Aerobic Biofilm Reactor Research Articles

Abatement of 4-Chlorophenol in Aqueous Phase by Ozonation Coupled with a Sequencing Batch Biofilm Reactor (SBBR)

The aim of this work was to assess the mineralization of 100 and 200 mg L−1 4-chlorophenol (4-CP) solutions by ozonation-biological treatment. The results show that starting from a 4-CP initial concentration from 100 to 500 mg L−1 and using an ozone flow rate of 5.44 and 7.57 g h−1, 4-CP was completely removed. A kinetic constant around 9·10−2 min−1 was calculated for the ozone direct attack. The biodegradability (BOD5/COD) of the pre-ozonated solutions increased from 0 until a range between 0.2–0.37. The combination of the ozonation and aerobic biological treatment in an aerobic sequencing batch biofilm reactor (SBBR) gave an abatement of more than 90% of the initial TOC.

Nitrifying bacterial communities and its activities in aerobic biofilm reactors under different temperature conditions

Tests were performed to investigate nitrifying bacterial communities and activities in aerobic biofilm reactors with different temperature conditions, denaturing gradient gel electrophoresis (DGGE) based on polymerase chain reaction targeting 16S rRNA and amoA gene, fluorescence in situ hybridization (FISH) and dehydrogenase activity (DHA). T1, T2 and T3 reactors operated at different temperatures (5, 10 and 30 °C, respectively) were set up in the thermostat and acclimated. Nitrification was considerably limited in T1 and T2 reactors. DGGE revealed specific genera of ammonium-oxidizing bacteria (AOB) and some Nitrosomonas genera endured at the low temperatures. FISH revealed a decreased distribution ratio between AOB and nitrate-oxidizing bacteria at 5 °C, and showed that the decrease of AOB also affected the nitrification failure in the aerobic biofilm reactor. The mean attached biomass of the T1, T2 and T3 reactors was 69.6, 80.6 and 112.9 mg/L, respectively, and the 2-(p-iodophenyl)-3-(p-nitrophenyl)-5-phenyl tetrazolium chloride dehydrogenase activity of the respective reactors was 73.6, 87.4 and 134.2 mgO 2 * /g VSS/day. The results demonstrate that a low temperature condition in an aerobic biofilm reactor decreases the attached biomass, distribution ratio and activity of nitrifying bacteria, and produces a change in the composition of the AOB species, which results in the failure of nitrification.

Analysis of nitrifying bacterial communities in aerobic biofilm reactors with different DO conditions using molecular techniques

In order to assess the relationship between the dissolved oxygen (DO) concentration and the characteristics of nitrifying bacterial communities in an aerobic biofilm reactor, molecular techniques including denaturing gradient gel electrophoresis (DGGE)/cloning based on PCR targeting 16S rRNA and the amoA gene and fluorescence in situ hybridisation (FISH) were conducted. The D-1, D-2, D-3 and D-4 reactors with different DO concentrations (1, 3, 5 and 7 mg/L, respectively) were set up in the thermostat and acclimated. The optimal DO concentration with stable nitrification efficiency was above 5.0 mg/L. As was shown by the results of DGGE and cloning, the community of ammonia-oxidising bacteria (AOB) and the ratio of Nitrosomonas sp. changed only slightly despite their differing nitrification efficiencies. The results of FISH indicated that higher DO concentrations resulted in an increase in AOB and nitrite-oxidising bacteria (NOB), and a reduction in heterotrophic microorganisms. The INT-dehydrogenase activity (DHA) test demonstrated that the activity of AOB decreased with reductions in the DO concentration. This means that the DO concentration does not influence the community of AOB, but rather the activity of AOB. In the relationship between the attached biomass and the nitrification efficiency, only the active biomass affected the nitrification efficiencies.

Kinetics of Particulate Organic Matter Removal as a Response to Bioflocculation in Aerobic Biofilm Reactors

Recent research has identified that the major fraction of chemical oxygen demand in domestic wastewaters is in particulate form. The research presented herein develops the kinetics of particle removal as a response to bioflocculation at the surface of aerobic biofilms. This study focuses on the removal of particles that are maintained in aqueous suspension after 30 minutes of gravity settling. It is helpful to consider the particulate organics removal process in biofilms as the sum of four steps, namely (1) external transport of the particles to the biofilm surface, (2) bioflocculation, (3) organic particulate hydrolysis, and (4) diffusion and reaction of the solubilized organics by the bacterial cells comprising the biofilm. Organic (native corn starch) and inorganic particle (Min-U-Sil 10 [U.S. Silica Company, Berkeley Springs, West Virginia]) suspensions, with micronutrients, were continuously fed to a rotating disc biofilm reactor to verify a first-order kinetic expression that has been used to describe bioflocculation and to demonstrate that bioflocculation is the primary particle removal mechanism. Extracellular polymeric substances were extracted and quantified to describe the role they play in the bioflocculation process.

