Effective biofilm control in a membrane biofilm reactor using a quenching bacterium (Rhodococcus sp. BH4).

The biofilm thickness in membrane biofilm reactors (MBfRs) is an important factor affecting system performance because excessive biofilm formation on the membrane surface inhibits gas diffusion to the interior of the biofilm, resulting in a significant reduction in the performance of contaminant removal. This study provides innovative insights into the control of biofilm thickness in O2 -based MBfRs by using the quorum quenching (QQ) method. The study was carried out in MBfRs operated at different gas pressures and hydraulic retention times (HRTs) using QQ beads containing Rhodococcus sp. BH4 at different amounts. The highest performance was observed in reactors operated with 0.21 ml QQ bead/cm2 membrane surface area, 12 HRTs and 1.40 atm. Over this period, the performance increase in chemical oxygen demand (COD) removal was 25%, while the biofilm thickness on the membrane surface was determined to be 250 µm. Moreover, acetate and equivalent oxygen flux results reached 6080 and 10 640 mg·m-2 ·d-1 maximum values, respectively. The extracellular polymeric substances of the biofilm decreased significantly with the increase of gas pressure and QQ beads amount. Polymerase chain reaction denaturing gradient gel electrophoresis results showed that the microbial community in the MBfR system changed depending on operating conditions and bead amount. The results showed that the QQ method was an effective method to control the biofilm thickness in MBfR and provide insights for future research.

Simultaneous oxidation of ammonium and tetracycline in a membrane aerated biofilm reactor.

The membrane aerated biofilms reactor (MABR) is an emerging technology in wastewater treatment with particular advantages including high rate nitrification, and very high oxygen transfer efficiencies. In this study a synthetic feed water incorporating tetracycline (TC) was investigated in a MABR. Simultaneous removal of ammonium and tetracycline (TC) in the reactor, formation of TC transformation products (TPs), and microbial community analysis in the biofilm growing on the membrane were performed. A range of TC and ammonium loading rates and the effect of different intra-membrane oxygen pressures were on treatment performance were systematically investigated. Successful nitrification and TC degradation were achieved with the highest TC removal (63%) obtained at a HRT of 18 h HRT and 0.41 bar gas pressure. It has shown that different operating conditions (HRT and gas pressure) do not cause a significant change in ammonium removal. The concentration of TPs such as ETC, EATC, and ATC was determined to be at the ppb level. Molecular results showed that MABR reactor was mainly dominated by ß-proteobacteria. The relative abundance of this group decreased in parallel with the increasing ammonium and TC loading.

Degradation of oxytetracycline under autotrophic nitrifying conditions in a membrane aerated biofilm reactor and community fingerprinting.

Pharmaceuticals in waterbodies are a growing concern due to their extensive uses and adverse effects on aquatic life. Oxytetracycline (OTC) is one of tetracycline antibiotic group used for treatment of animals and humans. This study evaluates the simultaneous oxidation of OTC and ammonium under autotrophic nitrifying conditions by using a membrane aerated biofilm reactor (MABR) as it provides an appropriate environment for the antibiotic-degrading bacteria. The results showed that MABR achieved fluxes of 1.62 mg OTC/m2.d and 1117 mg N/m2.d while the fluxes of O2 (JOTC-O2) utilized for OTC and NH4-N (JNH4-N-O2) oxidation were calculated to be 2.94 and 5105 mg O2/m2.d, respectively. Three transformation products, 4-Epi-OTC, α-Apo-OTC and ß-Apo-OTC, were identified and measured at ppb levels. The biofilm community comprised of Bacteria environmental samples, b-proteobacteria, CFB group bacteria, g-proteobacteria, d-proteobacteria and a-proteobacteria.

Comprehensive evaluation of autohydrogenotrophic membrane biofilm reactor treating OTC-enriched water medium.

