical yield from pretreated spruce with the flocculating strain. Combination of SSFF with encapsulated xylose fermenting strain facilitated simultaneous glucose and xylose utilisation when applied to pretreated wheat straw; this resulted in complete glucose consumption and 80% xylose utilisation and consequently, 90% ethanol yield of the theoretical level. High solids loading of 12% SS of pretreated birch resulted in 47.2 g/L ethanol concentration and kept bacterial infection under control; only 2.9 g/L of lactic acid was produced at the end of fermentation, which lasted for 160 h while high lactic acid concentrations of 42.6 g/L and 35.5 g/L were produced from 10% SS and 8% SS, respectively. Phosphoric acid pretreatment as well as combination of fungal and phosphoric pretreatment improved the ethanol yield of raw OPEFB from 15% to 89% and 63% of the theoretical value, respectively. In conclusion, these studies show that SSFF can potentially replace the conventional methods of lignocellulosic ethanol production and that high solids loading can be used to suppress bacterial infections during ethanol productions, as well as that phosphoric acid pretreatment can improve ethanol yield from lignocellulosic biomass. / <p>Thesis for the degree of Doctor of Philosophy at the University of Borås to be publicly defended on 31 October 2014, 10.00 a. m. in room E310, University of Borås, Allégatan 1, Borås.</p>

Fruits are among the most important commodities in global trading due to its fundamental nutritional values. In 2012, the fruits supply was 115 kg/person/year, however, only 50 % of the fruits reached their consumers and the rest ended up as waste during the long fruit supply chain. The waste from fruits is mostly dumped or burned, creating a serious environmental problem. A more sustainable handling of the waste is therefore highly desirable. One of them is conversion of the fruits wastes into biogas through anaerobic digestion. One challenge with the conversion of fruits wastes into biogas is the presence of antimicrobial compounds in the fruits, which reduce the biogas yield or even cause a total failure of the process. Fruit flavors have been reported to have antimicrobial activity against several microorganisms and being responsible for the defense system in the fruits. However, there is only scarce information about the effect of fruit flavors on anaerobic digesting microbia. The objectives of the present thesis were: 1) to investigate the inhibitory activity of the fruit flavors on anaerobic digestion; 2) to remove the flavor compound by pretreatment; and 3) to protect the cell from the flavor compounds using a membrane bioreactor. The inhibitory activity of the fruit flavors was examined from different groups of flavors by adding a single flavor compound into the batch anaerobic digesting system, at three different concentrations. Among the flavors added, myrcene and octanol were found to exhibit a strong inhibitory activity, with 50 % reduction of the methane production at low concentrations, ca. 0.005–0.05 %. These flavors can be found in oranges, strawberries, grapes, plums, and mangoes. The other flavors tested showed moderate and low inhibitory activity, which might not affect the anaerobic digestion of the fruits wastes. In order to overcome the inhibitory effects of the fruit flavor, two approaches were proposed in this thesis, namely, fruit flavor removal by leaching pretreatment and cell protection from fruit flavor using a membrane bioreactor. Orange peel waste and D-limonene were used as a model of fruit waste and inhibitor, respectively. The leaching pretreatment uses solvent to extract the limonene from the orange peel. The methane yield increased by 356 % from 0.061 Nm3/kg VS to 0.217 Nm3/kg VS, by pretreating the peel using hexane with peel and a hexane ratio of 1:12 at room temperature for 10 min. Alternative to limonene removal, the cells were encased in a hydrophilic membrane, which is impermeable to hydrophobic limonene. This method yielded more than six times higher methane yield, compared to the free cell. At the highest organic loading rate, examined in this work, 3 g VS/L/day, the methane yield of the reactor containing the free cell was only 0.05 Nm3/kg VS, corresponding to 10 % of the theoretical yield, whereas 0.33 Nm3/kg VS methane yield was achieved using a membrane bioreactor corresponding to 75 % of the theoretical yield. / <p>Thesis for the degree of Doctor of Philosophy at the University of Borås to be publicly defended on November 27th 2014, 10.00 a.m. in room E310, University of Borås, Allégatan 1, Borås.</p>