Factors affecting simultaneous nitrification and denitrification in an SBBR treating domestic wastewater

An aerobic sequencing batch biofilm reactor (SBBR) packed with Bauer rings was used to treat real domestic wastewater for simultaneous nitrification and denitrification. The SBBR is advantageous for creating an anoxic condition, and the biofilm can absorb and store carbon for good nitrification and denitrification. An average concentration of oxygen ranging from 0.8 to 4.0 mg/L was proved very efficient for nitrification and denitrification. Volumetric loads of TN dropped dramatically and effluent TN concentration increased quickly when the concentration of average dissolved oxygen was more than 4.0 mg/L. The efficiency of simultaneous nitrification and denitrification (SND) increased with increasing thickness of the biofilm. The influent concentration hardly affected the TN removal efficiency, but the effluent TN increased with increasing influent concentration. It is suggested that a subsequence for denitrification be added or influent amount be decreased to meet effluent quality requirements. At optimum operating parameters, the TN removal efficiency of 74%–82% could be achieved.

Simultaneous removal of COD and ammonium from landfill leachate using an anaerobic–aerobic moving-bed biofilm reactor system

The performance of a moving-bed biofilm reactor (MBBR) system with an anaerobic–aerobic arrangement was investigated to treat landfill leachate for simultaneous removal of COD and ammonium. It was found that the anaerobic MBBR played a major role in COD removal due to methanogenesis, and the aerobic MBBR acted as COD-polishing and ammonium removal step. The contribution of the anaerobic MBBR to total COD removal efficiency reached 91% at an organic loading rate (OLR) of 4.08 kgCOD/(m 3 d), and gradually decreased to 86% when feed OLR was increased to 15.70 kgCOD/(m 3 d). Because of the complementary function of the aerobic reactor, the total COD removal efficiency of the system had a slight decrease from 94% to 92% even though the feed OLR was increased from 4.08 to 15.70 kgCOD/(m 3 d). Hydraulic retention time (HRT) had a significant effect on NH 4 + -N removal; more than 97% of the total NH 4 + -N removal efficiency could be achieved when the HRT of the aerobic MBBR was more than 1.25 days. The anaerobic–aerobic system had a strong tolerance to shock loading. A decrease in COD removal efficiency of only 7% was observed when the OLR was increased by four times and shock duration was 24 h, and the system could recover the original removal efficiency in 3 days. The average sludge yield of the anaerobic reactor was estimated to be 0.0538 gVSS/gCOD rem.

Fluorescence in situ hybridization and INT-dehydrogenase activity test to assess the effect of DO concentration in aerobic biofilm reactor

To assess the effect of DO concentration in aerobic biofilm reactor, we investigated the bacterial communities and their activity utilizing the combination of two methods, fluorescence in situ hybridization (FISH) and INTdehydrogenase activity test. D-1, D-2, D-3 and D-4 reactor with different DO concentrations (1, 3, 5 and 7 mg/L, respectively) were set up in the thermostat and acclimated. The optimal DO concentration with stable nitrification efficiency in aerobic biofilm reactor was above 5.0 mg/L. FISH method showed us that higher DO concentration led to the increase of ammonia-oxidizing bacteria and nitrite-oxidizing bacteria ratios and the decrease of heterotrophs ratio. The INT-DHA activities of each reactor were 203, 153, 36 and 45 mgO2*/g VSS/day, respectively. The INT-DHA activities in D-1 and D-2 reactors were higher than those of D-3 and D-4 reactors, which indicates that filamentous microorganisms affected the INT-DHA activity. In the case of D-3 and D-4 reactors, as nitrification efficiency increased, INT-DHA activity also increased. In the relationship between the attached biomass and nitrification efficiency, only active biomass influenced the nitrification efficiency.

