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The effect of naturally produced volatile fatty acids (VFAs) on the removal of 2, 4-D from a wastewater during the denitrification process was studied in this thesis. The VFAs were generated from an anaerobic digester using soya flour solution as a synthetic feed. The digester was operated at an SRT and HRT of 10 days. The pH (4.8 ± 0.2) and temperature (32 ± 3 ℃) of the digester were not controlled. A mean VFA concentration of 3153 ± 801 mg/L was achieved with acid speciation results of acetic (51.4 %), propionic (27.5 %), n-butyric (19.6 %) and iso-valeric (1.4 %). The specific VFA production rate was 0.014 mg VFA/mg VSS/day. The extent of the digestion process converting the substrate from a particulate to soluble form was evaluated as the specific TOC solubilization rate (0.007 mg TOC/mg VSS/day), soluble COD production rate (0.022 mg SCOD/mg VSS/day) and percent VSS reduction (14 %). The low solubilization rate is possibly due to high feed solids (3.4%) which led to a heavily overloaded bioreactor. It also suggests that the particulate substrate was not entirely amenable to solubilization. The acclimation of 2, 4-D degrading bacteria was developed successfully in an SBR fed with sewage and 2, 4-D (30-100 mg/L) as carbon and energy sources. A mean MLSS of 3653 ± 547 mg/L and an SRT of 20 ± 9 days were observed during the research period. The settleability of the SBR sludge was excellent evidenced by a low sludge volume index (SVI) of 101 ± 50 mL/g and less than 5 mg/L of effluent suspended solids. The specific 2, 4-D degradation rate was 0.046 ± 0.018 mg/mg MLSS/day. However, the removal of 2, 4-D during 60 minutes of non-aerated phase was negligible while more than 90 % of the 2, 4-D was removed within 240 minutes of the aerated phase. The successful degradation of 2, 4-D is related to the length of the acclimation period, as the acclimation period increased, the specific biodegradation rate increased. A biosorption study using ultrasound pre-treatment of the SBR acclimated biomass suggested that less than 10 % of the removal of 2, 4-D was due to biosorption, while more than 90 % removal of the 2, 4-D was likely due to biodegradation. Denitrification batch tests (using SBR-acclimated biomass) demonstrated that the addition of a digester effluent rich in naturally-produced VFAs increased both the 2 specific denitrification rate and the 2, 4-D degradation efficiency, as compared to that using 2, 4-D as a sole carbon source. In particular, the specific denitrification rates increased from 0.0119 ± 0.0039 to 0.0192 ± 0.0079 to 0.024 ± 0.003 g NO₃-N/g VSS per day, when using 2, 4-D alone, 2, 4-D plus natural VFAs and natural VFAs alone as carbon sources. The percent 2, 4-D removal increased from 28.33 ± 11.88 using 2, 4-D alone as a carbon source to 54.17 ± 21.89 using 2, 4-D plus natural VFAs as carbon sources. The specific 2, 4-D degradation rate and 2, 4-D removal efficiency of unacclimated biomass were 2.0 to 2.5 times less than those of the acclimated biomass. Natural VFAs and synthetic VFAs were found to be identical in denitrification batch tests in terms of their use as a carbon source. The mean specific denitrification and VFA-C consumption rates as well as the mean specific 2, 4-D degradation rate derived from experiments using natural VFAs and 2, 4-D as carbon sources were close to the valuess from experiments using synthetic VFAs and 2, 4-D as carbon sources. Further exploration of 2, 4-D degradation behaviour with pulsed additions of NO₃-N did not find further significant 2, 4-D removal, although almost all of NO₃-N was used by the end of the experimental run due to endogenous carbon sources used for cell maintenance and growth. However, the higher the concentration of biomass used in the denitrification batch system, the larger the amount of 2, 4-D degraded and the faster the VFA-C and NO₃-N were consumed. Further research with respect to optimisation of the acid-phase anaerobic digestion process (e.g. to adjust SRT and HRT or to lower the solid content of synthetic feed) would improve the specific VFA production rate and the solubilization rate. More research on the SBR could be carried out to investigate its maximum 2, 4-D removal capability as well as the removal of other structurally related herbicides. Attempts could be made to stimulate the growth of denitrifiers in the SBR (e.g. to add certain amounts of NO₃-N according to proper C: N ratios or to increase the length of non-aerated time). More microbiological studies of 2, 4-D degrading bacteria may also be helpful to understand the combined SBR/denitrification and 2, 4-D degradation process. More theoretical aspects of modelling kinetics could be developed to apply the combined process in-situ at 2, 4-D contaminated sites.

