Phenol Loading Research Articles

Surface Modification of Okara Cellulose Crystals with Phenolic Acids to Prepare Multifunction Emulsifier with Antioxidant Capacity and Lipolysis Retardation Effect.

Emulsion-based foods are widely consumed, and their characteristics involving colloidal and oxidative stabilities should be considered. The fabrication of the interfaces by selecting the emulsifier may improve stability and trigger lipolysis, thereby reducing energy uptake from the emulsified food. The present work aimed to develop Okara cellulose crystals (OCs) as a multifunction emulsifier to preserve the physical and chemical stability of a Pickering emulsion via surface modification with phenolic acids. The modification of OC was performed by grafting with the selected phenolics to produce OC-gallic acid (OC-G) and OC-tannic acid (OC-T) complexes. There was a higher phenolic loading efficiency when the OC reacted with gallic acid (ca. 70%) than with tannic acid (ca. 50%). This trend was concomitant with better antioxidant activity of the OC-G than OC-T. Surface modification based on grafting with phenolic acids improved capability of the OC to enhance both the colloidal and oxidative stability of the emulsion. In addition, the cellulosic materials had a retardation effect on the in vitro lipolysis compared to a protein-stabilized emulsion. Surface modification by grafting with phenolic acids successfully provided OC as an innovative emulsifier to promote physico-chemical stability and lower lipolysis of the emulsion.

Comparative Phytochemical Analyses of Flowers from Primula veris subsp. veris Growing Wild and from Ex Situ Cultivation in Greece.

In the last decades, Primula veris subsp. veris (roots and flowers) has been over harvested through legal and illegal ways in Greece, due to its extremely high commercial demand, as it is used in industry because of its well-known therapeutic properties. As ex situ cultures of the plant have been already developed, in the current comparative study, the herbal teas (infusions) from both flowers of cowslip growing wild in the Prespa Lake Park (NW Greece), and from ex situ propagated and cultivated plant material, have been investigated, with the ultimate goal of assessing them qualitatively. Furthermore, through classic phytochemical studies, the ten most abundant metabolites, belonging to the chemical categories of flavonol-glycosides and methoxy flavones, have been identified and structurally determined. The chemical profile of both infusions has been further analyzed through UHPLC-HRMS, showing that they show only light differences. The total phenolic content (TPC) of both studied samples (wild and ex situ cultivation), was determined by the Folin-Ciocalteau method, followed by an antioxidant activity assay though DPPH where, in both cases, wild plants exerted higher phenolic load and stronger antioxidative properties. According to the reported results, it could be proposed that the ex situ cultivated plant material could facilitate the mass production of plants and the sustainable cultivation of cowslip in the Greek mountains.

Assessing the impact of increasing phenol loads on the performance and stability of an aerobic granular sludge system

This work evaluated the impact of phenol on the performance and stability of an aerobic granular sludge (AGS) sequencing batch reactor (SBR) operated under alternating anaerobic-aerobic conditions for simultaneous organic matter, nitrogen, and phosphorus removal. The reactor was fed with synthetic wastewater whose phenol concentration was gradually increased from 2 to 200 mg L−1, while the other carbon source (acetate) was reduced proportionally to keep the organic loading rate invariable. Up to 20 mg L−1 of phenol, the average COD removal was above 90%, while practically full ammonium, phosphorus, and phenol removal was achieved. However, at higher phenol concentrations, the activity of polyphosphate-accumulating organisms and nitrifiers was affected. Although the overall COD removal was only slightly affected by increasing phenol loads, replacing the main carbon source from acetate to phenol changed the organic matter removal profile over the cycle, with the latter being converted mainly within the aerated stage of the SBR. As a result, there was filamentous growth that deteriorated the settling properties of the granules. The establishment of an anaerobic feast-aerobic famine regime over the non-aerated and aerated phases of the AGS SBR and the presence of a readily biodegradable substrate (such as acetate) proved to be crucial for maintaining granules stability. Having phenol as the sole organic carbon source led to complete process failure regarding nutrient removal capability.

