This thesis deals with an agricultural wastewater treatment (liquid digestate) by membrane technology. There is a fundamental description of characteristics of membrane technology with regard to application of agricultural wastewater treatment in this thesis. Experimental device for treatment of liquid digestate is designed and it consists of three steps – microfiltration, ultrafiltration and reverse osmosis. The first step consists of four filters with different pore sizes (80, 25, 10 and 5 µm). The second step is ultrafiltration and the third and key step is reverse osmosis. In the final step monovalent ions such as NH4+ are separated. Reverse osmosis consists of two stage system which results in higher recovery. Three experiments were carried out in order to verify the efficiency of separation dissolved solids.

Les déchets liés à l'élevage intensif ont un impact environnemental reconnu du fait de leur composition riche en en matière organique et minérale. Il apparait opportun de promouvoir des procédés de traitement permettant de maitriser l'impact environnemental de ce retour au sol, voire d'ouvrir de nouvelles valorisations au travers de la récupération d'énergie ou de l'exportation de co-produits (azotés et phosphatés notamment). Ce travail entre dans cette démarche en proposant de compléter les étapes de digestion anaérobie de ces déchets par des étapes de séparation sur membranes perm-sélectives. Les essais ont été réalisés sur unités pilotes de laboratoire en utilisant des digestats réels de diverses origines prélevés sur sites. Pour l'étape de clarification par ultrafiltration, la conduite d'une séparation en mode tangentiel est obligatoire au regard de la concentration des suspensions à traiter. La viscosité des suspensions, d'autant plus importante que la suspension est concentrée, apparait comme un paramètre déterminant pour le choix du protocole opératoire. Dans tous les cas, l'opération d'ultra-filtration (UF) permet une rétention conséquente (de 80 à 90%) de la fraction organique encore présente dans les digestats, à l'inverse, la rétention de la fraction minérale soluble est restée négligeable comme attendu. Le seuil de coupure de la membrane d'UF n'est pas apparu déterminant sur cette rétention. Malgré le mode tangentiel de séparation, l'opération de filtration induit une accumulation de composés au voisinage de la membrane qui diminue significativement la perméabilité du milieu filtrant. Cette chute de perméabilité apparaît d'autant plus importante que la suspension présente une concentration en demande chimique en oxygène (DCO) élevée. Ce critère apparaît alors comme le facteur limitant pour atteindre un facteur de concentration volumique (FCV) élevé (réduction des volumes). La surface membranaire à développer est directement liée à la perméabilité membranaire, elle-même dépendante de la concentration de la suspension à traiter donc de la nature du digestat et du FCV à atteindre. Le coût opérationnel de l'opération apparaît directement lié à l'énergie nécessaire pour assurer le mode tangentiel de filtration. Pour l'étape de concentration des sels d'intérêts, la rétention des composés minéraux solubles par osmose inverse haute pression dépasse 90% quels que soient les ions ciblés ou l'origine du digestat. A l'inverse, cette rétention est dépendante de l'ion ciblé et de l'origine du digestat pour les opérations de nano-filtration et d'osmose inverse basse pression. Dans tous les cas, la rétention de la fraction organique résiduelle est importante (>90%) permettant une décoloration du perméat très poussée (elle dépend toutefois du seuil de coupure de la membrane et du FCV choisi). La perméabilité membranaire diminue d'autant plus que la conductivité électrique (CE) de la solution à traiter est importante du fait de la pression osmotique et de l'accumulation de composés solubles au voisinage de la barrière membranaire. Cette conductivité, dépendante du digestat initial et du FCV choisi, apparaît alors comme le paramètre déterminant pour le dimensionnement de l'unité. Sur le plan énergétique, l'énergie liée à la mise sous pression des unités NF/OI est dominante par rapport à la circulation tangentielle du rétentat. Ce travail a permis de confirmer l'intérêt des séparations membranaires pour le traitement des digestats, afin d'une part, d'obtenir une eau de qualité permettant sa réutilisation ou son rejet dans le milieu naturel et d'autre part de récupérer et de concentrer des composés d'intérêt dans les différents rétentats. Ce travail a fait l'objet d'un soutien financier de l'ANR dans le cadre du programme BIOENERGIE 2010 (projet DIVA). / Intense spreading of livestock wastes are recognized to be detrimental to the environment due to their content of organic matter and mineral fraction. Then, it would appear to be necessary to promote greens treatments processes. In fact, anaerobic digestion allows the production of biogas (extremely useful source of renewable energy), whilst digestate should be a highly valuable biofertilizer This work enters in this approach by proposing to complete anaerobic digestion steps by the use of perm-selective membrane separation process. The first step is a clarification step by ultrafiltration, following by a soluble mineral concentration step by nanofiltration, low pressure and/or high pressure reverse osmosis (LPRO, HPRO). The tests were performed in a laboratory-scale pilot unit using real digestates. For clarification step, a cross-flow mode separation is obligate in view of suspended solid concentrations and viscosity which appeared as a determining factor for the choice of operative protocol. In any case, the ultra-filtration operation allows a high organic retention rate (of 80 to 90%). Conversely, soluble mineral retention remained at negligible as expected. The cut-off of ultrafiltration membrane is not a determining factor for this retention. Despite the cross-flow mode separation filtration induces a compound accumulation on the membrane which decreases significantly the permeability of filtering media. This permeability drop appears greater when suspension presents a high COD concentration. This criterion appears as a limiting factor to achieve a high volumic concentration factor (VCF). Membrane surface to develop is then directly related to the membrane permeability which depends on the digestate origin and VCF. The operational cost is linked directly to the energy required to ensure cross-flow mode. The retention of soluble mineral compounds by HPRO exceeds 90% whatever the target ions or the origine of digestate are. However, for NF and LPRO steps, this rejection depends on the target ions or the origine of digestate. In any case, organic retention is important (more than 90%) which allows significant discoloration of permeate. The, the more the electronic conductivity (EC) is, the more permeability decreases of suspension is important, due to an osmotic pressure and soluble compound accumulation on the membrane that increases with EC. This conductivity depends on initial digestate and, of course, of the chosen VCF target, which appears as decisive parameter for unit dimensioning. On the efficient energy, energy linked to separation step chosen is dominant in the absence of cross-flow mode of retentate. This work has allowed to confirm the potential interest of membrane separation to (i) obtain a final effluent: named fresh or new water and (ii) and (ii) to allow the production of liquid fertilizers.This work is financially supported by the National French Agency (Bio-Energy Program 2010, DIVA Project) and by TRIMATEC competitiveness cluster.

