Wastes, anaerobic treatment

The anaerobic filter, UASB, and fluidized bed reac tors have all been used for anaerobic treatment of industrial wastes, as each is especially suited for use in anaerobic treatment. Table 25-44 presents results from these applications. 

This process is an extension of the anaerobic treatment of waste diseussed in Chapter 2, and is also similar to the natural process operating in landfill sites, which evolves methane. By treatment of biomass with bacteria in the absence of air a gas rich in methane can be produced a typical digester may produce over 300 m of gas containing over 50% methane per tonne of dry biomass. The economics of biogas generation for use as a fuel are currently unfavourable. The plants that do exist have been built because of the need to treat waste such as sewage sludge. 

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. 

Vidal, G., Jiang, Z.P., Omil, F., Thalasso, F., Mendez, R., and Lema, J.M., Continuous anaerobic treatment of waste-waters containing formaldehyde and urea, Biores. Technol., 70, 283-291, 1999. 

Zoutberg, G.R. and Frankin, R., Anaerobic treatment of chemical and brewery waste water with a new type of anaerobic reactor the Biobed EGSB reactor, Water Sci. Technol., 34, 375-381, 1996. 

Bekker de, P., Jans, T., and Piscaer, P., Anaerobic treatment of formaldehyde containing waste water, in Proc. European Symposium AW, van den Brink, W.J., Ed., November 23-25, 1983, Noordwijkerhout, TNO Corporate Communication Department, The Hague, The Netherlands, pp. 449-463, 1983. 

Silicones are ecologically inert, having no effect on aerobic or anaerobic bacteria. Thus they do not inhibit the biological processes taking place during waste water treatment. 

The most widespread biological application of three-phase fluidization at a commercial scale is in wastewater treatment. Several large scale applications exist for fermentation processes, as well, and, recently, applications in cell culture have been developed. Each of these areas have particular features that make three-phase fluidization particularly well-suited for them Wastewater Treatment. As can be seen in Tables 14a to 14d, numerous examples of the application of three-phase fluidization to waste-water treatment exist. Laboratory studies in the 1970 s were followed by large scale commercial units in the early 1980 s, with aerobic applications preceding anaerobic systems (Heijnen et al., 1989). The technique is well accepted as a viable tool for wastewater treatment for municipal sewage, food process waste streams, and other industrial effluents. Though pure cultures known to degrade a particular waste component are occasionally used (Sreekrishnan et al., 1991 Austermann-Haun et al., 1994 Lazarova et al., 1994), most applications use a mixed culture enriched from a similar waste stream or treatment facility or no inoculation at all (Sanz and Fdez-Polanco, 1990). 

Converti, A., Del Borghi, M., and Ferraiolo, G., Influence of Organic Loading Rate on the Anaerobic Treatment of High Strength Semisynthetic Waste Waters in a Biological Fluidized Bed, Chem. Eng. J., 52 B21 (1993)... 

Heijnen, J. J., Mulder, A., Enger, W., and Hoeks, F., Review on the Application of Anaerobic Fluidized Bed Reactors in Waste-Water Treatment, Chem. Eng. J., 41 B37 (1989)... 

McCarty, P.L., Jens, J.S. and Murdoch, W. (1962) The Significance of Individual Volatile Acids in Anaerobic Treatment. Proceedings of the 17th Purdue Industrial Waste Conference. 

One of the principal challenges to anaerobic treatment is balancing the rates of growth. The acid forming bacteria operate at about 3 times the rate of the methane forming bacteria, and without a balanced microbial population the wastes will turn acidic and all methane production will stop. 

Figure 5. UASB Treatment Train for Tomato and Bean Wastes Note both aerobic and anaerobic treatment streams in sequence.

Elliot, S.E. Jennet, J.C. Rgand, M.C. Anaerobic treatment of S3mthesized organic chemical pharmaceutical wastes. Proceedings of the 33rd Industrial Waste Conference, Purdue University, West Lafayette, IN, 1978 507-514. 

HaU, E.R. Anaerobic treatment of wastewaters in suspended growth and fixed film processes. In Design of Anaerobic Processes for the Treatment of Industrial and Municipal Wastes , Malin, J.F. Pohland, F.G., Eds. Technomics Lancaster, PA, 1992, 41-118. 

Rintala, J. A. Puhakka, J. A. (1994). Anaerobic treatment in pulp- and paper-mill waste management a review. Bioresource Technology, 47, 1-18. 

Geer, R.D. 1978. Predicting the anaerobic degradation of organic chemical pollutants in waste water treatment plants from their electrochemical reduction behavior. In Montana University Joint Water Resources Research Center, Bozeman, MT, Completion Report No. 96... 

In practice, unfixed disperse dyes discharged from spent dyebaths to waste-water treatment plants are easily eliminated by coprecipitation with the sewage sludge and may be anaerobically degraded in the digestion process. 

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