Screening and evaluation of phenol utilization and growth in Acinetobacter baumannii W29 of wastewater

Phenols are ubiquitous pollutants, mainly from industrial effluent, causing pollution of natural water resources. The research focused on screening efficient phenol-degrading bacteria and kinetic modelling of phenol biodegradation and growth. Membrane filtration was used for the isolation of bacteria from the wastewater sample. The screening of phenol-degrading bacteria was based on the efficiency of phenol utilization. The strain with efficient phenol degradation capacity was characterized by 16S rDNA sequencing and designated Acinetobacter baumannii W29. Biomass growth and phenol utilization rate of the strain were evaluated at different initial phenol concentrations (100-800 mgL-1). Specific growth rate data were fitted to five models, i.e. Monod, Haldane, Aiba, Teisser, and Webb model. The yield coefficient at different initial phenol concentrations was calculated from the slope of the specific growth rate (μ) versus the specific phenol utilization rate (q). The strain showed complete phenol degradation potential up to 1000 mgL-1. The maximal growth rate was achieved at 400 mgL-1 , which coincided with the maximum substrate utilization rate at the same concentration. The specific growth rate showed the best fit with the Haldane model. The strain had a yield coefficient of 0.70 (mg cell mg-1 phenol). The value of µ and Ks revealed the affinity of the strain for high-concentration phenol and the its ability to withstand high phenol concentrations. The kinetic growth behaviour of the strain fitted well with the Haldane model. The findings of the study could be applied to wastewater treatment with a high phenol load.

Impact of gradually-achieved high phenol loads on the nitrification and COD removal performance of an MBBR fed with synthetic wastewater

ABSTRACT Phenol is a noteworthy pollutant, found in effluents of many industrial processes, like oil refining and drugs production, which can impair the treatment efficiency of bioreactors. This study evaluated the performance of phenol, COD, and nitrogen removal of an aerobic bench-scale Moving Bed Biofilm Reactor (MBBR) exposed to gradually increasing phenol content over 233 days. The reactor had Hydraulic Retention Time (HRT) set at 3 h and 40% filling degree (K1 media), and was fed with synthetic wastewater containing phenol (10, 20, 50, 100, 250 and 400 mg/L), glucose (400 mgCOD/L), and 40 mgN-NH3/L. Phenol, COD, and ammoniacal nitrogen removal averages were high – above 88%, 81%, and 82%, respectively –, even when the MBBR was exposed to the greatest phenol loads, indicating that the biofilm was able to acclimate and resist high phenol concentrations. However, the intense EPS production revealed the impact caused by phenol to the biofilm from the concentration of 250 mg/L onwards. Even though, at this concentration, the average removals of COD and phenol were 87.2% and 89.7%. The removal of ammoniacal nitrogen by nitrification was compromised, being 91.6% of the ammoniacal nitrogen removed by assimilation and only 0.35% removed by nitrification. At 400 mg phenol/L, the reactor provided COD and phenol average removals equal 88.6% and 80.9%, respectively. On the last day of operation, the removal of COD dropped to 55.4% and phenol removal was equal 49.0%. Novel microscopical evaluation of the MBBR’s biofilm revealed some negative effects of the phenol on the microbiota composition.