Anaerobic digestion is a biochemical process in which organic carbon is biodegraded in an oxygen free environment through a microbial consortium. Engineered biological systems used for resource recovery often utilize anaerobic digestion to treat anthropogenic organic wastes by reclaiming the carbon as energy (methane gas) and a soil amendment (biosolids). Small-scale, or household, semi-continuous anaerobic digesters have been used in developed and developing countries for many decades to produce biogas from human and livestock waste, which is used for heating, lighting, and cooking. This application has been shown to improve the quality of life of the user. Although there is great potential for small-scale semi-continuous anaerobic digestion to provide much needed resource recovery functions and quality of life improvements in future development, the manner in which these systems are operated could lead to unintended consequences on human health because human waste often contains resistant pathogens. This paradigm is best demonstrated by soil-transmitted helminths that are known to be highly resilient in mesophilic anaerobic digestion environments and endemic to many developing countries. The idea that soil-transmitted helminths survive mesophilic anaerobic digestion is exacerbated when the biosolids from the digesters are land applied as a soil-amendment because this process fits perfectly into the lifecycle of soil-transmitted helminths that need soil environments to develop into infective larva. This research was divided into three sections to investigate the fate of human pathogens during semi-continuous anaerobic digestion and investigate techniques to enhance their removal. The sections were: 1) an examination into the fate (embryonation, development, inactivation, destruction) of Ascaris suum ova during mesophilic semi-continuous anaerobic digestion, with an emphasis on increased inactivation, 2) an investigation into the performance (volatile solids (VS) removal, E. coli and Salmonella destruction, methane production) of semi-continuous mesophilic anaerobic digesters and the effect of variations to solids retention time (SRT) and feeding frequency, and 3) development and application of mathematical models for pathogen inactivation kinetics and typical semi-continuous reactor residence time distributions to predict the removal efficiency of Ascaris suum ova during semi-continuous anaerobic digestion under different operating conditions. Results of these studies showed that during semi-continuous mesophilic anaerobic digestion variations in feeding frequency did not impact the fate of Ascaris suum ova or Salmonella; however it was observed that better removal of E. coli and higher methane production was achieved at the longer feeding interval (weekly). Additional results indicated that embryonated ova were destroyed faster than unembryonated ova under the experimental conditions, which suggests a potential mechanism to enhance removal of this common pathogen. Since an increased feeding interval proved to be beneficial for digester performance our findings suggest that wastes containing Ascaris suum ova could be stored in an aerated environment, for a period of time that does not negatively impact resource recovery, to lengthen the time between feedings and promote ova embryonation and ensuing destruction during digestion. Modeling results indicate that under mesophilic conditions (35oC) the ova of Ascaris suum could survive for 22 days and will not be completely removed from the effluent under typical feeding frequencies and average SRT were examined. Therefore, the use of anaerobic digestion as a resource recovery technology where soil-transmitted helminths proliferate should be applied with extra operational safeguards or be included as one step of several in a small-scale treatment train.

The urban sprawl creates a gap between producers and consumers and the a sustainable circuitof nutrients and energy is difficult to maintain. Many times the waste that is created in urbanareas is not reused and the circuit is lost. In this project, wastewater treatment is looked atwith the view point that resource recovery is possible through energy production and reuse ofnutrients. In order to optimally run each process step at a wastewater treatment plant forimproved resource recovery, more knowledge is needed in order to not disregard the finaleffluent quality. The goal of this project was to develop a model in MATLAB/Simulink for achemically enhanced primary clarifier at a wastewater treatment plant. The potential ofproducing more biogas and reducing the aeration energy needed in the biological treatmentstep was looked at by focusing on describing the settling velocity of suspended solids.Experimental analysis on settling