An efficient management of organic fertilizers (here animal manure and digestate) is of large concern in today´s agriculture. When evaluating the efficiency of alternative management systems, differences in nutrient losses (emissions) must be taken into consideration. Those can be rather specific for e.g. a geographical region and agricultural system. This literature study aimed at identifying emission factors and uncertainty ranges, that are relevant to use in comparative system studies of different organic fertilizer management systems in South Swedish climate. Emissions from manure and digestate storage, application and field losses were considered. For carbon, the sequestration of organic carbon in the soil was considered instead of the carbon dioxide emissions from manure/digestate decomposition in soils. The values were very variable, and the median value was used as the selected emission factor. From storage of liquid cow manure, the ammonia emission for storage with cover was 3 % of the ammonium content, and 10 % without cover. It was about the same for both liquid pig manure (8 %) and solid cattle manure (10 %). The methane emissions during storage were 10 % of the maximum methane potential. Ammonia emissions during application ranged from 10-20 % of ammonium-nitrogen. Two studies of manure carbon sequestration were found that was applicable for the Swedish climate. They indicated that about 8-11 % of the carbon applied as solid manure was sequestered, compared to about 4 % for liquid manure.

The Brazilian sugarcane and ethanol industries produce lot of waste which has potential for energy production. Anaerobic digestion (AD) can be effectively utilized for producing biogas from these wastes. During the AD process, huge volumes of digestate are produced with some being employed in fertilizer application whilst large volumes are mostly stored in uncovered tanks. This result in emission of residual methane and loss of energy which can be recovered through post- digestion approaches. To analyse optimal utilization of this digestate and enhanced biogas production, co- digestion of post- digestate from a continuously stirred reactor (CSTR) performing co-digestion of sugarcane waste from Brazil (Vinasse, filter cake and straw) with addition of different glycerol concentrations were studied. The addition of glycerol characterised by its biodegradability and high organic content makes it a suitable substrate to enhance biogas production. A biomethane potential was assessed when the digestate was co-digested with 15% and 25% CODg/L of glycerol. The batch test lasted for 39 days. The results demonstrated that, co-digestion of digestate with glycerol has the potential of increasing cumulative methane and biogas yield with 25% addition producing the highest methane and biogas yield (318 Nml/gCOD and 196 Nml/gCOD) which was approximately 6 times higher compared to mono-digestion of the digestate. Anaerobic co-digestion of digestate and glycerol was examined in two lab scale reactors (CSTR) at mesophilic conditions (35oC) and were run for 90 days. The reactor (R1) performing co-digestion increased methane and biogas production by 300% and 170% when glycerol concentrations of 15% and 25% of influent COD were added, respectively. Moreover, there was a decrease in CH4 yield when the reactors were continuously fed with 15% and 25% CODg/L of glycerol. This was an indication that, microorganisms easily digested glycerol addition at the early stages. Glycerol addition (50% CODg/L) resulted in a decrease in CH4 and biogas production.  This result shows, CH4 yields in the post-digester can be enhanced with glycerol addition if it does not exceed a limiting of 50% of the organic loading rates of the feed.