Enhancing phenol removal from waste water by adding powder activated carbon to the lab-scale activated sludge system

In this study, the commercial powder activated carbon (PAC) was added to a bench scale conventional activated sludge (CAS) system to enhance phenol removal. The mixed liquor suspended solid (MLSS) concentration of CAS with adding PAC was stable in all stages of operation, while MLSS concentrations in CAS without PAC addition sharply decreased as the Phenol loading reached 1.8 g phenol/L.day. Higher removal of chemical oxygen demand (COD) and Phenol achieved with the CAS by PAC addition compared with those achieved with CAS without PAC addition. The difference in COD removal efficiency was 7 - 9% in stages 3 and 4 (0.8 and 1.2 g phenol/L.day, respectively), and about 33% in stage 5 (1.8 g phenol/L.day). The advantage of CAS with PAC addition was clearly observed in the highest phenol loading (1.8 g phenol/L.day) because the MLVSS/MLSS ratio of CAS with PAC addition increased and the COD and phenol removal efficiencies kept stable in this stage, while reverse trends were found for CAS without PAC addition. The results indicated that the adaptive ability of the CAS by adding PAC was significantly higher than the CAS without AC addition. This study offers useful preliminary results for applying a hybrid system between CAS and adsorption with PAC for further research and application in future.

Antioxidant Power on Dermal Cells by Textiles Dyed with an Onion (Allium cepa L.) Skin Extract.

In this study, the phenol loading and antioxidant activity of wool yarn prepared with the aqueous extract of onion (Allium cepa L.) skin was enhanced by implementing the dyeing process with the use of alum as a mordant. Spectrophotometric and chromatographic methods were applied for the characterization of polyphenolic substances loaded on the wool yarn. The antioxidant/anti-inflammatory properties were evaluated by determining the level of intra- and extra-cellular reactive oxygen species (ROS) production in keratinocytes and dermal fibroblasts pre-treated with lipopolysaccharide put in contact with artificial sweat. An elevated dye uptake on wool was observed for the pre-mordanted sample, as demonstrated by high absorbance values in the UV-Visible spectral range. Chromatographic results showed that protocatechuic acid and its glucoside were the main phenolic acid released in artificial sweat by the wool yarns, while quercetin-4′-glucoside and its aglycone quercetin were more retained. The extract released from the textile immersed in artificial sweat showed a significant reducing effect on the intra-and extracellular ROS levels in the two cell lines considered. Cytofluorimetric analyses demonstrated that the selected mordant was safe at the concentration used in the dyeing procedure. Therefore, alum pre-mordanted textiles dyed with onion-skin extracts may represent an interesting tool against skin diseases.

Anaerobic Conversion of Saline Phenol-Containing Wastewater Under Thermophilic Conditions in a Membrane Bioreactor.

Closing water loops in chemical industries result in hot and highly saline residual streams, often characterized by high strength and the presence of refractory or toxic compounds. These streams are attractive for anaerobic technologies, provided the chemical compounds are biodegradable. However, under such harsh conditions, effective biomass immobilization is difficult, limiting the use of the commonly applied sludge bed reactors. In this study, we assessed the long-term phenol conversion capacity of a lab-scale anaerobic membrane bioreactor (AnMBR) operated at 55°C, and high salinity (18 gNa+.L–1). Over 388 days, bioreactor performance and microbial community dynamics were monitored using specific methanogenic activity (SMA) assays, phenol conversion rate assays, volatile fatty acids permeate characterization and Illumina MiSeq analysis of 16S rRNA gene sequences. Phenol accumulation to concentrations exceeding 600 mgPh.L–1 in the reactor significantly reduced methanogenesis at different phases of operation, while applying a phenol volumetric loading rate of 0.12 gPh.L–1.d–1. Stable AnMBR reactor performance could be attained by applying a sludge phenol loading rate of about 20 mgPh.gVSS–1.d–1. In situ maximum phenol conversion rates of 21.3 mgPh.gVSS–1.d–1 were achieved, whereas conversion rates of 32.8 mgPh.gVSS–1.d–1 were assessed in ex situ batch tests at the end of the operation. The absence of caproate as intermediate inferred that the phenol conversion pathway likely occurred via carboxylation to benzoate. Strikingly, the hydrogenotrophic SMA of 0.34 gCOD-CH4.gVSS–1.d–1 of the AnMBR biomass significantly exceeded the acetotrophic SMA, which only reached 0.15 gCOD-CH4.gVSS–1.d–1. Our results indicated that during the course of the experiment, acetate conversion gradually changed from acetoclastic methanogenesis to acetate oxidation coupled to hydrogenotrophic methanogenesis. Correspondingly, hydrogenotrophic methanogens of the class Methanomicrobia, together with Synergistia, Thermotogae, and Clostridia classes, dominated the microbial community and were enriched during the three phases of operation, while the aceticlastic Methanosaeta species remarkably decreased. Our findings clearly showed that highly saline phenolic wastewaters could be satisfactorily treated in a thermophilic AnMBR and that the specific phenol conversion capacity was limiting the treatment process. The possibility of efficient chemical wastewater treatment under the challenging studied conditions would represent a major breakthrough for the widespread application of AnMBR technology.

