Decolourization of reactive azo dyes with microorganisms growing on soft wood chips

The decolourization of a mixture of 200 mg L⁻¹ each of Reactive Black 5 and Reactive Red 2 dye was studied in batch experiments using microorganisms growing on forest residue wood chips in combination with or without added white-rot fungus, Bjerkandera sp. BOL 13. The study was performed as a first stage in the development of a relatively simple treatment process for textile wastewater, designed to work in developing countries. Forest residue wood chips contain a mixture of fungi and bacteria which is an advantage when complex molecules should be degraded. The wood chips furthermore provide the microorganisms with carbon source which make the addition of e.g. glucose unnecessary. The results showed that the microorganisms growing on the forest residue wood chips decolourized the mixture of the two dyes; adding extra nutrients approximately doubled the decolourization rate. The time needed for decolourization was approximately 18 days when nutrients were added. Lignocellulosic material is complex and so were the analysis, microorganisms were therefore transferred to ordinary soft wood chips from forest residue wood chips. Decolourization was measured with spectrophotometer and in order to determine intermediates HPLC was used.     

Decolorization of synthetic and real textile wastewater by the use of white-rot fungi

Batch and continuous reactors inoculated with white-rot fungi were operated in order to study decolorization of textile dyes. Synthetic wastewater containing either Reactive Blue 4 (a blue anthraquinone dye) or Reactive Red 2 (a red azo dye) was used during the first part of the study while real wastewater from a textile industry in Tanzania was used in the later part. Trametes versicolor was shown to decolorize both Reactive Blue 4 and Reactive Red 2 if glucose was added as a carbon source. Reactive Blue 4 was also decolorized when the fungus was allowed to grow on birch wood discs in a continuous biological rotating contactor reactor. The absorbance at 595 nm, the wavelength at which the dye absorbs at a maximum, decreased by 70% during treatment. The initial dye concentration in the medium was 200 mg/l and the hydraulic retention time in the reactor 3 days. No glucose was added in this experiment. Changes of the absorbance in the UV range indicated that the aromatic structures of the dyes were altered. Real textile wastewater was decolorized by Pleurotus flabellatus growing on luffa sponge packed in a continuous reactor. The reactor was operated at a hydraulic retention time of 25 h. The absorbance at 584 nm, the wavelength at which the wastewater absorbed the most, decreased from 0.3 in the inlet to approximately 0.1 in the effluent from the reactor.     

Decolorization of Reactive Red 159 by a consortium of photosynthetic bacteria using an anaerobic sequencing batch reactor (AnSBR)

This experiment aimed to decolorize Reactive Red 159 using a high potential of a consortium of purple nonsulfur bacteria (PNSB) with an application of response surface methodology through a central composite design in open system. The three factors of hydraulic retention time (HRT), sludge retention time (SRT) and dye concentration were applied to the design. The decolorization was operated in an anaerobic sequencing batch reactor until the system reached to a pseudosteady state for 30?cycles in each experiment. The optimal condition was 6,500?mg/L of Reactive Red 159 concentration with 20 days of SRT and 8 days of HRT, achieving dye effluent of 142.62?±?5.35?mg/L, decolorization rate of 264.54?±?7.13?mg/L/h and decolorization efficiency of 97.68?±?0.74%. The results revealed that PNSB efficiently decolorized the high concentration of Reactive Red 159 and they were a high potential of microorganisms for dyes contaminated wastewater treatment.     

Biotechnological strategies for phytoremediation of the sulfonated azo dye Direct Red 5B using Blumea malcolmii Hook

Tissue cultured shrub plants of Blumea malcolmii were found to decolorize Malachite green, Red HE8B, Methyl orange, Reactive Red 2 and Direct Red 5B at 20 mg L⁻¹ concentration to varying extent within three days. A significant induction in the activities of lignin peroxidase, tyrosinase, DCIP (2,6-dichlorophenol-indophenol) reductase, azoreductase and riboflavin reductase in the roots was observed during the decolorization of Direct Red 5B, which indicated their crucial role in the metabolism of the dye. HPLC (High Performance Liquid Chromatography) and FTIR (Fourier Transform Infrared Spectroscopy) analysis of the samples before and after decolorization of the dye confirmed the phytotransformation of Direct Red 5B. The GC–MS (Gas Chromatography Mass Spectroscopy) analysis of the products led us to the identification of three metabolites formed after phytotransformation of the dye as 4-(4-amino-phenylazo)-benzene sulfonic acid, 3-amino-7-carboxyamino-4-hydroxy-naphthalene-2-sulfonic acid and 7-carboxyamino-naphthalene-2-sulfonic acid.     

