Biological Fixed Film
Transcript of Biological Fixed Film
1060 Water Environment Research, Volume 85, Number 10—Copyright © 2013 Water Environment Federation
Biological Fixed Film
Jeongdong Choi, Md. Shahinoor Islam, Fahmida Tumpa, Yang Liu*
ABSTRACT: The review includes literature published
during the year 2012 regarding the use of biofilms and
bioreactors to treat wastewater. Topics considered are:
biofilm formation and factors that impact biofilm
formation; extracellular polymeric substance and its
extraction from biofilms; biofilm consortia and quorum
sensing; biofilm imaging techniques; biofilm reactors and
modeling.
KEYWORDS: biofilm, biofilm reactors, Extracellular
polymeric substance, biofilm carrier and wastewater.
doi: 10.2175/106143013X13698672321904
Introduction
Overview. This review focuses on aerobic
biological fixed film systems used for the purpose of water
and wastewater treatment. Research related to medical and
dental biofilms, biofilms for the treatment of air pollution,
*Department of Civil & Environmental Engineering,
Markin/CNRL Natural Resources Engineering Facility,
University of Alberta, Edmonton, AB T6G 2W2, Canada;
*Corresponding author phone: 780-492-5515; Fax. 780-492-
0249; E-mail: [email protected]
and biofilms in the natural environment has not been
included.
Organization and Coverage. The review has
two sections. (1) Biofilms-biofilm formation and impact of
parameters such as shear stress, surface properties,
nutrients, and bioaugmentation; extracellular polymeric
substances (EPS) and EPS extraction from biofilms;
biofilm consortia and quorum sensing (QS); and; biofilm
imaging and characterization. (2) Biofilm Reactors—
biofilm carriers; types of reactors and various
configurations of biofilm reactors; reactor performance for
wastewater treatment, and reactor comparisons.
1. Biofilms
Biofilm Formation and Impact Parameters
Bacterial Adhesion to Surfaces. By correlating
the initial adhesion kinetics parameter with surface tension
data, the optimal condition for the immobilization of
Pseudomonas putida mt2 was determined to be 24.7 mN/m
by Montag et al. (2012). Higher optimal surface tensions
(known as hydrophilic) could reduce adhesion by creating
an exclusion zone, with highly ordered water structure
close to the surface and lower surface tension than optimal
(commonly termed hydrophobic), and inhibiting the
adhesion by making a depletion thin layer.
Peixoto and Pinto (2012) studied biofilm growth
and hydrodynamic behaviour in a biological plate tower
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(BPT) with scale-up modification, with and without the
hanging biomass (BPT-HB). After some physical
alteration, several testing results concluded the BPT-HB
with concurrent flow rates to be the best option from a
hydrodynamic point of view.
Stewart et al. (2012) examined the ability of
Legionella pneumophila, along with other types of aquatic
bacteria, to persist under dynamic flow conditions in a
bioreactor having a steel surface and with minimal
nutrients. Other bacteria, Klebsiella pneumoniaem,
Flavobacterium sp. and Pseudomonas fluorescens
promoted the existence of L. pneumophila in these dynamic
biofilms. In contrast, this species could not persist within
the biofilm formed by Pseudomonas aeruginosa, reportedly
because some bacteria encourage persistance while some
are antagonistic. Doiron et al. (2012) studied the dynamic
approaches of mixed-species biofilm formation. Interaction
between bacteria and diatoms in biofilms was investigated
using Pseudoalteromonas sp. and two benthic diatoms
(Amphora coffeaeormis and Cylindrotheca closterium).
They concluded the attachment and growth evolution in
biofilm formation to be dependent on each species of
diatoms in biofilms.
Kim, Park, et al. (2012) reviewed microfluidic
approaches to bacterial biofilm formation. Gene expression,
environmental conditions, medium characteristics, or a
combination of factors may influence biofilm formation
and may be addressed using approaches to control
hydrodynamic conditions, stabilize chemical gradients,
monitor in real-time, as well as create in vivo like in vitro
culture devices.
Mitra et al. (2012) investigated the impact on
riboflavin production of surface attachment of Candida
famata and aeration, and used polymethylmethacrylate
(PMMA) conico-cylindrical flasks (CCF) with hydrophobic
surfaces (PMMA-CCF) or hydrophilic glass surfaces (GS-
CCF), and Erlenmeyer flasks (EF) for comparison. The
results showed that riboflavin production increased with
increments in aeration and that earlier maturity of a well-
developed biofilm was observed on GS-CCF compared to
PMMA-CCF. The hydrophilic surface, aeration, biofilm
formation, and riboflavin production were all strongly
related.
Staphylococcus biofilm formation and antibiotic
susceptibility tests were conducted on polystyrene and
metal surfaces by Coraca-Huber et al. (2012). The authors
found biofilm growth in all models and that gentamicin and
rifampicin were the most effective inhibitors. They
recommended an MBEC (TM)-HTP assay for rapid testing
of multiple substances and TMZF (R) CrCo discs for
limited-number antibiotic susceptibility tests and for
microscopic analysis. A study conducted by Miller et al.
(2012) determined the effectiveness of using polydopamine
and polydopamine-g-poly (ethylene glycol) for membrane
modification to avoid biofouling. Short-term adhesion tests
were performed under a static no-flow condition using
bovine serum albumin and Pseudomonas aeruginosa (a
common gram-negative bacteria). Biofouling testing with
the modified membranes and spacers for a short-terra
adhesion test showed significant adhesion reduction, while
the longer biofouling experiments resulted in no reduction
in biofouling.
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Impact of Shear Stress. Hassan et al. (2012)
studied the effect of shear and roughness for reducing the
attachment of Oscillatoria sp. algal filament onto stainless
steel (SS314) coupons. From this study it was shown that
an increase in the average surface roughness would
increase the algae deposition, and the opposite would
happen for increasing the shear.
Paul et al. (2012) found an exponential and
asymptotic decrease in biofilm thickness and mass, and an
increase in density with increments in shear stress. At any
cultural condition, a basal layer resisted the high shear
stress. Compression prevailed for the basal layers, whereas
detachment prevailed for the upper part of the biofilm. The
impact of flow velocity, substrate concentration and
hydraulic cleaning on biofouling in the reverse osmosis
process was studied by Radu et al. (2012). Higher liquid
velocity lessened the biofilm concentration by the
increasing shear stress. With an increased biofilm
thickness, the increased substrate consumption rate led to a
decreased substrate concentration in the biofilm.
To control thick, dense biofilm by combining
hydrodynamic and enzymatic treatments, Pechaud et al.
(2012) grew thick, mainly aerobic heterotrophic, biofilm on
plastic plates in a Couette-Taylor reactor (CTR) using a
paper-industry white water sample. A constant high
COD/N ratio, well-defined shear stress, and external
aeration were maintained leading to well-controlled growth
ratio (G) and gamma values. Combined treatment allowed
approximately 80% biofilm mass removal (COD), with
more removal of the large basal layer compared to
enzymatic treatment.
Abbas et al. (2012) investigated detachment rate
functions for long-term behavior of one-dimensional
biofilm models, based on non-shear and shear stresses.
They observed that a specific detachment rate function can
affect the model’s prediction of persistence or wash out of
biofilms, and that both the bulk-flow Reynolds number and
a specific mechanism driving the flow influence the long-
term behaviour of biofilms to a great extent.
Impact of Surface Properties. RO membrane
mineral scaling was studied by Thompson et al. (2012) in
the presence of biofilm. They suggested the mineral scaling
may not be the tail element in RO plants; rather the biofilm
can increase concentration polarization. Pons et al. (2012)
peroxidized and incubated polyethylene for long periods in
two different municipal solid waste leachates. From their
data analyses, they observed that the depletion of carbonyl
groups and of carboxylic acids followed first-order kinetics.