Metagenomic insights into quorum sensing in membrane-aerated biofilm reactors for phenolic wastewater treatment

ABSTRACT Quorum sensing (QS) is of crucial importance for the formation and performance of biofilms adhered to aerated membranes. In this study, the QS-related genes in membrane-aerated biofilm reactors (MABR) for phenolic wastewater treatment were investigated through high-throughput metagenomic sequencing. Results showed that numerous regulatory QS-related genes were associated with the production of signals including acyl-homoserine lactones (AHLs) and diguanylate monophosphate (c-di-GMP), indicating that the biofilms were potentially regulated by the AHL-mediated QS and c-di-GMP-mediated QS systems. Species and functional contribution analysis demonstrated that Pseudomonas, Achromobacter, Rhodococcus, Granulicoccus and Thauera were the key QS-related gene carriers. Redundancy analysis and Spearman correlation analysis showed that high influent phenolic loading gave rise to a high relative abundance of QS bacteria within the biofilm community. Thus, QS-related genes likely play an important role in strengthening biofilm resistance to phenolics, as well as the removal of phenolic contaminants.

Effects of phenol on extracellular polymeric substances and microbial communities from aerobic granular sludge treating low strength and salinity wastewater

The effects of phenol on aerobic granular sludge including extracellular polymeric substances (EPS) and microbial community were investigated for low strength and salinity wastewater treatment. Elevated phenol over 20 mg/L stimulated biological phosphorus removal mainly via co-metabolism with nearly complete phenol degradation, whereas resulted in significant accumulation of nitrate around 4 mg/L. Aerobic granules kept structural stability via enhancing production of extracellular polymeric substances (EPS), especially folds of polysaccharides (PS) and varying functional groups identified through EEM, FTIR and XPS spectral characterizations at increasing phenol loads. Illumina MiSeq sequencing results indicated that elevated phenol decreased the bacterial diversity and richness, and caused remarkable variations in structural and compositions of microbial population. Multiple halophilic bacteria including Stappia, Luteococcus, and Formosa laid the biological basis for stability of aerobic granules and efficient biological nutrients and phenol removal. Redundancy analysis (RDA) suggested the key role of phenol in shaping the relative abundances and predominant genera. This study proved that aerobic granular sludge was feasible for low-saline and phenol-laden low-strength wastewater treatment.

Small bioreactor platform capsules provide persistent digestive biomass for continuous bioreactors operated under short hydraulic retention times