Performances and microbial features of an aerobic packed-bed biofilm reactor developed to post-treat an olive mill effluent from an anaerobic GAC reactor

BackgroundOlive mill wastewater (OMW) is the aqueous effluent of olive oil producing processes. Given its high COD and content of phenols, it has to be decontaminated before being discharged. Anaerobic digestion is one of the most promising treatment process for such an effluent, as it combines high decontamination efficiency with methane production. The large scale anaerobic digestion of OMWs is normally conducted in dispersed-growth reactors, where however are generally achieved unsatisfactory COD removal and methane production yields. The possibility of intensifying the performance of the process using a packed bed biofilm reactor, as anaerobic treatment alternative, was demonstrated. Even in this case, however, a post-treatment step is required to further reduce the COD. In this work, a biological post-treatment, consisting of an aerobic biological "Manville" silica bead-packed bed aerobic reactor, was developed, tested for its ability to complete COD removal from the anaerobic digestion effluents, and characterized biologically through molecular tools.ResultsThe aerobic post-treatment was assessed through a 2 month-continuous feeding with the digested effluent at 50.42 and 2.04 gl-1day-1 of COD and phenol loading rates, respectively. It was found to be a stable process, able to remove 24 and 39% of such organic loads, respectively, and to account for 1/4 of the overall decontamination efficiency displayed by the anaerobic-aerobic integrated system when fed with an amended OMW at 31.74 and 1.70 gl-1day-1 of COD and phenol loading rates, respectively. Analysis of 16S rRNA gene sequences of biomass samples from the aerobic reactor biofilm revealed that it was colonized by Rhodobacterales, Bacteroidales, Pseudomonadales, Enterobacteriales, Rhodocyclales and genera incertae sedis TM7. Some taxons occurring in the influent were not detected in the biofilm, whereas others, such as Paracoccus, Pseudomonas, Acinetobacter and Enterobacter, enriched significantly in the biofilter throughout the treatment.ConclusionThe silica-bead packed bed biofilm reactor developed and characterized in this study was able to significantly decontaminate anaerobically digested OMWs. Therefore, the application of an integrated anaerobic-aerobic process resulted in an improved system for valorization and decontamination of OMWs.

Biological nutrient removal in simple dual sludge system with an UMBR (upflow multi-layer bioreactor) and aerobic biofilm reactor

In this study, a simple dual sludge process was developed for small sewage treatment. It is a hybrid system that consists of upflow multi-layer bioreactor (UMBR) as anaerobic and anoxic reactor with suspended growth microorganisms and post aerobic biofilm reactor with inclined plates. UMBR is a multifunction reactor that acts as primary sedimentation tank, anaerobic reactor, anoxic reactor, and thickener. The sludge blanket in the UMBR is maintained at a constant level by automatic control so that clear water (30 mg-SS/L) can flow into the post aerobic biofilm reactor. It leads to improving performance of the biofilm reactor due to preventing of excess microbial attachment on the media surface and no requirment for a large clarifier caused by low solid loading. The HRT in the UMBR and the aerobic biofilm reactor were about 5.8 h and 6.4 h, respectively. The temperature in the reactor during this study varied from 12.5 degrees C to 28.3 degrees C. The results obtained from this study show that effluent concentrations of TCOD, TBOD, SS, TN, and TP were 29.7 mg/L, 6.0 mg/L, 10.3 mg/L, 12.0 mg/L, and 1.8 mg/L, which corresponded to a removal efficiency of 92.7%, 96.4%, 96.4%, 74.9%, and 76.5%, respectively. The sludge biomass index (SBI) of the excess sludge in the UMBR was about 0.55, which means that the sludge in the UMBR was sufficiently stabilized and may not require further treatment prior to disposal.

Degradation of trichloroethylene in a coupled anaerobic–aerobic bioreactor: Modeling and experiment

This work studied trichloroethylene (TCE) degradation in a single stage coupled anaerobic–aerobic granular biofilm reactor. The co-existence of aerobic methanotrophic and anaerobic methanogenic bacteria in this reactor was expected to allow for a combination of reductive and oxidative pathways of TCE degradation and result in mineralization of TCE. First, the anaerobic–aerobic coupling was simulated using a mathematical model. Simulations of TCE degradation under different operating conditions suggested the superiority of the coupled reactor system over either aerobic or anaerobic process alone. Next, the approach of combining aerobic–anaerobic TCE degradation was validated in a reactor experiment. The experiment confirmed degradation of TCE due to the co-existence of methanogenic and methanotrophic populations in a single reactor.