Dynamics of microbial community for X-3B wastewater decolorization coping with high-salt and metal ions conditions

In this study, decolorization of Reactive Brilliant Red X-3B wastewater by the biological process coping with high salinity and metal ions conditions was investigated, and 16S rDNA based fingerprint technique was used to investigate microbial population dynamics. Results of sequencing batch tests showed that the microbial community could keep efficient with high concentration of dye (1100 mg L⁻¹), salt (150 g L⁻¹ NaCl) and some metal ions such as Mg²⁺, Ca²⁺ (1–10 mmol L⁻¹) and Pb²⁺ (1 mmol L⁻¹). 16S rDNA-based molecular analysis techniques demonstrated that the microbial community shifted during the acclimatization process affected by salt or metal ions. Some stains similar to Bacillus, Sedimentibacter, Pseudomonas, Clostridiales, Streptomyces and some uncultured clones acted for the dynamic succession, supposed as potential decolorization bacteria. This study provided insights on the decolorization capability and the population dynamic shifts during decolorization process of azo dye wastewater coping with salt and metal ions.     

Bioinformatics aided microbial approach for bioremediation of wastewater containing textile dyes

Four textile azo dyes, Joyfix Red, Remazol Red, Reactive Red and Reactive Yellow, were studied for decolorization. Of nineteen soil bacterial isolates, two novel strains were found to highly decolorize Joyfix Red and were identified as Lysinibacillus sphaericus (KF032717) and Aeromonas hydrophila (KF032718) through 16S rDNA analysis. Laccase and Azoreductase enzyme modeling and enzyme–dye interaction performed using Schrödinger Suite imitated decolorization percentage. Results based on cumulative Glide score (Dry laboratory) and decolorization percentage of the other three dyes based on ultraviolet–visible (UV–vis) spectroscopy (Wet laboratory) were reliable. Biodegradation of Joyfix Red was confirmed by high-performance liquid chromatography (HPTLC) elution profile which showed four peaks at 1.522, 1.800, 3.068 and 3.804 min with that of parent dye which showed single peak at 1.472 min. Fourier transform infrared spectroscopy (FT-IR) analysis supported the biotransformation of Joyfix Red. Gas chromatography–mass spectroscopy (GC–MS) analysis showed sodium (3E,5Z)-4-amino-6-hydroxyhexa-13,5-triene-2-sulfonate was formed as end product during biodegradation. From these findings, it can be inferred that enzyme and dye interaction studies can assist in examining decolorization efficiency of bacteria and its enzyme, thereby enhancing the bioremediation process by reducing preliminary lengthy wet laboratory screening. This is the first report of a combinatorial in silico cum in vitro approach and its validation for the bioremediation of wastewater containing these textile azo dyes.     

Reactive red azo dye degradation in a UASB bioreactor: Mechanism and kinetics

Textile industry uses azo dyes in its processes, which are complex organic molecules that are not easy to be degraded. Reactive dyes are especially difficult to remove from wastewater because of the characteristics of the molecule: one or more azo bonds, naphthalene‐disulfonate, triazine or chloro‐triazine, and phenyl‐amine groups. The degradation of the azo dye reactive red 272 was studied under anaerobic conditions in a hybrid Upflow Anaerobic Sludge Bed reactor (UASB) with an activated carbon bed. An adapted consortium of microorganisms was used in the kinetic study (batch) and to inoculate the UASB reactor. The experimental design identified the main factors determining the dye reduction efficiency are the initial concentration of dye and dextrose (as electron donor) and the residence time in the reactor. Dye reduction rate was decreased as the concentration increases in the wastewater; as a result, a kinetic model with a change from first to second order is proposed. The kinetic study showed that the process is first abiotic (adsorption) and then biotic (biodegradation).     

Thermophilic anaerobic digestion of Lurgi coal gasification wastewater in a UASB reactor

Lurgi coal gasification wastewater (LCGW) is a refractory wastewater, whose anaerobic treatment has been a severe problem due to its toxicity and poor biodegradability. Using a mesophilic (35 ± 2 °C) reactor as a control, thermophilic anaerobic digestion (55 ± 2 °C) of LCGW was investigated in a UASB reactor. After 120 days of operation, the removal of COD and total phenols by the thermophilic reactor could reach 50-55% and 50-60% respectively, at an organic loading rate of 2.5 kg COD/(m³ d) and HRT of 24 h; the corresponding efficiencies were both only 20-30% in the mesophilic reactor. After thermophilic digestion, the wastewater concentrations of the aerobic effluent COD could reach below 200 mg/L compared with around 294 mg/L if mesophilic digestion was done and around 375 mg/L if sole aerobic pretreatment was done. The results suggested that thermophilic anaerobic digestion improved significantly both anaerobic and aerobic biodegradation of LCGW.     