Van Wey et al. (2012) proposed a reaction diffusion model
to describe the effective diffusion co-efficient (EDC). The
EDC was depth dependent for nutrient transport to the
biofilms through diffusion. The EDC for perpendicular
nutrient transport is lower than for parallel nutrient
transport to the substratum.
Impact of Nutrients, Trace Elements, and
Toxic Compounds. The development of vegetable-
associated Pseudomonas biofilm was observed by
Hamanaka et al. (2012) on polystyrene surfaces with
varying nutrient concentrations. The detected cell count in
the diluted nutrient scenario was higher. It was not clear
whether the removal treatment affected the biofilm
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structure, despite structural differences in normal and
diluted nutrient samples.
LapG is a calcium-dependent protease and is
required for biofilm formation by P. fluorescens (Pf 0-1)
(Boyd et al. 2012). This study showed that D134 and E136,
calcium-binding residues of LapG are required for its
activity, and that mutation at these sites led to its
inactivation when interacting with LapD. Thus calcium
chelator can also impact LapG activity and biofilm
formation.
An integrated study was performed using fixed-
bed fluid reactors by Barrionuevo and Vullo (2012) to
evaluate the impact of heavy metals, Cu(II), Cd(II), Zn(II),
Cr (VI), over the swimming, swarming chemostatic
response for three different bacteria sp., in order to develop
biofilm maintenance for metal-loaded wastewater
biotreatment. Different metal concentrations were used and
some species were not affected at all, whereas some others
showed different responses.
The effect of mercury stress was studied on
mercury-resistant bacteria, Escherichia coli Z1, E. coli Z3,
Pseudomonas putida Z2, Serratia marcescens Z4 and
Xanthomonas sp. Z5 (Essa 2012). The mer A (mercury
resistance) gene was detected and there was high similarity
between the merA region of the strains P. putida Z2 and
Xanthomonas sp. Z5 with those of Tn5053; the merA of E.
coli Z1 was analogous to those of Tn21. Based on the
community analysis, the bacterial strain E. coli Z3
containing a Tn5036-like determinant tolerated elevated
levels of mercury.
Jang et al. (2012) studied the effects in water
quality after phosphate addition on biofilm growth using
different pipe materials, stainless steel (STS) and ductile
cast iron (DCI) pipes. The addition of 5 mg/L phosphate
promoted a higher growth of biofilm and led to a greater
reduction in the rate of disinfection by-products in the DCI
pipe than in the STS pipe. PCR-DGGE and 16 S rDNA
sequences indicated that Proteobacteria (50%) was the most
detected phylum, followed by Firmicutes (10%) and
Actinobacteria (2%). Srinandan et al. (2012) studied the
impact of carbon sources in nitrate removal activity,
community structure and biofilm formation. Among
acetate, glucose, methanol, and ethanol used as carbon
sources, acetate-fed biofilm significantly reduced nitrate
(100%) while other efficiencies were in the order of
glucose> methanol > ethanol. Pseudomonas sp. were
mainly present in the acetate and ethanol-fed biofilm, while
Enterobacter sp. and Methylobacillus sp., predominated in
glucose and methanol biofilms respectively.
Lawrence et al. (2012) examined the effects of
three common contaminants, caffeine (CF), acetaminophen
(AC), diclofenac (DF) and their mixtures on biodegradation
and biofilm formation. denaturing gradient gel
electrophoresis (DGGE) analysis showed that all treatments
by the contaminants affected the microbial community
structure and that the archaeal community differed in
response to contaminant exposure.
The start-up pattern of biofilm formation and
microbial community analysis were investigated using the
simulated-river bioreactor (Xu et al. 2012). Natural
enrichment and artificial enhancement in the reactors were
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used and the biomass of mature biofilm was higher in the
artificially enhanced bioreactor. Heterotrophic bacteria
populations of biofilm decreased with artificial
enhancement, favoring formation of ammonia-oxidizing
biofilm. Yergeau et al. (2012) used rotating annular
reactors to investigate the effect on the meta-transcriptome
of river biofilm by different pharmaceutical products.
Pharmaceutical products produced little change in bacterial
communities at the phylum level, yet large shifts were
observed in the active community composition based on
taxonomic affiliations of mRNA sequences. Gene
expression related to nutrient cycling was significantly
affected by pharmaceuticals.
Impact of Bioaugmentation. A polyacrylamide
(PAM) degrading bacterium was isolated by Wen et al.
(2012) to study exogenous bacteria for bioaugmentation.
Contact oxidation reactors (COR) and sequencing batch
reactors (SBR) were bioaugmented by the strain
inoculation for PAM removal. The strain proved to be an
efficient exogenous bacteria for bioaugmentation with 70%
PAM removal in both reactors with single inoculation.
Extracellular Polymeric Substances and Their
Characterization
Extracellular Polymeric Substances. Zhu et al.
(2012) observed higher variation in the exopolymeric
proteins (PN) and in the PN over the polysaccharide (PS)
ratio when the sequencing airlift bioreactors (SABR) was
operated using 4-Cloroaniline (4-ClA) as substrate in
comparison to acetate and glucose. They observed that
some operating parameters such as gas velocity and settling
time can enhance the EPS production and sludge
granulation. With increments in PN content, the minimal
settling velocity, hydrophobicity, and surface charge
increased with a decrease in Sludge Volume Index (SVI).
The biofilm EPS influence over the resistance to
disinfection of biofilms and detached biofilms was
observed (Xue et al. 2012). The impact was assessed in
relation to biofilm viability, structure and dissolved organic
matter (DOM) removal; as well as the viability of detached
biofilm along with chlorine disinfection. Results of this
work showed an increase in resistance to chlorine for both
biofilms and detached biofilms with and without DOM.
By adding biofilm carrier in a conventional
membrane bioreactor (CMBR), a hybrid membrane
bioreactor (HMBR) was developed for a comparative study
of the EPS concentration impact on membrane fouling
control in municipal wastewater (Liu, Liu et al. 2012).
Results showed decreases in soluble EPS (S-EPS), loosely
bound EPS (LB-EPS) and tightly bound EPS (TB-EPS) by
42.9%, 41.6% and 1.5%, respectively, in HMBR. The LB-
EPS concentration was found to have high influence over
physical properties of activated sludge; hence, HMBR
operation could lead to more membrane fouling. Ercole et
al. (2012) studied how the extracellular polymeric materials
of bacteria, such as EPS and capsular polysaccharides
(CPS), lead to the formation of calcite crystals. By isolating
the organic matrices from calcifying bacteria, strains were
grown in synthetic media with and without calcium ions.
Analyses showed the EPS and CPS to form the calcium
crystallization.
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Romani et al. (2012) mentioned that extracellular
enzymes in aquatic biofilms play an important role in
microbial interactions and water quality. The common
extracellular enzymes consist of the decomposition of
polysaccharides, peptides and organic phosphorus
compounds. The authors concluded that interpretation of
extracellular enzyme activities will help in community
function analysis in relation to organic matter use and
cycling.
EPS Characterization. Gedda et al. (2012)
demonstrated electrospray ionization (ESI) and matrix-
assisted laser desorption/ionization (MALDI) mass
spectrometry (MS) as two powerful techniques to analyze
EPS secreted by E. coli. Physical and chemical (using
ethylenediaminetetra acetic acid (EDTA)) extraction
efficiencies were compared. Results indicated that chemical
extraction of EPS was much more efficient with EDTA
than with formaldehyde. Virdis et al. (2012) presented the
application of confocal Raman microscopy (CRM) as a
non-invasive, label-free in vivo characterization method of
acetate-oxidizing anodic biofilm to study biofilm growth
without disturbing structural or metabolic activity.
