Evaluation of integrated anaerobic/aerobic fixed-bed sequencing batch biofilm reactor for decolorization and biodegradation of azo dye acid red 18: comparison of using two types of packing media

Study on the performance of a new type of combined packing biofilm reactor treating wastewater

The present work investigates the performance of a biofilm reactor filled with a new type of combined packing used to treat wastewater and explores a new technology approach for the application of coral sand and waste non-woven fabric. The combined packing was made of coral sand and waste non-woven fabric, which was used as a biofilm carrier to treat sewage. The experimental results showed that the removal efficiencies of COD, NH4+-N and TN in the biofilm reactor containing the combined packing were 92.9%, 72.9% and 63.2%, respectively. The maximum removal efficiencies of COD, NH4+-N and TN in the biofilm reactor containing single packing were 89.0%, 63.4% and 55.2%, respectively. The properties of the combined packing were characterized by Fourier Transform Infrared (FTIR), specific surface area, SEM and dehydrogenase activity. Infrared analysis showed that there were hydroxyl, carboxyl and carbonyl groups on the surface of coral sand and non-woven fabric which were beneficial for biofilm growth and wastewater treatment. The large pores in the interior of coral sand and non-woven fabric could provide a comfortable environment for microbes to grow and reproduce. The dehydrogenase activity of the biofilm on the surface of coral sand in the third biofilm reactor was 49.91 μgTF·g-1·h-1, which was significantly higher than that of the other two biofilm reactors. The new type of combined packing is suitable for biofilm carriers with low cost, which can be applied to actual sewage treatment projects. This study provides a reference for the practical application of the technique.

Adsorptive removal of acid red 18 dye from aqueous solution using hexadecyl-trimethyl ammonium chloride modified nano-pumice

Discharging untreated dye-containing wastewater gives rise to environmental pollution. The present study investigated the removal efficiency and adsorption mechanism of Acid Red 18 (AR18) utilizing hexadecyl-trimethyl ammonium chloride (HDTMA.Cl) modified Nano-pumice (HMNP), which is a novel adsorbent for AR18 removal. The HDTMA.Cl is characterized by XRD, XRF, FESEM, TEM, BET and FTIR analysis. pH, contact time, initial concentration of dye and adsorbent dose were the four different parameters for investigating their effects on the adsorption process. Response surface methodology-central composite design was used to model and improve the study to reduce expenses and the number of experiments. According to the findings, at the ideal conditions (pH = 4.5, sorbent dosage = 2.375 g/l, AR18 concentration = 25 mg/l, and contact time = 70 min), the maximum removal effectiveness was 99%. The Langmuir (R2 = 0.996) and pseudo-second-order (R2 = 0.999) models were obeyed by the adsorption isotherm and kinetic, respectively. The nature of HMNP was discovered to be spontaneous, and thermodynamic investigations revealed that the AR18 adsorption process is endothermic. By tracking the adsorption capacity of the adsorbent for five cycles under ideal conditions, the reusability of HMNP was examined, which showed a reduction in HMNP's adsorption effectiveness from 99 to 85% after five consecutive recycles.

Biotreatment of azo dye containing textile industry effluent by a developed bacterial consortium immobilised on brick pieces in an indigenously designed packed bed biofilm reactor

This study highlights the development of a lab-scale, indigenously designed; Packed-Bed Biofilm Reactor (PBBR) packed with brick pieces. The developed biofilm in the reactor was used for the decolourisation and biodegradation of the textile industry effluent. The PBBR was continuously operated for 264 days, during which 301 cycles of batch and continuous treatment were operated. In batch mode under optimised conditions, more than 99% dye decolourisation and ≥ 92% COD reduction were achieved in 6 h of contact time upon supplementation of effluent with 0.25 g L^-1 glucose, 0.25 g L^-1 urea, and 0.1 g L^-1 phosphates. A decolourisation rate of 133.94 ADMI units h^-1 was achieved in the process. PBBR, when operated in continuous mode, showed ≥ 95% and ≥ 92% reduction in ADMI and COD values. Subsequent aeration and passage through the charcoal reactor assisted in achieving a ≥ 96% reduction in COD and ADMI values. An overall increase of 81% in dye-laden effluent decolourisation rate, from 62 to 262 mg L^-1 h^-1, was observed upon increasing the flow rate from 18 to 210 mL h^-1. Dye biodegradation was determined by UV-Vis and FTIR spectroscopy and toxicity study. SEM analysis showed the morphology of the attached-growth biofilm.

