Biofilm Fixed Film Systems | Sewage Treatment

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  Water    2011 , 3 , 843-868; doi:10.3390/w3030843 water  ISSN 2073-4441  Review Biofilm Fixed Film Systems Harvey Gullicks 1, *, Hasibul Hasan 1 , Dipesh Das 1 , Charles Moretti 1  and Yung-Tse Hung 2   1 Department of Civil Engineering, University of North Dakota, Grand Forks, ND 58202, USA; E-Mails: (H.H.); (D.D.); (C.M.) 2 Department of Civil and Environmental Engineering, Cleveland State University, Cleveland, OH 44115, USA; E-Mail: * Author to whom correspondence should be addressed; E-Mail:; Tel.: +1-701-777-3779; Fax: +1-701-777-3782.   Received: 31 May 2011; in revised form: 12 July 2011 / Accepted: 31 August 2011 /  Published: 9 September 2011 Abstract:  The work reviewed here was published between 2008 and 2010 and describes research that involved aerobic and anoxic biofilm treatment of water pollutants. Biofilm denitrification systems are covered when appropriate. References catalogued here are divided on the basis of fundamental research area or reactor types. Fundamental research into biofilms is presented in two sections, Biofilm Measurement and Characterization and Growth and Modeling. The reactor types covered are: trickling filters, rotating biological contactors, fluidized bed bioreactors, submerged bed biofilm reactors, biological granular activated carbon, membrane bioreactors, and immobilized cell reactors. Innovative reactors, not easily classified, are then presented, followed by a section on biofilms on sand, soil and sediment. Keywords:  biofilm; wastewater treatment systems; fixed film models; trickling filters;  biotowers; rotating biological contactors; biomembrane processes; submerged fixed film; xenobiotics; nutrient removal; nitrification; denitrification; biological phosphorus removal; extracellular polymeric substances OPEN ACCESS   Water    2011 , 3   844 1. Introduction  The scope of research in the area of biofilm fixed film systems continues to expand beyond the traditional trickling filters, biotowers, and rotating biological contactors (RBCs) into biofilm measurement and characterization methods, growth and modeling, new biofilm growth media, innovative bioreactors (including various membrane bioreactors and hybrid reactors), fixed-film xenobiotics removal, bioelectricy generation, and the roles of biofilms to remove nutrients and recalcitrant contaminants in the natural environment. Biofilm fixed film systems will continue to have relevance in the treatment of wastewater as technological advances, such as membrane bioreactors and their hybrids, evolve. Natural biofilm attenuation, accumulation and destruction of nutrients,  pharmaceuticals and personal care products (PPCPs), and recalcitrant contaminants may open up new applications of biofilm systems. 2. Biofilm Measurement and Characterization 2.1. Sensors and Microsensors Downing and Nerenberg [1,2] used microsensors to measure nitrogen forms produced by biofilms on aerated submerged membranes. They also used fluorescence in situ  hybridization (FISH) tests on  biofilm to reveal three distinct biofilm regions: ammonia-oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) near the membrane, strictly AOB at intermediate biofilm depth and AOB and heterotrophs near the outer biofilm/bulk liquid interface. McLamore et al.  [3] used noninvasive, microsensor techniques to quantify real time changes in oxygen and proton flux for Nitrosomonas europaea and Pseudomonas aeruginosa biofilms following exposure to environmental toxins in membrane-aerated bioreactors. 2.2. Biofilm Attachment and Detachment Biofilm formation and adherence properties of 13 bacterial strains commonly found in wastewater treatment systems were studied by Andersson et al.  [4]. Four different culture media were used and it was found that the medium composition strongly affected biofilm formation. Adherence properties of  pure and multi-strain biofilms were assessed. Strongest biofilm formation was observed when mixtures of all 13 bacteria were grown together. Bacterial biofilm development in tertiary treatment processes was characterized by molecular biological methods by Shoji et al.  [5]. Low assimilable organic carbon hindered heterotrophic bacteria and favored autotrophs and oligotrophs. Ammonia load affected the two dominant Nitrospirae-related (nitrite oxidizing) and Acidobacteria-related (oligotrophic) bacteria species and their ratio in biofilm more than other operational conditions. Roeselers et al.  [6] reported that a matrix of substances secreted by phototrophs and heterotrophs enhances the attachment of  biofilm community. Jechalke, et al.  [7] studied biofilm development on coconut fibers and polypropylene textiles for enhancing biodegradation of low-concentration methyl tert-butyl ether (MTBE), benzene, and ammonium from groundwater in aerated treatment ponds. Coconut fibers were more effective biofilm support media than polypropylene textiles for recruitment and development of biofilms for MTBE  Water    2011 , 3   845 degradation. Benzene metabolizing bacteria biofilms did not exhibit a preference for one support medium over the other. Confocal laser scanning microscopy (CLSM) and denaturing gradient gel electrophoresis (DGGE) techniques were used to study the microbial community and structure in the biofilm. 2.3. Microscopy Guzzon et al.  [8] performed elemental analysis by energy filtering transmission electron microscopy to show subcellular localization of phosphorus and confirm the accumulation in  phototrophic microorganisms in biofilms grown in high light conditions. Tian et al.  [9] conducted research on integrative membrane coagulation adsorption bioreactors (MCABR) for the purpose of removal of organic matter, including biodegradable dissolved organic carbon (BDOC), assimilable organic carbon (AOC), and disinfection byproducts. Biofilm on the membrane provided additional rejection of dissolved organic matter, and the biofouling of the membrane was observed using scanning electron microscopy (SEM) in conjunction with CLSM. Biofouling of membranes by river waters containing BDOC was also studied by Marconnet et al  . [10]. Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy and CLSM were used to determine the composition and organization of the biofilm fouling on the membrane. 2.4. Novel Techniques Increased popularity of attached-growth wastewater treatment systems (e.g., biological aerated filtration processes-BAF and various hybrids of membrane biological reactors-MBR) has created the need for a rapid and reliable method of characterizing biofilms. Spettmann et al.  [11] used fluorescently labeled foulants filtered through and deposited on a polyethersulfone ultrafiltration membrane to study the fouling from inorganic salt precipitants, polysaccharides, organic and inorganic  particles, and microbial biofilms. CLSM in conjunction with image analysis allowed three-dimensional visualization of the three-dimensional distribution of fluorescently labeled foulants in multi-layered deposits and cleaning or deposit removal efficiency evaluation. Fluorochrome stains, CLSM, and an image analysis program were similarly used by Bjerkey and Fiksdal [12] to study biofilm structure on curved membrane surfaces, such as hollow fiber membranes. Thickness, volume of biomass, porosity, and roughness of biofilms were calculated. Delatolla et al.  [13] described a simple, rapid, and reliable technical procedure that enabled biofilm samples attached to polystyrene beads to be characterized in terms of the biofilm mass and nitrogen content and proposed a protocol that demonstrated 99.9% removal of the biofilm from polystyrene  beads. The application of molecular techniques to the study of wastewater treatment systems by Wojnowska-Baryla et al.  [14] suggested that microbial groups may be organized in various spatial structures such as activated sludge flocs, biofilm or granules and represented by single coherent  phylogenic groups such as ammonia-oxidizing bacteria (AOB) and polyphosphate-accumulating organisms (PAO). The microbial community structure of biomembrane in biological contact oxidation  packing was analyzed by He et al.  [15] to assess growth of the biomembrane and mechanisms of the water purification process using 16S rDNA and amoA gene based amplification and denaturing gradient gel electrophoresis (PCR-DGGE).  Water    2011 , 3   846 2.5. Extracellular Polymeric Substances (EPS) During the past decade, biofilm reactors have been successfully applied for production of many value added products, often because of EPS. Advances in biofilm reactors were investigated by Cheng et al.  [16], and biofilm reactors with novel applications and designs were summarized in a review. Phototrophic biofilm samples from a wastewater treatment plant were studied by Di Pippo et al.  [17] in microcosm experiments under varying irradiances, temperatures and flow regimes to assess the effects of environmental variables and phototrophic biomass on capsular exopolysaccharides (CPS). The results suggested that CPS have a stable spatial conformation and a complex monosaccharide composition. They noted the potential of cyanobacteria and diatoms in removal of residual nutrients and noxious cations. Avella et al.  [18] examined three paper mill wastewater treatment plant (WWTP) sludge flocs using size exclusion chromatography and CLSM observations and identified that a sludge with good settling characteristics involved an important EPS production in the presence of nitrification and phosphate nutrient. The other two sludges had poor settling properties and the EPS production was weak. Although these sludges were from activated sludge WWTPs, this suggests that EPS production may have importance to a wide range of WWTP processes. 2.6. Metal and Radionucleotide Sorption Lin et al.  [19] derived a biodegradation model for anaerobic fixed-biofilm reactor simultaneous removal of phenol with chromium (VI) reduction. The model, based on diffusive mass transfer and double Monod kinetics, was tested against a laboratory column reactor and showed close agreement. 2.7. Ammonia Removal  Nitrification processes have served as an important basis for the development of today’s understanding and mathematical models for many wastewater treatment processes (activated sludge,  biofilm reactors) and self-purification processes in rivers, in the view of Gujer [20]. Redundancy analysis demonstration of the relevance of the temperature to ammonia oxidizing was investigated  by Park et al.  [21] and temperature was more significant than salt concentration effects on AOB compositions and dynamics. 2.8. Microbial Community Structure In order to monitor and control engineered microbial structure in wastewater treatment systems, it is necessary to understand the relationships between the microbial community structure and the process  performance. The review by Wojnowska-Baryla et al.  [14] focused on bacterial communities in wastewater treatment processes, the quantity of microorganisms and structure of microbial consortia in wastewater treatment bioreactors. The study by Weber et al.  [22] on the diversity of fungi in aerobic sewage granules by gene sequence analysis suggested that fungal community composition in granules depended on the wastewater type and the phase of granule development. Potential of biofilm-based biofuel production was investigated by Wang and Chen [23]. Biofilm advantages include cell-associated hydrolytic enzymes concentration at the biofilm-substrate interface
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