Significant changes in the vibration properties of Cyt C due
to the shift in anodic potential at different redox conditions
were demonstrated in electrochemically active biofilm.
Bodirlu et al. (2012) obtained chemically modified corn
starch and plasticized corn starch. Characterization was
performed with micro-particle preparation using corn
starch, and malic acid modified MA-SM) biofilm, corn
starch biofilm, and MA-SM-plasticized corn starch biofilm
were prepared and analyzed. With increasing MA-SM
content, tensile yield strength and Young’s modulus of
biofilm increased with a decrease in water uptake.
Biofilm Consortia and Quorum Sensing
Biofilm Consortia. Chun et al. (2012) found
diversification in microbial communities in biofouled
cartridge filters (CFs) and RO membrane samples; from
samples collected in one desalination plant. Predominant in
the CF samples were the communities of Proteobacteria
and Firmicutes, whereas in the RO sample Proteobacteria,
Planctomycetacia and Planctomycetes were prominent. A
complete genomic sequence of Acinetobacter calcoceticus
PHEA-2 (a non-pathogenic phenol degrading bacteria) was
established and compared with two other species with
different lifestyles, one pathogenic human-adapted strain
(Acinetobacter baumannii AYE) and one soil-living strain
(Acinetobacter baylui ADP1) (Zhan et al. 2012). For a long
period of time the concerned strain was considered similar
to the pathogenic ones. The study also revealed the
horizontal gene transfer mechanism for acquiring
environmental adaptation. Compare to the other two
strains, the PHEA-2 strain genome had a higher proportion
of transport-related proteins.
Ye et al. (2012) studied the nitrifying activity
during long-term starvation in a moving bed biofilm
reactors (MBBR) treating ROC (reverse osmosis
concentrate). By studying the decay rates of ammonia-
oxidizing bacteria (AOB) and nitrite-oxidizing bacteria
(NOB), they concluded that activity loss for both kinds of
bacteria was comparatively minor (around 20%) within 10
days of starvation, with a quick recovery of ammonium
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removal after resuming the normal condition. For more
than 20 days starvation, the activity loss observed was 60-
80%, with slower recovery for ammonium removal at the
revealed normal condition. White et al. (2012) surveyed
microbial communities in a full-scale, biologically active
filter for drinking water treatment. The results revealed that
Nitrosomonas, Nitrospira, Sphingomonadales, and
Rhizobiales dominated the clone libraries in drinking water,
and that alternative treatment methods were needed.
Ammonia-oxidizing bacteria dynamics in a pilot scale
wastewater treatment plant were analyzed using terminal
restriction fragment length polymorphism (T-RFLP)
(Wang, Wen et al. 2012). Results indicated that AOB
community structures were not stable for the test with
stable nitrification and the average change rate of AOB
population reached 10%. The dynamics of the AOB
community correlated with dissolved oxygen, effluent
ammonia, effluent biological oxygen demand and
temperature.
Despland et al. (2012) investigated the diversity
of microbial communities in an attached growth system. In
this study, Bauxsol pellets were used as support media and
community analysis revealed that heterogeneous bacterial
communities were present in the pellets made of inorganic
carbon. Bacteria involved in nitrogen removal, such as
AOBs, denitrifiers and anammox organisms, coexisted in
the attached growth system. Gao et al. (2012) studied the
bacterial diversity, community structure and function of
biofilm in a biological aerated filter using a marine
aquaculture system. Ammonia removal reached 30% after
70 days of reactor operation. Community analysis revealed
that bacterial diversity and population increased gradually,
and in particular, clones relevant to Denitromonas
increased from 1.7% to 6.5%. Homogeneity and
synchronous dynamics of communities in particulate
biofilms were investigated (Gevaudan et al. 2012).
Nitrifying biofilms as a model ecosystem were grown in an
inverse turbulent bed reactor containing small particles, and
the biomass content was evaluated using quantitative PCR
and other molecular fingerprinting techniques.
Extraordinary particle homogeneity was observed and was
dominant in minor non-nitrifying bacteria. Pal et al. (2012)
investigated total bacterial and ammonia-oxidizing
community structure in MBBR treating municipal
wastewater (MW) and inorganic synthetic ammonium
solution (AS). Compared with nitrification activity in MW-
MBBR and AS-MBBR, AS-reactors showed higher
nitrification and higher populations of Nitrosomonadaceae
and Nitrospiraceae families. A small microbial switch in
the general bacteria community was observed. The results
indicated that community structural change is highly
associated with influent characteristics.
Bo and Xin (2012) studied the diversity and
microbial community change in anaerobic biofilms of a
laboratory-scale wastewater treatment pond. After biofilm
development on glass slides, a Methanospirillum-like
methanogen was found within 36 h and Methanosarcina
was observed within 4 days. Mature biofilm contained the
domain Archaea, belonging to the acetoclastic
methanogens.
Li, Yuen, et al. (2012) investigated the impact of
backwash intensity and frequency on microbial community
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structure in fixed-bed biofilm reactors designed to remove
perchlorate from drinking water. The removal efficiency of
perchlorate and abundance of perchlorate-reducing bacteria
decreased when backwash intensity increased. The
variation in backwash frequency influences fewer
disturbances in the microbial community. Nava-Arenas et
al. (2012) studied the acclimation of a microbial
community degrading organochlorine herbicides in a
biofilm reactor. Eight genes were involved in the
biodegradation of four herbicides: atzA, atzB, atzC, and
atzD encoding enzymes of the catabolic pathway of
atrazine and simazine; the tfdA, tfdC and tfdD genes that
encode enzymes of the catabolic pathway of 2,4-
dichlorophenoxyacetic acid; and the puhB gene encoding
the first enzyme of the degradation of diuron. The
acclimation of the microbial community was achieved by
changes in metabolic activity of bacteria.
Microbial community structure and diversity
were examined in a membrane biofilm during initial stages
of filtration (Piasecka et al. 2012). The bacterial community
in activated sludge significantly differed from that of the
membrane biofilm, and phylogenetic analysis results
indicated 25 pioneer operational taxonomic units (OTU)
were involved in forming membrane surface colonization.
Quorum Sensing. Piper betle extract (PBE) was
investigated as an anti-quorum sensing mechanism to
diminish biofouling (Siddiqui et al. 2012). PBE was found
to lessen biofouling, by inhibiting auto-inducer (AI)
production, and have an effect over the production of EPS
and biofilm.
Shrout and Nerenberg (2012) reported a critical
review of quorum sensing (QS) which aimed to identify the
importance of further study. These authors described how
QS-controlled genes related to the formation and function
of biofilms might be important for water and wastewater
treatment.
Quorum-quenching bacteria encapsulated inside a
microbial vessel were used to inhibit biofouling in
submerged MBRs, by interrupting N-acyl homoserine
lactone (AHL) mediated quorum sequencing (Jahangir et
al. 2012). The effect was more prominent by positioning
the vessel closer to the filtration membrane in MBR, and
was highly dependent on the recirculation rate of mixed
liquor between the bioreactor and the membrane tank.
Jiang and Liu (2012) concluded that adenosine tri-
phosphate (ATP)-dependent N-acylhomoserine Lactones
(AHLs) and EPS production positively impact aerobic
granulation. ATP synthesis inhibition leads to the reduction
of AHLs and EPS production, resulting in the prevention of
aerobic granulation.
Biofilm Imaging and Characterization. Novel
atomic force microscopy was used to characterize spin-
coated engineered E. coli biofilms (Tsoligkas et al. 2012).