In the recent years, there has been considerable debate about the potential impacts of antibiotics present in various environments on the public health and ecology. Oxytetracycline (OTC) is one of tetracycline antibiotic group used for growth and treatment of animals and humans. In this study, OTC and nitrate (NO3-N) were simultaneously reduced using a hydrogen-based membrane biofilm reactor (H2-MBfR). The system successfully accomplished OTC and nitrate removals. The fluxes of OTC and NO3-N were 8.96 mg OTC/m2 day and 1100 mg N/m2 day, respectively. On the other hand, the fluxes of H2 utilized for OTC and NO3-N reductions were calculated as maximum values of 1.71 and 395 mg H2/m2 day, respectively. The concentrations of transformation products of OTC formed at ppb levels. The dominant species in all the experimental periods with OTC biodegradation referred to Naxibacter sp., Uncultured Beta proteobacterium, Janthinobacterium sp. and Alicycliphilus denitrificans in autotrophic biofilm community degrading OTC.

Performance and microbial shift during acidification of a real pharmaceutical wastewater by using an anaerobic sequencing batch reactor (AnSBR).

In this study, a lab-scale anaerobic sequencing batch reactor (AnSBR) was used for the acidification of a pharmaceutical wastewater sourced from etodolac chemical synthesis tanks. The effects of the organic loading rate (OLR), and etodolac and sulfate concentrations on the acidification rate and microbial community in AnSBR were investigated at 35 °C with a hydraulic retention time (HRT) of 37 h, a pH of 5, and OLRs up to 5.2 kgCOD/m3·day. The AnSBR accomplished a 60% acidification ratio and 50-60% etodolac removal at OLRs up to 2.6 kgCOD/m3·day. However, at OLR = 3.9 kgCOD/m3·day, acidification was not achieved due to sulfite inhibition; pre-ozonation was applied to overcome this sulfite inhibition. Although etodolac and COD removals were improved, the wastewater was not successfully acidified. Real-time polymerase chain reaction (Q-PCR) and fluorescent in situ hybridization (FISH) analyses revealed that acidification was inhibited by the dominance of sulfate reducing bacteria (SRB) over acidification bacteria in the AnSBR. However, increasing the OLR to 5.2 kgCOD/m3·day led to toxicity stress in the SRB due to increased sulfite concentrations. Sulfate load fundamentally affected acidification process and microbial community composition. The presence of etodolac with concentration up to 56 mg/L did not have a significant effect on VFA production and the microbial community.

Chlortetracycline removal by using hydrogen based membrane biofilm reactor.

In the last years, increasing attention has been paid on the presence of antibiotics in aqueous environments due to their ecological damage and potential adverse effects on organisms. Membrane biofilm reactors (MBfR) have been gained a significant popularity as an advanced wastewater treatment technology in removing of organic micro-pollutants. In this study, the performance of H2-MBfR for simultaneous removal of nitrate and chlortetracycline, formation of transformation products and community analysis of the biofilm grown on the gas permeable hollow fiber membranes was evaluated by considering effect of the hydraulic retention time, surface loadings of target pollutants and H2 pressure. The results showed that the simultaneous chlortetracycline (96%) and nitrate removal (99%) took placed successfully under the conditions of 5h HRT and 2psi H2 pressure. It has been determined that the main elimination process was biodegradation and Betaproteobacteria species was responsible for chlortetracycline degradation.

Hydrogen-based membrane biofilm reactor for tetracycline removal: biodegradation, transformation products, and microbial community.