Volatile fatty acids (VFA) are important products of ruminal fermentation. The VFA are not only the major source of energy to the ruminant animals but also influence methane production in the rumen. Therefore it is important to understand mechanism controlling VFA production and to depict VFA production in a model. This will allow us to devise strategies to enhance energy utilization and reduce methane production in ruminant livestock. An evaluation of a mechanistic model in predicting VFA production was conducted and equations were introduced into the model to improve the predictions. Later a continuous culture experiment was conducted to test the hypothesis on which those equations were based on. A mechanistic model -" Molly, was evaluated using a dataset with reported VFA production rates. The results of residual error analysis indicated that the root mean square prediction errors (RMSPE) were 63, 63, and 49% for acetate, propionate and butyrate, respectively. An assessment from two studies reporting VFA production revealed a potential of reducing errors of prediction by representing interconversion among VFA. In the second study, equations based on thermodynamics influence of pH and VFA concentration were introduced in the model to represent interconversion among VFA. The parameters for de novo VFA production and VFA absorption were re derived with (VFAInt) and without (BASE) the new interconversion equations. There were some improvements in the VFA concentration predictions but the improvements were both in VFAInt and BASE models. The RMSPE of VFA production were still above 50% for acetate, propionate and butyrate. The larger errors of predictions were attributed to measurement variation in VFA production literature, or possible incorrect rate constants for interconversion equations. Finally, a third study was conducted to assess the effect of pH, and VFA concentration on VFA and methane production in continuous culture. The treatments consisted of control, 20 mmol/d acetate infusion (INFAC), 7 mmol/d propionate infusion (INFPR), and low pH (LOWPH). Individual isotopes of acetate, propionate and butyrate were infused in the fermenters to estimate interconversions among VFA. With LOWPH treatment methane emission was reduced whereas production of propionate was increased. Hydrogen production was higher in INFAC indicating that some of the acetate could have been degraded to CO2 and H2. It was estimated that around 3 % of de novo acetate was converted to propionate and 9 % to butyrate. Exchange between propionate and butyrate was insignificant and below 1% of de novo production of either VFA. However, treatments did not affect interconversion rates among VFA. These results indicated that pH and VFA concentration do not have thermodynamic influence on VFA interconversion as hypothesized. / Ph. D.

Resumo: Investigou-se a influência da utilização de inóculos sobre a digestão anaeróbia de resíduos de aves de postura, frangos de corte e suínos em biodigestores modelo batelada com volume útil de 60 L operados à temperatura ambiente, por meio da caracterização do potencial e distribuição da produção de biogás ao longo do tempo, o estudo da redução de sólidos, a análise das características dos efluentes quanto à concentração de ácidos graxos voláteis e por meio da determinação do número mais provável (NMP) de coliformes fecais e totais nos afluentes e efluentes. Avaliou-se também a atividade metanogênica nos biodigestores com 10 % de inóculo. Foram testadas três concentrações de inóculo: 0, 10 e 15 %. Os resultados mostraram que os resíduos de aves de postura, frangos de corte e suínos são bons substratos para o processo de digestão anaeróbia, apresentando potenciais médios que variaram de 0,3828 a 0,4403 m3, de 0,3495 a 0, 3915 m3, e de 0,1949 a 0,4466 m3 de biogás por kg de ST adicionados, respectivamente para resíduos de aves de postura, frangos de corte e suínos. Com base em todos os parâmetros estudados, as concentrações de inóculo que promoveram melhores resultados foram 10 % para resíduos de aves de postura e frangos de corte, e 15 % para resíduos de suínos. O tratamento anaeróbio revelou-se eficiente na remoção de coliformes totais e fecais independente da concentração de inóculo, alcançando porcentagens médias de redução de NMP que variaram de 99,71 % de 1,09 x 102 a 100 %. A atividade metanogênica específica foi mais elevada nas amostras provenientes dos biodigestores operados com resíduos de aves de postura (0,0340 mmol CH4 g-1 SV h-1), seguida pelos resíduos de frangos de corte (0,0188 mmol CH4 g-1 SV h-1) e suínos (0,0029 mmol CH4 g-1 SV h-1). Estes resultados parecem estar mais associados aos teores...(Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This study was carried out in 60 L volume batch digesters at ambient temperature and investigated the inoculums concentration effects on anaerobic digestion of laying hens, poultry and piggery wastes through evaluation of potential and distribution of biogas production along the time, solids removal, analyze of volatile fatty acids efluent concentration and by monitoring the most probable number (MNP) of total and faecal coliforms in the inffluents and effluents. Specific methanogenic activity (SMA) into the 10 % inoculum digesters was also measured. Three inoculum concentrations (0, 10 and 15 %) were tested. Results showed that laying hens, poultry litter and piggery wastes are good substrats to anaerobic digestion. The potential biogas production varied from 0.03828 to 0.4403 m3, 0.3495 to 0.3915 m3 and 0.1949 to 0.4466 m3 of biogas kg-1 of total solids added, respectively for laying hens, poultry and piggery wastes. The best results for inoculum concentration were 10 % for laying hens and poultry wastes, and 15 % for piggery wastes. Anaerobic digestion was efficient for reduction of the most probable mean number of total and faecal coliforms. Reduction of MNP mean varied from 99.71 of 1,09 x 102 to 100 %. SMA test showed the best activity was from laying hens wastes (0,03400 mmol CH4 g-1 SV h-1), followed by poultry wastes (0,01877 mmol CH4 g-1 SV h- 1) and by piggery wastes (0,00293 mmol CH4 g-1 SV h-1). Results of SMA test appear to be most affected by volatile solids content of the samples than the best ability of the microrganisms to convert substrate. The best organic load rate for activity test were 0,25 g DQO g-1 SV. / Orientador: Jorge de Lucas Junior / Coorientador: Roberto Alves de Oliveira / Banca: Rosana Filomena Vazoller / Banca: Edson Aparecido Abdul Nour / Mestre

Ruminant livestock maintain an important role in meeting the nutrient requirements of the global population through their unique ability to convert plant fiber into human-edible meat and milk products. Volatile fatty acids (VFA) produced by rumen microbial fermentation of feed substrates represent around 70% of the ruminant animal's metabolic energy supply. Rumen fermentation profiles may directly impact productivity because the types of VFA produced are utilized at differing efficiencies by the animal. Improving our understanding of factors that control these fermentative outcomes would therefore aid in optimizing the productive efficiency of ruminant livestock. Improvements in animal efficiency are now more important than ever as the livestock industry must adapt to continue meeting the nutritional needs of a growing global population in the context of increased resource restrictions and requirements to lower the environmental impact of production. The relationship between diet and VFA ultimately supplied to the animal is complex and poorly understood due to the influence of numerous nutritional, biochemical, and microbial variables. The central aim of this body of work was therefore to explore and characterize how fermentation dynamics, rumen environmental characteristics, and the rumen microbiome behave in response to variations in the supply of fermentative substrate. The objective of our first experiment was to describe a novel in vitro laboratory technique to rank livestock feeds based on their starch degradability. This experiment also compared the starch degradation rates estimated by the in vitro method to the rates estimated by a traditional in situ method using sheep. A relationship between the degradation rates determined by these two procedures was observed, but only when feed nutrient content was accounted for. While this in vitro approach may not be able to reflect actual ruminal starch degradation rates, it holds potential as a useful laboratory technique for assessing relative differences in starch degradability between various feeds. Our second experiment aimed to measure changes in VFA dynamics, rumen environmental characteristics, and rumen epithelial gene expression levels in response to dietary sources of fiber and protein designed to differ in their rumen availabilities. Conducted in sheep, this study utilized beet pulp and timothy hay as the more and less available fiber source treatments, respectively, and soybean meal and heat-treated soybean meal as the more and less available protein source treatments, respectively. Results indicated that rumen environmental parameters and epithelial gene expression levels were not significantly altered by treatment. However, numerous shifts in response to both protein and fiber treatments were observed in fermentation dynamics, especially in interconversions of VFA. The objective of the third investigation was to assess whether the rumen microbiome can serve as an accurate predictor of beef and dairy cattle performance measurements and compare its predictive ability to that of diet explanatory variables. The available literature was assembled into a meta-analysis and models predicting dry matter intake, feed efficiency, average daily gain, and milk yield were derived using microbial and diet explanatory variables. Comparison of model quality revealed that the microbiome-based predictions may have comparable accuracy to diet-based predictions and that microbial variables may