Spin-coated biofilms had stronger adhesion to the glass
substrate than did conventional biofilms.
A new optode-based O2 imaging technique was
applied to membrane fouling simulators (MFS) to enable a
quantitative and non-destructive method of analyzing O2
dynamics in biofilms during biofouling (Prest et al. 2012).
Both the oxygen concentration and consumption rates were
observed, and the biofilm activity was characterized. Low
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and high activity areas, flow channels and stagnant areas
could be distinguished and determined easily.
Mahendran et al. (2012) studies the structural,
physicochemical and microbial properties of biofilms and
flocs in integrated fixed-film activated sludge. Flocs had a
higher negative surface charge and were more hydrophobic
than biofilms. They also had a higher EPS content, with
more protein than polysaccharide; this was in opposition to
biofilms having a higher proportion of DNA when
compared to the flocs. Karcz et al. (2012) applied
lyophilization to prepare nitrifying bacteria biofilms for
imaging with scanning electron microscopy (SEM).
Compared with other preparation methods, the lyophilized
material offered better imaging in high resolution. From the
lyophilized images taken, two immobilization patterns of
the biofilms were revealed. Clark et al. (2012) performed
transcriptomic and proteomic analyses on mature biofilm
cells of Disulfovibrio vulgaris (SRB) and compared their
results with reactor planktonic populations. From the
genomic analysis, these authors found the biofilm cells to
be different than the planktonic cells, although both
perform the same redox reactions. Insight into adaptation in
biofilms during biofilm-contaminant interactions was
gained using non-invasive magnetic resonance imaging
(MRI) and spectroscopy (MRS) (Cao et al. 2012). Studying
the metabolic responses of Shewanella oneidensis MR-1
biofilm to uranyl (U IV) and chromate (Cr IV), the overall
biomass distribution was not altered by either U IV or Cr
IV, and significant contaminant-induced changes of
structural or hydrodynamic properties were observed by
MRI and spatial mapping of diffusion.
Alhede et al. (2012) combined SEM with other
microscopic techniques, such as conventional SEM and
Focused Ion Beam (FIB)-SEM, and confocal laser scanning
microscopy (CLSM) with SEM techniques cyro-SEM and
environmental SEM (E-SEM) to study biofilm structure
and composition. This study found that combined processes
can avoid the cell dehydration requirement for SEM, and
result in more authentic images.
Biswas and Turner (2012) investigated the
community composition of two municipal MBBR systems
treating municipal sewage using molecular tools such as
16S rRNA gene libraries, fluorescence in situ hybridization
(FISH) and automated ribosomal intergenic spacer analysis
(ARISA). Clostridia and sulfate-reducing bacteria were
dominant in both plants and Deltaproteobateria were
detected in FISH images. Both plants were dominated by
diverse aerobic bacteria, including Gammaproteobacteria
and Betaproteobacteria.
Methane-oxidizing biofilm was characterized
using microarray and confocal microscopy (Kim, Yi et al.
2012). Community analysis revealed that methanotrophic
organisms are dominant and Methylocystis was most
abundant followed by Methylosinus. Image analysis
showed that a high abundance of methanotrophs were
present at a depth of 5µm in biofilm and geostatistical
analyses revealed differing concentrations of
methanotrophic organisms with decreasing depth and
randomness between spatial locations and population
levels.
2. Biofilm Reactors
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Impact of Packing Materials
The biogenic stimulating properties of self-made
sludge-ceramsite were compared to other commonly used
ceramsites (Zou et al. 2012) The experimental ceramsite
showed from 79.1 to 86.4% conversion of NH4+-N to NOx-
N, with removal of 43.9-51% TN at COD/NH4+-N ratios
from 4 to 10, which compared favorably to the other
biofilters.
The influence of zeolite particle size in nitrifying
batch reactors was examined (Mery et al. 2012). The
reactor having 0.5 mm zeolite showed high ammonia
removal and maximum desorption values. Similar
microbial populations were observed in the reactors, which
contained major species of Gammaproteobacteria with
minor species of ammonium oxidant Betaprotebacteria. Li,
Lei et al. (2012) studied the combined effect of flow rate
and light on biofilm growth using four identical biological
reactors with polyethylene terephthalate carriers for biofilm
cultivation. These authors demonstrated that an increase in
flow rate and the light condition enhanced microbial
activity and the concentrations of total biomass, EPS, and
active biomass.
Bulking control using Galactomyces geotrichum
was investigated using biofilm carriers in sequencing batch
reactors (SBR) (Matos et al. 2012). The bulking was
successfully controlled by different carrier concentrations,
and the carrier concentration of 10-20% effectively
suppressed the overgrowth of filamentous fungus because
of the effect of a decreased biomass loading rate and an
increased shear stress. Microbial community analysis
showed that the biofilm carrier affects the differences of
bacterial community structure in SBR.
Rotating Biological Contactor
A three-stage rotating biological contactor (RBC)
was used for the treatment of non-aqueous phase liquid
(NAPL) in a mixture having aqueous-non aqueous phases
(Mukherji and Chavan 2012). The aqueous effluent
containing 0.6% diesel oil was used as a model NAPL.
Burkholderia cepacia along with a sessile algal culture
were used to grow biofilm in batch mode, and the reactor
then operated in flow through mode having different
conditions of HRT and organic loading rate (OLR). More
than 99% removal of total petroleum hydrocarbon (TPH)
was obtained with a TPH loading up to 31.8 g TPH/m2·d.
The existing models in the literature were not applicable for
predicting the removal efficiency of soluble substrate in
this experiment. Jeswani and Mukherji (2012) reported
that a three-stage RBC removed from 63.3% to 92.6%
COD at varied OLRs from 3.3 to 14 g/m2·d in the treatment
of synthetic biomass gassifier wastewater containing
phenolics, heterocyclics and polynuclear aromatic
hydrocarbons. When the pyrene degrader Exiguobacterium
aurantiacum was inoculated into the RBC, a complete
removal of all components was observed at the lowest
applied OLR of 3.3 g COD/m2.d.
Pakshirajan and Kheria (2012) applied a RBC
for the treatment of colored wastewater from a textile
dyeing industry using the white rot fungus Phanerochaete
chrysosporium. The color removal range was 64-83% and
consistent COD removal was obtained when the
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wastewater was diluted with media containing glucose. The
results correlated with the activities of manganese
peroxidase (MnP) and lignin peroxidase (Lip) enzymes of
the fungus, which was found to play a significant role in the
decolorization of the wastewater.
In another study of colored textile wastewater
treatment, Novotny et al. (2012) used the fungus
Dichomitus squalens as the reactor inoculum in a RBC. The
results of the study suggested that D. squalens formed a
thick biofilm on the inert and lignocellulosic supports. The
percent removals of color from the wastewater containing
Remazol Brilliant Blue R, heterocyclic Methylene Blue and
Azure B dyes were 99%, 93%, and 59% at HRTs of 7, 40
and 200 h, respectively.
Algal-microbial biofilm developed on photo-
RBC reactor discs removed various metals in the treatment
of acid-mining drainage wastewater (Orandi et al. 2012).
This study suggested that the metal removals ranged from
20 to 50%, with removal orders of Cu > Ni > Mn > Zn > Sb
> Se > Co > Al, when using an indigenous microbial
consortium predominantly consisting of Ulothrix sp. The
biofilm was developed on the photo-RBC's disc within 60
days under a batch-mode operation. The reactors were then
operated continuously for 70 days with a 24 h HRT.
Singh and Mittal (2012) used a four-stage RBC
for the treatment of synthetic wastewater, and identified
microbial community structure (categorized based on the
nitrate reduction, biochemical reactions, gram staining and
morphology) from each stage of RBC during operation.