properties for solids was performed on sampled wastewaterentering the primary settler after changing the addition of chemicals prior in the process line.The wastewater samples were homogenized and then rapidly vacuum pumped up in a column.The solids in the column could thereafter settle and was retained in a cup at the bottom. Themass of total suspended solids (TSS) was classified in five different settling velocity classes,each class assigned a characteristic settling velocity. The experimental procedure followed theViCA's protocol (French acronym for Settling Velocity for Wastewater). A settler, much likethe secondary settler in the Benchmark Simulation Model No. 2 (BSM2), a 10 layer nonreactivetank was modeled. The mass balance in each layer of the settler was decided by thevertical solid flux in the tank and built on the characteristic settling velocity gained from theexperiments. Re-circulation of excess sludge from the subsequent steps at the plant showed toeffect the settling properties of the sludge in the primary settler. The components of TSSshowed to have the largest effect on the distribution of settling velocity. The variation in doseof both coagulant and cationic polymer prior the primary settling tank showed to effect theparticle settling distribution somewhat. A first simulation with an applicable dynamic influentscenario was run. Despite any proper calibration the model gave fairly good predictions ofmeasured TSS in the effluent and sludge outtake water. / När urbana områden växer uppstår svårigheter i att bibehålla ett hållbart kretslopp av energioch näringsämnen. Avståndet mellan producent och konsument ökar och många gångeråteranvänds inte det avfall som städerna producerar och det hållbara kretsloppet bryts. Dettaprojekt har fokuserat på resursåteranvändningen i avloppsvattenhanteringen genommöjligheterna som finns i energiproduktion i form av biogas samt återanvändning avnäringsämnen genom slamåterförsel. Mer kunskap behövs inom varje processteg för attoptimalt använda avloppsreningsverk för förbättrad resurs-återvinning så att inte utgåendevattenkvalitet blir lidande. Målet med projektet var att utveckla en modell iMATLAB/Simulink för primärsedimentering med kemisk fällning. Experimentelltanalyserades sedimentationsegenskaperna hos primärslam genom provtagning avavloppsvatten inkommande till försedimenteringen efter tillsatser av fällnings-kemikalier.Proverna homogeniserades och vakuumpumpades sedan snabbt upp i en kolonn. Detpartikulära materialet i kolonnen kunde därefter sedimentera och fångades upp i en kopp ibotten. Den sedimenterade massan av totalt suspenderat material (TSS) klassificerades i femolika sedimenteringshastighetsklasser och varje klass tilldelades en karakteristisksedimentationshastighet Det experimentella förfarandet följde ViCA’s protokoll (franskförkortning för sedimentationshastigheter för avloppsvatten). En modell av ensedimentationstank, ungefär som för sekundär-sedimenteringen i Benchmark SimulationModel No. 2 (BSM2), utvecklades som en 10 lager icke reaktiv tank. Massbalansen i varjelager bestämdes av det vertikala flödet av partiklar och beräknades med de experimentelltframtagna karakteristiska sedimentationshastigheterna. Återcirkulering av överskottsslam frånde efterföljande reningsstegen visade sig ha stor påverkan på slammetssedimentationsegenskaper i försedimenteringen. Typen av TSS-komponenter hade den störstainverkan på fördelningen av sedimentationshastigheter. Variationen i dos av bådefällningskemikalie och katjonspolymer före primär-sedimenteringstanken hade en visspåverkan på fördelningen. En första simulering med ett sannolikt dynamisk inflödesscenariokördes. Utan någon riktig kalibrering av modellen gav den ändå en relativt realistisk prognospå TSS i utgående vatten och i slamuttaget. / I samarbete med forskningsgruppen ModelEAU, Quebec, Kanada

The subject of this essay is waste and waste management in Sweden during the years1975-2005. The purpose of this investigation is to identify which factors that have affectedthe development of waste management from a political angle in order to identifycharacteristic features of the period in terms of waste management regime. The investigationorigins from Ylva Sjöstrand’s thesis about resource recovery, incineration and tippingof waste in Stockholm 1900-1975 and the theoretical framework in this essay is based onher thesis.By analysing three propositions from the years 1975, 1993 and 2003 concerning wasteand waste management I will argue that the new waste management regime that dominatedSweden during 1975-2005 is called sustainability regime. The name sustainabilityregime is therefore the result which this essay leads to.