Removal of nutrients from pulp and paper biorefinery effluent: Operation, kinetic modelling and optimization by response surface methodology

This study investigated the effectiveness of extended aeration system (EAS) and rice straw activated carbon-extended aeration system (RAC-EAS) in the treatment of pulp and paper biorefinery effluent (PPBE). RAC-EAS focused on the efficient utilization of lignocellulosic biomass waste (rice straw) as a biosorbent in the treatment process. The experiment was designed by response surface methodology (RSM) and conducted using a bioreactor that operated at 1-3 days hydraulic retention times (HRT) with PPBE concentrations at 20, 60 and 100%. The bioreactor was fed with real PPBE having initial ammonia-N and total phosphorus (TP) concentrations that varied between 11.74 and 59.02 mg/L and 31-161 mg/L, respectively. Findings from the optimized approach by RSM indicated 84.51% and 91.71% ammonia-N and 77.62% and 84.64% total phosphorus reduction in concentration for EAS and RAC-EAS, respectively, with high nitrification rate observed in both bioreactors. Kinetic model optimization indicated that modified stover models was the best suited and were statistically significant (R² ≥ 0.98) in the analysis of substrate removal rates for ammonia-N and total phosphorus. Maximum nutrients elimination was attained at 60% PPBE and 48 h HRT. Therefore, the model can be utilized in the design and optimization of EAS and RAC-EAS systems and consequently in the prediction of bioreactor behavior.

An abundant porous biochar material derived from wakame (Undaria pinnatifida) with high adsorption performance for three organic dyes

In this study, an activated wakame biochar material (AWBM) was prepared by a one-step calcination and activation method, whose adsorption performances for methylene blue (MB), Rhodamine B (RB) and malachite green (MG) were also analyzed. The results showed AWBM was a mesoporous fluffy structure material with a higher specific surface (1156.25 m2/g), exhibiting superior adsorption capacities for MB (841.64 mg/g), RB (533.77 mg/g) and MG (4066.96 mg/g), respectively. In addition, FT-IR analysis showed that AWBM possessed abundant active groups (such as -OH, -CO and -CH), further enhancing the adsorption efficiencies. The Langmuir model could better fit the three dyes adsorption isotherms process using AWBM, and the Pseudo-second-order model could better describe the adsorption kinetic experimental data. The thermodynamic analysis showed that the three dyes adsorption using AWBM was spontaneous endothermic reaction. This study suggests AWBM has enormous potential in the application of removing organic dyes from wastewater.

Role of Salvinia molesta in biodecolorization of methyl orange dye from water

In the present study, the potential of Salvinia molesta for biodecolorization of methyl orange (MO) dye from water was examined. Six glass vessels were filled with 4 L of water contaminated with MO with three concentrations (5, 15, and 25 mg/L), three with plants and another three without plant as contaminant control. The influence of operational parameters, including initial dye concentration, pH, temperature, and plant growth, on the efficacy of the biodecolorization process by S. molesta was determined. Temperature and pH was in the range of 25-26 °C and 6.3 to 7.3, respectively. Phytotransformation was monitored after 10 days through Fourier transform infrared (FTIR) spectroscopy, and a significant variation in the peak positions was demonstrated when compared to the control plant spectrum, indicating the adsorption of MO. The highest biodecolorization was 42% in a 5 mg/L MO dye concentration at pH 7.3 and at 27 °C. According to the FTIR results, a potential method for the biodecolourization of MO dye by S. molesta was proven. Salvinia molesta can be successfully used for upcoming eco-friendly phytoremediation purposes for dye removal.