be used in combination with diet to improve predictions. In our fourth experiment, the objective was to investigate rumen microbial responses to the fiber and protein diet treatments detailed in Experiment 2. Responses of interest included relative abundances of bacterial populations at three taxonomic levels (phylum, family, and genus) in addition to estimations of community richness and diversity. Numerous population shifts were observed in response to fiber treatment. Prominent fibrolytic population abundances as well as richness and diversity estimations were found to be greater with timothy hay treatment and lower with beet pulp whereas pectin degraders increased in abundance on beet pulp. Microbial responses associated with protein treatment were not as numerous but appeared to reflect taxa with roles in protein metabolism. These four investigations revealed that significant changes can occur in VFA fermentation and rumen microbial populations when sources of nutrient substrates provided in a ruminant animal's diet are altered and that a new approach may be useful in investigating degradation of another important substrate for fermentation (starch) in a laboratory setting. Our findings also determined that animal performance can be predicted to a certain extent by rumen microbial characteristics. Collectively, these investigations offer an improved understanding of factors that influence the process of converting feed to energy sources in the ruminant animal. / Doctor of Philosophy / Ruminant animals, such as beef cattle, dairy cattle, and sheep, play a major role in delivering essential nutrients to the human population through their provision of meat and dairy products. The current growth projections of the global population, in addition to increased concerns surrounding greenhouse gas emissions and restrictions on resources such as land and water make it important for us to consider ways of optimizing the productivity of these animals. A unique feature of ruminants is their ability to conduct microbial fermentation of large amounts of plant matter in their rumens to produce energetically valuable compounds called volatile fatty acids (VFA), which are the primary source of energy that the animals use for growth, reproduction, and milk production. One promising way of improving animal productivity is to increase the amount of energy from the diet that becomes available to fuel the animal's body processes; however, the process of converting feed to VFA is complicated and currently not well understood. The overall aim of this body of work was therefore to explore various nutritional, ruminal, and microbial factors that are known to impact fermentation in order to 1) increase our understanding of how these factors interconnect and 2) put us in a better position to manipulate these factors for optimal animal performance. The goal of our first experiment was to devise and use a novel laboratory technique to rank livestock feeds based on the degradability of their starch content, which is an important substrate for VFA fermentation. Our observations indicate that this technique may be a useful tool to help us determine relative differences between feeds based on their starch degradabilities in a laboratory setting. Our second experiment investigated the effects of feeding varying sources of fiber (beet pulp and timothy hay) and protein (heat-treated and untreated soybean meals) to sheep in terms of their VFA fermentation, rumen conditions, and the expression of certain key genes in the epithelial tissue of the rumen wall. While rumen environmental characteristics and epithelial gene expression remained largely unchanged, numerous key aspects of VFA fermentation, predominantly carbon exchanges between different VFA, were altered in response to nutrient source. The third investigation described in this work examined the ability of the microbial populations responsible for rumen fermentation to explain variation in beef and dairy cow productivity compared with the ability of diet characteristics to explain this variation. Using statistical methods to analyze the reports currently available in scientific literature, our findings indicate that the rumen microbiome and diet may exert independent effects on productivity levels and that the microbiome may be used to enhance diet-based predictions of animal performance. Finally, we explored variations in the sheep rumen microbiome in response to the diet treatments utilized in Experiment 2. We observed minimal impact of protein source on the microbiome, but numerous microbial responses were evident when fiber source was varied. These responses included decreases of fiber-degrading bacterial populations and increases in pectin-degrading populations when beet pulp was fed compared to timothy hay. Taken together, these experiments help to provide us with a more comprehensive picture of the numerous factors involved in the process of converting feed to a usable form of energy for ruminant livestock.