The aim of the diploma thesis is to discuss the gasification of biodegradable waste. The theoretical part deals with gasification with focus on gasification phases, types of gasification reactors and pollutants contained in the generated gas, especially tar. Further, there is listed the characteristic of alternative biomass fuels, namely digestate and sludge waste. The practical part is devoted to gasification on a fluidized bed reactor with the aim to test the possibilities of gasification of these fuels, to determine their specifications and the influence of various gasification media. In the final part there are discussed the results of the collected gases and tar.

This master thesis deals with the properties of digestate in combustion, design of construction solution of digestate boiler and experimental verification of boiler parameters. The first chapter deals with the properties of digestate as a fuel. It is followed by a chapter dealing with the existing measured results on a similar boiler. This is followed by a stoichiometric calculation of the digestate boiler. The next chapter is devoted to combustion chamber models. This chapter is followed by a chapter with experimental verification of chamber models and combustion process tuning. The last chapter contains design of construction and operational measures.

This diploma thesis deals with the solution of ammonia separation from waste raw materials of agricultural production. It focuses on determining the efficiency of desorption from an experimental stripping device depending on the measurement temperature. Ammonia water solutions and liquid digestate samples from technical practice were used to verify the functionality of the equipment. Increasing separation efficiency with increasing temperature has been demonstrated. The device was gradually improved during the measurement for a better profitability of the separation process. The results of the experiments are discussed concerning the theoretical assumptions and compared with other methods of ammonia separation.

Digestate produced during anaerobic digestion of food waste is recognised as a good alternative to mineral fertilizer which could also be used to amend soil properties. This has conventionally been applied directly and unprocessed to nearby farms or processed and transported elsewhere. The latter option has gained recognition due to environmental restrictions coupled with soil nutrient management objectives but is an expensive venture. With increasing biogas production and AD plants across Europe, production of digestate has however exceeded its demand. Improving the dewaterability of the digestate has the benefit of reducing the cost and time of processing and handling. The principal aim of this experiment was to enhance the dewaterability of food waste digestate by the addition of pulp fibre to the AD process. In doing so, the study also investigated the effect of co-digestion of food waste and pulp fibre on the performance and stability of the digestion. Source separated food waste was digested at OLR of 3.5 ±0.1 g VS/L*d-1 for 163 days in 3 CSTRs with a working volume of 6L at HRT OF 23-26 days. Soft- and hardwood pulp fibres were added to 2 designated digesters for 104 days and increased stepwise at OLR of 0.5 ±0.1 g VS/L*d-1 PF until 1.5 ±0.1 g VS/L*d-1 PF with the 3rd digester serving as a control. 3 other post-digesters, each with a working volume of 1.41L were operated for 104 days with sludge from the 3 main digesters serving as inoculum and substrate. This was run at HRT of 7 days.  Pulp fibre addition of 1.5 ±0.1 g VS/L*d-1 OLR to 3.5 ±0.1 g VS/L*d-1 food waste increased the total biogas and methane production to 35-40% and 21-32% respectively. Though recording a higher biogas production, the corresponding specific methane production from the fibre addition was 12-8% lower than food waste digestion. Analysis of the digestate from post digestion showed that CST increased linearly from 595 ±13s for food waste digestate to 962 ±19s for pulp fibre addition. The experiment established a positive correlation between CST and organic matter content. Suspended solids increased from 128 ±10 mg/l for FW digestate to 177 ±12 – 237 ±10 mg/l for fibre addition. Addition of kraft pulp fibre types did not enhance the dewaterability of the digestate. However, the total methane production was enhanced by the addition of pulp fibre. / <p>Parts of the thesis is scheduled to be published in a scientific journal</p>

