Performance of a fluidized‐bed bioreactor with hydrogel biomass carrier under extremely low‐nitrogen availability and effect of nitrogen amendments

BACKGROUND: Because of the lower fluidization energy required and the protection against shock loading and starvation due to their sorption capacity, light adsorbents such as hydrogels could be used as biofilm carrier media in fluidized bed bioreactors for wastewater processing. This work explores the feasibility of a cyclodextrin hydrogel as biomass support to degrade phenol under extremely low‐nitrogen availability and under nitrogen amendments. RESULTS: Phenol removal capacity was low (mean 0.589 kg m^?3 day^?1) under extreme nitrogen‐limited conditions (mean C:N ratio 3830). A pulsed nitrogen amendment increased the elimination capacity (up to 1.97 kg m^?3 day^?1) controlling the biofilm thickness. An 8‐h nitrogen pulse had a highly efficient long‐term effect removing 93.5 mg‐C mg^?1‐N in 300 h. The continuous nitrogen amendment enhanced the elimination capacity (up to 5.84 kg m^?3 day^?1) although rapidly increasing the biomass growth. The inhibiting phenol concentration was smaller during the nitrogen‐limited period (below 100 mg L^?1) than in the nitrogen‐amendment periods (140 mg L^?1). Low liquid velocities were needed to fluidize the bioparticles (less than 3.1 mm s^?1) during the entire experimentation. CONCLUSION: This work shows that a fluidized‐bed bioreactor with mixed culture on cyclodextrin‐based particles can be operated for long periods at extreme nitrogen limitation, and that a limited nitrogen supply with periodic pulsed amendments would be adequate for controlling the biofilm thickness. Copyright © 2011 Society of Chemical Industry     

Effects of oxygen supply condition and specific biofilm interfacial area on phenol removal rate in a three‐phase fluidized bed bioreactor

The effects of oxygen supply conditions and specific biofilm interfacial area on the phenol removal rate in a three‐phase fluidized bed bioreactor were evaluated. The experimental data were well‐explained by the semi‐theoretical equation based on the assumption that the reaction rate follows first‐order reaction kinetics with respect to oxygen and zero‐order one with respect to phenol. Two cases, biological reaction as rate‐controlling step and oxygen absorption as rate‐controlling step, were both explicable by this semi‐theoretical equation. The maximum volumetric phenol removal rate was 27.4 kg·m^?3·d^?1.     

Development of a membrane‐assisted hybrid bioreactor for ammonia and COD removal in wastewaters

A new membrane‐assisted hybrid bioreactor was developed to remove ammonia and organic matter. This system was composed of a hybrid circulating bed reactor (CBR) coupled in series to an ultrafiltration membrane module for biomass separation. The growth of biomass both in suspension and biofilms was promoted in the hybrid reactor. The system was operated for 103 days, during which a constant ammonia loading rate (ALR) was fed to the system. The COD/N‐NH₄⁺ ratio was manipulated between 0 and 4, in order to study the effects of different organic matter concentrations on the nitrification capacity of the system. Experimental results have shown that it was feasible to operate with a membrane hybrid system attaining 99% chemical oxygen demand (COD) removal and ammonia conversion. The ALR was 0.92 kg N‐NH₄⁺ m^?3 d^?1 and the organic loading rate (OLR) achieved up to 3.6 kg COD m^?3 d^?1. Also, the concentration of ammonia in the effluent was low, 1 mg N‐NH₄⁺ dm^?3. Specific activity determinations have shown that there was a certain degree of segregation of nitrifiers and heterotrophs between the two biomass phases in the system. Growth of the slow‐growing nitrifiers took place preferentially in the biofilm and the fast‐growing heterotrophs grew in suspension. This fact allowed the nitrifying activity in the biofilm be maintained around 0.8 g N g^?1 protein d^?1, regardless of the addition of organic matter in the influent. The specific nitrifying activity of suspended biomass varied between 0.3 and 0.4 g N g^?1 VSS d^?1. Copyright © 2004 Society of Chemical Industry     