Feasibility study on the removal of nitrous compounds with a hollow-fiber membrane biofilm reactor

The objective of this study was to develop an integrated nitrogen treatment system using autotrophic organisms. A treatment system consists of an aerobic hollow-fiber membrane biofilm reactor (HfMBR) and anaerobic HfMBR. In the aerobic HfMBR, a mixture gas of air and O2 was supplied through the fibers for nitrification. Denitrification occurred in the anaerobic HfMBR using H2 as the electron donor. The treatment system was continuously operated for 190 days. NH4-N removal efficiencies ranging from 95% to 97% were achieved at NH4-N concentrations of influent ranging from 50 to 100 mg N/L. When glucose was added to the influent, the simultaneous nitrification and denitrification occurred in the aerobic HfMBR, and nitrogen removal rates were changed according to the COD/NH4-N ratio of influent. In the anaerobic HfMBR, autotrophic denitrification using H2 occurred and the removal rates achieved in this study were 23-58 mg N/m2 d. In this study, the achieved removal efficiency was lower than other study findings; however, the result suggested that this hybrid HfMBR system can be used effectively for nitrogen removal in oligotrophic water.

Evaluation of a Novel Integrated Bioreactor—AOS System for Treating Oil-Containing Restaurant Wastewater on Site in Hong Kong

AOS system is an anaerobic digestion reactor (A-section, UASB or UBF), oxidation degradation reactor (O-section, aerobic biofilm reactor), and physical sedimentation tank (S-section) 3-in-1 integrated reactor. The compact bioreactor was applied to treat oil-containing restaurant's wastewater on site in Hong Kong. The treatment efficiency was observed at different HRT. Experimental results indicated that the AOS system for treating oil-containing restaurant wastewater on site was feasible when HRT at 0.6 days above. During the running period, the net sludge generation rate of the AOS system was only about 0.08–0.09 g g-1 removed COD, and the utmost COD specific volumetric removal rate (SVRR) of the system reached 2.77 gL-1 d-1. The utmost specific biomass substrate utilization rate (SBSUR) of COD in O-section and A-section reached 1.22 d-1 and 0.128 d-1, respectively. In addition, the experiment results showed that the AOS system with a filter in UASB (that is UBF's AOS system) could bear much more great HLR comparing with UASB's AOS and was more efficient for treating oil-containing restaurant's wastewater on site.

Biomass characteristics in three sequencing batch reactors treating a wastewater containing synthetic organic chemicals

The physical and biochemical characteristics of the biomass in three lab-scale sequencing batch reactors (SBR) treating a synthetic wastewater at a 20-day target solids retention time (SRT) were investigated. The synthetic wastewater feed contained biogenic compounds and 22 organic priming compounds, chosen to represent a wide variety of chemical structures with different N, P and S functional groups. At a two-day hydraulic retention time (HRT), the oxidation-reduction potential (ORP) cycled between -100 (anoxic) and 100 mV (aerobic) in the anoxic/aerobic SBR, while it remained in a range of 126+/-18 and 249+/-18 mV in the aerobic sequencing batch biofilm reactor (SBBR) and the aerobic SBR reactor, respectively. A granular activated sludge with excellent settleability (SVI=98+/-31 L mg(-1)) developed only in the anoxic/aerobic SBR, compared to a bulky sludge with poor settling characteristics in the aerobic SBR and SBBR. While all reactors had very good COD removal (>90%) and displayed nitrification, substantial nitrogen removal (74%) was only achieved in the anoxic/aerobic SBR. During the entire operational period, benzoate, theophylline and 4-chlorophenol were completely removed in all reactors. In contrast, effluent 3-nitrobenzoate was recorded when its influent concentration was increased to 5 mg L(-1) and dropped only to below 1 mg L(-1) after 300 days of operation. The competent (active) biomass fractions for these compounds were between 0.04% and 5.52% of the total biomass inferred from substrate-specific microbial enumerations. The measured competent biomass fractions for 4-chlorophenol and 3-nitrobenzoate degradation were significantly lower than the influent COD fractions of these compounds. Correspondent to the highest competent biomass fraction for benzoate degradation among the test SOCs, benzoate oxidation could be quantified with an extant respirometric technique, with the highest specific oxygen uptake rate (SOUR(benzoate), 0.026 g O2 h(-1) g(-1) XCOD) in the anoxic/aerobic SBR. These combined results suggest that operating SBRs with alternative anoxic/aerobic cycles might facilitate the formation of granular sludge with good settleability, and retain comparable removal of nitrogen and synthetic organic compounds. Hence, the practice of anoxic/aerobic cycling should be considered in wastewater treatment systems whenever possible.

