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


(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.


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


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


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.


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


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


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


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


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


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


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.


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


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


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.


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


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


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.


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.


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


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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