Biogas är en förnyelsebar energikälla som tillverkas genom att organiskt material som matavfall bryts ner av mikroorganismer under anaeroba (syrefria) förhållanden. Regeringen har satt upp mål för en högre matavfallsutsortering vilket leder till ökad mängd tillgängligt substrat till biogasproduktion. Matavfallet som samlas in börjar brytas ner under tiden det transporteras och lagras. Syftet med studien var att undersöka hur länge matavfall lagras, ta fram ett representativt recept på ett genomsnittligt matavfall i Sverige och utvärdera hur mycket metanpotential som försvinner från matavfall med avseende på lagringstid, insamlingssystem (papper- och plastpåse) och lagringstemperatur (22°C och 6°C) genom laboratorieförsök. Den genomsnittliga lagringstiden för matavfall från villor och flerbostadshus i undersökningen var sex dagar. Ett recept för matavfall har tagits fram med hjälp av litteratursökning och modifiering av recept i Avfall Sveriges rapport U2010:10. Laboratorieförsöken visade att skillnaden i metanpotential mellan plast och papper var tydlig vid 22°C, då metanpotentialen sjunker, men obefintlig vid 6°C. För att uppnå maximal metangasproduktion från matavfall under den varma delen av året så är plastpåsar bättre då de har en mer konserverande effekt på matavfallet än papperspåsar. Detta kan relateras till att plast är tätare än papper och därför håller inne flyktiga ämnen. / Biogas is a renewable energy source that is produced when organic materials like food waste is degraded by microorganisms under anaerobic (oxygen-free) conditions. The Swedish Government has set goals for a higher sorting of food waste, leading to increased amounts of available substrate for biogas production. Collected food waste begin to break down during the time it is transported and stored. The purpose of this study was to investigate the length of the storage, produce a representative recipe for an average food waste in Sweden and evaluate how much methane potential is lost from food waste with respect to the storage time, collection method (paper or plastic bag) and storage temperature (22°C and 6°C) through laboratory tests. The average storage time of food waste from houses and apartment buildings in the survey was six days. A recipe for food waste has been developed with the help of literature search and modification of recipes in ‘’Avfall Sverige’’ report U2010:10. Laboratory tests showed that the difference in methane potential between the plastic and paper were clear at 22°C, with decreasing methane potential, but non-existent at 6°C. To achieve maximum methane production from food waste during the warmer part of the year, plastic bags are better because they have a preservative effect on the food waste. This can be related to the fact that plastic are denser than paper and therefore holds volatile compounds better.

The effects of UV pretreatment on alkaline bleaching (EOP) wastewater from a kraft pulp and paper mill were investigated prior to anaerobic digestion (AD) in an upflow anaerobic sludge blanket (UASB) reactor. The aim was to enhance the methane production, increase the reduction of total organic carbon (TOC) and determine the best UV exposure time. The exposure time of 2.6 minutes partially degraded the organic material in the EOP wastewater since it generated higher biogas and methane production than the reference period, while it also increased the reductions of solved chemical oxygen demand (CODsol) and TOCsol. The exposure time of 16 minutes, on the other hand, did not show any significant improvement regarding increased biogas and methane production nor did it increase the reduction of CODsol. However, it did increase the reduction of TOCsol, but not to the same extent as the exposure time of 2.6 minutes. The presence of unwanted microbial growth in the system during the experiment might have affected the effectiveness of the UV pretreatment more during the exposure time of 16 minutes as the amount of growth was more substantial during this period of time. Furthermore, no optimal exposure time could be determined due to lack of time.