The microbial community analysis suggested a higher
relative abundance of Paracoccus pantotrophus in the first
stage as compared to subsequent stages; other nitrifiers and
heterotrophs were dominant in other stages. Total nitrogen
(TN) removal of up to 68% was obtained.
Fluidized Bed Biofilm Reactor
In their study evaluating the available literature,
Andalib et al. (2012) proposed a new equation for bed
expansion index and voidage for fluidized biofilm-coated
particles. Based on Archimedes number rather than
Reynold's number, the new equation predicted less standard
average error for estimating the physical properties of
biofilm-coated particles.
A respirometric approach was used to evaluate
in situ heterotrophic biofilm kinetics in a pilot-scale liquid-
solid circulating fluidized bed (LSCFB) bioreactor with
lava rock as the biofilm support material (Chowdhury et al.
2012). Maximum specific growth rates (µmax) of 3.69 ±
0.44 /d and biomass yields (YH) of 0.36 ± 0.03 g COD/g
COD were observed in the fluidized bed respirometers. A
higher Monod half-saturation coefficient (KS) of 186-219
mg COD/L was observed in the fluidized bed
respirometers, when compared to the 49-58 mg COD/L of
conventional respirometers, revealing the presence of mass
transfer resistance in the LSCFB despite fluidization.
Eldyasti et al. (2012) studied a calibration
protocol of a particulate biofilm model BioWin®. To verify
the predictability of the calibration protocol, biological
nutrient removal (BNR) data from a circulating-FBBR
system was used. A fluidized bed respirometric study of the
biofilm stoichiometry and kinetics was considered to verify
and validate the proposed calibration protocol. This study
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enhanced the applicability of BioWin® for predicting most
of the performance parameters with an average percentage
error (APE) of 0-20%.
Wastewater having high organic matter and
aromatic compounds from a petrochemical industry was
treated using an integrated anaerobic and aerobic FBBR
(Estrada-Arriaga et al. 2012). The FBBR removed 85% of
the COD at an HRT of 2.7 h and 94% at an HRT of 2.2 h.
High removal of aromatics was also observed. Cane sugar
wastewater at different HRTs and OLRs was treated using
a three-phase FBBR (Jin, Liu et al. 2012). The maximum
COD and NH4+-N removals were 91.38% and 92.39% at
the HRTs of 3 and 3.5 h, respectively. The applied OLRs
were 2.3 kg COD/m3·d to 5.1kg COD/m3·d, and the results
suggested that the FBBR had high operational flexibility
and a capability to resist shock loading. Simultaneous
carbon and nitrogen biodegradation was observed in a
circulating-FBBR where bioparticles are slowly transferred
from the riser (anoxic column) to the down comer (aerobic
column) for enhancing BNR (Li, Nakhla et al. 2012). The
designated reaction zone for simultaneous nitrification
denitrification (SND) was 4 L for evaluating the circulation
effect. Long-term (285 days) simultaneous COD (with
sodium acetate as the carbon source) and TN (with NH4Cl
as nitrogen source) removals were achieved with an
extremely low sludge production of 0.034-0.1 g volatile
suspended solids (VSS)/g COD.
An FBBR with nylon support particles was
used to treat synthetic sulfide wastewater (Midha et al.
2012). The reactor was inoculated from activated sludge of
tannery wastewater and operated at different HRTs and
different up-flow velocities. A 42 ± 3 µm biofilm thickness
was reached after 15 days of reactor start-up and the results
indicated that up to 92% sulfide oxidation was achieved at
all HRTs. The highest sulfide oxidation was obtained at an
HRT of 75 min and up-flow velocity of 14 m/h.
A three-phase airlift FBBR was operated at an
11.9 min HRT with granular activated carbon (GAC) as its
support media for the treatment of fish culture wastewater
(Sanchez and Matsumoto 2012). The average removal
efficiencies of BOD, COD, phosphorous, total ammonia
nitrogen (TAN) and TN were 47%, 77%, 38%, 27% and
24%, respectively.
The removal of NH4+, COD and TN was
studied for modeling SND in an FBBR (Seifi and
Fazaelipoor 2012). Considerations in the model included
dispersion and convection in the liquid phase, simultaneous
diffusion and reaction of the chemical species within the
biofilm, and different types of microorganisms namely,
heterotrophic aerobes, nitrifying and denitrifying bacteria.
The model was verified using experimental results from a
bench-scale bioreactor, and the study suggested that the
model predicted the NH4+, COD, NO3- and TN profiles
along the height of the bioreactor reasonably well. Urban
wastewater was treated using a four-stage, step-feed
wastewater treatment system combined with an FBBR
(Wang, Wang, et al. 2012). Study results suggested
removal rates for COD, NH4+-N and TN of 88.2%, 95.7%,
and 86.4%, respectively. More nitrobacteria were observed
in the activated sludge than in the biofilm, although the
bacterial activity of the biofilm biomass and the activated
sludge were similar.
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Integrated Fixed Film Activated Sludge
An integrated fixed-film activated sludge (IFAS)
system with a working volume of 560.7 L was used to treat
industrial effluent (Li, Li et al. 2012). The steady-state
removals of COD, NH4+-N and TN were 74, 93 and 76%,
respectively. Fluorescence in situ hybridization (FISH)
results showed that there were more nitrifying bacteria in
the suspended-growth biomass than in the attached-growth
biomass, but that fewer denitrifying bacteria in the former
biomass. The average sludge age (θC) values of activated
sludge process (ASP) biofilms were determined and
verified experimentally; the stability and safety factor
against θC were also investigated through graphical studies
(Fouad and Bhargava 2012). The study suggested that θC of
ASP was found to be applicable to the hybrid system after
including the biofilm, and the authors’ proposed curves
were simple and easy to modify. Cortes-Lorenzo et al.
(2012) investigated the impact of salinity (NaCl
concentration in influent: 0, 3.7, 24.1 and 44.1 g/L) on the
activities of hydrolytic enzymes (acid phosphatase, alkaline
phosphatase, glucosidase, protease and esterase) released
by microorganisms in a submerged fixed bed bioreactor
(SFBBR) for urban wastewater treatment. The results
suggested that the enzymatic activities decreased with an
increase in NaCl concentration in the influent, and that as a
consequence, the biotransformation of organic matter
significantly decreased in the SFBBR. Using a Monte Carlo
permutation test, a negative correlation was observed
between enzymatic activities and physic-chemical
parameters.
Moving Bed Biofilm Reactor
The removal of bisphenol A, oseltamivir, and
atrazine from wastewater was evaluated with or without use
of a moving bed biofilm carrier (MBBC) (Accinelli et al.
2012). The results from the experiment with 10 d
incubation without MBBC media suggested that the
removals of C-14-labeled bisphenol A, oseltamivir, or
atrazine were approximately 18%, 7% and 3.5%,
respectively. In the reactor with MBBC media, the removal
rates increased to 34%, 49%, and 66%, respectively.
Removal efficiencies of the reactors with MBBC were
increased further by addition of bioremediation bacterial
strains.
Three MBBRs (two in continuous and one in
sequencing batch mode) were operated to investigate the
impact of different operational conditions on biofilm
development and nitrification (Bassin et al. 2012).
Continuous stepwise reduction of influent COD caused a
decrease in total polysaccharide and protein content, and an
enrichment of the biofilm by nitrifiers was observed. The
study suggested that the polysaccharide and protein
concentrations might be good indicators of biomass
development and detachment in MBBR systems.