Bioaugmentation treatments in general and the use of encapsulated selected microbial cultures in particular are gaining significant attention as a promising approach for the treatment of wastewater containing phenols and other organic pollutants. Thus, the purpose of this study is to investigate the biodegradation performance of a Pseudomonas putida culture encapsulated in a unique 3-D capsule known as the small bioreactor platform (SBP). Batch and continuous bioreactors, bioaugmented with two different P. putida culture states, i.e., encapsulated and free suspended cells, were operated under different phenol loadings. During the batch experiments, the biodegradation rate of the suspended culture was equal to or higher than the encapsulated culture, except for the highest phenol concentration of 1000 mg/L, where the encapsulated bacterial culture exhibited a superior biodegradation rate (45 mg/L/h) relative to the free culture (16.7 mg/L/h). In addition, in the continuous bioreactor, at a hydraulic retention time (HRT) of up to 1 h, the encapsulated P. putida completely biodegraded the phenol in the influent with 50 mg/L phenol, showing a maximal biodegradation rate of 45 mg/L/h. However, decreasing the HRT to 0.5 and 0.25 h resulted in incomplete biodegradation, despite higher biodegradation rates (90 and 70 mg/L/h, respectively). Furthermore, a sharp decrease in the biodegradation process efficiency was observed when the suspended culture was released from the SBP capsules by cutting the microfiltration membrane of the capsules. Therefore, this study demonstrates that, compared with suspended cultures, SBP culture encapsulation achieves superior performance as a bioaugmentation strategy, especially in continuous bioreactors, such that it can be applied in the treatment of phenol rich wastewater.

Impact of high phenol loading on aerobic granules from two different kinds of industrial sludge along with thiocyanate and ammonium

Two sequencing batch reactors inoculated with two different kinds of industrial sludge; refinery sludge (R1) and brewery sludge (R2), were operated to observe the impact of high phenol loading (5.71 kg COD m−3 day−1) along with 100 mg L−1 of ammonia–nitrogen and thiocyanate on the granular stability and performance. R2 granules were stable and degraded all the pollutants up to an organic loading of 5.71 kg COD m−3 day−1 with the large size and high extracellular polymeric substances of 2769.94 ± 62.26 µm and 114.83 ± 1.33 mg gVSS−1, respectively, whereas R1 granules disintegrated at an organic loading of more than 3.32 kg COD m−3 day−1. At higher phenol loading, granular biomass activity was 3.43 and 16.35 mg COD removed mgVSS−1 day−1 in R1 and R2, respectively, from the initial sludge activities of 8.01 (refinery sludge) and 6.56 (brewery sludge) mg COD removed mgVSS−1 day−1.

Anaerobic phenol biodegradation: kinetic study and microbial community shifts under high-concentration dynamic loading.

The anaerobic biodegradation of phenol has been realised in a sequencing batch reactor (SBR) under anaerobic conditions with phenol as sole carbon and energy source and with glucose as co-substrate. A step-change increase of phenol loading (from 100 up to 2000mg/L of phenol concentration in the feed solution) has been applied during the acclimation phase in order to progressively induce the development of a specialised microbial consortium. This approach, combined with the dynamic sequence of operations characterising SBRs and with the high biomass retention time, led to satisfactory phenol and COD removal efficiencies with values > 70% for the highest phenol input (2000mg/L) fed as the single carbon and energy source. Analysis of removal efficiencies and biodegradation rates suggested that the use of glucose as co-substrate did not induce a significant improvement in process performance. Kinetic tests have been performed at different initial phenol (400-1000mg/L) and glucose (1880-0mg/L) concentrations to kinetically characterise the developed biomass: estimated kinetic constants are suitable for application and no inhibitory effect due to high concentrations of phenol has been observed in all investigated conditions. The microbial community has been characterised at different operating conditions through molecular tools: results confirm the successful adaptation-operation approach of the microbial consortium showing a gradual increase in richness and diversity and the occurrence and selection of a high proportion of phenol-degrading genera at the end of the experimentation. Key Points • Anaerobic phenol removal in the range of 70-99% in a sequencing batch reactor. • Negligible effect of co-substrate onremoval efficiencies and biodegradation rates. • No biomass inhibition due to phenol concentration in the range of 400-1000mg/L. • Increasing phenol loads promoted the culture enrichment of phenol-degrading genera.