Improved purified terephthalic acid wastewater treatment using combined UAFB-SBR system: At mesophilic and ambient temperature

In this study, a combined UAFB-SBR process was introduced to improve the treatment efficiency of PTA wastewater. The techno-economic feasibility of the process was evaluated in terms of organic removal efficiencies under mesophilic (37 °C) and ambient temperature (15-25 °C) during the long-term run. The lab-scale study revealed that all organic compounds present in the PTA wastewater could be efficiently removed under both mesophilic and ambient temperature, and p-toluic acid is probably the critical pollutant regulating the overall process performance in anaerobic stage, which should be seriously considered. The Miseq Sequencing results suggested that, along with the system temperature variation from mesophilic to ambient temperature, greater effects on bacterial community than archaeal community were detected in the UAFB reactor, while only slight variations were observed in the SBR reactor. Further taxonomy analysis demonstrated that within the UAFB reactor, the syntrophic partnership of Syntrophorhabdus, Syntrophus and Desulfovibrio with hydrogenotrophic methanogens were the main impetus for aromatic organics reduction. In the meanwhile, the intensively identified Thauera and Azoarcus groups were speculated of important roles in the aerobic degradation of aromatic compounds.

Azo dyes decolorization under high alkalinity and salinity conditions by Halomonas sp. in batch and packed bed reactor

Biodecolorization and biodegradation of azo dyes are a challenge due to their recalcitrance and the characteristics of textile effluents. This study presents the use of Halomonas sp. in the decolorization of azo dyes Reactive Black 5 (RB5), Remazol Brilliant Violet 5R (RV5), and Reactive Orange 16 (RO16) under high alkalinity and salinity conditions. Firstly, the effect of air supply, pH, salinity and dye concentration was evaluated. Halomonas sp. was able to remove above 84% of all dyes in a wide range of pH (6-11) and salt concentrations (2-10%). The decolorization efficiency of RB5, RV5, and RO16 was found to be ≥ 90% after 24, 13 and 3 h, respectively, at 50 mg L^-1 of dyes. The process was monitored by HPLC-DAD, finding a reduction of dyes along the time. Further, Halomonas sp. was immobilized in volcanic rocks and used in a packed bed reactor for 72 days, achieving a removal rate of 3.48, 5.73, and 8.52 mg L^-1 h^-1, for RB5, RV5 and RO16, respectively, at 11.8 h. The study has confirmed the potential of Halomonas sp. to decolorize azo dyes under high salinity and alkalinity conditions and opened a scope for future research in the treatment of textile effluents.

Microbial degradation of azo dye carmoisine in aqueous medium using Saccharomyces cerevisiae ATCC 9763

Carmoisine is an azo dye widely used in many industries, and therefore frequently occurs in the effluent of many factories. To our knowledge, biological degradation of carmoisine has received little attention. The present study investigates the capability of Saccharomyces cerevisiae ATCC 9763 for degradation of carmoisine. Spectrophotometry data indicates that carmoisine (50 mg/l) was eliminated from the aqueous medium after approximately 7 h of incubation with Saccharomyces under anaerobic shaking conditions. Thin layer chromatography (TLC) revealed the removal of carmoisine as well as the appearance of aromatic amines in samples collected from the decolourized medium by S. cerevisiae and this was subsequently confirmed by Fourier transform infrared (FTIR) spectroscopy. Liquid chromatography mass spectrometry (LC/MS) was carried out on fractions from consecutive column chromatography and two-dimensional (2D) chromatography. LC/MS indicated degradation of carmoisine into its constituent aromatic amines. In addition, investigating the effect of environmental conditions on the decolourization process indicated that yeast extract could positively affect decolourization rates; shaking significantly accelerated decolourization and shortened the time required for complete biodecolourization from ≃ 8 days to ≃ 7 h; and Saccharomyces was able to consume sucrose as a carbon source and remove the carmoisine despite the presence of sunset yellow, which remained unaffected.

Mutagenicity and genotoxicity evaluation of textile industry wastewater using bacterial and plant bioassays

Textile industrial wastewater samples were taken from the Panki site 5 industrial area of Kanpur city, India. Atomic Absorption spectrophotometer and Gas Chromatography-Mass spectrometry techniques have shown that the wastewater contained several heavy metals and organic pollutants (Khan and Malik, 2017) [1]. Further, in order to explore the potential toxicity of these pollutants present in the effluent, a battery of short-term biological assays (Ames test, DNA repair defective mutation assay and Allium cepa chromosomal aberration test) were used. Wastewater samples were concentrated with XAD-4/8 resins and liquid-liquid extraction procedure. XAD-concentrated samples were more mutagenic than the liquid-liquid extracted samples. Ames TA98 and polA (SOS defective) strains were the most responsive strains. The wastewater also resulted in significant decline in mitotic index and induced chromosomal aberrations in A. cepa roots. The findings thus showed that the combination of physico-chemical analysis alongwith the toxicity assessment (using short term biological assays) would provide valuable and more realistic information about the joint toxicity of chemical pollutants present in the textile effluent.