Background: Enteric methane from rumen methanogens is responsible for 25.9 % of total methane emissions in the United States. Rumen methanogens also contribute to decreased animal feed efficiency. For methane mitigation strategies to be successful, it is important to establish which factors influence the rumen methanogen community and rumen volatile fatty acids (VFA). In the present study, we used next-generation sequencing to determine if dairy breed and/or days in milk (DIM) (high-fiber periparturient versus high-starch postpartum diets) affect the rumen environment and methanogen community of primiparous Holstein, Jersey, and Holstein-Jersey crossbreeds. Results: When the 16S rRNA gene sequences were processed and assigned to operational taxonomic units (OTU), a core methanogen community was identified, consisting of Methanobrevibacter (Mbr.) smithii, Mbr. thaueri, Mbr. ruminantium, and Mbr. millerae. The 16S rRNA gene sequence reads clustered at 3 DIM, but not by breed. At 3 DIM, the mean % abundance of Mbr. thaueri was lower in Jerseys (26.9 %) and higher in Holsteins (30.7 %) and Holstein-Jersey crossbreeds (30.3 %) (P < 0.001). The molar concentrations of total VFA were higher at 3 DIM than at 93, 183, and 273 DIM, whereas the molar proportions of propionate were increased at 3 and 93 DIM, relative to 183 and 273 DIM. Rumen methanogen densities, distributions of the Mbr. species, and VFA molar proportions did not differ by breed. Conclusions: The data from the present study suggest that a core methanogen community is present among dairy breeds, through out a lactation. Furthermore, the methanogen communities were more influenced by DIM and the breed by DIM interactions than breed differences.

Master of Science / Department of Animal Sciences and Industry / Barry Bradford / Angiopoietin-like protein 4 (ANGPTL4) is a 55-kDa secreted glycoprotein which is an important factor for regulation of energy and lipid metabolism. Plasma ANGPTL4 has the ability to inhibit lipoprotein lipase (LPL) function by preventing it from catalyzing hydrolysis of lipoprotein triglyceride, which contributes to ANGPTL4’s ability to decrease fat storage. Furthermore, research in mice suggests that gut microbes suppress gastrointestinal ANGPTL4 production, and that decreased plasma ANGPTL4 concentrations promote fat storage. In our previous work, we found that bovine ruminal epithelial cells expressed ANGPTL4 to a greater extent than liver hepatocytes, which are usually considered the predominant source of circulating ANGPTL4. Therefore, 3 studies were conducted to evaluate the hypothesis that ruminal expression and plasma concentrations of ANGPTL4 could be influenced by alterations in ruminal fermentation. The first and second studies utilized dietary treatments intended to alter ruminal fermentability. Diets with relatively low or high forage content were fed to 12 non-lactating dairy cows (study 1) and 8 beef cattle (study 2) prior to collection of ruminal fluid and ruminal tissue samples. The results suggested that increasing the dietary concentrate decreased ruminal expression of ANGPTL4 but did not significantly alter plasma ANGPTL4 concentrations. The third study was designed to assess whether effects of diet fermentability on ruminal ANGPTL4 synthesis are mediated by changes in volatile fatty acid concentrations. In this study, 6 lactating cows were infused with acetate, propionate, or butyrate in a Latin square design. Results showed that ANGPTL4 expression was not significantly altered by volatile fatty acid infusions, but that expression was correlated with ruminal pH and total volatile fatty acid concentration. The mechanism by which ANGPTL4 regulates intracellular lipid metabolism also remains unclear. Although ANGPTL4 is known to associate with β1 and β5 integrins, it is unknown if these extracellular matrix proteins mediate the effects of ANGPTL4 in adipose tissue or muscle. The objective of the last experiment was to detect the ANGPTL4 receptor or mediator in muscle satellite cells and adipose tissue. We successfully expressed recombinant bovine ANGPTL4 with a cell free glycoprotein synthesis system. However, we did not detect the ANGPTL4–receptor complex following exposure to bovine adipose tissue explants or cultured bovine muscle satellite cells. Overall, these research projects determined that the ruminal ANGPTL4 production is influenced by fermentation, but it remains unclear whether fermentation products or direct host/microbe interactions are responsible. Finally, it will be important to identify the ANGPTL4 receptor or mediator to better understand the downstream regulatory mechanisms involved in mediating the metabolic effects of ANGPTL4.