Tetracycline (TC) in aqueous environment could be reductively degraded by using a hydrogen-based membrane biofilm reactor (H2-MBfR) under denitrifying conditions as it provides an appropriate environment for the antibiotic-degrading bacteria in biofilm communities. This study evaluates the performance of H2-MBfR for simultaneous removal of nitrate and TC, formation of degradation products of TC, and community analysis of the biofilm grown on the gas-permeable hollow fiber membranes. Hence, a H2-MBfR receiving approximately 20 mg N/l nitrate and 0.5 mg/l TC was operated under different H2 pressures, hydraulic retention times (HRTs), and influent TC concentrations in order to provide various nitrate and TC loadings. The results showed that H2-MBfR accomplished successfully the degradation of TC, and it reached TC removal of 80-95 % at 10 h of HRT and 6 psi (0.41 atm) of H2 gas pressure. TC degradation took placed at increased HRT and H2 pressures while nitrate was the preferred electron acceptor for most of the electrons generated from H2 oxidation used for denitrification. The transformation products of TC were found at part per billion levels through all the experiments, and the concentrations decreased with the increasing HRT regardless of H2 pressure. Analyses from clone library showed that the microbial diversity at the optimal conditions was higher than that at the other periods. The dominant species were revealed to be Betaproteobacteria, Acidovorax caeni, and Alicycliphilus denitrificans.

Combination of a novel electrode material and artificial mediators to enhance power generation in an MFC.

This study focuses on two main aspects: developing a novel cost-effective electrode material and power production from domestic wastewater using three different mediators. Methylene blue (MB), neutral red (NR) and 2-hydroxy-1,4-naphthoquinone (HNQ) were selected as electrode mediators with different concentrations. A tin-coated copper mesh electrode was tested as anode electrode. Maximum power density of the microbial fuel cell (MFC) with 300 µM MB was 636 mW/m². Optimal mediator concentrations with respect to the achieved maximum power output for MB, NR and HNQ were 300 µM, 200 µM and 50 µM, respectively. The results demonstrate that tin-coated copper mesh showed a higher biocompatibility and electrical conductivity.

Comprehensive comparison of a new tin-coated copper mesh and a graphite plate electrode as an anode material in microbial fuel cell.

This paper summarizes the comparison of a new tin-coated copper (t-coating Cu) mesh electrode with a graphite plate electrode for potential power generation and biocompatibility in a microbial fuel cell (MFC). The study, which used domestic wastewater, demonstrated that t-coating Cu mesh electrode produced a power density (271 mW/m(2)) approximately three times higher than that produced by a graphite electrode (87 mW/m(2)). Scanning electron microscopy (SEM) results revealed that bacterial morphology on the two electrodes significantly varied. The t-coating Cu mesh electrode surface had higher bacterial diversity because the open three-dimensional macro-mesh structure allowed an excellent electro-biofilm attachment. Kinetic performances evaluated using the Nernst-Monod equation demonstrated that the t-coating Cu mesh electrode had both higher power density and good biocompatibility in a large surface area, high chemical stability, and favorable metallic conductivity.

Bio-reduction of tetrachloroethen using a H2-based membrane biofilm reactor and community fingerprinting.

Chlorinated ethenes in drinking water could be reductively dechlorinated to non-toxic ethene by using a hydrogen based membrane biofilm reactor (H2-MBfR) under denitrifying conditions as it provides an appropriate environment for dechlorinating bacteria in biofilm communities. This study evaluates the reductive dechlorination of perchloroethene (PCE) to non-toxic ethene (ETH) and comparative community analysis of the biofilm grown on the gas permeable membrane fibers. For these purposes, three H2-MBfRs receiving three different chlorinated ethenes (PCE, TCE and DCE) were operated under different hydraulic retention times (HRTs) and H2 pressures. Among these reactors, the H2-MBfR fed with PCE (H2-MBfR 1) accomplished a complete dechlorination, whereas cis-DCE accumulated in the TCE receiving H2-MBfR 2 and no dechlorination was detected in the DCE receiving H2-MBfR 3. The results showed that 95% of PCE dechlorinated to ETH together with over 99.8% dechlorination efficiency. Nitrate was the preferred electron acceptor as the most of electrons generated from H2 oxidation used for denitrification and dechlorination started under nitrate deficient conditions at increased H2 pressures. PCR-DGGE analysis showed that Dehalococcoides were present in autotrophic biofilm community dechlorinating PCE to ethene, and RDase genes analysis revealed that pceA, tceA, bvcA and vcrA, responsible for complete dechlorination step, were available in Dehalococcoides strains.