Application of response surface methodology in physicochemical removal of dyes from wastewater: A critical review

Response surface methodology (RSM) is a powerful tool in designing the experiments and optimizing different environmental processes. However, when it comes to wastewater treatment and specifically dye-containing wastewater, two questions arise; "Is RSM being used correctly?" and "Are all capabilities of RSM being exploited properly?". The current review paper aims to answer these questions by scrutinizing different physicochemical processes that utilized RSM in dye removal. The literature that applied RSM to adsorption, advanced oxidation processes, coagulation/flocculation and electrocoagulation processes were critically reviewed in this paper. The common errors in applying RSM to physicochemical removal of dyes are identified and some suggestions are made for future studies.

Influence of the Hybrid Sewage Treatment Plant’s Exploitation on Its Operation Effectiveness in Rural Areas

The article evaluates the effectiveness of the removal of organic pollutants—nitrogen and phosphorus—from household sewage in a hybrid bioreactor with a submerged fixed bed. The experiment was carried out in two exploitation variants that were both conducted in a laboratory model of the hybrid bioreactor: (I) cycles of 120 min of aeration and 60 min of no aeration with a constant sewage dosage, and (II) cycles 60 min of aeration and 60 min of no aeration, with a periodic sewage dosage in the no-aeration phase. The experiment was carried out on real sewage primarily treated in a septic tank. The amount of pollution removal was calculated and compared with the mandatory standards according to Polish law. Moreover, the susceptibility of the sewage to the biological treatment, nitrification, and denitrification activity was determined. The research shows a higher effectiveness for the 60/60 model in comparison to the 120/60 model. High operation efficiency was observed regarding the removal of organic pollution and nitrate nitrogen. The tested structure showed very low nitrification activity combined with intense denitrification. These processes were observed in the 60/60 variant. The structure was often overloaded with the nitrate nitrogen, which was considered to be the nitrification process inhibitor. It was suggested that phosphorus was also removed by the denitrifying bacteria.

Effect of SBR feeding strategy and feed composition on the stability of aerobic granular sludge in the treatment of a simulated textile wastewater

Treatment of the highly polluting and variable textile industry wastewater using aerobic granular sludge (AGS) sequencing batch reactors (SBRs) has been recently suggested. Aiming to develop this technology application, two feeding strategies were compared regarding the capacity of anaerobic-aerobic SBRs to deal with disturbances in the composition of the simulated textile wastewater feed. Both a statically fed, anaerobic-aerobic SBR and an anaerobic plug-flow fed, anaerobic-aerobic SBR could cope with shocks of high azo dye concentration and organic load, the overall chemical oxygen demand and color removal yields being rapidly restored to 80%. Yet, subsequent azo dye metabolite bioconversion was not observed, along the 315-day run. Moreover, switching from a starch-based substrate to acetate in the feed composition deteriorated AGS stability. Overall, the plug-flow fed SBR recovered more rapidly from the imposed disturbances. Further research is needed towards guaranteeing long-term AGS stability during the treatment of textile wastewater.

Treatment of a simulated textile wastewater containing the Reactive Orange 16 azo dye by a combination of ozonation and moving-bed biofilm reactor: evaluating the performance, toxicity, and oxidation by-products