Lignocellulosic biomasses are considered promising feedstocks for the next generation of biofuels and chemicals; however, the recalcitrance of lignocellulose remains a barrier to its utilisation over conventional sources. Pyrolysis is the heating of biomass to several hundred degrees Celsius in the absence of oxygen, which can thermally depolymerise lignocellulose. Products of pyrolysis are a solid biochar, liquid bio-oil and syngas. Biochar has roles in both carbon sequestration and soil amendment however bio-oil has no defined use, despite a high concentration of fermentable sugars. Bio-oil is a complex organic microemulsion with a host of biocatalyst inhibitors that makes its microbial degradation a challenge. In this work, the use of aerobic cultures using microbial communities isolated from natural environments saw limited potential; however, the use of anaerobic digestion (AD) successfully generated a higher volume of biogas from reactors with bio-oil than controls. Biogas yield test reactors were set up with anaerobic digestate from a wastewater treatment plant as the substrate for degradation and conversion of bio-oils. Next-generation 16S rRNA gene sequencing was utilised to characterise the communities in the reactors while the ultrahigh resolution mass spectrometry technique of Fourier transform ion cyclotron resonance (FT-ICR) was used for characterisation of the chemical changes occurring during AD. Both sets of high-resolution data were additionally combined for multivariate analysis and modelling of the microbial genera that correlated best with the changes in digestate chemistry. This represents a novel analysis method for the microbial degradation of complex organic products. Bio-oil from common lignocellulosic feedstock was the most easily degradable by the AD communities, with significant inhibition observed when bio-oils from anaerobic digestate and macroalgae were used. Additionally it was found that the inclusion of biochars that were pre-incubated in anaerobic digestate prior to use in AD were capable of significantly reducing the lag time observed for biogas production in bio-oil-supplemented reactors. The addition of biochars that were not pre-incubated had no effect on biogas production. Specific inhibition of methanogenesis was also capable of causing the digestates to accumulate volatile fatty acids (VFAs) as a product of greater value than biogas. Scale-up experiments will be required to confirm the precise practicalities of the addition of bio-oil to AD as well as to establish the potential for isolation and purification of VFAs.