Removal of tetracycline and oxytetracycline by microscale zerovalent iron and formation of transformation products.

The main objective of this study was to determine the removal mechanism of tetracycline (TC) and oxytetracycline (OTC) by microscale zerovalent iron (mZVI) and the formation of transformation products during their removal studies. Solution pH, iron dose, and reaction temperature were studied with a batch experimental series in order to evaluate the removal efficiency of TC and OTC and the adsorption kinetics. The results showed that pH was a key factor in removing both tetracycline compounds, although increasing the temperature and iron dose enhanced their removal efficiency. The optimal pH was similarly found as 3 for both tetracycline and oxytetracycline. The kinetics of adsorption fitted the pseudo-second-order model perfectly. The adsorption data was interpreted by the Langmuir model with the maximum adsorption capacity of 23.98 and 34.01 mg g(-1) (60 °C) of TC and OTC on mZVI, respectively. The main transformation product was 4-epi-tetracycline for TC which quickly sorbed onto mZVI within 15 min. ß-Apo-OTC and α-Apo-OTC were found as OTC transformation products. The removal mechanism of TC and OTC using mZVI surface was due to the adsorption rather than the degradation process.

Effect of biogas sparging with different membrane modules on membrane fouling in anaerobic submerged membrane bioreactor (AnSMBR).

This study focused on the effect of biogas sparging and different membrane modules such as cylinder shaped, funnel-shaped, and U-shaped on the membrane fouling behavior in a lab-scale submerged anaerobic membrane bioreactor (AnSMBR) which was operated for over 60 days. In order to investigate the membrane fouling behavior, a series of analysis such as SMP, EPS, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), particle size distribution, and filtration resistances were performed. Although the rapid generation of cake layer took placed in case of the absence of biogas sparging, the membrane module design mostly influenced the membrane resistance when biogas sparging was applied. Total resistance was the highest for U-shaped module. The permeate fluxes with biogas sparging were higher about one half and two times than those without biogas sparging. Cylinder-shaped module had the lowest SMP and EPS concentrations followed by U-shaped and funnel-shaped modules under both cases with and without biogas sparging. The total resistances of all membrane modules without biogas sparging were found to be very high compared the pore blocking resistances (Rp).

Bioelectricity production using a new electrode in a microbial fuel cell.

Electrode materials play a key role in enhancing the electricity generation in the microbial fuel cell (MFC). In this study, a new material (Ti-TiO(2)) was used as an anode electrode and compared with a graphite electrode for electricity generation. Current densities were 476.6 and 31 mA/m(2) for Ti-TiO(2) and graphite electrodes, respectively. The PCR-DGGE analysis of enriched microbial communities from estuary revealed that MFC reactors were dominated by Shewanella haliotis, Enterococcus sp., and Enterobacter sp. Bioelectrochemical kinetic works in the MFC with Ti-TiO(2) electrode revealed that the parameters by non-linear curve fitting with the confidence bounds of 95% gave good fit with the kinetic constants of η (difference between the anode potential and anode potential giving one-half of the maximum current density) = 0.35 V, K (s) (Half-saturation constant) = 2.93 mM and J (max) = 0.39 A/m(2) for T = 298 K and F = 96.485 C/mol-e(-). From the results observed, it is clear that Ti-TiO(2) electrode is a promising candidate for electricity generation in MFC.

Performance of a sulfide-oxidizing, sulfur-producing membrane biofilm reactor treating sulfide-containing bioreactor effluent.