Anaerobic digestion (AD) is widely used in wastewater treatment plants for stabilisation of primary and waste activated sludges. Increasingly energy prices as well as stringent environmental and public health regulations ensure the ongoing popularity of anaerobic digestion. Reduction of volatile solids, methane production and pathogen reduction are the major objectives of anaerobic digestion. Phased anaerobic digestion is a promising technology that may allow improved volatile solids destruction and methane gas production. In AD models, microbially-mediated processes are described by functionally-grouped microorganisms. Ignoring the presence of functionally-different species in the separate phases may influence the output of AD modeling. The objective of this research was to thoroughly investigate the kinetics of hydrolysis, acetogenesis (i.e., propionate oxidation) and methanogenesis (i.e., acetoclastic) in phased anaerobic digestion systems. Using a denaturing gradient gel electrophoresis (DGGE) technique, bacterial and archaeal communities were compared to complement kinetics studies. Four phased digesters including Mesophilic-Mesophilic, Thermophilic-Mesophilic, Thermophilic-Thermophilic and Mesophilic-Thermophilic were employed to investigate the influence of phase separation and temperature on the microbial activity of the digestion systems. Two more digesters were used as control, one at mesophilic 35 0C (C1) and one at thermophilic 55 0C (C2) temperatures. The HRTs in the first-phase, second-phase and single-phase digesters were approximately 3.5, 14, and 17 days, respectively. All the digesters were fed a mixture of primary and secondary sludges. Following achievement of steady-state in the digesters, a series of batch experiments were conducted off-line to study the impact of the digester conditions on the kinetics of above-mentioned processes. A Monod-type equation was used to study the kinetics of acetoclastic methanogens and POB in the digesters, while a first-order model was used for the investigation of hydrolysis kinetics. Application of an elevated temperature (55 0C) in the first-phase was found to be effective in enhancing solubilisation of particulate organics. This improvement was more significant for nitrogen-containing material (28%) as compared to the PCOD removal (5%) when the M1 and T1 digesters were compared. Among all the configurations, the highest PCOD removal was achieved in the T1T2 system (pvalue<0.05). In contrast to the solubilisation efficiencies, the mesophilic digesters (C1, M1M2 and T1M3) outperformed the thermophilic digesters (C2, T1T2 and M1T3) in COD removal. The highest COD removal was obtained in the T1M3 digestion system, indicating a COD removal efficiency of 50.7±2.1%. The DGGE fingerprints from digesters demonstrated that digester parameters (i.e., phase separation and temperature) influenced the structure of the bacterial and archaeal communities. This resulted in distinct clustering of DGGE profiles from the 1st-phase digesters as compared to the 2nd-phase digesters and from the mesophilic digesters as compared to the thermophilic ones. Based on the bio-kinetic parameters estimated for the various digesters and analysis of the confidence regions of the kinetic sets (kmax and Ks), the batch experiment studies revealed that the kinetic characteristics of the acetoclastic methanogens and POB developed in the heavily loaded digesters (M1 and T1) were different from those species developed in the remaining mesophilic digesters (M2, M3 and C1). As with the results from the mesophilic digesters, a similar observation was made for the thermophilic digesters. The species of acetoclastic methanogens and POB within the T1 digester had greater kmax and Ks values in comparison to the values of the T3 and C2 digesters. However, the bio-kinetic parameters of the T2 digester showed a confidence region that overlapped with both the T1 and T3 digesters. The acetate and propionate concentrations in the digesters supported these results. The acetate and propionate concentrations in the M1 digesters were, respectively, 338±48 and 219±17 mgCOD/L, while those of the M2, M3 and C1 digesters were less than 60 mg/L as COD. The acetate and propionate concentrations were, respectively, 872±38 and 1220±66 in T1 digester, whereas their concentrations ranged 140-184 and 209-309 mg/L as COD in the T2, T3 and C2 digesters. In addition, the DGGE results displayed further evidence on the differing microbial community in the 1st- and 2nd-phase digesters. Two first-order hydrolysis models (single- and dual-pathway) were employed to study the hydrolysis process in the phased and single-stage digesters. The results demonstrated that the dual-pathway hydrolysis model better fit the particulate COD solubilisation as compared to the single-pathway model. The slowly (F0,s) and rapidly (F0,r) hydrolysable fractions of the raw sludge were 36% and 25%, respectively. A comparison of the estimated coefficients for the mesophilic digesters revealed that the hydrolysis coefficients (both Khyd,s and Khyd,r) of the M1 digester were greater than those of the M2 and M3 digesters. In the thermophilic digesters it was observed that the Khyd,r value of the T1 digester differed from those of the T2, T3 and C2 digesters; whereas, the hydrolysis rate of slowly hydrolysable matter (i.e., Khyd,s) did not differ significantly among these digesters. The influence of the facultative bacteria, that originated from the WAS fraction of the raw sludge, and/or the presence of hydrolytic biomass with different enzymatic systems may have contributed to the different hydrolysis rates in the M1 and T1 digesters from the corresponding mesophilic (i.e, M2 and M3) and thermophilic (i.e., T2 and T3) 2nd-phase digesters.

