Biomedical subjects

S Uyanik

Publications and source records attributed to S Uyanik.

4 recordsLinked to original sources

PubMed2003

Granule development in a split-feed anaerobic baffled reactor.

Operating anaerobic reactors at high organic loading rates during start-up can lead to instability, accumulation of volatile fatty acids and low pH, such problems being exacerbated in reactors that exhibit plug-flow characteristics. Moreover, plug-flow conditions increase the exposure of biomass to any toxic components in the feed. To overcome these limitations, an anaerobic baffled reactor (ABR), a reactor exhibiting partial plug-flow characteristics, was modified by splitting the feed between the individual compartments to produce the split-feed ABR (SFABR). Consequently, more favourable conditions were created in the initial compartments, such as lower, longer hydraulic retention time and longer cell retention time; conditions in the final compartments were also improved by the increased food availability for microorganisms. Other benefits included better gas mixing characteristics as a result of the more balanced gas production across the reactor. Granule development was compared in SFABR and normally fed ABR by analysing sludge samples, taken during start-up and continuous operation, using scanning electron microscopy. Photomicrographs allowed tentative conclusions to be made concerning the effect of split-feeding on the distribution of bacterial populations within the granule architecture and the role of extracellular polymers on granule formation.

Anaerobiosis↗

PubMed2002

The effect of polymer addition on granulation in an anaerobic baffled reactor (ABR). Part I: process performance.

The stability and performance of an anaerobic baffled reactor (ABR) treating an ice-cream wastewater at several organic loading rates have been investigated. Specifically, it was determined whether an ABR would promote phase separation and if a polymer additive was capable of enhancing granule formation in an ABR. In order to achieve these goals, two ABRs, having identical dimensions and configurations, were used to study the above objectives using a synthetic ice-cream wastewater. The ABR proved to be an efficient reactor configuration for the treatment of a high-strength synthetic ice-cream wastewater. An organic loading rate of around 15 kg CODm(-3) d(-1) was treated with a 99% COD removal efficiency. From the jar test and inhibition assay, it was concluded that Kymene SLX-2 was the most effective and least inhibitory polymer tested. The methane yield was higher in the polymer-amended reactor compared to the control reactor. In addition, polymer addition resulted in a considerably higher degree of biomass retention and lower solids washout from the ABR. Consequently, it demonstrated that there was a considerable potential for sludge conditioning in ABRs by facilitating better biomass retention within the reactor which in turn led to better process performance. Granulation was achieved in both ABRs within 3 months. However, the granules from the polymer-amended reactor appeared earlier and were generally larger and more compact, although this was not quantified in detail during the present study. The main advantage of using an ABR comes from its compartmentalised structure. The first compartment of an ABR may act as a buffer zone to all toxic and inhibitory material in the feed thus allowing the later compartments to be loaded with a relatively harmless, balanced and mostly acidified influent. In this respect, the latter compartments would be more likely to support active populations of the relatively sensitive methanogenic bacteria and partly explains why the best granules and the highest methane yield were obtained in Compartment 2. It is unlikely that a complete separation of phases (acidogenic and methanogenic) occurred within the ABRs since methane production was observed in all compartments, although this was low (approximately 40% of all gas composition) in Compartment 1, becoming higher (approximately 70%) in the following compartments.

Bacteria, Anaerobic↗

PubMed2002

The effect of polymer addition on granulation in an anaerobic baffled reactor (ABR). Part II: compartmentalization of bacterial populations.

The microbial ecology of wastewater treatment plants remains one of the least understood aspects in both aerobic and anaerobic systems, despite the fact that both processes are ultimately dependent on an active biomass for operational efficiency. Ultimately, future developments in anaerobic treatment processes will require a much greater understanding of the fundamental relationships between bacterial populations within the biomass if optimum process efficiency is to be fully realised. This study assesses the influence of polymer addition on granule formation within an ABR and compares the ecology of the biomass in each compartment of two ABRs treating ice-cream wastewater. To our knowledge, this is the first reported characterisation of the microbiology of acidogenic and methanogenic bacteria in the individual compartments of an ABR. The polymer-amended reactor contained sludge that had a greater density of anaerobic bacteria and larger and denser granules than the control reactor, indicating that polymer addition possibly contributed to the retention of active biomass within the ABR. The average fraction of autofluorescent methanogens was lower, with 1.5% being in the initial compartments of the ABRs, compared to the last compartment which had 15%, showing that each compartment of an ABR had a unique microbial composition. Partial spatial separation of anaerobic bacteria appeared to have taken place with acidogenic bacteria predominating in the initial compartments and methanogenic bacteria predominating in the final compartments. Scanning electron micrographs have revealed that the dominant bacteria in the initial compartments of the ABR (Compartments 1 and 2) were those which could consume H2/CO2 and formate as substrate, i.e. Methanobrevibacter, Methanococcus, with populations shifting to acetate utilisers, i.e. Methanosaeta, Methanosarcina, in the final compartments (Compartments 3 and 4). In addition, there appeared to be a stratified structure to the bacterial genera present within the granules.

Bacteria, Anaerobic↗

PubMed2002

Improved split feed anaerobic baffled reactor (SFABR) for shorter start-up period and higher process performance.

In this paper, the Split Feed Anaerobic Baffled Reactor (SFABR) is introduced and investigations into the use of modified seed material are described. It was shown that shorter and reliable start-up times could be achieved with SFABR when using improved seed material, even for the treatment of particularly problematic wastewater, i.e. ice-cream wastewater. Scanning electron photo-micrographs (SEM) revealed that granulation process occurs relatively rapidly in the SFABR compared with other reactor configurations, and that the reactor contained a highly mixed population of methanogens in all compartments. The use of polymer-conditioned anaerobic sludge and granular sludge as seed proved advantageous over the use of suspended growth anaerobic sludge, and the "improved" SFABR consequently performed more efficiently and also showed greater stability than the conventional ABR.

Bacteria, Anaerobic↗