Sulfide-containing waste streams are generated in mining, petrochemical plants, tanneries, viscose rayon manufacture, and the gasification of coal. Colorless sulfur bacteria can oxidize sulfide to elemental sulfur (S°), which can be recovered, when oxygen is their electron acceptor. This study evaluated sulfide oxidation and S° recovery in an oxygen-based membrane biofilm reactor (MBfR) treating the effluent from a sulfidogenic anaerobic baffled reactor. Sulfide oxidation efficiency (37-99%) and S° recovery (64-89% of oxidized sulfide) could be controlled by manipulating the sulfide loading, oxygen pressure to the fibers, and hydraulic retention time (HRT). For example, too-low oxygen pressure decreased S° recovery due to decreased sulfide oxidation, but too-high oxygen pressure lowered S° recovery due to its oxidation to sulfate. Most importantly, high sulfide oxidation (>98%) and conversion to S° (>75%) could be achieved together when the sulfide loading was less than 1.7 mol/m²·d and the O2 pressure was sufficient to give an O2 flux of at least 1.5 mol/m²·d. However, higher sulfide loading could be compensated by a higher O2 pressure, and the best performance occurred when the sulfide loading was high (2 molS/m²·d), the O2 pressure was high (∼1 atm), and the HRT was short (1.9 h). Membrane fouling caused a low O2 flux, which led to low sulfide-oxidation efficiency, but fouling could be reversed by mild acid washing.

Effect of anions on removing Cu2+, Mn2+ and Zn2+ in electrocoagulation process using aluminum electrodes.

In the present study, the performance of electrocoagulation process with aluminum electrodes in the treatment of Cu(2+), Zn(2+) and Mn(2+) containing aqueous solutions was investigated by depending on type of anion in solution, considering some operating conditions such as initial metal concentration and pH. Results obtained from synthetic wastewater showed that type of anion in solutions has a significant effect on the metal removal. The initial concentration of zinc influenced significantly the performance of electrocoagulation process as compared with the results obtained from Mn and Cu metals. Anions studied did not generate an important difference between pH variations. Best removals for three metals were achieved with increasing the pH in the presence of both anions. Total removals of copper and zinc reached almost 100% after 5 min at pH values > 7. At the end of the experiments for 35 min, the Mn removals were 85 and 80% in the presence of sulfate and chloride anions, respectively.

Joint treatment of landfill leachate with municipal wastewater by submerged membrane bioreactor.

Young leachate was a high strength wastewater with regard to carbon and nitrogen matter, and up to now many researchers have focused on a number of treatment methods to treat the leachate. By using various treatment processes, joint treatment of leachate with domestic wastewater, resulted from same community, is one of the most significant methods because domestic wastewater has either larger mass or lower strength than leachate. In this study, a submerged membrane bioreactor (sMBR) was used for treatment of blending wastewater, including differential mixture ratios of domestic wastewater and leachate. In raw leachate, BOD(5)/COD was between 0.40 and 0.67 and total phosphorus was between 17 and 24 mg/l. After the leachate was blended with domestic wastewater in the ratios of 1/5-1/20, the influent COD decreased from 8,500-14,200 mg/l to 750-2,400 mg/l as ammonium decreased from 1,100-2,150 mg/l to 30-180 mg/l. The sMBR, which was aerated intermittently, accomplished both COD oxidation and nutrient removal at optimal conditions without adding the external phosphorus source, providing < 15 mg COD/l, <1.3 mg NH(4) (+)-N/l, and <2.0 mg P/l on average at solid retention times (SRT) higher than 10 days. Consequently, the results showed the mixture of leachate and domestic wastewater could be an acceptable alternative by means of membrane bioreactor technology.

Removal of Pb from sewage sludge by electrokinetics: effect of pH and washing solution type.

