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Sludge Reactors (sludge + reactor)
Selected AbstractsTrace Metals in Anaerobic Granular Sludge Reactors: Bioavailability and Dosing StrategiesENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 3 2006H. Zandvoort Abstract The trace metal dynamics in anaerobic granular sludge bed reactors and their influence on reactor performance is reviewed in this paper. An insight into the metal dynamics is required from a practical point of view in order to be able to early recognize limitations for essential trace elements, viz., to know when dosing of these elements is required in full-scale anaerobic bioreactor applications. Further such knowledge is indispensable for a rational dosage of these metals, e.g., to ensure maximum substrate conversion rates and to prevent disturbances in reactor performance using a minimum amount of metals. Therefore, the retention, accumulation and release of trace metals in anaerobic granular sludge and the factors affecting these processes need to be known. [source] Development of a correlation to study parameters affecting nitrification in a domestic wastewater treatment plantJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 3 2008Gulnur Coskuner Abstract BACKGROUND: Nitrification performance of an activated sludge reactor treating weak domestic wastewater was investigated for 11 months. Ammonia nitrogen removals were investigated as a function of wastewater composition and operational conditions. Backward elimination experimental design was used to determine the influence of the most important independent variables on NH3 -N removal efficiencies. Influent ammonia and biological oxygen demand (BOD5) concentrations, hydraulic retention time (HRT), mixed liquid suspended solids (MLSS), temperature, pH and dissolved oxygen (DO) concentration were considered as independent variables. This study aimed to find the most important parameters to describe nitrification performance. RESULTS: The presence of nitrification was confirmed by ammonia and nitrate variations throughout the reactor; ammonia oxidizing bacteria (AOB) populations were determined using a fluorescence in situ hybridization (FISH) method. MLSS concentration, influent BOD5 concentration and temperature were found to be the most influential factors on nitrification performance. The empirical correlation using multiple linear regressions was statistically significant and produced an adjusted coefficient of multiple determinations (R2adj) of 92.5%. CONCLUSION: Correlation provides a good understanding of the various parameters that affect the nitrification process, and could be extended to other case studies. Using these results, operators can apply proper operational strategies to maintain nitrification in wastewater treatment plants. Copyright © 2007 Society of Chemical Industry [source] Microscopic observation of aerobic granulation in sequential aerobic sludge blanket reactorJOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2001J.-H. Tay Aims: This paper attempts to provide visual evidence of how aerobic granulation evolves in sequential aerobic sludge blanket reactors. Methods and Results: A series of experiments were conducted in two column-type sequential aerobic sludge reactors fed with glucose and acetate as sole carbon source, respectively. The evolution of aerobic granulation was monitored using image analysis and optical and scanning electron microscopy. The results indicated that the formation of aerobic granules was a gradual process from seed sludge to compact aggregates, further to granular sludge and finally to mature granules with the sequential operation proceeding. Glucose- and acetate-fed granules have comparable characteristics in terms of settling velocity, size, shape, biomass density and microbial activity. However, the microbial diversity of the granules was associated with the carbon source supplied. In this work, an important aerobic starvation phase was identified during sequential operation cycles. It was found that periodical aerobic starvation was an effective trigger for microbial aggregation in the reactor and further strengthened cell,cell interaction to form dense aggregates, which was an essential step of granulation. The periodical starvation-induced aggregates would finally be shaped to granules by hydrodynamic shear and flow. Conclusions: Aerobic granules can be formed within 3 weeks in the systems. The periodical starvation and hydrodynamic conditions would play a crucial role in the granulation process. Significance and Impact of the Study: Aerobic granules have excellent physical characteristics as compared with conventional activated sludge flocs. This research could be helpful for the development of an aerobic granule-based novel type of reactor for handling high strength organic wastewater. [source] Effect of activation type on bioregeneration of various activated carbons loaded with phenolJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 7 2006Özgür Akta Abstract Thermally and chemically activated powdered carbons (PAC), and their granular countertypes (GAC) with similar physical characteristics were used to investigate the extent of bioregeneration in laboratory-scale activated sludge reactors. Bioregeneration of activated carbon was determined by measurement of bulk phenol concentrations and loadings remaining on activated carbon. It was also followed by oxygen uptake rate measurements. For the carbons used in this study, bioregeneration of chemically activated carbons was found to be higher than thermally activated ones. This was in accordance with their higher reversibility of adsorption and showed that bioregeneration was controlled by the reversibility of adsorption. Oxidative polymerization of phenol was a plausible explanation for low bioregeneration of thermally activated carbons. However, bioregeneration efficiencies of thermally activated carbons were much higher than their total desorbabilities. This unexpectedly high bioregeneration indicated that some exoenzymatic reactions had occurred. These results suggest that carbon activation type is of crucial importance for bioregeneration. PAC and GAC countertypes showed comparable bioregeneration efficiencies indicating that carbon size was not an effective factor. The environmental scanning electron microscopy (ESEM) studies showed that microorganisms were attached both on the external surface and interval cavities of activated carbon particles. Copyright © 2006 Society of Chemical Industry [source] Addition of activated carbon to batch activated sludge reactors in the treatment of landfill leachate and domestic wastewaterJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 8 2001Özgür Akta Abstract Leachate from a municipal landfill was combined with domestic wastewater and was treated in batch activated sludge systems. The effectiveness and applicability of the addition of Powdered Activated Carbon (PAC) to activated sludge reactors was investigated. Isotherm tests were carried out with PAC in order to estimate the extent of adsorption of organic matter onto PAC. Then, in activated sludge reactors COD (Chemical Oxygen Demand) removal and nitrification were studied both in the absence and presence of PAC for comparison purposes. In both cases, Oxygen Uptake Rates (OUR) were measured with respect to time in order to investigate substrate removal and change in microbial activity. Addition of PAC to activated sludge increased COD removal by removing mainly the non-biodegradable fraction in leachate. The COD decreases in batch reactors were best expressed by a first-order kinetic model that incorporated this non-biodegradable leachate fraction. With added PAC, nitrification was also enhanced. But in all of the batch runs a significant accumulation of NO2 -N took place, indicating that the second step of nitrification was still inhibited. © 2001 Society of Chemical Industry [source] | ||||||||||