In this study, an aqueous solution containing the azo dye Reactive Orange 16 (RO16) was subjected to two sequential treatment processes, namely: ozonation and biological treatment in a moving-bed biofilm reactor (MBBR). The most appropriate ozonation pretreatment conditions for the biological process and the toxicity of the by-products resulting from RO16 ozone oxidation were evaluated. The results showed that more than 97 % of color removal from the dye solutions with RO16 concentrations ranging from 25 to 100 mg/L was observed in 5 min of ozone exposure. However, the maximum total organic carbon removal achieved by ozonation was only 48 %, indicating partial mineralization of the dye. Eleven intermediate organic compounds resulting from ozone treatment of RO16 solution were identified by LC/MS analyses at different contact times. The toxicity of the dye-containing solution decreased after 2 min of ozonation, but increased at longer contact times. The results further demonstrated that the ozonolysis products did not affect the performance of the subsequent MBBR, which achieved an average chemical oxygen demand (COD) and ammonium removal of 93 ± 1 and 97 ± 2 %, respectively. A second MBBR system fed with non-ozonated dye-containing wastewater was run in parallel for comparison purposes. This reactor also showed an appreciable COD (90 ± 1 %) and ammonium removal (97 ± 2 %), but was not effective in removing color, which remained practically invariable over the system. The use of short ozonation times (5 min) and a compact MBBR has shown to be effective for the treatment of the simulated textile wastewater containing the RO16 azo dye.

A new device to select carriers for biomass immobilization and application in an aerobic/anaerobic fixed-bed sequencing batch biofilm reactor for nitrogen removal

This study proposes a new approach to selecting a biofilm carrier for immobilization using dissolved oxygen (DO) microsensors to measure the thickness of aerobic and anaerobic layers in biofilm. The biofilm carriers tested were polyurethane foam, mineral coal (MC), basaltic gravel, and low-density polyethylene. Development of layers in the biofilm carrier surface was evaluated using a flow cell device, and DO profiles were conducted to determine the size of the layers (aerobic and anaerobic). MC was the biofilm carrier selected due to allowing the development of larger aerobic and anaerobic layers in the biofilm (896 and 1,058 μm, respectively). This ability is supposed to improve simultaneous nitrogen removal by nitrification and denitrification biological processes. Thus, as a biofilm carrier, MC was used in a fixed-bed sequencing batch biofilm reactor (FB-SBBR) for treatment of wastewater with a high ammonia concentration (100-400 mgNH₄⁺-N L^-1). The FB-SBBR (15.0 L) was filled with matrices of the carrier and operated under alternating aeration and non-aeration periods of 6 h each. At a mean nitrogen loading rate of 0.55 ± 0.10 kgNH₄⁺-N m^-3 d^-1, the reactor attained a mean nitrification efficiency of 95 ± 9% with nitrite as the main product (aerobic period). Mean denitrification efficiency during the anoxic period was 72 ± 13%.

Comparison of three combined sequencing batch reactor followed by enhanced Fenton process for an azo dye degradation: Bio-decolorization kinetics study

The purpose of this research was to compare three combined sequencing batch reactor (SBR) - Fenton processes as post-treatment for the treatment of azo dye Acid Red 18 (AR18). Three combined treatment systems (CTS1, CTS2 and CTS3) were operated to investigate the biomass concentration, COD removal, AR18 dye decolorization and kinetics study. The MLSS concentration of CTS2 reached 7200 mg/L due to the use of external feeding in the SBR reactor of CTS2. The COD concentration remained 273 mg/L and 95 mg/L (initial COD=3270 mg/L) at the end of alternating anaerobic-aerobic SBR with external feeding (An-A MSBR) and CTS2, respectively, resulting in almost 65% of Fenton process efficiency. The dye concentration of 500 mg/L was finally reduced to less than 10mg/L in all systems indicating almost complete AR18 decolorization, which was also confirmed by UV-vis analysis. The dye was removed following two successive parts as parts 1 and 2 with pseudo zero-order and pseudo first-order kinetics, respectively, in all CTSs. Higher intermediate metabolites degradation was obtained using HPLC analysis in CTS2. Accordingly, a combined treatment system can be proposed as an appropriate and environmentally-friendly system for the treatment of the azo dye AR18 in wastewater.