ABSTRACT Bioreactor landfill operation has been promoted as a means of accelerating the degradation of waste for over 30 years. Accelerating the degradation of waste enables better predictability in biogas production and reduces aftercare costs. Most bioreactor landfill trials focus on the effect of leachate recirculation on otherwise conventional landfill cells. However, there is a range of design and operational measures that can be implemented with standard landfilling machinery to further enhance degradation. This thesis explores degradation rates that can be achieved in a landfill cell, designed to maximise degradation rate, with the constraint that it be constructed by standard earthmoving equipment, the waste be crudely shredded by sheep foot compactors to expose waste, and leachate recirculation be operable by landfill personnel. The major departures of these test cells from a conventional landfill cell operation were: the cells were only 3m deep; MSW loaded into the cell was crushed and bags ruptured with a sheep foot compactor; MSW was pre-mixed prior placement with digested sludge, as a ratio such that the buffering capacity of the sludge was equivalent to an amount of NaHCO3 known to successfully buffer the digestion of packed beds of MSW (10gL-1 NaHCO3 in packed bed at field capacity moisture content plus excess leachate equal to 10% of the bed volume (Lai et al 2001); and the waste was placed rather than compacted into the cell. The thesis examines the performance of two test cells, the second only containing MSW and inoculated and buffered by sequencing with the first. These performances are compared with an exhaustive set of control digestions in 200L laboratory reactors. The laboratory reactors were packed with 50kg sub-samples of the waste used in the cells, shredded to sub 5cm size. The laboratory reactors primarily focussed on the effect of temperature on degradation rates, to identify the optimum degradation rate for this sludge and MSW mixture. The laboratory scale reactors produced 231 L and 202 L of methane per kgVS at the mesophilic temperatures of 38°C and 45°C respectively. The degradation was faster in the 45°C reactor where methane production was completely exhausted after 35 days. A laboratory reactor operated at 55°C reactor showed little degradation activity. The pH of this reactor was initially over 8.5, and ammonia inhibition was suspected. However, the reactor did not respond to pH adjustments with hydrochloric acid, and subsequent step decreases in temperature did not have an effect until 47°C, where degradation suddenly accelerated. This suggests the methanogenic consortia in the sludge could not adapt to thermophilic temperatures. This was confirmed in the 63°C reactor which acidified and did not produce methane, until leachate from this reactor was transferred to the 45°C reactor where an established methanogenic community converted the soluble COD to methane. In order to compare laboratory reactor performance with the general literature, pure cellulose was added in a fed-batch fashion to the stabilised 38°C and 47°C leach-beds. The beds were fed under starved conditions, to clearly distinguish degradation products from the cellulose from background levels. This also allowed for the estimation of biomass growth by measuring the uptake of NH4-N, as all other bio-available N sources such as protein and amino acids were reduced to NH4-N under these starved conditions. Hydrolysis rates were determined to be 0.12±0.01 d-1 and 0.14±0.026 d-1 at the 38°C and 47°C temperatures. Degradation in the two test cells was completed within a 7 month period. Temperature in the cells was maintained between 25 – 30°C by biological activity, levels that were above ambient temperatures, but below ideal mesophilic conditions. Methane composition rapidly approached 50% in both cells, and biogas flow rates were consistent with a degradation timeframe in the order of less than year. Full flow rate data was not obtained from these trials due to mechanical problems with flow meters, however vigorous gas production was evident throughout the trial by monitoring gas composition, and the ballooning effect of the top cover. To confirm the degradation rates in the test cells, samples were collected from the second test cell and digested in laboratory reactors. Methane yields were only 2.4 and 6.4 L CH4 kgVS-1 confirming virtual exhaustion of biogas potential within 7 months of sequencing this MSW cell with the first MSW:sludge test cell. This is the first systematic experimental program that places the degradation performance of a test cell in the context of the potential degradation rate achievable with fine shredding, temperature control and thorough inoculation and buffering. Economically, in cases where degradation residues are left insitu as in landfills, the degradation enhancement in the test cells would effectively yield as much benefit as enhancing the degradation rate to a two to three week timeframe typical of an anaerobic digester (Clarke 2000).

Municipal wastewater and industrial wastewaters like those effluents from brewery, citric acid production, tannery, pulp and paper industry, and mussel processing contain sulphate ranging from 20 mg.L-1 to 11400 mg.L-1. When these wastewaters are treated in an anaerobic system like prefermentors or anaerobic digesters the sulphate is reduced to sulphide by sulphate reducing bacteria (SRB). The presence of sulphate reduction is not desirable as it may reduce methane yield due to partial substrate utilisation by SRB, causes system toxicity and the production of malodor H2S in the gas phase. In this thesis, the effects of operational conditions on sulphate transformation and assimilation was studied in a laboratory scale anaerobic wastewater treatment system. The laboratory scale system consisted of two reactors the first one a well-mixed fermentor (referred to as an acidogenic reactor) and the second an expanded granular sludge blanket reactor (referred to as a methanogenic reactor) with pH and temperature control. Two sets of studies were performed; in the first set both reactors were connected serially to represent a two-stage high-rate anaerobic treatment system. The system was fed molasses and operated at temperature of 35oC. The acidogenic reactor was controlled at pH of 6 while the methanogenic reactor was controlled at pH of 7.2 by automatic addition of caustic. In the second set of experiments