In this study, the effect of pH and washing solution on the removal of lead from sewage sludge by electrokinetics was investigated. The six experimental runs were carried out at two different pH values--3 and 4--using acetic acid, nitric acid and phosphoric acid. In addition, the sequential chemical extraction scheme according to the BCR's (Community Bureau of Reference) guidelines was applied to the sludge samples to evaluate the effect of acidic solutions on Pb fractionation during electrokinetic processes. Using nitric acid as the washing solution resulted in the highest removal efficiency of Pb (39%) amongst all the experiments. Acetic acid also provided similar removal percentages (37% and 38%) at different pre-acidification conditions. On the other hand, the removal efficiencies were 36% and 27% with pre-acidification using phosphoric acid at pH 3 and 4, respectively, resulting in the lowest efficiencies. The results obtained by BCR analysis showed that the metal present near the anode partitioned in to more mobile forms while the metal near the cathode partitioned in to less mobile forms, such as precipitated or adsorbed forms, as the electrokinetic process proceeded. The inter-fractional transformations of Pb formed only when using acetic acid. The similar percentages obtained by using different washing solutions indicated that the type of acid used as washing solution was less effective than the values of pH for removal of Pb from sewage sludge during the electrokinetic process.

Stripping/flocculation/membrane bioreactor/reverse osmosis treatment of municipal landfill leachate.

This study presents a configuration for the complete treatment of landfill leachate with high organic and ammonium concentrations. Ammonia stripping is performed to overcome the ammonia toxicity to aerobic microorganisms. By coagulation-flocculation process, COD and suspended solids (SS) were removed 36 and 46%, respectively. After pretreatment, an aerobic/anoxic membrane bioreactor (Aer/An MBR) accomplished the COD and total inorganic nitrogen (total-N(i)) removals above 90 and 92%, respectively, at SRT of 30 days. Concentrations of COD and total-N(i) (not considering organic nitrogen) in the Aer/An MBR effluent decreased to 450 and 40 mg/l, respectively, by significant organic oxidation and nitrification/denitrification processes. As an advanced treatment for the leachate, the reverse osmosis (RO) was applied to the collected Aer/An MBR effluents. Reverse osmosis provided high quality effluent by reducing the effluent COD from MBR to less than 4.0mg/l at SRT of 30 days.

Effect of EDTA as washing solution on removing of heavy metals from sewage sludge by electrokinetic.

This paper presents the effect of ethylene diamine tetraacetic acid (EDTA) as a washing solution on the electrokinetic process for removal of Cr, Pb and Zn from sewage sludge. The sequential chemical extraction scheme according to the guidelines of BCR (Community Bureau of Reference) was applied to the sludge samples to evaluate the effect of EDTA on metal fractionation during electrokinetic processes. The highest removals of the heavy metals were 34% for Cr, 27% for Pb and 20% for Zn with 0.1N EDTA. The removal priority of the metals by electrokinetic process was found to be Cr>Pb>Zn. According to the results of BCR analysis, addition of EDTA did not create the inter-transformation of Cr, Pb and Zn although the metal concentration decreased.

Simultaneous removal of organic matter and nitrogen compounds by combining a membrane bioreactor and a membrane biofilm reactor.

Hydrogen-based membrane biofilm reactors (MBfR) have been applied to the denitrification of nitrate-containing water and wastewater. Adding an aerobic membrane bioreactor (MBR) to a MBfR provides significant nitrification and organic oxidation because most wastewater also contains a significant concentration of organic material and ammonium nitrogen. This study describes experiments that investigate the removal of organic and nitrogenous compounds in the combined MBR/MBfR system. The experiments demonstrate that the MBR/MBfR combination successfully performs COD oxidation and nitrogen removal for organic and ammonium loads in the ranges of 1000-4300gCOD/m(3)-d and 200-230gN/m(3)-d, respectively. Total-nitrogen removal was controlled by nitrification in the MBR, because the MBfR denitrified all of the NO(3)(-) provided by the MBR. The nitrate flux in the MBfR was in the range of 4-8gN/m(2)-d for cases of almost complete denitrification (>99 %); the H(2) flux was varied from 1.4 to 2.8gH(2)/m(2)-d.