Biodegradation of phenolic compounds in high saline wastewater by biofilms adhering on aerated membranes

High saline phenolic wastewater is a typical toxic and refractory industrial wastewater. A single membrane–aerated biofilm reactor (MABR) was used to treat wastewater containing phenol, p–nitrophenol and hydroquinone under increasing phenolic loading and salinity conditions. More than 95 % of phenolic compounds were removed, and a removal efficiency of 8.9 g/m2 d for total phenolic (TP) contents was achieved under conditions with 32 g/L of salt and 763 mg/L of influent TP contents. The microbial diversity, structure and function of a biofilm exposed to different conditions were investigated by high–throughput 16S rRNA gene sequencing and metagenomics. Salinity and specific TP loading substantially affected the bacterial community. Gammaproteobacteria, Actinobacteria and Betaproteobacteria contributed more to initial phenolic compound degradation than other classes, with Pseudomonas and Rhodococcus as the main contributing genera. The key phenolic–degrading genes of different metabolic pathways were explored, and their relative abundance was strengthened with increasing phenolic loading and salinity. The diverse cooperation and competition patterns of these microorganisms further promoted the high removal efficiency of multiple phenolic contaminants in the biofilms. These results demonstrate the feasibility of MABR for degrading multiple phenolic compounds in high saline wastewater.

Supercritical water gasification of phenol over Ni-Ru bimetallic catalyst: Intermediates and kinetics

Phenol is gasified in supercritical water at 400−500 °C under a pressure of 25 MPa over Ni-Ru bimetallic catalyst. Several liquid products including cyclohexanol, 2-methyl cyclopentanone, toluene, alkylphenol etc. are identified and possible reaction paths among them are proposed. Gaseous products consist of H2, CH4 and CO2. We develop a quantitative kinetic model based on a simplified reaction network in which intermediates are lumped. The model accurately captures the trends of concentration variation for phenol and gaseous products. Steam reforming of phenol to form CO is the main source of H2 and nearly all CH4 is formed from methanation of CO under 450 °C. Concentration of H2 is most sensitive to steam reforming to form CO2 while steam reforming to form CO strongly affects CH4 production at 450 °C. The model has predictive capacity when varying initial phenol loading while it lose some accuracy for a higher water density condition.

A comparison of Al-Fe pillared Iraqi clays for Catalytic wet air oxidation

Five types of Al-Fe pillared Iraqi clays have been selected depending on a natural clays regions (Anbar- Mosul- Basra- Baghdad- and Erbil) have been used in preparation it, and tested for catalytic wet air oxidation (CWAO) using phenol as target compound at different parameters (temperature, pressure, phenol loading, catalyst loading). The Al-Fe pillared of Anbar- Mosul –and Erbil clay showed a higher activity than Baghdad and Basra for phenol oxidation in Batch reactor. After 8 days continues test for activating AL-Fe PC in PBR, Deactivation appears on catalyst of Anbar in different temperature, but in Erbil with increase temperature, Mosul catalyst has higher activity than other catalyst. Mosul catalyst has higher stability than Erbil and Anbar in blocking of surface area, Leaching Fe was negligible, Fairly different values of apparent activation energy were obtained for this reaction with these five types of catalysts, suggesting that the prevailing pathway in air decomposition is different. From all above discussion, Mosul catalyst in considered the best catalyst.

Supercritical impregnation of olive leaf extract to obtain bioactive films effective in cherry tomato preservation

Abstract The promising prospective in the use of natural extracts has encouraged researchers to study techniques for its incorporation into polymers. This study has focused on supercritical solvent impregnation (SSI) of polyethylene terephthalate/polypropylene (PET/PP) films with olive leaf extract (OLE). The % co-solvent and the ratio OLE/polymer (w/w) were evaluated for producing antioxidant (AO) films. Besides, the antimicrobial (AM) capacity of both OLE and impregnated films were studied against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Salmonella enteritidis. The highest AO capacity and phenolic loading were found in films impregnated at 7% co-solvent and a ratio OLE/polymer of 1, where c.a. 5 mg AO/g and 60 μg total polyphenols/g films were obtained. The antimicrobial capacity of the impregnated films varied respecting that found in the extract, especially in the case of S. enteritidis and P. aeruginosa, The bioactivity of films was also demonstrated by extending cherry tomatoes’ shelf-life by 20 days.