Biodegradation of Polychlorinated Biphenyls Using Acclimadzed Biofilmina Three-Phase Fluidized Bed Aerobic Reactor

This paper investigates the ability of microorganisms in a biofilm to degrade polychlorinated biphenyls (PCBs) using a three-phase fluidized bed aerobic biofilm reactor. Water was spiked with PCBs that contain mainly Aroclor 1260 to simulate PCB-contaminated water. The contaminated water was batch fed into the reactor to acclimatize the microorganisms in the biofilm. The degradation of PCBs was monitored through the decrease in concentration of Aroclor 1260. Samples were analyzed using gas chromatography equipped with an electron capture detector (ECD). Batch experimental runs with an initial concentration of around 70 ppm showed PCB degradation of up to 93% after 8 h. After the runs that usen contaminated water, the batch runs using feed that contain easily degradable organic chemicals were performed to determine the effect of contact with PCB on the biofilm. Their latter runs showed that the COD degradation rate had no significant difference with the COD runs before the PCB batch runs. These results showed that biofilm formed in a three-phase fluidized bed Aerobic is capable of degrading PCB in water and that the microorganisms are not significantly affected by exposure to PCB.

An aerobic fixed-phase biofilm reactor system for the degradation of the low-molecular weight aromatic compounds occurring in the effluents of anaerobic digestors treating olive mill wastewaters

An aerobic co-culture, prepared by combining Ralstonia sp. LD35 and Pseudomonas putida DSM1868, was recently found to be capable of extensively degrading many of the hydroxylated and/or methoxylated benzoic, phenylacetic and 3-phenyl-2-propenoic acids occurring in the olive mill wastewaters (OMWs). In the perspective of developing a biotechnological process for the degradation of low-molecular weight (MW) aromatic compounds occurring in the effluents of anaerobic digestors treating OMWs, the capability of this bacterial co-culture of biodegrading a synthetic mix of the above mentioned compounds and the aromatic compounds of an anaerobic OMW-treatment plant effluent in the physiological state of immobilised cells was investigated. Two aerobic fixed-bed biofilm reactors were developed by immobilising the co-culture cells on Manville silica beads and on polyurethane foam cubes. Both supports were found to give rise to a microbiologically stable and biologically active biofilm. The two biofilm reactors were found to be similarly capable of rapidly and completely biodegrading the components of a synthetic mix of nine monocyclic aromatic acids typically present in OMWs and the low-MW aromatic compounds occurring in the anaerobic effluent in batch conditions. However, in the same conditions, the silica bead-packed reactor was found to be more effective in the removal of high-MW phenolic compounds from the anaerobic effluent with respect to the polyurethane cube-packed reactor. These results are encouraging in the perspective of using the co-culture as immobilized cells for developing a continuous biotechnological process for the post-treatment of effluents with low-MW aromatic compounds produced by anaerobic digestors treating OMWs.

Metabolic response of biofilm to shear stress in fixed-film culture.

In a biofilm reactor, detachment force resulting from hydraulic shear is a major factor that determines the formation and structure of steady state biofilm. The metabolic response of biofilm to change in shear stress was therefore investigated. A conventional annular reactor made of PVC was used, in which shearing over the rotating disc surface was strictly defined. Results from the steady state aerobic biofilm reactor showed that the biofilm structure (density and thickness) and metabolic behaviour (growth yield and dehydrogenase activity) were closely related to the shear stress exerted on the biofilm. Smooth, dense and stable biofilm formed at relatively high shear stress. Higher dehydrogenase activity and lower growth yield were obtained when the shear stress was raised. Growth yield was inversely correlated with the catabolic activity of biofilm. The reduced growth yield, together with the enhanced catabolic activity, suggests that a dissociation of catabolism from anabolism would occur at high shear stress. Biofilms may respond to shear stress by regulating metabolic pathways associated with the substrate flux flowing between catabolism and anabolism. A biological phenomenon, besides a simple physical effect, is underlying the observed relation between the shear stress and resulting biofilm structure. A hypothesis is proposed that the shear-induced energy spilling would be associated with a stimulated proton translocation across the cell membrane, which favours formation of a stronger biofilm. This research may provide a basis for experimental data on biofilm obtained at different shear stresses to be interpreted in relation to energy.

