Bioreactor anaerobic-aerobic

Keywords Advanced oxidation-biological processes, Anaerobic-aerobic bacterial process, Azo dyes, Biodegradation, Bioreactor, Decolorization, Integrated processes, Textile wastewater... 

Combined Anaerobic-Aerobic Treatment of Azo Dye-Containing Wastewaters in Bioreactors... 

Acknowledgments The authors gratefully acknowledge Dr. F.P. van der Zee and S. Villaverde (Combined anaerobic-aerobic treatment of azo dyes - a short review of bioreactor studies), whose work was much helpful for us. 

Anaerobic bioreactors have been used since the 1880s to treat wastewaters with large amounts of suspended solids. However, anaerobic reactors are sensitive to toxic pollutants and vulnerable to process upsets, and have been used mainly for municipal sludge digestion. For methane production the sequential metabolism of the anaerobic consortia must be balanced, and the methanogens in particular are vulnerable to process upsets. Recently, anaerobic-aerobic processes (Figure 1.1) have been developed for the mineralization of xenobiotics. These processes take advantage of an anaerobic reactor for the initial reductive dechlorination of polychlorinated compounds or the reduction of nitro substituents to amino substituents. If the reduced compounds are more readily mineralized in an aerobic reactor, an anaerobic-aerobic process is feasible. 

Degradation constant k = 3.2-M/h for anaerobic batch experiment in serum bottles k = 2.4 -M/h for dechlorination in anaerobic batch or continuous bioreactor k = 2.4 -M/h in the sequential anaerobic-aerobic continuous reactor system (Armenante et al. 1999)... 

Del Pozo, R. and Diez, V. (2003). Organic matter removal in combined anaerobic-aerobic fixed-film bioreactors. Water Res. 37, 3561. 

Plum, A. and Rehorek, A. (2005) Strategies for continuous on-line high performance liquid chromatography coupled with diode array detection and electrospray tandem mass spectrometry for process monitoring of sulfonated azo dyes and their intermediates in anaerobic-aerobic bioreactors. J Chrom A, 1084 (1-2), 119-133. 

Some of these preventive and protective measures are described in Mitigation of Landfiii Gas Emissions. Special attention is given to the application of anaerobic, aerobic and semi-aerobic bioreactor landfills for control of landfill gas emission. Different types of biotic systems for the oxidation of methane and trace gases, such as biocovers, biofilters, and biowindows, are also presented. 

Methane has also been used in aerobic bioreactors that are part of a pump-and-treat operation, and toluene and phenol have also been used as co-substrates at the pilot scale (29). Anaerobic reactors have also been developed for treating trichloroethylene. Eor example, Wu and co-workers (30) have developed a successful upflow anaerobic methanogenic bioreactor that converts trichloroethylene and several other halogenated compounds to ethylene. 

There have been numerous communications on the subject of biodegradation test methods, including aerobic compost (30), anaerobic bioreactor (31), general methodology and future directions (32—34), and a fine review article (24). ASTM (22) and MITI (35) have also set forth standard testing protocols for plastics, as shown in Table 2, whereas OECD test methods (29) are more suited to water-soluble polymers. 

A bioreactor is a vessel in which an organism is cultivated and grown in a controlled manner to form the by-product. In some cases specialised organisms are cultivated to produce very specific products such as antibiotics. The laboratory scale of a bioreactor is in the range 2-100 litres, but in commercial processes or in large-scale operation this may be up to 100 m3.4,5 Initially the term fermenter was used to describe these vessels, but in strict teims fermentation is an anaerobic process whereas the major proportion of fermenter uses aerobic conditions. The term bioreactor has been introduced to describe fermentation vessels for growing the microorganisms under aerobic or anaerobic conditions. 

Hybrid (aerobic-anaerobic). The hybrid bioreactor landfill accelerates waste degradation by employing a sequential aerobic-anaerobic treatment to rapidly degrade organics in the upper sections of the landfill and collect gas from lower sections. Operation as a hybrid results in an earlier onset of methanogenesis compared to aerobic landfills. 

Different kinds of bioreactors and configurations have been used to treat wastewater containing formaldehyde and urea, and three different kinds of treatments can be applied anaerobic treatment, aerobic treatment, and combined nitrification and denitrification treatments. 

The significance of this approach is that not only were the wastes treated at a very concentrated level using anaerobic and aerobic treatment, but the removals were extremely good. The implications for enhanced bioremediation suggest that some combination of aerobic and/anaerobic processes where nutrients are applied to the waste site and collected beneath the waste site could turn the entire waste site into an efficient bioreactor. These are interesting possibilities and the possibility of using a flooded system or other top down distribution system which recycles wastes from beneath the contaminated sites and returns it to the surface is an... 

The Bio-FGD process converts sulfur dioxide to sulfur via wet reduction (10). The sulfur dioxide gas and an aqueous solution of sodium hydroxide are contacted in an absorber. The sodium hydroxide reacts with the sulfur dioxide to form sodium sulfite. A sulfate-reducing bacteria converts the sodium sulfite to hydrogen sulfide in an anaerobic biological reactor. In a second bioreactor, the hydrogen sulfide is converted to elemental sulfur by Thiobacilh. The sulfur from the aerobic second reactor is separated from the solution and processed as a sulfur cake or liquid. The process, developed by Paques BV and Hoogovens Technical Services Energy and Environment BV, can achieve 98% sulfur recovery. This process is similar to the Thiopaq Bioscrubber process for hydrogen sulfide removal offered by Paques. 

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