Assessment of a bioaugmentation strategy with polyphosphate accumulating organisms in a nitrification/denitrification sequencing batch reactor

Different alternative configurations and strategies for the simultaneous biological removal of organic matter and nutrients (N and P) in wastewater have been proposed in the literature. This work demonstrates a new successful strategy to bring in enhanced biological phosphorus removal (EBPR) to a conventional nitrification/denitrification system by means of bioaugmentation with an enriched culture of phosphorus accumulating organisms (PAO). This strategy was tested in a sequencing batch reactor (SBR), where an 8 h configuration with 3 h anoxic, 4.5 h aerobic and 25 min of settling confirmed that nitrification, denitrification and PAO activity could be maintained for a minimum of 60 days of operation after the bioaugmentation step. The successful bioaugmentation strategy opens new possibilities for retrofitting full-scale WWTP originally designed for only nitrification/denitrification. These systems could remove P simultaneously to COD and N if they were bioaugmented with waste purge of an anaerobic/aerobic SBR operated in parallel treating part of the influent wastewater.     

Sudden failure of biological nitrogen and carbon removal in the full-scale pre-denitrification process treating cokes wastewater

A full-scale pre-denitrification process treating cokes wastewater containing toxic compounds such as phenols, cyanides and thiocyanate has shown good performance in carbon and nitrogen removal. However, field operators have been having trouble with its instability without being able to identify the causes. To clarify the main cause of these sudden failures of the process, comprehensive studies were conducted on the pre-denitrification process using a lab-scale reactor system with real cokes wastewater. First, the shock loading effects of three major pollutants were investigated individually. As the loading amount of phenol increased to 600 mg/L, more COD, TOC and phenol itself were flowed into the aerobic reactor, but phenol itself did not inhibit nitrification and denitrification, owing to the effect of dilution and its rapid biodegradation. Higher loading of ammonia or thiocyanate slightly enhanced the removal efficiency of organic matter, but caused the final discharge concentration of total nitrogen to be above its legal limit of 60 mg-N/L. Meanwhile, continuous inflow of abnormal wastewater collected during unstable operation of the full-scale pre-denitrification process, caused a sudden failure of nitrogen removal in the lab-scale process, like the removal pattern of the full-scale one. This was discovered to be due to the lack of inorganic carbon in the aerobic reactor where autotrophic nitrification occurs.     

Influence of food colorant and initial COD concentration on the efficiencies of micro-aerobic sequencing batch reactor (micro-aerobic SBR) for casein recovery under non-sterile condition by Lactobacillus casei TISTR 1500

The acid biocoagulants produced from non-sterile lactic acid fermentation by Lactobacillus casei TISTR 1500 were used to settle colloidal protein, mainly casein, at the isoelectric point in dairy effluent prior to secondary treatment. High concentration of azo dye (Ponceau 4R) in the dairy wastewater and the stress of starvation decreased the efficiencies of the micro-aerobic SBR. Consequently, low casein recovery obtained and organic removal suffered a decline. The number of lactic acid bacteria (LAB) also declined from log 7.4 to log 5.30 in the system fed with 400 mg L⁻¹ of the dye containing wastewater. The recovery of the system, however, showed that 25,000 mg COD L⁻¹ influent with 200 mg L⁻¹ of the dye maintained the growth of LAB in the range of log 7.74–8.12, with lactic and acetic production (2597 and 197 mg L⁻¹) and 83% protein removal. The results in this study suggested that the inhibitory effects were compensated with high organic content feeding.     

Optimisation for enhanced decolourization and degradation of Reactive Red BS C.I. 111 by Pseudomonas aeruginosa NGKCTS

Soil samples collected from dye contaminated sites of Vatva, Gujarat, India were studied for the screening and isolation of organisms capable of decolourizing textile dyes. The most efficient isolate, which showed decolourization zone of 48 mm on 300 ppm Reactive Red BS (C.I.111) containing plate, was identified as Pseudomonas aeruginosa. Reactive Red BS (C.I.111) was used as a model dye for the study. The isolated culture exhibited 91% decolourization of 300 ppm dye within 5.5 h over a wide pH range from 5.0 to 10.5 and temperature ranging from 30 to 40°C. The culture was able to decolourize more than 91% of Reactive Red BS under static conditions in presence of either glucose, peptone or yeast extract. Addition of 300 ppm of Reactive Red BS, in each step, in ongoing dye decolourization flask, gave more than 90% decolourization within 2 h corresponding to 136 mg l⁻¹ h⁻¹ dye removal rate. The isolate had the ability to decolourize six different reactive dyes tested as well as the actual dye manufacturing industry’s effluent. The degradation of the dye was confirmed by HPTLC.     