Verification of necessity for bioaugmentation—lessons from two batch case studies for bioremediation of diesel‐contaminated soils

BACKGROUND: Two bio‐pile studies undertaken in a controlled laboratory were aimed at deciding optimal strategies to remediate two different artificial diesel‐contaminated soils. Bioaugmentation with various inoculations, biostimulation with various levels of biosurfactant rhamnolipid, and nutrient enhancement were the proposed remediation courses. RESULTS: In Case I, the average of the first‐order kinetic degradation rate constants during the first degradation stage for the bioaugmentation/biostimulation treatments was 0.0195 ± 0.0056 d^?1, which was about 2.6‐fold higher than that of the control batch (0.0075 d^?1). Conversely, in Case II, the rate constants for treatments with amendments and those for the control batch were found to be comparable, 0.0172 ± 0.0015 d^?1 and 0.0158 d^?1, respectively. Microarray results indicated a less diverse indigenous bacterial community in Case I and an abundant indigenous community in Case II, both from the control batches on Day 0. The dynamics of the two microbial communities, revealed by NMS plots, emphasized the similarity among the different treatments during the first degradation stage. CONCLUSIONS: Prior to a remediation project, the usefulness of a bioaugmentation approach can be investigated using an ITS oligonucliotide microarray. Results from the microarray answered why the bioaugmentation approach was useful in Case I, but not in Case II. The abundance of the diesel‐degrading community determined the usefulness of bioaugmentation. Relatively quantified TRFLP results analyzed via the NMS plots demonstrated comparable microbial communities during the first degradation stage, regardless of differences between the two batches. The bacterial community structure might shift with the availability of hydrocarbons. Copyright © 2009 Society of Chemical Industry     

Simultaneous phenol removal and biological reduction of hexavalent chromium in a packed‐bed reactor

BACKGROUND: Phenol and hexavalent chromium are considered industrial pollutants that pose severe threats to human health and the environment. The two pollutants can be found together in aquatic environments originating from mixed discharges of many industrial processes, or from a single industry discharge. The main objective of this work was to study the feasibility of using phenol as an electron donor for Cr(VI) reduction, thus achieving the simultaneous biological removal/reduction of the two pollutants in a packed‐bed reactor. RESULTS: A pilot‐scale packed‐bed reactor was used to estimate phenol removal with simultaneous Cr(VI) reduction through biological mechanisms, using a new mixed bacterial culture originated from Cr(VI)‐reducing and phenol‐degrading bacteria, operated in draw–fill mode with recirculation. Experiments were performed for feed Cr(VI) concentration of about 5.5 mg L^?1, while phenol concentration ranged from 350 to 1500 mg L^?1. The maximum reduction/removal rates achieved were 0.062 g Cr(VI) L^?1 d^?1 and 3.574 g phenol L^?1 d^?1, for a phenol concentration of 500 mg L^?1. CONCLUSION: Phenol removal with simultaneous biological Cr(VI) reduction is feasible in a packed‐bed attached growth bioreactor. Phenol was found to inhibit Cr(VI) reduction, while phenol removal was rather unaffected by Cr(VI) concentration increase. However, the recorded removal rates of phenol and Cr(VI) were found to be much lower than those obtained from previous research, where the two pollutants were examined separately. Copyright © 2008 Society of Chemical Industry     

Start‐up and enrichment of a granular anammox SBR to treat high nitrogen load wastewaters

