Biofilm aerobic

Biofihn concentrations attached onto the surface of the sands and gravels in the aerobic tank were measured at 120 different location of the constructed wetland at different times (6 months, 12 months, 18 months and 24 months). The concentrations of the biofilm increased continuously upto 6 month operation, but thereafter remained almost imchanged upto 24 months. Figure 7 and 8 show the concentrations and distributions of biofilms attached onto the the surface of the sands and gravels of the aerobic tank, respectively. The attached biofilm was well distributed over the aerobic tank, and the total volume of the attached biofilm occupied just about 0.5% of the initial void volume of the aerobic tank. 

SRB, a diverse group of anaerobic bacteria isolated from a variety of environments, use sulfate in the absence of oxygen as the terminal electron acceptor in respiration. During biofilm formation, if the aerobic respiration rate within a biofilm is greater than the oxygen diffusion rate, the metal/biofilm interface can become anaerobic and provide a niche for sulfide production by SRB. The critical thickness of the biofilm required to produce anaerobie conditions depends on the availability of oxygen and the rate of respiration. The corrosion rate of iron and copper alloys in the presence of hydrogen sulfide is accelerated by the formation of iron sulfide minerals that stimulate the cathodic reaction. 

N. J. E. Dowling, J. Guezennec, and D. C. White. Facilitation of corrosion of stainless steel exposed to aerobic seawater by microbial biofilms containing both facultative and absolute anaerobes. In Proceedings Volume. Inst Petrol Microbiol Comm Microbial Problems in the Offshore Oil Ind Int Conf (Aberdeen, Scotland, 4/15-4/17), 1986. 

Case 3 Leachate Treatment Using an Aerobic Biofilm Reactor. 583... 

The use of an attached growth aerobic biofilm reactor to treat leachate is relatively new. Past studies on anaerobic biofilters showed excellent organic removal up to 90%, and the retention time needed to treat high-strength effluent was between 3 and 5 d. The use of aerobic biofilters using... 

Idris, A. and Abdullah, A.G.L., Leachate Treatment Using Aerobic Biofilm Reactor, Proc. JSPS-VCC Seminar on Water Resource Management, Kota Kinabalu, Malaysia, 2001. 

Kryst K, Karamanev DG (2001) Aerobic phenol biodegradation in an inverse fluidized-bed biofilm reactor. Ind Eng Chem Res 40 5436—5439... 

Particle sizes used for aerobic waste treatment generally range from 100-1000 pm in size, with most being less than 500 pm in diameter, and reported biofilm thicknesses range from 40-1200 pm, with 100-200 pm being typical (Fan, 1989). 

Mass transfer considerations are critical in any bioprocess. In typical, aerobic, suspended cell fermentations, the major concern is the oxygen transfer rate, determined by the overall mass transfer coefficient, kft, and the driving force. In three-phase biofluidization, in which the cells are immobilized as a biofilm or within carrier particles, the situation is further complicated by possible intraparticle diffusion limitations. Numerous recent studies have addressed these issues. 

Ryhiner, G., Petrozzi, S., and Dunn, I. J., Operation of a Three-Phase Biofilm Fluidized Sand Bed Reactor for Aerobic Wastewater Treatment, ... 

Chemical weathering of minerals during pedogenesis can be enhanced by microbial activity by a factor as high as 106 (Kurek 2002). Microorganisms can dissolve minerals by direct and indirect actions under aerobic and anaerobic conditions (Robert and Berthelin 1986 Ehrlich 2002 Kurek 2002). In some cases of attack, the microorganisms may be dispersed in the soil solution in others, they may grow in biofilms on the surface of susceptible minerals. 

Aerobic activated sludge granules (spherical biofilms)... 

Weber SD, Ludwig W, Schleifer KH, Fried J (2007) Microbial composition and structure of aerobic granular sewage biofilms. Appl Env Microbiol 73 6233-6240... 

Coughlin MF, Kinkle BK, Bishop PL (2002) Degradation of Acid Orange 7 in an aerobic biofilm. Chemosphere 46 11-19... 

Mixed liquor from a municipal WW treatment plant Acid orange 8 Acid orange 10 Acid red 14 Rotating drum biofilm reactor Continuous Aerobic B Drum 22 7... 

Activated sludge from a municipal WW treatment plant Acid orange 7 Rotating drum biofilm Batch and continuous Aerobic B Drum 15-50 25 7.7-8... 

The role of cell respiration has been taken into account to interpret the azo-dye conversion by particle-supported biofilm under aerobic conditions [5, 24]. The rapid depletion of oxygen expected/measured as one moves inside the biofilm promotes the establishment of the anoxic conditions needed for azo-dye conversion. 

Results suggest that the biofilm was stable over 2 months. The microorganism appeared vital and active even after repeated cyclic exposure to anaerobic conditions. In fact, phenol uptake measured was always recorded as soon as aerobic conditions were established. A slight increase of the phenol concentration was... 

Fig. 6 Acid orange 7 and phenol concentration in the internal loop airlift reactor operated with Pseudomonas sp. 0X1 biofilm on natural pumice. (A) Aerobic phase. Gas air. Liquid continuous feeding of phenol supplemented synthetic medium. (AN) Anaerobic phase. Gas nitrogen. Liquid batch conditions, dye supplemented medium...

A dynamic model has been developed to simulate the behavior of a Pseudomonas sp. 0X1 biofilm reactor for phenol and azo-dye conversion during the aerobic-anaerobic cyclic operation. Phenol and oxygen were considered as the limiting substrates for growth kinetics. 

Aerobic phase Steady state values of phenol concentration (40 mg/L) and biofilm thickness (170 pm) were approached after a 5 h transient period, which reproduces fairly well the experimental dynamical patterns reported in Fig. 6. However, biomass was present also in the liquid phase as a consequence of biofilm detachment. 

Jiang H, Bishop PL (1994) Aerobic biodegradation of azo dyes in biofilms. Water Sci Technol 29 525-530... 

As stated earlier, the biodegradation of azo dyes requires an anaerobic and aerobic phase for the complete mineralization. The required condition can be implemented either by spatial separation of the two sludge using a sequential anaerobic-aerobic reactor system or in one reactor in the so-called integrated anaerobic-aerobic reactor system. In recent years, combined anaerobic-aerobic treatment technologies are extensively applied in the treatment of azo dye-containing wastewaters. Table 1 lists the systems based on combined anaerobic-aerobic treatment in separate reactors. Table 2 lists SBR based on temporal separation of the anaerobic and the aerobic phase. Table 3 lists the other systems, either hybrids with aerated zones or micro-aerobic systems based on the principle of limited oxygen diffuse in microbial biofilms [91]. 

Coughlin MF, Kinkle BK, Tepper A, Bishop PL (1997) Characterization of aerobic azo dyedegrading bacteria and their activity in biofilms. Water Sci Tech 36 215-220... 

A 4 km intercepting sewer with diameter D = 0.5 m is flowing half full. The DO consumption rate, rf, of the sewer biofilm is measured, and an average value of 0.6 g02 m-2 h-1 was estimated. The biofilm yield constant of the heterotrophic biomass was not measured but was estimated as Yf= 0.55 gCOD biomass produced per gCOD substrate consumed. Only aerobic heterotrophic transformations in the biofilm are expected to proceed. 

A prerequisite condition for the validity of this result is that only aerobic microbial processes proceed. If anaerobic processes take place in the inner part of the biofilm, a reduction in the biomass production will take place, for example, see comments related to Figure 6.2. 

---