The anaerobic methane fermentation process has long been used in the field of wastewater engineering in sludge processing, mainly for waste stabilization and solids reduction. Recently, major advances in the fundamental understanding of the process microbiology and biochemistry, along with the development of new reactor configurations have promoted a resurgence of interest in the use of this technology for the processing of liquid industrial and municipal wastewaters. Three of these new processes, the anaerobic filter, expanded/fluidized bed, and upflow anaerobic sludge blanket, are discussed.Each of these processes is a fixed film process, which enables the attainment of high solids retention times for good system efficiency and stability, with low hydraulic retention times for system economy. Fixed film anaerobic processes are able to realize many of the benefits of anaerobic processes while overcoming many of the problems historically associated with anaerobic processes.Each of the processes is described, and examples are presented for industrial and municipal applications. Finally, the processes are qualitatively compared. At present, it is not possible to say which reactor configuration is best. In fact, the selection is often dependent on wastewater characteristics, local factors, and several other factors. More full-scale data and operating experience along with basic research needs are needed to clarify further this situation, and to design these systems optimally.
"For larger plants, the combined unit is expected to be feasible only, if the discharge limits are strict so that tertiary treatment may be necessary in case of using conventional primary treatment. The important factors that should be studied in pilot-scale flocculation facilities are the appropriate chemical dose, the effect of mixing energy and the effect of mixing time, which are achieved experimentally using the jar test  . Chemical coagulants that are commonly used in wastewater treatment include alum (A1 2 (SO 4 ) 3 AE18H 2 O), ferric chloride ( "
[Show abstract][Hide abstract] ABSTRACT: The potentials of using the hydraulic technique in combined unit for municipal wastewater treatment were studied. A combined unit in which processes of coagulation, flocculation and sedimentation, has been designed utilizing hydraulic mixing instead of mechanical mixing. A jar test treatability study has been conducted to locate the optimum dose of the coagulants to be used. Alum, ferrous sulfate, ferric sulfate, a mixture of ferric and ferrous sulfates, and mixture of lime and ferrous sulfate were all tested. A pilot unit was constructed in the existing wastewater treatment plant at El Mansoura governorate located in north Egypt. The optimum dose of coagulants used in the combined unit gives removal efficiencies for COD, BOD, and total phosphorous as 65%, 55%, and 83%, respectively.
Journal of Advanced Research 10/2012; 3(4):331–336. DOI:10.1016/j.jare.2011.10.004
"Compiled from Lettinga et al. (1980), Switzembaum (1983), Fox and Pohland (1994), Lettinga (1995), Rebac et al. (1997), Zoutberg and De Been (1997), Kroiss and Svardal (1999) and Verstraete et al. (2002). soluble organic matter, being adversely impacted by the presence of high concentrations of influent suspended solids (Grin et al., 1985; de Man et al., 1986; Sayed, 1987; Mahmoud, 2002). "
[Show abstract][Hide abstract] ABSTRACT: This study presents a literature review on the treatment of domestic sewage in controlled environments having the anaerobic process and specifically the upflow anaerobic sludge blanket (UASB) concept as the core, under natural hot conditions. The UASB process application is however beset by the preponderance of suspended solids, and the paper looks at its optimization via pre- and post-treatments to curb the prevailing problems, in the light of possible discharge and re-use/recycling/resource recovery, leading to efficient environmental protection. Pre-treatment clarification could be done with ferric chloride/polyelectrolyte, so that phosphate precipitates during the process. The pre-treated liquid phase can be submitted to a high rate anaerobic process, using the simple and robust UASB technology. In a subsequent post-treatment step, ammonium can be removed by ion exchange using a zeolite column through which the wastewater percolates after leaving the anaerobic digester. The various stages can also eliminate a large fraction of the pathogens present in the raw wastewater, mainly through the pre-treatment sedimentation and the ion exchange filtration. The sludge produced in the precipitation stage can be stabilized in a conventional anaerobic digester. Integration of the different treatment steps provides a sustainable technology to treat domestic sewage under hot climate conditions.
"In spite of both adverse incidents, removals of chlorophenols remained extraordinarily high. Also, this is a strong recommendation to FBBR as reactor configuration for its robustness and resistance to adverse episodes (Iza, 1991; Switzenbaum, 1983; Zárate- Segura et al., 2004). "
[Show abstract][Hide abstract] ABSTRACT: A fluidized bed bioreactor (FBBR) was operated for more than 1000 days under two regimes, Methanogenic (M) and Methanogenic-Aerobic (M-A), to remove 2,4,6-trichlorophenol (TCP) and phenol (Phe) from a synthetic wastewater, containing different amounts of TCP and Phe, using different aeration flow-rates (0, 2.13, and 1.06 NL O(2)/L.day). M conditions (80:20 mg/L of TCP:Phe, 0 NL O(2)/L.day) showed similar TCP and Phe removal (>95%). Nevertheless accumulation of 4-chlorophenol (4CP) up to 16 mg/L and Phe up to 4 mg/L was observed, while in M-A conditions (80:20 mg/L of TCP:Phe, 2.13 NL O(2)/L.day) TCP and Phe removal achieved 99.9(+)% and after 70 days no accumulation of intermediates were detected. The increase of TCP and Phe in the influent under M-A conditions from 80:20 to 120:30 mg/L of TCP:Phe did not negatively affect the removal of TCP, intermediates and Phe; in fact, they were similar to those in previous M-A conditions. The decrease in the oxygen flow rate from 2.13 to 1.06 NL O(2)/L.day had no negative effect on pollutant removals, which were as high as in previous two M-A conditions. The specific methanogenic activity of bioparticles of the fluidized bed decreased with long-term partial aeration, starting from 1.097 mmol CH(4)/h.g(TKN) in the M regime (day 60) to <0.02 mmolCH(4)/h.g(TKN) at day 1050, suggesting aerobic regime in the bioreactor rather than an M-A regime. In conclusion, complete removal of TCP and less chlorinated intermediates could be achieved in an initially methanogenic FBBR under conditions of partial aeration, although long-term operation seemed to negatively affect the methanogenic activity of biomass. It is also likely that after extended aeration the microbial community was finally enriched with strains with the ability to attack 2,4,6-TCP under aerobic conditions. This report represents the first evidence of a long exposure to oxygen of an anaerobic microbial consortium that efficiently remove TCP.
Biotechnology and Bioengineering 08/2006; 94(5):949-60. DOI:10.1002/bit.20918 · 4.13 Impact Factor
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