only the first reactor was used to represent a prefermentor and the first stage of the two stage. The reactor was fed with glucose at various concentrations, operated at pH of 6 and temperature of 35oC. Information gained from these studies was encapsulated in a mathematical model to describe sulphate reduction in anaerobic treatment systems. This model was also validated using data generated from the experiments. The experimental study showed that · At low sulphate concentrations of about 250 mg.L-1 and COD concentration of 10,000 mg.L-1 in feed, relatively high percentage (up to 35 %) of produced sulphide was assimilated by biomass, while the rest of the sulphur was distributed as unconverted sulphate, dissolved sulphide, H2S gas and to a lesser extent as metallic sulphide precipitates. · The major electron donor for sulphate reduction in both the acidogenic and the methanogenic reactor was hydrogen gas. Therefore, sulphate reduction not only competed with hydrogen utilising methanogens for the available hydrogen, but also changed the distributions of organic acids, which were directly or indirectly influenced by the H2 partial pressure. · Sulphide concentrations of up to 6.5 mM free hydrogen sulphide) at pH of 7.2 was not inhibitory to methanogens · Sulphate reducing bacteria were able to grow even at a low hydraulic retention time of 1.2 hours in the well-mixed acidogenic reactor. It was estimated that the maximum specific growth rate (m) and half saturation constant (ks) of SRB was 1.31 h-1 and 3.8 mg S.L-1, respectively. These values were higher than those reported in literature. · Sulphate reduction was suppressed at high concentration of carbon in the feed. Accumulation of high concentration of volatile organic acids at high feed-carbon concentrations had little effect on sulphate reduction. However, extent of sulphate reduction had a negative correlation with total concentration of biomass. A non-competitive biomass inhibition function was proposed to model the correlation. From this fit it was estimated that a biomass concentration of about 3300 mg-COD.L-1 will completely inhibit sulphate reduction. · Sulphate reduction was affected by redox potential control and pH in the acidogenic reactor. High pH and low redox potential values were essential for sulphate reduction to proceed. At redox potential control of -300 mV, sulphate reduction was inhibited more at pH of 6 than it was at pH of 7. At redox potential values of -250 mV or higher, about 90 % inhibition of sulphate reduction was observed at both pH of 6 and 7. An existing model describing carbohydrate degradation was extended to include sulphate reduction processes. Despite experimentally observing that sulphate reduction only took place from hydrogen, all possible substrates for sulphate reducion was considered. These included: lactic acid, butyric acid, propionic acid, acetic acid and hydrogen. Kinetic parameters for sulphate reduction processes were obtained from documented literature. Inhibition of sulphate reduction by biomass and sulphur assimilation by biomass were included in the model. A new approach to calculate caustic consumption at given pH values was also included. A modification to hydrogen regulation function was also made to better predict product distributions as a function of gas-phase hydrogen concentration. Model validation was performed using data from dynamic experiments. Comparison to actual data was undertaken on several key variables in the acidogenic and methanogenic reactors such as: organic acid concentrations, gas compositions, gas production rates, sulphate and sulphide concentrations and caustic consumption rates. The model satisfactorily predicted sulphate and sulphide concentrations in both reactors. However, discrepancy between predicted and experimental data on organic carbon concentrations was seen, especially during organic carbon concentration step changes.

Municipal wastewater and industrial wastewaters like those effluents from brewery, citric acid production, tannery, pulp and paper industry, and mussel processing contain sulphate ranging from 20 mg.L-1 to 11400 mg.L-1. When these wastewaters are treated in an anaerobic system like prefermentors or anaerobic digesters the sulphate is reduced to sulphide by sulphate reducing bacteria (SRB). The presence of sulphate reduction is not desirable as it may reduce methane yield due to partial substrate utilisation by SRB, causes system toxicity and the production of malodor H2S in the gas phase. In this thesis, the effects of operational conditions on sulphate transformation and assimilation was studied in a laboratory scale anaerobic wastewater treatment system. The laboratory scale system consisted of two reactors the first one a well-mixed fermentor (referred to as an acidogenic reactor) and the second an expanded granular sludge blanket reactor (referred to as a methanogenic reactor) with pH and temperature control. Two sets of studies were performed; in the first set both reactors were connected serially to represent a two-stage high-rate anaerobic treatment system. The system was fed molasses and operated at temperature of 35oC. The acidogenic reactor was controlled at pH of 6 while the methanogenic reactor was controlled at pH of 7.2 by automatic addition of caustic. In the second set of experiments only the first reactor was used to represent a prefermentor and the first stage of the two stage. The reactor was fed with glucose at various concentrations, operated at pH of 6 and temperature of 35oC. Information gained from these studies was encapsulated in a mathematical model to describe sulphate reduction in anaerobic treatment systems. This model was also validated using data generated from the experiments. The experimental study showed that · At low sulphate concentrations of about 250 mg.L-1 and COD concentration of 10,000 mg.L-1 in feed, relatively high percentage (up to 35 %) of produced sulphide was assimilated by biomass, while the rest of the sulphur was distributed as unconverted sulphate, dissolved sulphide, H2S gas and to a lesser extent as metallic sulphide precipitates. · The major electron donor for sulphate reduction in both the acidogenic and the methanogenic reactor was hydrogen gas. Therefore, sulphate reduction not only competed with hydrogen utilising methanogens for the available hydrogen, but also changed the distributions of organic acids, which were directly or indirectly