Effect of an azo dye on the performance of an aerobic granular sludge sequencing batch reactor treating a simulated textile wastewater

This study analyzed the effect of an azo dye (Acid Red 14) on the performance of an aerobic granular sludge (AGS) sequencing batch reactor (SBR) system operated with 6-h anaerobic-aerobic cycles for the treatment of a synthetic textile wastewater. In this sense, two SBRs inoculated with AGS from a domestic wastewater treatment plant were run in parallel, being one supplied with the dye and the other used as a dye-free control. The AGS successfully adapted to the new hydrodynamic conditions forming smaller, denser granules in both reactors, with optimal sludge volume index values of 19 and 17 mL g(-1) after 5-min and 30-min settling, respectively. As a result, high biomass concentration levels and sludge age values were registered, up to 13 gTSS L(-1) and 40 days, respectively, when deliberate biomass wastage was limited to the sampling needs. Stable dye removal yields above 90% were attained during the anaerobic reaction phase, confirmed by the formation of one of the aromatic amines arising from azo bond reduction. The control of the sludge retention time (SRT) to 15 days triggered a 30% reduction in the biodecolorization yield. However, the increase of the SRT values back to levels above 25 days reverted this effect and also promoted the complete bioconversion of the identified aromatic amine during the aerobic reaction phase. The dye and its breakdown products did not negatively affect the treatment performance, as organic load removal yields higher than 80% were attained in both reactors, up to 77% occurring in the anaerobic phase. These high anaerobic organic removal levels were correlated to an increase of Defluviicoccus-related glycogen accumulating organisms in the biomass. Also, the capacity of the system to deal with shocks of high dye concentration and organic load was successfully demonstrated. Granule breakup after long-term operation only occurred in the dye-free control SBR, suggesting that the azo dye plays an important role in improving granule stability. Fluorescence in situ hybridization (FISH) analysis confirmed the compact structure of the dye-fed granules, microbial activity being apparently maintained in the granule core, as opposed to the dye-free control. These findings support the potential application of the AGS technology for textile wastewater treatment.

Integrating sequencing batch reactor with bio-electrochemical treatment for augmenting remediation efficiency of complex petrochemical wastewater

The present study evaluates the sequential integration of two advanced biological treatment methods viz., sequencing batch reactor (SBR) and bioelectrochemical treatment systems (BET) for the treatment of real-field petrochemical wastewater (PCW). Initially two SBR reactors were operated in aerobic (SBR(Ae)) and anoxic (SBR(Ax)) microenvironments with an organic loading rate (OLR) of 9.68 kg COD/m(3)-day. Relatively, SBR(Ax) showed higher substrate degradation (3.34 kg COD/m(3)-day) compared to SBR(Ae) (2.9 kg COD/m(3)-day). To further improve treatment efficiency, the effluents from SBR process were fed to BET reactors. BET(Ax) depicted higher SDR (1.92 kg COD/m(3)-day) with simultaneous power generation (17.12 mW/m(2)) followed by BET(Ae) (1.80 kg COD/m(3)-day; 14.25 mW/m(2)). Integrating both the processes documented significant improvement in COD removal efficiency due to the flexibility of combining multiple microenvironments sequentially. Results were supported with GC-MS and FTIR, which confirmed the increment in biodegradability of wastewater.

Biomineralization of azo dye bearing wastewater in periodic discontinuous batch reactor: Effect of microaerophilic conditions on treatment efficiency

The present study illustrates the influence of microaerophilic condition on periodic discontinuous batch reactor (PDBR) operation in treating azo dye containing wastewater. The process performance was evaluated with the function of various dye load operations (50-750 mg/l) by keeping the organic load (1.6 kg COD/m(3)-day) constant. Initially, lower dye operation (50mg dye/l) resulted in higher dye [45 mg dye/l (90%)] and COD [SDR: 1.29 kg COD/m(3)-day (92%)] removal efficiencies. Higher dye load operation (750 mg dye/l) also showed non-inhibitory performance with respect to dye [600 mg dye/l (80%)] and COD [1.25 kg COD/m(3)-day (80%)] removal efficiencies. Increment in dye load showed increment in azo reductase and dehydrogenase activities (39.6 U; 4.96 μg/ml; 750 mg/l). UV-Vis spectroscopy (200-800 nm), FTIR and (1)H NMR studies revealed the disappearance of azo bond (-NN-). First derivative cyclic voltammogram supported the involvement of various membrane bound redox shuttlers, viz., cytochrome-C, cytochrome-bc1 and flavoproteins (FAD (H)).