BACKGROUND: Landfill leachate is characterized by low biodegradable organic matter that presents difficulties for the complete biological nitrogen removal usually performed by conventional biological nitrification/denitrification processes. To achieve this, the anaerobic ammonium oxidation (anammox) process is a promising biological treatment. This paper presents an anammox start‐up and enrichment methodology for treating high nitrogen load wastewaters using sequencing batch reactor (SBR) technology. RESULTS: The methodology is based on the gradual increase of the nitrite‐to‐ammonium molar ratio in the influent (from 0.76 to 1.32 mole NO₂^?‐N mole^?1NH₄⁺‐N) and on the exponential increase of the nitrogen loading rate (NLR, from 0.01 to 1.60 kg N m^?3 d^?1). 60 days after start‐up, anammox organisms were identified by polymerase chain reaction (PCR) technique as Candidatus Brocadia anammoxidans. After one year of operation, NLR had reached a value of 1.60 kg N m^?3 d^?1 with a nitrogen (ammonium plus nitrite) removal efficiency of 99.7%. The anammox biomass activity was verified by nitrogen mass balances with 1.32 ± 0.05 mole of nitrite removed per mole of ammonium removed and 0.23 ± 0.05 mole of nitrate produced per mole of ammonium removed. Also, enrichment of anammox bacteria was quantified by fluorescence in situ hybridization (FISH) analysis as 85.0 ± 1.8%. CONCLUSIONS: This paper provides a methodology for the enrichment of the anammox biomass in a SBR to treat high nitrogen loaded wastewaters. Copyright © 2007 Society of Chemical Industry     

Enhanced biodegradation of 2‐chloronitro‐benzene using a coupled zero‐valent iron column and sequencing batch reactor system

BACKGROUND: This study focused on the effectiveness of the zero‐valent iron (ZVI) pre‐treatment for enhancing the biodegradability of 2‐chloronitrobenzene (2‐ClNB), and further to evaluate the performance and mechanism of a coupled ZVI column–sequencing batch reactor (SBR) system treating 2‐ClNB contained wastewater. RESULTS: 2‐ClNB was readily transformed into 2‐chloroaniline (2‐ClAn) with the efficiency over 99.9% by ZVI column, and its biodegradability was significantly enhanced via ZVI pretreatment. The transformed effluent was subsequently fed into the SBR followed by 2‐ClAn loading of 3.4–117.2 g m^?3 d^?1 and COD loading around 1000 g m^?3 d^?1. A 2‐ClAn removal efficiency over 99.9% and COD removal efficiency of 82.0–98.1% were obtained. Moreover, 91.9 ± 0.1% TOC removal efficiency and 107.1 ± 6.0% chloride recovery efficiency during one cycle confirmed the complete biodegradation of 2‐ClAn in the coupled system. 16S rDNA PCR‐DGGE analysis suggested that ZVI pretreatment enhanced the diversity of the microbial community and promoted enrichment of the functional microorganisms degrading 2‐ClAn in the following SBR. CONCLUSION: ZVI pretreatment significantly enhanced the biodegradability of 2‐ClNB, and the coupled ZVI–SBR system demonstrated excellent performance when treating wastewater containing 2‐ClNB. Copyright © 2011 Society of Chemical Industry     

Phenol degradation in a fixed‐bed bioreactor using micro‐cellular polymer‐immobilized Pseudomonas syringae

Highly porous (85% void volume) polymer beads with interconnecting micro‐pores were prepared for the immobilization of Pseudomonas syringae for the degradation of phenol in a fixed‐bed column bioreactor. The internal architecture of this support material (also known as PolyHIPE Polymer) could be controlled through processing before the polymerization stage. The transient and steady state phenol utilization rates were measured as a function of substrate solution flow rate and initial substrate concentration. The spatial concentration of the bacteria on the micro‐porous support particles as well as within them was studied using scanning electron microscopy at various time intervals during the continuous operation of the bioreactor. It was found that although bacterial penetration into the porous support was present after 20 days, bacterial viability however, was compromised after 120 days as a result of the formation of a biofilm on the support particles. The steady state phenol utilization at an initial phenol concentration of 200 mg cm^?3 was 100% provided that the flow rate was less than 7 cm³ min^?1. Substrate inhibition at a constant flow rate of 4.5 cm³ min^?1 was found to begin at 720 mg dm^?3. The critical dilution rate for bacteria washout was high as a result of the highly hydrophobic nature of the support and the reduction of pore interconnect size due to bacterial growth within the pores in the vicinity of the surface of the support. Copyright © 2004 Society of Chemical Industry     