A study was carried out using different types of
carriers in a lab-scale MBBR for the treatment of urban
wastewater at three different conditions of HRT and carrier
filling ratios (FR) (Calderon et al. 2012). The results from a
cluster analysis of temperature gradient gel electrophoresis
technique (TGGE) fingerprints suggested that a significant
difference in community structure was observed at the
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different operational conditions applied. Phylogenetic
analysis of PCR-reamplified and sequenced TGGE bands
showed that the prevalent bacteria populations in the
biofilm were Betaproteobacteria (46%), Firmicutes (34%),
Alphaproteobacteria (14%) and Gammaproteobacteria
(9%). A comparative performance study of MBBR and
ASP was used for the treatment of petrochemical
wastewater (Cao and Zhao 2012). The optimal conditions
of air flow rate and HRT for the MBBR were 1.25 L/min
and 8 h, respectively, and the removal of COD was 80% at
an OLR of 1.0 kg COD/m3·d and 70% at an OLR of 2.0 kg
COD/m3·d. The study suggested that the MBBR had higher
efficiency than ASP under the optimal condition. Feng,
Wang, et al. (2012) studied the impact of packing rates for
the treatment of artificial sewage in three aerobic MBBRs.
The results suggested that the increase in removal of
organics with polyurethane foam (PUF) packing (20%,
30% and 40%) was negligible (around 81%). At an HRT of
5 h, the NH4+-N removal efficiency increased from 37.4%
at a 20% packing rate to 96.3% with a 40% packing rate.
Pyrosequencing analysis of the biofilm showed that
Proteobacteria, Bacteroidetes and Verrucomicrobia were
the three most abundant phyla, but that the proportions of
each microbial community varied along with the packing
rate of the PUF carrier.
Gong et al. (2012) investigated SND from rural
domestic sewage by using an integrated anoxic fixed-bed
biofilm reactor, an oxic MBBR and a settler. SND removal
was increased by 37.7 - 42.2% at high influent C/N ratio of
2.5-4.0. TN removal was 69.3%, even at a high internal
recycling ratio (IR) of 2, and less (<3%) biomass
integration was observed. The authors suggested that the
integrated bioreactors were economic with simplified
sludge disposal.
An integrated electrocoagulation-MBBR was
used for the treatment of urban wastewater by using K1
from AnoxKaldnes® and AQWISE ABC5 from Aqwise
carriers at three different filling ratios (FR) (20, 35, and
50%) (Lopez-Lopez et al. 2012). The maximum COD
removals in this MBBR system were 65.8% ± 1.4% and
78.4% ± 0.1% for K1 and Aqwise ABC5 carriers,
respectively. The bacterial diversity of the biofilm using
PCR-TGGE suggested that the predominant bacterial
populations were β-Proteobacteria, α-Proteobacteria, and
Actinobacteria. Martin-Pascual et al. (2012) investigated
the impact of three different carriers, HRT, and FR on the
removal of COD from a moving bed reactor. The maximum
COD removals obtained for carrier 1, carrier 2 and carrier 3
were 56.97%, 58.92% and 46.13%, at 15 h of HRT and a
FR of 50%. The kinetic constants obtained by the
respirometry method suggested a similar trend to the values
obtained from the observed sCOD removals.
Shore et al. (2012) applied a bench-scale
MBBR to treat synthetic and industrial wastewater
effluents at high temperature (35-45 °C), and quantified
different community structures of AOB and NOB in the
wastewater. The results suggested that greater than 90% of
the influent ammonia was removed from both the synthetic
and industrial wastewaters. qPCR results showed that
Nitrosomonas oligotropha was the dominant AOB in the
biofilm in the first phase of reactor operation, whereas
Nitrosomonas nitrosa was observed to be dominant in later
1074 Water Environment Research, Volume 85, Number 10—Copyright © 2013 Water Environment Federation
phases. Ye et al. (2012) applied a two-stage MBBR to
investigate the decay rates of AOB and NOB, and the
biofilm detachment in the MBBR during a starvation period
of one month. The results suggested that the activity of
both AOB and NOB was reduced by 60-80% after
starvation for more than 20 days, and a slow recovery of
starvation loss was observed. For a starvation period of less
than 20 days, quick recovery of activity loss of both AOB
and NOB was observed and the apparent biomass
detachment from carriers was negligible.
Packed Bed Biofilm Reactor
A fixed-film reactor was used to investigate the
As (III) oxidation by using a Thiomonas arsenivorans B6
bacterium strain at an influent concentration of As (III) of
500-4000 mg/L and HRTs of 0.2-1 d for a duration of 137
days (Dastidar and Wang 2012). The As (III) oxidation
efficiencies were in the range between 48.2% to 99.3%
during the entire operation with seven steady-state
conditions. The As mass balance revealed that the As (III)
was mainly oxidized to As (V).
An aerobic two-stage rectangular packed-bed
biofilm reactor (2S-RPBR) was used for biodegradation of
the sulfonated azo dyes, Acid Orange 7 (AO7) and Acid
Red 88 (AR88), by a bacterial consortium isolated from
water and soil samples obtained from sites receiving
discharges from textile industries (de los Cobos-
Vasconcelos et al. 2012). Complete biodegradation of azo
dyes was attained at loading rates, up to 40 mg/L·d.
The feasibility of an innovative up-flow
packed-bed reactor system using porous sulfur and lime
ceramic media (CERAMED-L and CERAMED-SL) was
studied to remove nitrogen in wastewater treatment (Han
and Park 2012). The results suggested that the specific
nitrification rate was 1.73-2.29 kg NH4+-N/m3 CERAMED-
L·d with a F/M ratio in the range 0.08-0.31 g NH4+-N/g
VS·d. Autotrophic denitrification efficiencies were in the
range of 83-96% during the test period, and the average
specific denitrification rates were 0.97-1.92 kg NO3-N/m3
CERAMED-L·d and 0.19-0.36 g NO3-N/g VS·d. A study
investigated the performance of an ultra-compact biofilm
reactor (UCBR) for the treatment of domestic wastewater
(DWW); the DWW gradually shifted to a mono-type
carbon source synthetic wastewater (SWW) combined with
DDW (CWW) and then finally to SWW (Koh et al. 2012).
The UCBR was able to achieve average total COD removal
efficiencies of 70 ± 10% and 80 ± 4% for DWW and
SWW, respectively. The study suggested a better removal
of organics from mono-type SWW compared to diverse
carbon sources such as DWW in the presence of
heterotrophs in the UCBR.
Ferrous ion bio-oxidation was carried out by
using a flooded packed-bed bioreactor (FPB) where
siliceous stone served as the support material for biofilm
formation (Mazuelos et al. 2012). The authors assessed the
impact of pH and found that pH was the key parameter for
operational control in the reactor. The microbial population
was characterized at a pH range from 2.3 to 0.8; at pHs
above 1.3 Acidithiobacillus ferrooxidans was the dominant
microorganism, whereas at pHs below 1.3 Leptospirillum
ferrooxidans dominated.
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A newly configured acrylic fixed-bed reactor
with a working volume of 6.1 L was used under conditions
of continuous feeding and intermittent aeration (2 h aerated
and 1 h non-aerated) (Moura et al. 2012). The reactor was
operated at three HRTs and the removals of COD and TN
were 82% and 89%, respectively at an HRT of 12 h.
Although high COD removal efficiencies of 85% and 88%
were obtained for Phases II and III, respectively, low TN
removals of 49% and 45% were obtained for HRTs of 8
and 10 h, respectively. Mousavi et al. (2012) applied a
twin-chamber up-flow bio-electrochemical packed bed
reactor with palm shell granular activated carbon was used
as the biocarrier, and a third electrode was applied for SND
of a nitrogen-rich wastewater at different operating
conditions. The experiments were carried out at a constant
pH but with varying electric current and HRT. The results
suggested that the optimum ammonium oxidation of 90%
was obtained at applied current of 32 mA and HRT of 19.2
h.