An innovative combined on-site process for the remote rural solid waste treatment--a pilot scale case study in China

The aim of this study was to find a feasible method for the treatment of solid waste generated in the remote rural, where the transportation costs are prohibitive and the resources to construct and maintain conventional treatment plants are not available. This process, consisted of two types of simulated bioreactor landfill (one was recirculated bioreactor landfill, and the other was comprised of fresh and aged refuse reactor) and a soil infiltration system, was operated in ambient temperature for 180 days all together. After treated by the system of fresh and aged refuse reactor, the refuse and leachate reached a strongly degraded and stable state. The remaining leachate can be treated by the soil infiltration system, and 87.5 ± 2.1%, 98.6 ± 1.0% and 95.7 ± 1.7% were achieved by 60 cm soil depths for organic matter, ammonium nitrogen and total nitrogen removal, respectively.     

Mechanistic investigation of decolorization and degradation of Reactive Red 120 by Bacillus lentus BI377

Bacillus lentus BI377, isolated from textile effluent-contaminated soil, was able to degrade 97% and 92% of Reactive Red 120 dye when 1200 and 1500 mg/l, respectively, of dye was added to nutrient broth (NB) at 35 °C within 12 h. UV-vis spectroscopy, GC-MS, FTIR and ¹H NMR revealed the formation of catechol which may be further utilized by the bacterium via the TCA cycle, leading to complete mineralization. Structural analysis of metabolites in conjunction with enzyme activity studies confirmed the involvement of azoreductase, cytochrome P450 monooxygenase and other antioxidant enzymes. Decreases in total organic carbon and in biological and chemical oxygen demand suggest formation of low molecular weight metabolites that could be completely mineralized. These results suggest the potential use of B. lentus BI377 towards online treatment of textile dye effluents by using an appropriate bioreactor over a wide range of pH. This study opens-up a dependable and proficient way to use industrially viable non-pathogenic strains for biotransformation of carcinogenic dyes to ecofriendly compounds.     

Decolorization of anthraquinone dye by Shewanella decolorationis S12

A new species of genus Shewanella, Shewanella decolorationis S12, from activated sludge of a textile-printing wastewater treatment plant, can decolorize Reactive Brilliant Blue K-GR, one kind of anthraquinone dye, with flocculation first. Although S. decolorationis displayed good growth in an aerobic condition, color removal was the best in an anaerobic condition. For color removal, the most suitable pH values and temperatures were pH 6.0–8.0 and 30–37°C under anaerobic culture. More than 99% of Reactive Brilliant Blue K-GR was removed in color within 15 h at a dye concentration of 50 mg/l. Lactate was the suitable carbon source for the dye decolorization. A metal compound, HgCl₂, had the inhibitory effect on decolorization of Reactive Brilliant Blue K-GR, but a nearly complete decolorization also could be observed at a HgCl₂ concentration of 10 mg/l. The enzyme activities, which mediate the tested dye decolorization, were not significantly affected by preadaptation of the bacterium to the dye.     

Aerobic granulation with low strength wastewater at low aeration rate in A/O/A SBR reactor

The formation of aerobic granules with low organic loading synthetic wastewater (150-200 mg L⁻¹ of influent COD, acetate/propionate = 1/3) at low aeration rate (0.6 cm s⁻¹ of superficial gas velocity) had been investigated in the anaerobic/oxic/anoxic SBR. Aerobic granules with smooth surface and compact structure were successfully obtained after 50 days. However, these aerobic granules were unstable when the d(0.9) of granules increased to more than 1 mm. The results suggested that the aerobic granules with small diameter (smaller than 1000 μm) were more favorable for treating the low substrate loading wastewater at the low aeration rate. The cycle test revealed that most of the influent COD was removed at the anaerobic stage. The effluent concentrations of N-NH₄⁺ and P-PO₄³⁻ were lower than 1 mg L⁻¹, and the effluent concentration of nitrate gradually decreased with the granulation. Phosphate accumulating organisms were found to utilize O₂ or NO_x⁻ as electron acceptor for phosphorus removal in the study. Simultaneous nitrogen and phosphorus removal occurred inside the granules.     