This research study's the use of biological sulfate reduction technologies for the treatment of Sasol Secunda's coal-mine drainage (CMD) using Fischer-Tropsch Reaction Water (FTRW) as a cost-efficient carbon source. The research aims to develop a prototype dynamic model that describes this co-treatment of FTRW and CMD in both a continuously stirred tank reactor (CSTR) biological sulfate reduction (BSR) system and a BSR gas-lift (BSR-GL) integrated system. The BSR-GL system recovers elemental sulfur (S0 ) from the H2S produced and stripped from the BSR unit. Furthermore, this study aims to use the prototype model for a quantitative comparison of the CSTR-BSR and BSR-GL systems. Two bench-scale 5-litre CSTR-BSR and a 20-litre BSR-GL system were operated, under varying feed COD concentrations and hydraulic retention times (HRTs), to generate datasets for use in verification and a rudimentary validation of the prototype model. The BSR-GL integrated system includes 1) a 1-litre H2S gas reactive absorption (ABS) unit utilising an aqueous ferric solution for the recovery of elemental sulfur (S0 ) from sulfide and 2) ferrous biological oxidation reactor to regenerate ferric from the ferrous for re-supply to the ABS unit. The datasets generated in the experimental study allowed for the identification, mathematical modelling and reaction verification of 32 components that interact as reactants and products in 23 reactions observed in the two BSR systems. The prototype model is presented in a mass and charge balanced Gujer matrix that includes, i) 5 SRB mediated processes, ii) 2 liquid-gas mass transfer processes, iii) 3 processes describing the ABS and Fe2+ bio-oxidation units, iv) 4 processes describing sulfide and elemental sulfur oxidation and v) the S0 and poly-sulfide aqueous equilibrium and vi) 9 processes describing death regeneration and BPO hydrolysis. This prototype model was implemented in the DHI WEST® software for initial stage simulation trials. The experimental datasets allowed for the first-stage estimation of the best-fit reaction rate equations and the calibration of the kinetic parameters related to the 23 reactions, using MATLAB® curve fitting toolbox. A pre-processor that describe the pH and equilibrium chemistry of the components of the artificially prepared FTRW+CMD feed mixture batches under varying total concentrations have also been developed in this research. This was done to generated influent file to the DHI WEST® simulations that incorporated the dynamics related to the FTRW+CMD feed mixtures. The sulfate utilisation rate (gSO4 -2 .l-1 .d-1 ) of the GL-BSR and CSTR-BSR systems were compared to determine which system had the best sulfate removal. The results were found to be as follows; a. On comparison it was found that the sulfate substrate utilisation rate for the CSTR_BSR system is 39.28% of that of the BSR-GL_N2 system, where both systems were fed at feed mixture of COD of 2500mgCOD/l, where the COD:SO4 2- was 0.7, b. For the same systems fed a feed mixture of COD at 5000mgCOD/l (COD:SO4 2- = 0.7), the sulfate substrate utilisation rate for the CSTR_BSR system was found to be 17.86% less than that of the BSR_GLN2 system. c. Finally, it was also found that the substrate utilisation rate for the CSTR_BSR system was 30.06% less than that of the BSR_GLN2 system at Se of 4gCOD/l, for both systems fed substrate at 5000mgCOD/l. Thus, it can be concluded that the sulfate substrate utilisation rate for the BSR-GL system is higher than that of the CSTR_BSR system, for systems fed COD feed mixtures at 2.5 or 5gCOD/l where both systems have the same effluent substrate concentrations. However, the difference in the comparative substrate utilisation rate is less at higher feed substrate concentrations. This is the influence of substrate inhibition on the active SRB biomass, which increases with higher effluent substrate concentrations. Finally, this research found that the use of gas-lift reactor technologies is superior to CSTR technologies in the treatment of coal-mine drainage utilising biological sulfate reduction (BSR). The CSTR-BSR system, fed sulfate between 1.6 to 14gSO4 2- /l, produced effluent with high dissolved H2S concentrations, on average 285mgS/l and maximum at >600mgS/l. Releasing this effluent to the environment would be hazardous to aquatic and human health and corrosive to infrastructure. As such, the effluent from the CSTR-BSR system requires further treatment to stabilise the water for any use. The BSR-GL technology allows for the conversion of the H2S produced during BSR reactions to form elemental sulfur, which is a resource recovered from this process, thus complying to the circular economy aim of this study.

Proper disposal of industrial brine has been a critical environmental challenge. Driven by the even-tightening environment protection regulations, the Zero-Liquid-Discharge (ZLD) has gradually become mandatory option for brine disposal, but its application is limited by the intensive energy consumption. The recent development of solar crystallizer provides a new strategy to achieve ZLD brine disposal. However, the research on solar crystallizer, employing photothermal material to convert solar energy to heat for interfacial brine evaporation and crystallization, is still at the early stage. This dissertation thoroughly investigated the solar crystallizer-based ZLD technology in a broad scientific and application context. The scaling formation while treating real brine, which has been the major barrier to the application of solar crystallizer, was confirmed first with a solar crystallizer device. With a rational designed anti-scaling mechanism, the scaling-free crystallization behavior and stable high water evaporation rate of 2.42 kg m-2 h-1 was achieved when treating real seawater brine. After verifying the feasibility of solar crystallizer towards real brine treatment, its performance was further improved by integrating convective airflow, which provided considerable environmental energy for water evaporation. Both experiment results and COMSOL simulation results confirmed that the maximum environmental energy harvesting can be achieved with the proper size of solar crystallizer. At last, this dissertation pioneered a novel concept of integrating adsorption process into solar crystallizer for simultaneously ZLD brine treatment and potassium extraction. Owing to the special ion concentration behavior of solar crystallizer, the adsorption capacity and selectivity coefficient of absorbent was enhanced by 19.5% and 48.8%, respectively, comparing with traditional bulk adsorption. This dissertation potentially unlocks a new generation of ZLD technology with low carbon footprint and source recovery. More research efforts will be inspired on its applications in real scenarios.