Time and cost efficient biodegradation of diesel in a continuous‐upflow packed bed biofilm reactor and effect of surfactant GAELE

BACKGROUND: Biodegradation of diesel hydrocarbons using bioreactors has been proposed as an alternative for diesel contaminated sites remediation. To make this alternative feasible, several factors must be optimized or improved: reducing hydraulic retention times (HRT) and applying design methods to enhance the access of the microorganisms to low soluble and recalcitrant compounds like hydrocarbon fuels. In the present work a time and cost efficient continuous‐flow packed bed bioreactor at low HRT was designed and evaluated. The effect of non‐previously studied anionic surfactant GAELE (glycolic acid ethoxylate lauryl ether) was also investigated. RESULTS: A continuous‐upflow packed bed bioreactor (CPR) was built using an inexpensive support made of volcanic and alluvial stones. The biodegradation experiments conducted with a 12‐month‐old biofilm at a fixed HRT of 0.5 h, recorded removal of up to 97.9% at a diesel concentration of 1120 mg L^?1 with GAELE. A first‐order rate constant of 0.10 h^?1 was calculated. Kinetic analysis using Arvin's model, which introduces mass transfer to the biofilm, showed statistical differences in the kinetic rate parameters (P < 0.001). Moreover, GAELE significantly increased biodegradability at high concentrations, with BOD₅ and COD removals up to 90.8 and 80.7%, respectively. Putative hydrocarbon degrading bacteria responsible for the degradation under nitrate‐reducing conditions were positively identified. CONCLUSIONS: The continuous‐upflow packed bed reactor was capable of high percentage diesel biodegradation at short HRTs. The use of GAELE increased diesel availability and thus enhanced hydrocarbon removal. Therefore, CPR packed with volcanic and alluvial stones combined with GAELE showed potential for the remediation of diesel‐impacted sites. Copyright © 2012 Society of Chemical Industry     

Start‐up and recovery of a biogas‐reactor using a hierarchical neural network‐based control tool

Due to its intricate internal biological structure the process of anaerobic digestion is difficult to control. The aim of any applied process control is to maximize methane production and minimize the chemical oxygen demand of the effluent and surplus sludge production. Of special interest is the start‐up and adaptation phase of the bioreactor and the recovery of the biocoenose after a toxic event. It is shown that the anaerobic digestion of surplus sludge can be effectively modeled by means of a hierarchical system of neural networks and a prediction of biogas production and composition can be made several time‐steps in advance. Thus it was possible to optimally control the loading rate during the start‐up of a non‐adapted system and to recover an anaerobic reactor after a period of heavy organic overload. During the controlled period an optimal feeding profile that allowed a minimum loading rate of 6 kg COD m^?3 d^?1 to be maintained was found. Maximum loading rates higher than 12 kg COD m^?3 d^?1 were often reached without destabilizing the system. The control strategy resulted simultaneously in a high level of gas production of about 3 m³_biogas m^?3_reactor and a methane content in the biogas of about 70%. To visualize the effects of the control strategy on the reactor's operational space the data were processed using a data‐mining program based on Kohonen Self‐Organizing Maps. Copyright © 2003 Society of Chemical Industry     

Biological treatment of saline wastewaters from marine‐products processing factories by a fixed‐bed reactor