Lactic acid bacteria are essential as flavor producers of cheese and fermented products. They are capable of catabolizing aromatic, branched chain, and sulfur amino acids to flavor compounds. During cheese ripening the numbers of lactococcal colonies decrease, but lactococci survive without replication in culture. This prompted an investigation into possible mechanisms of catabolism of branched chain amino acids into branched chain fatty acids and the physiological relevance of amino acid catabolism to the bacteria. We hypothesized that lactococci catabolize branched chain amino acids to branched chain fatty acids during nonculturability. Lactococci, lactobacilli, and brevibacteria catabolized both branched chain amino acids and keto acids into branched chain fatty acids. Lactococci survived carbohydrate-limited conditions for over 4 yrs. Their survival was represented by maintaining intracellular ATP, enzyme activity, membrane integrity, capability of ATP- and PMF-dependent substrate transport, transcription, and catabolism of amino acids to fatty acids. Assays conducted with NMR spectroscopy coupled with in silico analysis showed that branched chain substrates are catabolized via keto acids, HMG-CoA, and acetyl-CoA to branched chain fatty acids. A short list of candidate genes was identified for the pathway by gene expression analysis coupled to NMR analysis. The expression of these genes and the presence of the related catabolites were identified in long-term starved cultures of nonculturable lactococci. This verified that catabolism of branched chain amino acids to branched chain fatty acids occurred during the nonculturable state only and in conditions of carbohydrate deprivation. The pathway also facilitated fixation of carbon by lactococci, revealing the mechanism of survival of lactococci over 4 yrs in culture without the addition of external carbon sources. Between strains the availability of carbohydrate and acid stress played significant roles in modulating their ability to produce branched chain catabolites. The ability of lactococci to catabolize branched chain amino acids during sugar starvation represents a shift in carbon catabolic routes. The identified pathway also represented a balance between catabolism and anabolism, suggesting that the bacteria were in a homeostatic state during nonculturability. We accepted the hypothesis that nonculturable lactococci catabolized branched chain amino acids to branched chain fatty acids during starvation./p>

<p>Hammarby Sjöstad is a new district of southern Stockholm built with focus on reduced environmental impact by recirculation of materials and sustainability. The environmental goals aim to cut the water consumption by half and a separate storm water treatment. Thus, the wastewater will be more concentrated and will originate from the households only. The Sjöstad project includes the idea of a local treatment plant for the household wastewater. To evaluate this possibility, Sjöstadsverket, an experimental treatment plant was constructed. New wastewater treatment processes are tested and evaluated and compared to conventional methods including both aerobic and anaerobic treatment processes.</p><p>One of the aerobic treatment processes includes enhanced biological phosphorus removal (EBPR or Bio-P) as the method for the removal of phosphorus. In biological phosphorus removal the wastewater is alternately being exposed to anaerobic and aerobic conditions, which favours a certain bacteria, which can accumulate more phosphorus than is required for their growth. For this phosphorus accumulation the bacteria need volatile fatty acids (VFA) to cover their energy demand, but normally there is a shortage in VFA in the incoming wastewater.</p><p>The main purpose of this master thesis work has been to create the best possible conditions in order to produce VFA by hydrolysis and fermentation of primary sludge. In this way the organic material in the incoming wastewater can be used in biological phosphorus removal.</p><p>The sludge temperature, total solids (TS) and retention time are regarded as important parameters for a successful biological phosphorus removal and a laboratory study was set up to investigate these conditions for the wastewater at the Hammarby Sjöstad experimental plant. These laboratory-scale hydrolysis experiments showed that high temperature and high TS favours VFA-production. The results have also shown that four to five days retention time is suitable at a process temperature higher than 23°C, but also that the retention time likely should be extended at lower temperatures.</p><p>In a full-scale process experiment, primary sludge was pumped from a primary clarifier to a hydrolysis tank and then back to the primary clarifier. The hydrolysis gave rise to increased VFA-production when TS was increased. A temperature difference between the primary sludge and the hydrolysis sludge of 3°C was observed. The reason behind the difference has not been determined, but is considered important, since the temperature affects the VFA-production. Further on, analyses with gas chromatograph (GC) have shown that acetate has been the most frequently occurring VFA, although significant levels of other VFA, such as propionate, has also been detected.</p><p>Phosphorus release tests in laboratory-scale, where phosphorus was released during an anaerobic phase and taken up during an aerobic phase, proved that biological phosphorus removal occurred at the full-scale experimental train.</p><p>The full-scale hydrolysis experiment has shown that the VFA contribution by the hydrolysis tank to the biological phosphorus removal was low. The main reason is that the sludge-flow through the hydrolysis tank has been insignificant compared to the incoming wastewater flow. The problem is most likely connected to the incoming wastewater characteristics, since the low share of suspended solids (SS) entailed that not enough organic material in the primary clarifier settled.</p> / I figur 57 på sidan 76 stämmer inte trendlinjernas ekvationer i den tryckta versionen. Dessa är nu korrigerade i den elektroniska versionen, så att rätt ekvationer finns i den aktuella figuren.