To-date, sanitation has mainly been approached from a public and environmental health perspective and this implies that excreta and other organic waste streams are seen not only as a hazard to quickly get rid of but also as a very costly menace to manage. However, looking at sanitation management from a resource recovery perspective provides an avenue for solutions with multiple co-benefits. Revenues from sanitation end-use products can act as an incentive for improving sanitation infrastructure while also covering part or all of the investment and operation costs for the same. Until now, estimating the potential for resource recovery from sanitation systems and technologies has largely been done on a case by case basis according to project or geography with no standardized universal tools or methodologies being used across the world. This study is aimed at developing a generic model for the rapid estimation of the quantities of various resources that can be recovered from sanitary waste streams in urban areas. Key waste streams from sanitation systems in low and middle income countries were identified and their major characterization parameters identified. The mathematical relationships between key waste stream characterization parameters and the potential amounts of resource products derived from treatment were determined and then used to develop the model in MS Excel. The model was then tested with waste stream flow rates and characterization data (for faecal sludge, sewage sludge and organic municipal solid waste) from the city of Kampala with two scenarios; the current collection amounts (390 m3 of faecal sludge, 66 tonnes of sewage sludge and 700 tonnes of organic solid waste) and the potential amounts with increased collection efficiency and coverage (900 m3 of faecal sludge, 282 tonnes of sewage sludge and 2199 tonnes of organic solid waste). The results were shared with Kampala city authorities to obtain feedback. The results showed that there is significant potential in utilizing the daily amounts of the three waste streams collected in Kampala. With increased collection coverage and efficiency, they could altogether yield; up to 361,200 Nm3 of biogas per day which could meet the daily energy needs of 824,000 people that are currently met by firewood. Alternatively, the three sources could produce, 752 tonnes of solid combustion fuel per day which could meet the daily energy needs of 1,108,700 people that are currently met by firewood. As a third alternative, the three sources could produce 198 tonnes of Black Soldier Fly prepupae per day which could substitute for 134 tonnes of dry fish per day currently used as animal feed ingredient and up to 909 tonnes of compost fertilizer per day which is enough to substitute two tonnes of urea that is currently used by farmers. The model thus proved to be a simple way to provide decision support by making rapid estimations of the potential for resource recovery in urban areas, without the burden of having to do full scale feasibility studies. It is expected that this model could be a useful complement to the excreta flow diagrams (SFDs) developed within the Sustainable Sanitation Alliance (SuSanA) and hence give a holistic picture of the potential of a closed loop approach to excreta and waste management in cities.

The rising use of mineral-based fertilizer and water for agricultural operations to feed a growing population has polluted water bodies and depleted resources. In addition, nutrient contamination has caused eutrophication and wastewater concerns that conventional wastewater treatment cannot solve. Thus, meeting new water treatment regulations and procuring more value-added products from these procedures is crucial. Conductive ultrafiltration membranes precipitate and extract struvite, an ecologically good fertilizer, from synthetic livestock effluent. This technique produces solid fertilizer and irrigation-quality water. Since the recovery process relies on electrochemical hydrolysis and local pH modulation along the membrane surface, pH correction does not need chemical additions. The system was tested using cow effluent with up to 1,000 mg/L of nitrogen and phosphorus. Analytical tests showed that the precipitates were struvite and that up to 65% of the phosphorus and nitrogen were removed in the first 30 minutes of electrochemical filtration. Low membrane fouling and flux drop made the recovery technique successful. A mathematical model of N, P, and Mg ions in an external electric field explained the fouling and precipitation tests. Thus, precipitation happens near the membrane but not on it. This reduces surface fouling. Forward osmosis was used to make struvite with less energy. A voltage near the FO membrane enabled magnesium to migrate opposite into the feed chamber, where it reacted with ammonium and phosphate in the feed solution to form struvite. Electrical charging increased struvite recovery by 77% and water recovery by 39%. Ion migration may have reduced dilutive and concentrative polarization on the draw and feed sides of the FO membrane, causing the rise. High external voltage, draw concentration, and draw pH made water recovery and struvite precipitation simpler. This study suggests that reverse salt flow might improve FO systems' nutrition and water recovery. These devices were combined with microbial electrolytic cells to generate electricity and prevent biofouling. FO treatment was investigated using vacuum membrane distillation for sustainability and zero discharge. Constant draw solution reconcentration yields more steady flux values than the typical lowering flux. The research will increase knowledge of treatment system synergy in water reclamation and nutrient recovery. It also identifies possible obstacles to development. / Environmental Engineering