Wastewaters generated by a factory processing marine products are characterized by high concentrations of organic compounds and salt constituents (>30 g dm^?3). Biological treatment of these saline wastewaters in conventional systems usually results in low chemical oxygen demand (COD) removal efficiency, because of the plasmolysis of the organisms. In order to overcome this problem a specific flora was adapted to the wastewater from the fish‐processing industry by a gradual increase in salt concentrations. Biological treatment of this effluent was then studied in a continuous fixed biofilm reactor. Experiments were conducted at different organic loading rates (OLR), varying from 250 to 1000 mg COD dm^?3 day^?1. Under low OLR (250 mg COD dm^?3 day^?1), COD and total organic carbon (TOC) removal efficiencies were 92.5 and 95.4%, respectively. Thereafter, fluctuations in COD and TOC were observed during the experiment, provoked by the progressive increase of OLR and the nature of the wastewater introduced. High COD (87%) and TOC (99%) removal efficiencies were obtained at 1000 mg COD dm^?3 day^?1. © 2002 Society of Chemical Industry     

Methanogenesis of black liquor in a two‐stage biphasic reactor system using an immobilized cell system

The methanogenesis of black liquor from pulp and paper mill was achieved using immobilized cell technology in a laboratory‐scale two‐stage reactor system run continuously for 340 days. The optimum organic loading rate for the anaerobic treatment of black liquor was 8.0 kgm^?3d^?1 at which the % COD removal, biogas production and methane content were 55%, 11 dm³d^?1 and 71%, respectively. Organic loading rates above 8.0 kgm^?3d^?1 were observed to be toxic to the methanogenic bacteria and resulted in decreased methane content, biogas and COD removal. The applicability of the system to the large‐scale processing and treatment of paper mill liquid waste is discussed. © 2001 Society of Chemical Industry     

Effects of cationic polymer on start‐up and granulation in upflow anaerobic sludge blanket reactors

The upflow anaerobic sludge blanket (UASB) has been used successfully to treat a variety of industrial wastewaters. It offers a high degree of organics removal, low sludge production and low energy consumption, along with energy production in the form of biogas. However, two major drawbacks are its long start‐up period and deficiency of active biogranules for proper functioning of the process. In this study, the influence of a coagulant polymer on start‐up, sludge granulation and the associated reactor performance was evaluated in four laboratory‐scale UASB reactors. A control reactor (R1) was operated without added polymer, while the other three reactors, designated R2, R3 and R4, were operated with polymer concentrations of 5 mg dm^?3, 10 mg dm^?3 and 20 mg dm^?3, respectively. Adding the polymer at a concentration of 20 mg dm^?3 markedly reduced the start‐up time. The time required to reach stable treatment at an organic loading rate (OLR) of 4.8 g COD dm^?3 d^?1 was reduced by more than 36% (R4) as compared with both R1 and R3, and by 46% as compared with R2. R4 was able to handle an OLR of 16 g COD dm^?3 d^?1 after 93 days of operation, while R1, R2 and R3 achieved the same loading rate only after 116, 116 and 109 days respectively. Compared with the control reactor, the start‐up time of R4 was shortened by about 20% at this OLR. Granule characterization indicated that the granules developed in R4 with 20 mg dm^?3 polymer exhibited the best settleability and methanogenic activity at all OLRs. The organic loading capacities of the reactors were also increased by the addition of polymer. The maximum organic loading of the control reactor (R1) without added polymer was 19.2 g COD dm^?3 d^?1, while the three polymer‐assisted reactors attained a marked increase in organic loading of 25.6 g COD dm^?3 d^?1. Adding the cationic polymer could result in shortening of start‐up time and enhancement of granulation, which may in turn lead to improvement in the efficiency of organics removal and loading capacity of the UASB system. Copyright © 2004 Society of Chemical Industry     