influenced by the H2 partial pressure. · Sulphide concentrations of up to 6.5 mM free hydrogen sulphide) at pH of 7.2 was not inhibitory to methanogens · Sulphate reducing bacteria were able to grow even at a low hydraulic retention time of 1.2 hours in the well-mixed acidogenic reactor. It was estimated that the maximum specific growth rate (m) and half saturation constant (ks) of SRB was 1.31 h-1 and 3.8 mg S.L-1, respectively. These values were higher than those reported in literature. · Sulphate reduction was suppressed at high concentration of carbon in the feed. Accumulation of high concentration of volatile organic acids at high feed-carbon concentrations had little effect on sulphate reduction. However, extent of sulphate reduction had a negative correlation with total concentration of biomass. A non-competitive biomass inhibition function was proposed to model the correlation. From this fit it was estimated that a biomass concentration of about 3300 mg-COD.L-1 will completely inhibit sulphate reduction. · Sulphate reduction was affected by redox potential control and pH in the acidogenic reactor. High pH and low redox potential values were essential for sulphate reduction to proceed. At redox potential control of -300 mV, sulphate reduction was inhibited more at pH of 6 than it was at pH of 7. At redox potential values of -250 mV or higher, about 90 % inhibition of sulphate reduction was observed at both pH of 6 and 7. An existing model describing carbohydrate degradation was extended to include sulphate reduction processes. Despite experimentally observing that sulphate reduction only took place from hydrogen, all possible substrates for sulphate reducion was considered. These included: lactic acid, butyric acid, propionic acid, acetic acid and hydrogen. Kinetic parameters for sulphate reduction processes were obtained from documented literature. Inhibition of sulphate reduction by biomass and sulphur assimilation by biomass were included in the model. A new approach to calculate caustic consumption at given pH values was also included. A modification to hydrogen regulation function was also made to better predict product distributions as a function of gas-phase hydrogen concentration. Model validation was performed using data from dynamic experiments. Comparison to actual data was undertaken on several key variables in the acidogenic and methanogenic reactors such as: organic acid concentrations, gas compositions, gas production rates, sulphate and sulphide concentrations and caustic consumption rates. The model satisfactorily predicted sulphate and sulphide concentrations in both reactors. However, discrepancy between predicted and experimental data on organic carbon concentrations was seen, especially during organic carbon concentration step changes.

Municipal wastewater and industrial wastewaters like those effluents from brewery, citric acid production, tannery, pulp and paper industry, and mussel processing contain sulphate ranging from 20 mg.L-1 to 11400 mg.L-1. When these wastewaters are treated in an anaerobic system like prefermentors or anaerobic digesters the sulphate is reduced to sulphide by sulphate reducing bacteria (SRB). The presence of sulphate reduction is not desirable as it may reduce methane yield due to partial substrate utilisation by SRB, causes system toxicity and the production of malodor H2S in the gas phase. In this thesis, the effects of operational conditions on sulphate transformation and assimilation was studied in a laboratory scale anaerobic wastewater treatment system. The laboratory scale system consisted of two reactors the first one a well-mixed fermentor (referred to as an acidogenic reactor) and the second an expanded granular sludge blanket reactor (referred to as a methanogenic reactor) with pH and temperature control. Two sets of studies were performed; in the first set both reactors were connected serially to represent a two-stage high-rate anaerobic treatment system. The system was fed molasses and operated at temperature of 35oC. The acidogenic reactor was controlled at pH of 6 while the methanogenic reactor was controlled at pH of 7.2 by automatic addition of caustic. In the second set of experiments only the first reactor was used to represent a prefermentor and the first stage of the two stage. The reactor was fed with glucose at various concentrations, operated at pH of 6 and temperature of 35oC. Information gained from these studies was encapsulated in a mathematical model to describe sulphate reduction in anaerobic treatment systems. This model was also validated using data generated from the experiments. The experimental study showed that · At low sulphate concentrations of about 250 mg.L-1 and COD concentration of 10,000 mg.L-1 in feed, relatively high percentage (up to 35 %) of produced sulphide was assimilated by biomass, while the rest of the sulphur was distributed as unconverted sulphate, dissolved sulphide, H2S gas and to a lesser extent as metallic sulphide precipitates. · The major electron donor for sulphate reduction in both the acidogenic and the methanogenic reactor was hydrogen gas. Therefore, sulphate reduction not only competed with hydrogen utilising methanogens for the available hydrogen, but also changed the distributions of organic acids, which were directly or indirectly influenced by the H2 partial pressure. · Sulphide concentrations of up to 6.5 mM free hydrogen sulphide) at pH of 7.2 was not inhibitory to methanogens · Sulphate reducing bacteria were able to grow even at a low hydraulic retention time of 1.2 hours in the well-mixed acidogenic reactor. It was estimated that the maximum specific growth rate (m) and half saturation constant (ks) of SRB was 1.31 h-1 and 3.8 mg S.L-1, respectively. These values were higher than those reported in literature. · Sulphate reduction was suppressed at high concentration of carbon in the feed. Accumulation of high concentration of volatile organic acids at high feed-carbon concentrations had little effect on sulphate reduction. However, extent of sulphate reduction had a negative correlation with total concentration of biomass. A non-competitive biomass inhibition function was proposed to model the correlation. From this fit it was estimated that a biomass concentration of about 3300 mg-COD.L-1 will completely inhibit sulphate reduction. · Sulphate reduction was affected by redox potential control and pH in the acidogenic reactor. High pH