An oxic fixed biofilm reactor was used for the
treatment of organic matter and nitrogen from domestic
wastewater (Zhang et al. 2012). The results from this study
were as follows: (i) a short microbial cultivation and a 10-
day acclimatization time were observed, (ii) HRT had a
significant influence on the COD and NH3-N removal
efficiencies, (iii) the carrier loofah material was an
excellent support for biofilm growth, and (iv) high
removals of COD (83.7%) and NH3-N (96.9%) were
obtained at influent concentrations of COD of 260.0 and
NH3-N of 26.8 mg/L, respectively.
Sequential Biofilm Batch Reactor
A pilot scale SBBR with granular activated
carbon (GAC) was operated at different HRTs for the post-
treatment of treated paper industry wastewater (Muhamad
et al. 2012a). The HRT effect on adsorbable organic
halogen and COD removals was determined. The authors
concluded that an HRT of 3 days, with an OLR of 0.008 kg
COD/m3·d, removed 100% of the COD and around 86% of
the pentachlorophenol (PCP). Muhamad et al. (2012b)
undertook a performance evaluation of a GAC-SBBR pilot
plant treating wastewater from the recycled paper industry.
Biodegradation of the incoming contaminant increased with
an HRT above 2 days, reaching around 90% removal
efficiency. A lower aeration rate led to lower removal
efficiency.
Jin, Ding et al. (2012) evaluated the performance
of an SBBR with different carbon-to-total nitrogen ratios
(C:N) to remove nitrogen and phosphorus from synthetic
municipal wastewater. An intelligent control system (ICS)
and conventional timer control system (TCS) were
investigated along with the effect of the control system.
Lower C:N ratios led to higher COD and TN removals in
ICS-SBBR.
Chang et al. (2012) studied the performance of an
IBBR in domestic water treatment. A stably operated IBBR
led to good removal of CODCr (Chromium-based method),
increasing the reflux ratio of nitrification. Aluminium
sulfate addition led to further TP removal. Luciano et al.
(2012) described the laboratory experiment to compare a
newly developed domestic wastewater plant to the
conventional one by adding biofilm airlift suspension
1076 Water Environment Research, Volume 85, Number 10—Copyright © 2013 Water Environment Federation
reactor (BAS) with biomass attached to tubular supports.
The coupled attached and suspended biomass ensured high
dissolved oxygen (DO) concentration led to higher removal
efficiency and higher effluent quality. The performance of
an MBSBR integrated with an intermittent aeration strategy
(IA-MBSBR) was evaluated (Lim et al. 2012). Stored
carbon substrate of biofilm located inside the polyurethane
foam facilitated the denitrification process and suspended-
growth biomass played a major role in the NH4+-N
oxidizing process. Lotito et al. (2012) characterized the
sludge produced from a sequencing batch biofilter granular
reactor (SBBGR). They studied physical properties such as
settling, dewaterability, and rheology and concluded that
the sludge had good settling and dewatering properties.
Trickling Filter
Albuquerque et al. (2012) studied the submerged
biological aerated filter (BAF) for its removal of low
concentrations of ammonia nitrogen in nutrient-enriched
river and lake waters. Ammonia removal was found to be
50-70% in the upper section of the process and
simultaneous removal of ammonia and nitrate was achieved
at the bottom of the reactor. A comparative study of biofilm
supports in up-flow biological aerated filters (BAF) was
performed using water quenched slag particles (WQSP)
and haydite as support media (Feng, Yu et al. 2012). The
WQSP showed higher porosity, larger surface area and
lower bulk density, indicating better efficiency of
wastewater treatment. Hu et al. (2012) investigated the
performance of aerated filter reactors using different media
for tertiary sewage treatment. They demonstrated that
submerged aerated filter reactors packed with wool fibre
removed more organics (93%) and solids (90%) than did
the reactors with commercial plastic pall rings.
Two carrier materials, macroporous polyurethane
and haydite, were used in BAFs to compare the removal
efficiencies of organic matter and ammonia (Jia et al.
2012). The reactor supported by macroporous polyurethane
showed higher values of ammonia removal and organic
treatment, indicating that the macroporous structure is
suitable for the immobilization of bacteria and for the
transmission of the soluble substrate.
Double-layer biofilters packed with coal fly ash
granules and inoculated with river sediment were used to
treat highly polluted river water (Jing et al. 2012). A
biofilter with a trickling upper layer contributed to
nitrification and one with a submerged lower layer
performed denitrification. With hydraulic loading rates of
4.0-5.0 m3/(m2 -d) and C:N of 6-10, the removal
efficiencies in the biofilter were found to be 80% for COD,
85% for ammonia nitrogen and 60% for total nitrogen.
Mehrdadi et al. (2012) investigated the effectiveness of a
bio-trickling filter to treat dairy wastewater. The bio-
trickling column packed with lava rocks was operated
under HRTs from 4 h to 5 days. The filter removed 96% of
the COD and 70% of the TKN at an HRT of 7 h.
Munoz-Sanchez and Reyes-Mazzoco (2012)
studied the robust organic matter and nitrogen removals in
a packing of trickling filters as a pretreatment process for
wetland polishing of wastewater. Under various organic
loads from 19.41 to 69.45 kg COD/m3-d, a total nitrogen
removal of 33% and an ammonium reduction of 57 % were
1077 Water Environment Research, Volume 85, Number 10—Copyright © 2013 Water Environment Federation
achieved. Their kinetic model based on organic loads
showed a lower constant with less specific area, indicating
that the removal efficiency is reduced when organic loads
are high. Two biofiltration reactors, trickle bed reactor
(TBR) and biofilter (BF), were used to treat paint solvent
mixtures, acetone, methyl ethyl ketone, methyl isobutyl
ketone, and n-butyl acetate (Paca et al. 2012). Under low
substrate loading rates, the BF outperformed the TBR not
only in the removal of aromatic hydrocarbons, but also in
that of polar substrates. The significant drop in removal
efficiency of polar and hydrophobic components was
observed when the loading rate was increased above a
threshold value of 31-36 g/m3-hr.
Marine bacteria inocula were used to remove
nutrients in hypersaline wastewater using an intermittently
aerated biological filter (IABF) (Shi et al. 2012). The bio-
enhanced IABF improved nutrient removal, with removal
efficiencies for COD, total nitrogen and total phosphorus
were increased by about 8.6%, 15.7% and 17.3%. The
inoculation of marine bacteria improved the active biofilm
formation in hypersaline environments.
Simsek et al. (2012) studied the fate of dissolved
organic nitrogen (DON) in a trickling filter process. DON
concentrations in the influent and effluent were 27% and
14% of total dissolved nitrogen (TDN). The trickling filter
removed about 62% and 72% of the influent and
biodegradable DON, respectively. The BioWin model
simulation showed that the maximum growth rate and half
saturation constant for ammonia oxidizers influenced the
ammonia and nitrate output. The effects of temperature,
hydraulics and loading rates on a full-scale trickling filter
were studied for ammonium, iron and manganese removal
in well water (Tekerlekopoulou et al. 2012). Removal
efficiency was dependant on temperature and hydraulic
loading, and in all operating conditions high removal
efficiencies were achieved.
A mathematical model of biomass and
decolourization process dynamics in a trickle-bed
bioreactor was investigated for the treatment of organic
dyes and textile industry wastewater (Skybova et al. 2012).