Phenol degradation in rotating biological contactors

The biodegradation of synthetically‐prepared phenol wastewater was studied in a single stage, bench‐scale rotating biological contactor (RBC). The effect of process variables, namely rotational speed (40–175 rpm), input phenol loading (1754–3508 mg phenol m^?2 h^?1), input hydraulic loading (8.77–23.42 dm³ m^?2 h^?1), and temperature of wastewater (20–30 °C) on the amount of phenol removed in the system was investigated. It was observed that an increase in the speed of rotation significantly improved the performance. An increase in the hydraulic loading rates caused a reduction in the phenol removal rate, while an increase in the organic loading rate resulted in an improvement in performance. An increase in temperature caused an increase in the microbial activity and therefore gave better performance. A mathematical model has been developed based on oxygen transfer and kinetics of biodegradation. © 2002 Society of Chemical Industry     

Highly stable Fe/γ‐Al2O3 catalyst for catalytic wet peroxide oxidation

BACKGROUND: A highly stable Fe/γ‐Al₂O₃ catalyst for catalytic wet peroxide oxidation has been studied using phenol as target pollutant. The catalyst was prepared by incipient wetness impregnation of γ‐Al₂O₃ with an aqueous solution of Fe(NO₃)₃· 9H₂O. The influence of pH, temperature, catalyst and H₂O₂ doses, as well as the initial phenol concentration has been analyzed. RESULTS: The reaction temperature and initial pH significantly affect both phenol conversion and total organic carbon removal. Working at 50 °C, an initial pH of 3, 100 mg L^?1 of phenol, a dose of H₂O₂ corresponding to the stoichiometric amount and 1250 mg L^?1 of catalyst, complete phenol conversion and a total organic carbon removal efficiency close to 80% were achieved. When the initial phenol concentration was increased to 1500 mg L^?1, a decreased efficiency in total organic carbon removal was observed with increased leaching of iron that can be related to a higher concentration of oxalic acid, as by‐product from catalytic wet peroxide oxidation of phenol. CONCLUSION: A laboratory synthesized γ‐Al₂O₃ supported Fe has shown potential application in catalytic wet peroxide oxidation of phenolic wastewaters. The catalyst showed remarkable stability in long‐term continuous experiments with limited Fe leaching, < 3% of the initial loading. Copyright © 2010 Society of Chemical Industry     

Electricity generation from Taihu Lake cyanobacteria by sediment microbial fuel cells

BACKGROUND: Cyanobacteria are rich in carbohydrates and proteins as well as other nutrients. In recent years, its efficient treatment and utilization has become an important topic for debate. The feasibility of electricity generation from Taihu Lake cyanobacteria by sediment microbial fuel cell (SMFC) was investigated and its performance evaluated by comparing with glucose‐fed and acetate‐fed SMFCs. RESULTS: A SMFC using acidic fermentation broth of Taihu Lake cyanobacteria generated a maximum power density of 72 mW m^?2 with COD removal of 76.2% and substrate degradation rate (SDR) 0.607 kgCOD m^?3 d^?1. A power density of 51 mW m^?2 with COD removal of 72.0% and SDR of 0.573 kgCOD m^?3 d^?1 were obtained with an acetate‐fed SMFC. The redox peaks in the voltammogram curves of the SMFC fed with acidic fermentation broth of Taihu Lake cyanobacteria suggested mediating compounds existed during its stable operation. The electron transfer was possibly carried out by cell‐bound redox components or biofilm formation with electroactive bacteria on the anode surface. CONCLUSIONS: This paper describes a potential method to recover sustainable electricity from Taihu Lake cyanobacteria, and the acidic fermentation of pretreated cybanobacteria could significantly enhance the power output and COD removal. Copyright © 2012 Society of Chemical Industry     

Continuous bioremediation of phenol‐polluted air in an external loop airlift bioreactor with a packed bed

An external loop airlift bioreactor with a small amount (99% porosity) of stainless steel mesh packing inserted in the riser section was used for bioremediation of a phenol‐polluted air stream. The packing enhanced volatile organic chemical and oxygen mass transfer rates and provided a large surface area for cell immobilization. Using a pure strain of Pseudomonas putida, fed‐batch and continuous runs at three different dilution rates were completed with phenol in the polluted air as the only source of growth substrate. 100% phenol removal was achieved at phenol loading rates up to 33 120 mg h^?1 m^?3 using only one‐third of the column, superior to any previously reported biodegradation rates of phenol‐polluted air with 100% efficiency. A mathematical model has been developed and is shown to accurately predict the transient and steady‐state data. Copyright © 2006 Society of Chemical Industry     