and low redox potential values were essential for sulphate reduction to proceed. At redox potential control of -300 mV, sulphate reduction was inhibited more at pH of 6 than it was at pH of 7. At redox potential values of -250 mV or higher, about 90 % inhibition of sulphate reduction was observed at both pH of 6 and 7. An existing model describing carbohydrate degradation was extended to include sulphate reduction processes. Despite experimentally observing that sulphate reduction only took place from hydrogen, all possible substrates for sulphate reducion was considered. These included: lactic acid, butyric acid, propionic acid, acetic acid and hydrogen. Kinetic parameters for sulphate reduction processes were obtained from documented literature. Inhibition of sulphate reduction by biomass and sulphur assimilation by biomass were included in the model. A new approach to calculate caustic consumption at given pH values was also included. A modification to hydrogen regulation function was also made to better predict product distributions as a function of gas-phase hydrogen concentration. Model validation was performed using data from dynamic experiments. Comparison to actual data was undertaken on several key variables in the acidogenic and methanogenic reactors such as: organic acid concentrations, gas compositions, gas production rates, sulphate and sulphide concentrations and caustic consumption rates. The model satisfactorily predicted sulphate and sulphide concentrations in both reactors. However, discrepancy between predicted and experimental data on organic carbon concentrations was seen, especially during organic carbon concentration step changes.

The antioxidant capacity of phenolic compounds in red wine is suggested to be responsible for their health-promoting effects. Compared to other wines, little information is available on phenolic compositions and antioxidant capacity of Australian wine. Information related to the fate of these phenolics in the body once consumed is also very limited. The overall aim of this research was to investigate the relevance of red wine consumption as a source of health-giving antioxidants in humans. The phenolic composition of wine was determined using the Folin-Ciocalteu (total phenolic), aluminium chloride (total flavonols), methyl cellulose precipitation (MCP) (total tannins), pH differential (total monomeric anthocyanins), bisulfite bleaching (total polymeric anthocyanin fractions), and liquid chromatographic (LC-MS) (individual phenolics) methods. Antioxidant activities were measured using 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2’-azino-bis-93-ethylbenzthiazoline-6-sulfonic acid (ABTS) and oxygen radical absorbance capacity (ORAC) assays. The phenolic and antioxidant data were then used to establish the relationship between these two parameters in wines from different varieties (Shiraz, Cabernet Sauvignon and Merlot) and winemaking stages (crushing, fermentations, oaking and bottling). By using an in vitro digestion model that mimics the upper gastrointestinal tract (GIT) digestion, the stability of the wine phenolics during digestion was examined. Finally, to gain a better understanding of the post-digestion absorption of wine phenolics, their permeability across Caco-2 cell monolayers was evaluated. A total of 8 monomeric anthocyanins and 17 other phenolic compounds were positively identified in the red wines using LC-MS analysis. Most of the phenolic categories showed some positive correlations with the antioxidant activities but none of the individual phenolic compounds showed a strong correlation with the total antioxidant activity of the wine, implying a combined contribution of many wine phenolics to antioxidant effects. The phenolic compositions and antioxidant activities of three of Australia’s most common red wines varieties - Shiraz, Cabernet Sauvignon and Merlot were not different from each other, possibly due to the variability within each grape cultivar. During the winemaking process, the total phenolic content and the associated antioxidant activity of the wine increased during the fermentation process, as more phenolics are being extracted from grape skin, seeds and stems into the wine. During oak and bottle ageing, the total phenolic contents were stabilised. Most of the wine phenolics were more stable under acidic conditions (pH 2 and 5.5) than neutral or alkaline conditions (pH 7.4 and 9). This may partly explain the stability of the wine phenolics subjected to the acidic (pH 2) gastric digestion and their loss following simulated pancreatic digestion (pH 7.4). In addition, sample pre-treatment procedures prior to LC-MS analysis may have removed some antioxidants in the form of degradation products and/or new polymeric compounds following the in vitro gastric and pancreatic digestion processes. The missing products appeared to be detected by both the Folin-Ciocalteu method and ORAC assay, which measured the phenolic compounds and their antioxidant activity, after the pancreatic digestion. This suggests that the instability of phenolic compounds at pH 7.4, results in the transformation of most of the oral phenolic antioxidants into more stable forms in the GIT, which in turn contribute positively to the overall antioxidant activities of the ingested wine. All of the original wine phenolics had very low permeabilities across Caco-2 cell monolayers, except for syringic acid, p-coumaric acid and an unknown phenolic acid. Limited surface area for absorption (0.33 cm2) and the limited peak detection sensitivity in the LC method may have contributed towards the difficulty in detecting and identifying compounds with low permeability. In addition, extensive metabolism of absorbed phenolics by the Caco-2 cells may occur based on the appearance of several new peaks. However, due to their low concentrations and lack of reference, the identities of the new products and metabolites remain unknown. The present in vitro study suggests that upon ingestion, most of the original phenolic compounds in red wine are lost either through degradation to new compounds and/or complexation with other compounds. However, these products seem to possess some antioxidant activity and may be the key compounds responsible for the health-promoting effects of red wine. The limitation of the present study in detecting and fully identifying these breakdown products and metabolites should be addressed in future studies.