Biosorption of Congo Red from aqueous solution by Bacillus weihenstephanensis RI12; effect of SPB1 biosurfactant addition on biodecolorization potency

Bacillus weihenstephanensis RI12, isolated from hydrocarbon contaminated soil, was assessed for Congo Red bio-treatment potency. Results suggested the potential of this bacterium for use in effective treatment of Congo Red contaminated wastewaters under shaking conditions at acidic and neutral pH value. The strain could tolerate higher doses of dyes as it could decolorize up to 1,000 mg/l of Congo Red. When used as microbial surfactant to enhance Congo Red biodecolorization, Bacillus subtilis SPB1-derived lipopeptide accelerated the decolorization rate and maximized the decolorization efficiency at an optimal concentration of biosurfactant of about 0.075%. Studies ensured that Congo Red removal by this strain could be due to an adsorption phenomena. Germination potencies of tomato seeds using the treated dyes under different conditions showed the efficient biotreatment of the azo dye Congo Red especially with the addition of SPB1 biosurfactant. To conclude, the addition of SPB1 bioemulsifier reduced energy costs by reducing the effective decolorization period; the biosurfactant stimulated bacterial decolorization method may provide a highly efficient, inexpensive and time-saving procedure in the treatment of textile effluents.

Steady-state inhibition model for the biodegradation of sulfonated amines in a packed bed reactor

Aromatic amines are important industrial products having in their molecular structure one or more aromatic rings. These are used as precursors for the synthesis of dyes, adhesives, pesticides, rubber, fertilizers and surfactants. The aromatic amines are common constituents of industrial effluents, generated mostly by the degradation of azo dyes. Several of them are a threat to human health because they can by toxic, allergenic, mutagenic or carcinogenic. The most common are benzenesulfonic amines, such as 4-ABS (4-aminobenzene sulfonic acid) and naphthalene sulfonic amines, such as 4-ANS (4-amino naphthalene sulfonic acid). Sometimes, the mixtures of toxic compounds are more toxic or inhibitory than the individual compounds, even for microorganisms capable of degrading them. Therefore, the aim of this study was to evaluate the degradation of the mixture 4-ANS plus 4-ABS by a bacterial community immobilized in fragments of volcanic stone, using a packed bed continuous reactor. In this reactor, the amines loading rates were varied from 5.5 up to 69 mg L(-1) h(-1). The removal of the amines was determined by high-performance liquid chromatography and chemical oxygen demand. With this information, we have studied the substrate inhibition of the removal rate of the aromatic amines during the degradation of the mixture of sulfonated aromatic amines by the immobilized microorganisms. Experimental results were fitted to parabolic, hyperbolic and linear inhibition models. The model that best characterizes the inhibition of the specific degradation rate in the biofilm reactor was a parabolic model with values of RXM=58.15±7.95 mg (10(9) cells h)(-1), Ks=0.73±0.31 mg L(-1), Sm=89.14±5.43 mg L(-1) and the exponent m=5. From the microbial community obtained, six cultivable bacterial strains were isolated and identified by sequencing their 16S rDNA genes. The strains belong to the genera Variovorax, Pseudomonas, Bacillus, Arthrobacter, Nocardioides and Microbacterium. This microbial consortium could use the mixture of aromatic amines as sources of carbon, nitrogen, energy and sulfur.

Induction of anoxic microenvironment in multi-phase metabolic shift strategy during periodic discontinuous batch mode operation enhances treatment of azo dye wastewater

Variation in anoxic microenvironment (multi-phase (MP) metabolic shift strategy) during cycle operation of periodic discontinuous batch/sequencing batch (PDBR/SBR) mode operation showed enhanced degradation of recalcitrant azo dye (C.I. Acid Black 10B) at higher dye load (1250mg/l). The process performance was evaluated by varying anoxic phasing period during cycle operation. Before multiphase (BMP) operation with 2.1% of anoxic period showed color/COD removal efficiency of 41.9%/46.3%. Increment in anoxic period responded favorable in enhancing treatment efficiency [AMPI (16.2%), 49.4%/52.4%; AMPII (26.6%), 54.7%/57.2%; AMPIII (34.9%), 58.4%/61.5%]. Relatively higher bio-electrochemical activity, persistent reductive behavior (redox catalytic currents, 0.26/-0.72μA), prevalence of redox shuttlers (Fe-S proteins, cytochromes, quinones) facilitating enhanced electron transfer by minimization of associated losses and higher enzyme activities were observed with induction of anoxic phase. Anoxic condition shifts system microenvironment between oxidation and reduction assisting reduction of dye to its intermediates followed by their mineralization.