Fate and biodegradability of sulfonated aromatic amines

Ten sulfonated aromatic amines were tested for their aerobic and anaerobic biodegradability and toxicity potential in a variety of environmental inocula. Of all the compounds tested, only two aminobenzenesulfonic acid (ABS) isomers, 2- and 4-ABS, were degraded. The observed degradation occurred only under aerobic conditions with inocula sources that were historically polluted with sulfonated aromatic amines. Bioreactor experiments, with non-sterile synthetic wastewater, confirmed the results from the aerobic batch degradation experiments. Both ABS isomers were degraded in long-term continuous experiment by abioaugmented enrichment culture. The maximum degradation rate in the aerobic bioreactor was 1.6–1.8 gl^–1 d^–1 for 2-ABS and a somewhat lower value for 4-ABS at hydraulic retention times (HRT) of 2.8–3.3h. Evidence for extensive mineralization of 2- and 4-ABS was based on oxygen uptake and carbon dioxide production during the batch experiments and the high levels of chemical oxygen demand (COD) removal in the bioreactor. Furthermore, mineralization of the sulfonate group was demonstrated by high recovery of sulfate. The sulfonated aromatic amines did not show any toxic effects on the aerobic and anaerobic bacterial populations tested. The poor biodegradability of sulfonated aromatic amines indicated under the laboratory conditions of this study suggests that these compounds may not be adequately removed during biological wastewater treatment.     

Biological conversion of olive pomace into compost by using Trichoderma harzianum and Phanerochaete chrysosporium

Olive pomace was composted by using a reactor for a period of 50 days in four bioreactors. Urea was added to adjust C/N ration between 25–30. At the end of 50 days of composting using Trichoderma harzianum and Phanerochaete chrysosporium, cellulose and lignin were highly degraded. It was found that after 30 days, P. chrysosporium and T. harzianum degraded approximately 71.9% of the lignin and 59.25% of the cellulose, respectively. The percent of ash content in the raw waste mixture was 13%. This percentage increased from 13% to 18.55% in treatment bioreactors and from 13% to 13.55% in control reactors during 50 day of composting process. The amount of CO₂ produced by the treated sample was 3 mg of CO₂/g organic carbon which is indicated that the treated sample was considered as stable compost. The results proved that the use of accelerating agents was found to be efficient in producing mature stable with nearly non-phytotoxicity compared to control sample in less than 50 days.     

A batch decolorization and kinetic study of Reactive Black 5 by a bacterial strain Enterobacter sp. GY-1

An Enterobacter strain (GY-1) with high activity of decolorization of Reactive Black 5 (RB 5) was isolated from textile wastewater treating sludge. The kinetic characteristics of dye decolorization by the strain GY-1 were determined quantitatively using the diazo dye, RB 5. Effects of different operation parameters (inoculum size, pH, temperature and salinity) and various electron donors on decolorization of the azo dye by GY-1 were systematically investigated to reveal the primary factors that determine the performance of the azo dye decolorization. The decolorization of RB 5 was attributed to extracellular enzymes. A kinetic model was established giving the dependence of decolorization rate on cell mass concentration (first order). Decolorization rate increased with increasing temperature from 20 to 35 °C, which can be predicted by Arrhenius equation with the activation energy (E_a) of 8.50 kcal mol⁻¹ and the frequency factor (A₀) of 6.28 × 10⁷ mg l g MLSS⁻¹ h⁻¹. Michaelis-Menten kinetics and Eadie-Hofstee plot were used to determine V_max, 1.05 mg l⁻¹ h⁻¹ and K_m, 24.06 mg l⁻¹.     

Treatment of coal gasification wastewater by a two-continuous UASB system with step-feed for COD and phenols removal

A two-continuous mesophilic (37 ± 2 °C) UASB system with step-feed was investigated as an attractive optimization strategy for enhancing COD and total phenols removal of the system and improving aerobic biodegradability of real coal gasification wastewater. Through the step-feed period, the maximum removal efficiencies of COD and total phenols reached 55-60% and 58-63% respectively in the system, at an influent flow distribution ratio of 0.2 and influent COD concentration of 2500 mg/L; the corresponding efficiencies were at low levels of 45-50% and 43-50% respectively at total HRT of 48 h during the single-feed period. The maximum specific methanogenic activity and substrate utilization rate were 592 ± 16 mg COD-CH₄/(gVSS d) and 89 ± 12 mg phenol/(gVSS d) during the step-feed operation. After the anaerobic digestion with step-feed, the aerobic effluent COD concentration decreased from 270 ± 9 to 215 ± 10 mg/L. The results suggested that step-feed enhanced the degradation of refractory organics in the second reactor.