In the pig and poultry production industries, energy forms the largest and the greatest cost pressure when a diet is formulated. In Australia, cereal grains such as barley, sorghum, and wheat are the main dietary energy sources, comprising more than 60 % of the diet in many cases. Traditionally, during diet formulation, the energy value of a grain has been represented by a single figure for that particular grain type. However, several studies have indicated that the energy availability from different grains fed to pigs and poultry varies significantly even within one grain cultivar. Given these findings, the use of a single value to represent the energy of each grain type during diet formulation, can lead to inefficient utilisation of dietary resources by animals, and thus decreased animal performance and consequently, a decrease in profit for the pig and poultry production industries. Thus, there is an opportunity to develop a rapid and reproducible in vitro assay to accurately assess the available energy values and nutritional quality of each grain type. In order to develop such an assay, further understanding of factors that affect the available energy values of grains need to be explored. Starch, which is hydrolysed into glucose by animals, is the most abundant energy component in cereal grains, and there is evidence suggesting that variations in digestible or metabolisable energy values may be related to the extent of starch digestibility. For example in poultry, variations in the in vitro digestibility of starch between several wheat cultivars have been shown to correlate with their in vivo available metabolisable energy values. However, it is not known to what extent starch digestibility varies between cultivars of other grain types such as barley and sorghum. There is an increasing body of evidence suggesting that differences in the physical and chemical properties of cereal grains may play an important role in influencing starch digestibility and, consequently, animal performance. Thus, the general hypothesis of this study was that starch digestibility varies between barley, sorghum and wheat, and between cultivars within grain types and this is related to specific chemical and physical characteristics of the grains. To examine this, the following issues were investigated using 18 barley, 15 sorghum and 10 wheat cultivars : 1 ) an in vitro glucose release index ( GRI ) assay was developed to assess starch digestibility within and between the cereal grain types and, 2 ) the GRI was correlated to both starch - related ( e.g., starch content, starch granule size, the amylose to amylopectin ratio, starch gelatinisation properties ) and non - starch - related ( e.g., non - starch polysaccharide composition, kernel hardness, the presence of protein matrix and milling quality ) physical / chemical characteristics within and between the cereal grains. Results revealed significant variations in the GRI both between grains and within a given grain type. The GRI values ranged between 27 - 45 %, 25 - 54 % and 32 - 53 % in barley, sorghum and wheat respectively. Correlation analysis revealed that the GRI in barley, sorghum and wheat was influenced by the physical and chemical characteristics of starch - and non - starch - related grain properties, although the type of characteristic influencing GRI was specific to the grain type. In barley, the ratio of amylose to amylopectin, starch gelatinisation and kernel hardness influenced the GRI. In sorghum, the GRI was influenced by the ratio of amylose to amylopectin, the presence of a protein matrix surrounding starch granules and kernel hardness. Finally in wheat, the presence of protein matrix and milling quality influenced the GRI. It was also shown that the extract viscosity of grains within barley and wheat, but not sorghum, varied significantly. In conclusion, the results from this study indicate that ; 1 ) the GRI assay may be used to identify some factors that affect in vivo starch digestibility within and between barley, sorghum and wheat, 2 ) starch digestibility ( as assessed by the GRI ) may be influenced by some physical and chemical characteristics of cereal grains, and that these characteristics are specific to the type of grain The physical and chemical characteristics that may influence starch digestion will be discussed in relation to their potential physiological effects on energy digestion, and utilisation in animals. The information generated will provide a basis for future studies that will ultimately assist in the design of in vitro assays to predict energy availability from barley, sorghum and wheat grains fed to pigs and poultry, and contribute to the more efficient use of grains in monogastric production systems. / Thesis (Ph.D.)--Department of Animal Science, 2002.