Bacterial biodegradation of phenol and 2,4‐dichlorophenol

Nine bacterial strains capable of utilising phenol and 2,4‐dichlorophenol (DCP) have been isolated from a mixed culture grown on substrates containing these compounds. One of these strains, a Micrococcus sp, was further investigated under aerobic conditions using phenol and DCP as sole carbon and energy sources at various pH values. Phenol degradation was enhanced under alkaline conditions, and up to 500 mg dm^?3 phenol was mineralised within 50 h at pH 10. DCP was more recalcitrant; however up to 883 mg g^?1 and 230 mg g^?1 were degraded within 10 days, when using initial DCP concentrations of 100 and 200 mg dm^?3, respectively. Biomass measurements showed cell growth, proving that both phenol and DCP are used as growth substrates for this isolate. Copyright © 2003 Society of Chemical Industry     

Effect of pre‐treatments based on UV photocatalysis and photo‐oxidation on toluene biofiltration performance

BACKGROUND: The integration of UV photocatalysis and biofiltration seems to be a promising combination of technologies for the removal of hydrophobic and poorly biodegradable air pollutants. The influence of pre‐treatments based on UV_{254 nm} photocatalysis and photo‐oxidation on the biofiltration of toluene as a target compound was evaluated in a controlled long‐term experimental study using different system configurations: a standalone biofilter, a combined UV photocatalytic reactor‐biofilter, and a combined UV photo‐oxidation reactor (without catalyst)‐biofilter. RESULTS: Under the operational conditions used (residence time of 2.7 s and toluene concentrations 600–1200 mg C m^?3), relatively low removal efficiencies (6–3%) were reached in the photocatalytic reactor and no degradation of toluene was found when the photo‐oxidation reactor was operated without catalyst. A noticeable improvement in the performance of the biofilter combined with a photocatalytic reactor was observed, and the elimination capacity of the biological process increased by more than 12 g C h^?1 m^?3 at the inlet loads studied of 50–100 g C h^?1 m^?3. No positive effect on toluene removal was observed for the combination of UV photoreactor and biofilter. CONCLUSIONS: Biofilter pre‐treatment based on UV_{254 nm} photocatalysis showed promising results for the removal of hydrophobic and recalcitrant air pollutants, providing synergistic improvement in the removal of toluene. Copyright © 2011 Society of Chemical Industry     

Anaerobic biogas generation from sugar industry wastewaters in three‐phase fluidized‐bed bioreactor

In the present study, attempts are made to optimize digestion time, initial feed pH, feed temperature, and feed flow rate (organic loading rate, OLR) for maximum yield of methane gas and maximum removal of chemical oxygen demand (COD) and biological oxygen demand (BOD) of sugar industry wastewaters in three‐phase fluidized‐bed bioreactor. Methane gas is analysed by using flame‐ionisation detector (FID). The optimum digestion time is 8 h and optimum initial pH of feed is observed as 7.5. The optimum temperature of feed is 40°C and optimum feed flow rate is 14 L/min with OLR 39.513 kg COD/m³ h. OLR is calculated on the basis of COD inlet in the bioreactor at different flow rates. The maximum methane gas concentration is 61.56% (v/v) of the total biogas generation at optimum biomethanation process parameters. The maximum biogas yield rate is 0.835 m³/kg COD/m³ h with maximum methane gas yield rate (61.56%, v/v) of 0.503 m³/kg COD/m³ h at optimum parameters. The maximum COD and BOD reduction of the sugar industry wastewaters are 76.82% (w/w) and 81.65% (w/w) at optimum biomethanation parameters, respectively.