Contributions of biofilm versus suspended bacteria in an aerobic circulating-bed biofilm reactor

This study demonstrated that, during the two-step biodegradation of toluene in an aerobic circulating-bed biofilm reactor, biofilm and suspended bacteria played critical roles. Although the suspended bacteria were less than 1% of the total amount of biomass in the system, they transformed up to 30% of the toluene into its intermediate in the bulk liquid phase. On the other hand, most of the toluene intermediate was removed inside the biofilm, where diffusion resistance reduced the toluene concentration, thereby relieving inhibition to the degradation reaction of the intermediate. The suspended bacteria are most important for rapidly biodegraded substrates, for which diffusion limitation controls the kinetics in the biofilm. They lose importance when the effects of an inhibiting substrate must be overcome.

Combined anaerobic treatment of wastewaters and sludges

One of the most recent and progressive reactor principles used in anaerobic wastewater treatment technology is a vertical compartmentalization, which is used in the USSB (Upflow Staged Sludge Bed) reactor. Thanks to its specific design and features the operation of such a reactor can be very flexible. Examples are given showing tested alternatives of operation with combined wastewater and sludge treatment. A high treatment efficiency and a very low specific sludge production was achieved with the operation of a technological system consisting of a USSB reactor and an aerobic biofilm reactor. In the USSB reactor wastewater and surplus sludge treatment can not only be combined but also anaerobic pretreatment and biological denitrification.

Kinetic analysis of simultaneous 2,4-dinitrotoluene (DNT) and 2, 6-DNT biodegradation in an aerobic fluidized-bed biofilm reactor.

We previously reported on the mineralization of 2,4-dinitrotoluene (2,4-DNT) and 2,6-dinitrotoluene (2,6-DNT) in an aerobic fluidized-bed bioreactor (FBBR) (Lendenmann et al. 1998 Environ Sci Technol 32:82-87). The current study examines the kinetics of 2, 4-DNT and 2,6-DNT mineralization at increasing loading rates in the FBBR with the goal of obtaining system-independent kinetic parameters. At each steady state, the FBBR was subjected to a set of transient load experiments in which substrate flux in the biofilm and bulk substrate concentrations were measured. The pseudo-steady-state data were used to estimate the biokinetic parameters for 2,4-DNT and 2,6-DNT removal using a mechanistic mathematical biofilm model and a routine that minimized the sum of the squared residuals (RSS). Estimated kinetic parameters varied slightly for each steady-state; retrieved parameters for qm were 0. 83 to 0.98 g DNT/g XCOD d for 2,4-DNT removal and 0.14 to 0.33 g DNT/g XCOD d for 2,6-DNT removal. Ks values for 2,4-DNT removal (0. 029 to 0.36 g DNT/m3) were consistently lower than Ks values for 2, 6-DNT removal (0.21 to 0.84 g DNT/m3). A new approach was introduced to estimate the fundamental biofilm kinetic parameter S*b,min from steady-state performance information. Values of S*b,min indicated that the FBBR performance was limited by growth potential. Adequate performance of the examined FBBR technology at higher loading rates will depend on an improvement in the growth potential. The obtained kinetic parameters, qm, Ks, and S*b,min, can be used to aid in the design of aerobic FBBRs treating waters containing DNT mixtures.

Removal of Polychlorinated Phenols in Sequential Anaerobic–Aerobic Biofilm Reactors Packed with Tire Chips

Scrap vehicle tire chips were used as packing material for sequential anaerobic–aerobic biofilm reactors to remove persistent chlorinated hydrocarbons. Adsorption capacity of scrap tires was greater under acidic conditions than under basic conditions. However, it was only approximately 0.04 to 0.3% of that of activated carbon. The amount of biomass that attached to the surface of scrap tires was 3.16 and 3.72 mg volatile suspended solids/cm2 after 14 and 37 days, respectively. Two laboratory‐scale, down‐flow anaerobic–aerobic biofilm reactors packed with tire chips were operated to remove 2,4‐dichlorophenol (DCP) and 4‐chlorophenol (CP). More than 98% of DCP was dehalogenated to CP in the anaerobic reactor, 70 to 98% of which was subsequently degraded in the aerobic reactor. Scrap tires did not cause any operational problems when used as biofilter media.