Municipal wastewater and industrial wastewaters like those effluents from brewery, citric acid production, tannery, pulp and paper industry, and mussel processing contain sulphate ranging from 20 mg.L-1 to 11400 mg.L-1. When these wastewaters are treated in an anaerobic system like prefermentors or anaerobic digesters the sulphate is reduced to sulphide by sulphate reducing bacteria (SRB). The presence of sulphate reduction is not desirable as it may reduce methane yield due to partial substrate utilisation by SRB, causes system toxicity and the production of malodor H2S in the gas phase. In this thesis, the effects of operational conditions on sulphate transformation and assimilation was studied in a laboratory scale anaerobic wastewater treatment system. The laboratory scale system consisted of two reactors the first one a well-mixed fermentor (referred to as an acidogenic reactor) and the second an expanded granular sludge blanket reactor (referred to as a methanogenic reactor) with pH and temperature control. Two sets of studies were performed; in the first set both reactors were connected serially to represent a two-stage high-rate anaerobic treatment system. The system was fed molasses and operated at temperature of 35oC. The acidogenic reactor was controlled at pH of 6 while the methanogenic reactor was controlled at pH of 7.2 by automatic addition of caustic. In the second set of experiments only the first reactor was used to represent a prefermentor and the first stage of the two stage. The reactor was fed with glucose at various concentrations, operated at pH of 6 and temperature of 35oC. Information gained from these studies was encapsulated in a mathematical model to describe sulphate reduction in anaerobic treatment systems. This model was also validated using data generated from the experiments. The experimental study showed that · At low sulphate concentrations of about 250 mg.L-1 and COD concentration of 10,000 mg.L-1 in feed, relatively high percentage (up to 35 %) of produced sulphide was assimilated by biomass, while the rest of the sulphur was distributed as unconverted sulphate, dissolved sulphide, H2S gas and to a lesser extent as metallic sulphide precipitates. · The major electron donor for sulphate reduction in both the acidogenic and the methanogenic reactor was hydrogen gas. Therefore, sulphate reduction not only competed with hydrogen utilising methanogens for the available hydrogen, but also changed the distributions of organic acids, which were directly or indirectly influenced by the H2 partial pressure. · Sulphide concentrations of up to 6.5 mM free hydrogen sulphide) at pH of 7.2 was not inhibitory to methanogens · Sulphate reducing bacteria were able to grow even at a low hydraulic retention time of 1.2 hours in the well-mixed acidogenic reactor. It was estimated that the maximum specific growth rate (m) and half saturation constant (ks) of SRB was 1.31 h-1 and 3.8 mg S.L-1, respectively. These values were higher than those reported in literature. · Sulphate reduction was suppressed at high concentration of carbon in the feed. Accumulation of high concentration of volatile organic acids at high feed-carbon concentrations had little effect on sulphate reduction. However, extent of sulphate reduction had a negative correlation with total concentration of biomass. A non-competitive biomass inhibition function was proposed to model the correlation. From this fit it was estimated that a biomass concentration of about 3300 mg-COD.L-1 will completely inhibit sulphate reduction. · Sulphate reduction was affected by redox potential control and pH in the acidogenic reactor. High pH and low redox potential values were essential for sulphate reduction to proceed. At redox potential control of -300 mV, sulphate reduction was inhibited more at pH of 6 than it was at pH of 7. At redox potential values of -250 mV or higher, about 90 % inhibition of sulphate reduction was observed at both pH of 6 and 7. An existing model describing carbohydrate degradation was extended to include sulphate reduction processes. Despite experimentally observing that sulphate reduction only took place from hydrogen, all possible substrates for sulphate reducion was considered. These included: lactic acid, butyric acid, propionic acid, acetic acid and hydrogen. Kinetic parameters for sulphate reduction processes were obtained from documented literature. Inhibition of sulphate reduction by biomass and sulphur assimilation by biomass were included in the model. A new approach to calculate caustic consumption at given pH values was also included. A modification to hydrogen regulation function was also made to better predict product distributions as a function of gas-phase hydrogen concentration. Model validation was performed using data from dynamic experiments. Comparison to actual data was undertaken on several key variables in the acidogenic and methanogenic reactors such as: organic acid concentrations, gas compositions, gas production rates, sulphate and sulphide concentrations and caustic consumption rates. The model satisfactorily predicted sulphate and sulphide concentrations in both reactors. However, discrepancy between predicted and experimental data on organic carbon concentrations was seen, especially during organic carbon concentration step changes.