Clean water and renewable energy are essential requirements to build resilience towards the adverse effects of climate change and global warming. Advanced wastewater treatment options may provide a unique opportunity to recover various useful resources such as energy (biogas), fertilizers, minerals, and metals embedded in the wastewater stream. However, considerable challenges remain when it comes to designing and planning sustainable wastewater treatment systems. This thesis focuses on the avenues of energy recovery from wastewater treatment plants (WWTP), by evaluating the potential for biogas recovery from wastewater and sewage sludge treatment in WWTPs. Various available technologies for biogas recovery are examined and evaluated to understand their viability in different applications and relative performance. Further, the methodologies and tools employed to assess such energy recovery systems are evaluated, covering the technical, economic, and environmental performance aspects. A sustainability assessment framework is then developed, using appropriate sustainability indicators to assess performance. The framework is applied to a case study of a WWTP in the emerging city of Tbilisi, Georgia. A spreadsheet tool is also developed to aid the sustainability (technoeconomic and environmental) assessments for the case study. The case study results reveal a significant biogas recovery potential, with annual energy generation potential of 130 GWh from combined heat and power (CHP) recovery, and a potential to avoid 28,200 tCO2eq emissions every year, when biogas is recovered only from the wastewater. The recovery potential increases when biogas is recovered from both wastewater and sewage sludge. Further, the contribution of overall resource (energy and nutrient) recovery in WWTPs to the Sustainable Development Goals is examined. By studying the linkage of various benefits to the different SDGs, the multilateral and cross-cutting nature of benefits from resource recovery is clearly illustrated. The thesis concludes with the discussion of possible future technologies and perspectives that can enhance the sustainability of WWTPs and help transform them into Wastewater Resource Recovery Facilities (WRRFs). / Rent vatten och förnybar energi är väsentliga krav för att bygga motståndskraft mot de negativa effekterna av klimatförändringar och global uppvärmning. Avancerade avloppsreningsalternativ kan ge en unik möjlighet att återvinna olika användbara resurser som energi (biogas), gödselmedel, mineraler och metaller inbäddade i avloppsvatten strömmen. Det finns emellertid stora utmaningar när det gäller att utforma och planera hållbara reningssystem. Denna avhandling fokuserar på möjligheterna till energiåtervinning från avloppsreningsverk (WWTP), genom att utvärdera potentialen för biogasåtervinning från avloppsvatten- och avloppssrening i WWTP. Olika tillgängliga tekniker för återvinning av biogas undersöks och utvärderas för att förstå deras livskraft i olika applikationer och relativa prestanda. Vidare utvärderas de metoder och verktyg som används för att utvärdera sådana system för energiåtervinning som täcker de tekniska, ekonomiska och miljömässiga aspekterna. En ram för hållbarhetsbedömning utvecklas sedan med hjälp av lämpliga hållbarhetsindikatorer för att bedöma prestanda. Ramverket tillämpas på en fallstudie av en WWTP i den framväxande staden Tbilisi, Georgien. Ett kalkylarkverktyg utvecklas också för att underlätta bedömningarna av hållbarhet (teknisk ekonomi och miljö) för fallstudien. Resultaten från fallstudien avslöjar en betydande återvinningspotential för biogas, med en årlig energiproduktions potential på 130 GWh från kombinerad värme och kraft (CHP), och en potential att undvika 28.200 ton CO2-utsläpp varje år, när biogas endast återvinns från avloppsvattnet. Återvinningspotentialen ökar när biogas utvinns från både avloppsvatten och avloppsslam. Vidare undersöks bidraget från den totala återhämtningen av energi (energi och näringsämnen) i WWTP till målen för hållbar utveckling. Genom att studera kopplingen mellan olika fördelar till de olika SDG: erna illustreras den multilaterala och tvärgående karaktären av fördelarna med resursåtervinning. Avhandlingen avslutas med diskussionen om möjliga framtida tekniker och perspektiv som kan förbättra WWTP: s hållbarhet och hjälpa till att omvandla dem till anläggning för återvinning av resurser från avloppsvatten.