Relative performance of biofilm configuration over suspended growth operation on azo dye based wastewater treatment in periodic discontinuous batch mode operation

Functional role of biofilm and suspended growth bioreactor configurations in response to the treatment of azo-dye (C.I. Acid Black 10B) bearing wastewater was evaluated in periodic discontinuous batch mode operation at varying dye concentrations. The biofilm system depicted higher dye removal efficiency (93.14%) compared to suspended mode (84.29%) at 350 mg dye/l operation. Both the reactor configurations did not show much process inhibition at higher dye loads studied. Azo reductase and dehydrogenase enzyme activities showed significant variation indicating the different metabolic capabilities of the native-microflora, stable proton shuttling between metabolic intermediates and differences in the delivery of reducing powers from the substrate metabolism towards dye removal. Voltammograms visualized marked variations in electron discharge properties with the function of reactor configuration, time intervals and dye load. Higher redox catalytic currents, lower Tafel slopes and polarization resistance showed good correlation with enzyme activities and dye removal.

Evaluation of integrated anaerobic-aerobic biofilm reactor for degradation of azo dye methyl orange

This study was to investigate the mineralization of wastewater containing methyl orange (MO) in integrated anaerobic-aerobic biofilm reactor with coconut fiber as bio-material. Different aeration periods (3h in phase 1 and 2; 3, 6 and 15 h in phase 3; 24 h in phase 4 and 5) in aerobic chamber were studied with different MO concentration 50, 100, 200, 200 and 300 mg/L as influent from phase 1-5. The color removals estimated from the standard curve of dye versus optical density at its maximum absorption wavelength were 97%, 96%, 97%, 97%, and 96% and COD removals were 75%, 72%, 63%, 81%, and 73% in phase 1-5, respectively. The MO decolorization and COD degradation followed first-order kinetic model and second-order kinetic model, respectively. GC-MS analysis indicated the symmetrical cleavage of azo bond and the reduction in aromatic peak ensured the partial mineralization of MO.

Biological treatment of mining wastewaters by fixed-bed bioreactors at high organic loading

Acid wastewaters contaminated with Fe - 1000 mg L(-1) and Cu - 100 mg L(-1) were remediated by microbial sulfate-reduction at high organic loading (theoretical TOC/SO4(2-) ratio 1.1) in a laboratory installation. The installation design includes a fixed-bed anaerobic bioreactor for sulfate-reduction, a chemical reactor, a settler and a three-sectional bioreactor for residual organic compounds and hydrogen sulfide removal. Sulfate-reducing bacteria are immobilized on saturated zeolite in the fixed-bed bioreactor. The source of carbon and energy for bacteria was concentrated solution, containing ethanol, glycerol, lactate and citrate. Heavy metals removal was achieved by produced H2S at sulfate loading rate 88 mg L(-1)h(-1). The effluent of the anaerobic bioreactor was characterized with high concentrations of acetate and ethanol. The design of the second bioreactor (presence of two aerobic and an anoxic zones) makes possible the occurrence of nitrification and denitrification as well as the efficiently removal of residual organic compounds and H2S.

Degradation of dyes from aqueous solution by Fenton processes: a review

Several industries are using dyes as coloring agents. The effluents from these industries are increasingly becoming an environmental problem. The removal of dyes from aqueous solution has a great potential in the field of environmental engineering. This paper reviews the classification, characteristics, and problems of dyes in detail. Advantages and disadvantages of different methods used for dye removal are also analyzed. Among these methods, Fenton process-based advanced oxidation processes are an emerging prospect in the field of dye removal. Fenton processes have been classified and represented as "Fenton circle". This paper analyzes the recent studies on Fenton processes. The studies include analyzing different configurations of reactors used for dye removal, its efficiency, and the effects of various operating parameters such as pH, catalyst concentration, H2O2 concentration, initial dye concentration, and temperature of Fenton processes. From the present study, it can be conclude that Fenton processes are very effective and environmentally friendly methods for dye removal.