Studying the Phenol Degradation in Synthetic Wastewater by Catalytic Wet Air Oxidation Process in Batch Reactor

The current paper studies the viability of using a Batch reactor, by five types of Al-Fe pillared clay that prepared from five regions in Iraq for phenol degradation in synthetic wastewater. The operation condition study through variables in (pH, pressure, temperature, pillared load, phenol load). The findings have illustrated that phenol degradation could be increase via incrementing temperature, pressure, pillared load and degrease in phenol load. Phenol good degradation proportion which was 97 %, has been achieved at optimum proportion (pH= 3.9, temperature = 150 °C, pressure = 3.5 MPa, in addition to phenol concentration = 500 mg/l). The two models power-law and Langmuir−Hinshelwood have been used to study the catalytic kinetics of the phenol degradation. From results shown the activation energy for every response equivalent to (37114.014 j/mol) for Anbar (37795, 48783.9, 36628, 40785 j/mol) for Erbil, Mosul, Baghdad and Basra respectively. It was proved that the reaction in this study is under kinetics control.

Studying the Phenol Degradation in Synthetic Wastewater by Catalytic Wet Air Oxidation Process in Batch Reactor

The current paper studies the viability of using a Batch reactor, by five types of Al-Fe pillared clay that prepared from five regions in Iraq for phenol degradation in synthetic wastewater. The operation condition study through variables in (pH, pressure, temperature, pillared load, phenol load). The findings have illustrated that phenol degradation could be increase via incrementing temperature, pressure, pillared load and degrease in phenol load. Phenol good degradation proportion which was 97 %, has been achieved at optimum proportion (pH= 3.9, temperature = 150 °C, pressure = 3.5 MPa, in addition to phenol concentration = 500 mg/l). The two models power-law and Langmuir−Hinshelwood have been used to study the catalytic kinetics of the phenol degradation. From results shown the activation energy for every response equivalent to (37114.014 j/mol) for Anbar (37795, 48783.9, 36628, 40785 j/mol) for Erbil, Mosul, Baghdad and Basra respectively. It was proved that the reaction in this study is under kinetics control.

Highly efficient phenol degradation in a batch moving bed biofilm reactor: benefiting from biofilm-enhancing bacteria.

In this study, the efficiency improvement of three moving bed biofilm reactors (MBBRs) was investigated by inoculation of activated sludge cells (R1), mixed culture of eight strong phenol-degrading bacteria consisted of Pseudomonas spp. and Acinetobacter spp. (R2) and the combination of both (R3). Biofilm formation ability of eight bacteria was assessed initially using different methods and media. Maximum degradation of phenol, COD, biomass growth and also changes in organic loading shock were used as parameters to measure the performance of reactors. According to the results, all eight strains were determined as enhanced biofilm forming bacteria (EBFB). Under optimum operating conditions, more than 90% of initial COD load of 2795mgL-1 was reduced at 24 HRT in R3 while this reduction efficiency was observed in concentrations of 1290mgL-1 and 1935mgL-1, in R1 and R2, respectively. When encountering phenol loading shock-twice greater than optimum amount-R1, R2 and R3 managed to return to the steady-state condition within 32, 24 and 18 days, respectively. SEM microscopy and biomass growth measurements confirmed the contribution of more cells to biofilm formation in R3 followed by R2. Additionally, established biofilm in R3 was more resistant to phenol loading shock which can be attributed to the enhancer role of EBFB strains in this reactor. It has been demonstrated that the bacteria with both biofilm-forming and contaminant-degrading abilities are not only able to promote the immobilization of other favorable activated sludge cells in biofilm structure, but also cooperate in contaminant degradation which all consequently lead to improvement of treatment efficiency.