Biogas is becoming a more important source of green, renewable energy however, its production results in a liquid wastewater, known as centrate, which must be treated due to its high levels of total dissolved solids (TDS), and chemical oxygen demand (COD). Currently, biogas generation facilities treat centrate using a combination of biological and physical treatments (via a membrane bioreactor (MBR)), which produces a stream known as MBR permeate. While MBR permeate achieves improved quality, MBR usage has several challenges including difficulty of scaling biological processes, and handling capacity limitations. In this study, membrane only treatment of centrate, collected from an operating biogas generation facility, was investigated to determine if similar quality permeates could be obtained without any biological treatments. Single- stage treatment of centrate using either polymeric or ceramic nanofiltration membranes with molecular weight cut offs between 400 and 800 Da, produced a permeate similar to MBR permeate. These membrane types caused average COD rejections of 92% and 90% respectively. However, the permeates from the nanofiltration membranes had very high levels of ammonia, which was not present in the MBR permeate. The ceramic nanofiltration membranes can achieve higher permeate fluxes than the polymeric nanofiltration membranes. Both membrane types experienced significant fouling which was removed using cleaning procedures. Two-stage treatment of centrate using ceramic nanofiltration membranes followed by polymeric reverse osmosis membranes further improved the quality of permeate and achieved COD rejections of 99% overall. While the reverse osmosis membranes did remove some ammonia, the levels were still higher than what was seen in the MBR permeate. The two-stage treatment of centrate can provide the permeate which is closest to the MBR permeate however, further studies are required to address the higher ammonia concentration values. The research shows that only using membranes is a potential treatment pathway for real centrate samples. / Thesis / Master of Applied Science (MASc) / The production of biogas, which is a green, renewable energy source results in a liquid wastewater known as centrate. This wastewater is very dirty and complex and requires treatment as it cannot be dumped and disposed of in its current state. Current treatment methods for centrate use combinations of biological treatment and filtration processes, which has its own challenges due to the complexity of biological treatments. An alternative treatment method for the centrate is nanofiltration membranes which offer the ability to treat large volumes of centrate wastewater without the complexity of relying on biological treatment options. Four different nanofiltration membranes, including two polymeric and two ceramic membranes, were used to treat real industrial wastewater samples of centrate collected from a biogas generation facility. Both types of nanofiltration membranes provided similar quality permeate to the current treatment method of centrate, which uses a combination of biological and physical treatment methods.

Surges of Sargassum have become more severe and at the time of writing the largest surge yet is set to hit the Caribbean islands, affecting tourism and marine life negatively. Tourism is Grenada’s single handedly largest economic sector, which is why it is important to research the use of Sargassum. Furthermore, for its fertiliser needs, Grenada relies largely on importing inorganic fertiliser, which has become more expensive in recent years. Sargassum as feedstock for biogas digesters and utilising the digestate as fertiliser could be a viable option, but challenges include high heavy metal content and low concentration of nutrients compared to inorganic fertiliser. The aim of this project is to examine heavy metals contents in digestate derived from Sargassum and gaining knowledge about the current agricultural situation, with regards to fertiliser, through interviewing farmers and relevant political figures. The results from the heavy metal analysis of the liquid digestate showed that the concentration of both arsenic and cadmium were below the average for commercial organic fertilisers. However, further testing is considered to be required to conclude whether the product is suitable to use. Gathered from the interviews was that many farmers were concerned about the impact inorganic fertiliser had on the land, however, the choice of fertiliser was, in general heavily dependent on which type was available. Sargassum-based digestate could be viable on the island but challenges of reducing, transporting and separating heavy metals from the digestate have to be solved making it difficult for the Sargassum to be cost-effective. Furthermore, the farmers were very clear that they wanted a product which was safe to use. / Sargassumblomningar har blivit allvarligare och i skrivande stund väntas den största vågen hittills att drabba de karibiska öarna, vilket har en negativ påverkan på turismen och det marina livet. Turismen är Grenadas enskilt största ekonomiska sektor, och därför är det viktigt att undersöka användningsområdet för Sargassum. Dessutom är Grenada, för sitt gödselbehov, till stor del beroende av import av oorganiskt gödningsmedel, vilket har ökat i pris de senaste åren. Sargassum som inmatning för biogasrötningsanläggningar och användning av rötrester som gödningsmedel skulle kunna vara ett lönsamt alternativ, men utmaningarna är bland annat det höga innehållet av tungmetaller och den låga koncentrationen av näringsämnen jämfört med oorganiska gödningsmedel. Syftet med detta projekt är att undersöka innehållet av tungmetaller i digestat från Sargassum och att få kunskap om den nuvarande jordbrukssituationen gällande gödningsmedel genom att intervjua jordbrukare och relevanta politiker. Resultatet av den tungmetallanalys som genomfördes av det vätskeformiga digestatet visade ett innehåll av kadmium och arsenik som låg under medelvärdet för kommersiella organiska gödningsmedel. Däremot är vidare testning är nödvändig för att säkerställa att produkten är lämplig att använda. Intervjustudien visade att många jordbrukare var oroade över hur oorganiska gödselmedel påverkar marken, men att valet av gödselmedel i allmänhet var starkt beroende av vilken typ av gödningsmedel som fanns tillgängligt. Sargassumbaserat digestat skulle kunna vara lönsamt för användning på ön, men problemen med reducering, transport och separering av tungmetaller från digestatet måste lösas, vilket gör det svårt för Sargassum att vara kostnadseffektivt. Bönderna var slutligen tydliga med att digestatet från Sargassum behövde generera en ökning eller likvärdig produktion av deras grödor.