Based on the mass balance of glucose and the dye in a
fungal biofilm and a liquid biofilm, optimal corrugation
values were 0.853 and 0.59 at initial dye concentrations of
0.09433 kg m-3 and 0.05284 kg m-3, respectively. A good
agreement between the simulated and experimental results
was achieved.
Trickling filter as pretreatment was used for
effective wastewater purification in subsurface flow
constructed wetland (Vucinic et al. 2012). The efficiency of
the process (TSS, BOD5, COD, NH4-N, NO2-N, PO4-P,
dissolved oxygen, temperature and pH) was monitored over
three years. The removal efficiency was increased with a
doubling of the nominal flow from 0.7 to 1.44 m3/d.
Wang, Li, et al. (2012) evaluated the effect of
different substrates (sand mixed with 1, 3, 5 or 7% of
cinder, diatomite, active carbon or fly ash) on nutrient
removal or poultry wastewater capacities in trickling
columns fed with reactive media. The best removal
efficiency was achieved using a 7% weight ratio of cinder
mixed with sand. In addition, bioaugumentation enhanced
the nutrient removal in the system.
1078 Water Environment Research, Volume 85, Number 10—Copyright © 2013 Water Environment Federation
An integrated process including chemically
enhanced primary treatment, trickling filter and
ultrafiltration was applied for domestic wastewater
treatment and reclamation (Zhao et al. 2012). High COD
and ammonium removal was achieved (95% and 88%,
respectively) while total phosphorus and suspended solids
were removed completely at a coagulant dosage of 2.5
mg/L in the primary treatment. Zielinski et al. (2013)
demonstrated the potential for improving wastewater
treatment by the application of microwave radiation (MW)
compared to convective heating (CH) of trickling filters.
The presence of continuous biofilm exposure to MW
resulted in a 20% higher rate of nitrification when
compared to an intermittent dosage of MW and CH.
Membrane Bioreactor
Liu, Tanaka, et al. (2012) investigated fouling
and structural changes when using a porous glass
membrane in aerobic wastewater treatment process treating
synthetic municipal wastewater. External membrane
fouling was observed and cleaned offline by ultrasonic,
thermal and acid treatment to remove organic and inorganic
foulants. Scanning electron micrographs revealed offline
cleaning methods were effective to remove membrane
external fouling and slightly increased the membrane
porosity and pore surface area. Tertiary treatment with
combined MBBR and ultrafiltration (UF) membrane
process was investigated in pilot-scale at a wastewater
treatment plant (Odegaard et al. 2012). Based on the
results, the MBBR-high rate separation-UF process
provided better performance and may be a good alternative
to the activated sludge-based membrane bioreactor.
Pervissian et al. (2012) studied the effect of
pretreatment on a combined MBBR and membrane
filtration system for industrial wastewater treatment. Of the
coagulation chemicals used (ferric chloride, polyaluminum
chloride and polyamine), ferric chloride provided the best
coagulation performance, reducing total fouling by 79%
and increasing consistency of reactor performance. A
comparative study of tetrabromobisphenol A (TBBPA)
removal was investigated using conventional activated
sludge (CAS) and membrane bioreactors (MBR) (Potvin et
al. 2012). Nitrification played a key role of TBBA removal
and significant TBBA removal was achieved in the MBR.
A hybrid vertical membrane bioreactor
(HVMBR) developed to obtain a compact module and low
energy requirement was evaluated for its efficiency at
wastewater treatment (Rodriguez-Hernandez et al. 2012).
BOD5 and suspended solids removal efficiencies were
found to be 96 and 99%, respectively. Total nitrogen
removal reached 80%, which is better than that when using
other HMBRs. The influence of activated sludge
characteristics on membrane fouling in an HMBR and a
CMBR was evaluated in pilot-scale (Wang, Hu, et al.
2012). The HMBR performed better for removing organics,
nitrogen and phosphorus. Considering the characteristics of
the activated sludge, the addition of biofilm carriers
provided not only a substantial increase of biomass
quantity, but also an improvement of the structure, size,
flocculability and settleability of the sludge particles.
1079 Water Environment Research, Volume 85, Number 10—Copyright © 2013 Water Environment Federation
Sun et al. (2012) compared membrane filtration
performance between biofilm-MBR and activated sludge
MBR (AS-MBR). In this study, AS-MBR had better
permeate quality and less membrane fouling. The authors
suggested to optimize operating conditions and system
configurations where the submicron colloidal component is
managed and controlled so as to obtain a sustainable
operation of a BF-MBR. Wang, Liu et al. (2012)
demonstrated biodegradation of acid orange 7 (AO7), and
its auto-oxidative decolorization product, in a membrane-
aerated biofilm reactor. In this study, oxygen supply
pressure had a remarkable impact on the reactor
performance and AO7 decolorization efficiency reached
98% in 6 h under an oxygen pressure of 0.03 MPa.
Microbial sequencing analysis revealed diverse bacteria
capable of decolorizing compounds in the reactor. A pilot
study of a membrane bioreactor using a mesh filter was
conducted for low-strength municipal wastewater treatment
(Wang, Sheng et al. 2012). The mesh filter effectively
retained biomass and a low effluent turbidity below 2 NTU
was observed. The COD and ammonium removal
efficiencies reached 86.3% and 98.2%, respectively. Yang
et al. (2012) examined different configurations of a hybrid
growth MBR for treatment of mixed wastewater. In this
study, the balance between MLSS and biofilm fractions
was important to obtain high removal efficiency and low
fouling in the reactors. Aeration conditions affected biofilm
growth and reactor performance.
Yu et al. (2012) reviewed recent advances in EPS
of bio-aggregates in MBRs. The main focus of the review
was on the effects of EPS on the settleability and
dewaterability of bio-aggregates and membrane pollution in
MBRs. EPS structure and composition affect the settling
and dewatering characteristics of sludge and the membrane
fouling by changing the sludge potential. Moreover, the
authors mentioned that the components and distribution of
EPS influence the formation and structural stability of
granulation.
Membrane Biofilm Reactor
Picard et al. (2012) quantified mass transfer
through a membrane-aerated heterotrophic biofilm using
the effective diffusivity. The effective diffusivity through
the biofilm was larger than in the bulk, indicating the
presence of dispersion generated by convection inside the
biofilm. Wei et al. (2012) investigated COD and nitrogen
removal in relation to feed flow control in a facilitated-
transfer membrane-aerated biofilm reactor (FT-MABR).
With an increase of flow velocity, resistance impact load
capability and oxygen utilization efficiency of the FT-
MABR were enhanced and ammonium was removed
preferentially compared with COD. At the feed flow
velocity of 0.05 m/s, when COD:N ratios were 3, 5 and 7,
the TN removal efficiency reached 50.7%, 72.8% and
83.5%, respectively.
The principles, applications and recent
developments in membrane biofilm reactor (MBfR)
technology for water and wastewater treatment was
reviewed (Martin and Nerenberg 2012). Biofilms in MBfR
have different behavior from conventional biofilms and can
be applied for numerous treatment applications. Major
advantages include their high gas utilization efficiency, low
1080 Water Environment Research, Volume 85, Number 10—Copyright © 2013 Water Environment Federation
energy consumption, and small reactor footprints, but
challenges were still faced with MBfR in areas such as
biofilm management, the design of scalable reactor types,
and the identification of cost effective membrane materials.
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Freeman, B. D.; Paul, D. R.; Whiteley, M. and
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Muhamad, M. H. Z.; Abdullah, S. R. S.; Mohamad, A.;
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1087 Water Environment Research, Volume 85, Number 10—Copyright © 2013 Water Environment Federation
Odegaard, H.; Mende, U.; Skjerping, E. O.; Simonsen, S.;
Strube, R. and Bundgaard, E. (2012). Compact
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