Influence of the azo-dye amaranth on the trophic structure of activated sludge in a model experiment

The textile industry generates significant amounts of wastewater containing high concentrations of azo dyes. An important point in the process of purification of azo dyes is their influence on the activated sludge (AS) in wastewater treatment plants. Azo dyes, such as amaranth, play the role of xenobiotics. This article seeks to answer the question of how organisms manage to respond to xenobiotics remains very important and open, i.e., how they will react to toxic conditions. The aim of this research was to study how these changes are expressed in terms of the different trophic levels of AS. In our experiment, it was found that the dominant trophic units are significantly changed due to the xenobiotic entering the system. The data reveal the significant development of the bacterial segment (genus Pseudomonas and azo-degrading bacteria) at times of large amaranth removal. In the most active phase of amaranth biodetoxification (48 h), the culturable bacteria of the genus Pseudomonas change by about 40%, while the azo-degrading bacteria change by about 2%. Fauna organisms have a sharp change in the dominant groups-from attached and crawling ciliates and testate amoebas to the mass development of small and large flagellates. This is of great importance because micro- and metafauna play an important role in the detoxification process by ingesting some of the xenobiotics. This role is expressed in the fact that after dying, macro-organisms release this xenobiotic in small portions so that it can then be effectively degraded by adapting to the amaranth biodegradation bacteria. In this study, it is clear that all these events lead to a decline in the quality of AS. But on the other hand, these allow AS to survive as a microbial community, and the fauna segment does not disappear completely.

Photolysis of Indigo Carmine solution by planar vacuum-ultraviolet (147 nm) light source

Advanced oxidation processes (AOPs) are an attractive method to decompose dye-containing wastewaters, because they avoid issues of secondary pollution. In particular, a vacuum-ultraviolet (VUV) process is the simplest method, because an oxidation accelerator or a catalyst is not required. Conventional VUV sources with wavelengths of 185 nm or 172 nm have been used. We predicted that a shorter wavelength VUV process would have a higher ability to decompose dyes in wastewater. We developed a new planar light source that could emit a resonance line at 147 nm and a broad molecular line at 172 nm. The irradiance was 8.7 mW/cm² at a distance of 20 mm from the emission surface to the UV power meter. We then conducted photocatalytic experiments of an Indigo Carmine solution at 3.33 × 10^-4 mol/L to confirm the decomposition abilities of the developed light source, an excimer lamp of 172 nm and a Hg lamp of 254 nm. From the HPLC results, changes in Indigo Carmine concentration with the developed light source were equivalent to those with the excimer lamp. However, the residual ratio of total organic carbon (TOC) with the developed light source was lower than those with the other lamps. Therefore, a wavelength of 147 nm is superior to the conventional wavelength of 172 nm for Indigo Carmine decomposition. In addition, the developed light source emits VUV from only one side, which is a flat emitting surface. Consequently, the developed light source would have reduced manufacturing and maintenance costs compared to current VUV processing equipment.

Treatment of olive mill wastewater through employing sequencing batch reactor: performance and microbial diversity assessment

This work describes the performance of a sequencing batch reactor (SBR) and the involvement of a novel reconstituted bacterial consortium in olive mill wastewater (OMW) treatment. The organic loading rate applied to the SBR was serially increased in terms of initial COD from 10 to 75 g L^-1 to allow gradual acclimatization of activated sludge to high concentrations of toxic compounds in OMW. After the acclimatization period, up to 60% of the total COD content were effectively biodegraded from OMW at 75 g L^-1 COD within 30 day hydraulic retention time. The diversity and community composition of cultivable bacteria participating in the aerobic process of treating OMW were further assessed. A total of 91 bacterial strains were isolated from the reactor and analyzed by amplification of the 16S-23S rRNA internal transcribed spacer (ITS) region and by 16S rRNA gene sequencing. The most abundant phylum was Firmicutes (57.1%) followed by Proteobacteria (35.2%) and Actinobacteria (7.7%). The use of the Biolog® Phenotype Microarray system to evaluate the ability of isolated strains to utilize OMW phenolic compounds is reported in this work for the first time. Interestingly, results showed that all species tested were able to utilize phenolics as sole carbon and energy sources. The removals of COD and phenolics from undiluted OMW by the reconstituted bacterial consortium were almost similar to those obtained by the acclimatized activated sludge, which suggest that cultivable bacteria play the major role in OMW biodegradation. Phytotoxicity assays using tomato seeds showed a significant improvement of seed germination values for treated OMW. Our overall results suggest that the novel developed bacterial consortium could be considered as a good prospect for phenolics-rich wastewaters bioremediation applications.

A review on the sustainability of textile industries wastewater with and without treatment methodologies

The textile industry in India plays a vital role in the economic growth of the nation. The growth of the textile industry not only impacts the economy of a country but also influences the global economy and mutual exchange of technology between the countries. However, the textile industry also generates an enormous quantity of waste as waste sludge, fibers and chemically polluted waters. The chemically polluted textile wastewater degrades the quality of the soil and water when it mixes with these natural resources and its dependent habitats and environment. Owing to the existing problem of solid and liquid waste, textile industries are facing major problems in environment pollution. Therefore, researchers and the textile industries are focusing on the reduction of textile wastewater and the formulation of alternative efficient treatment techniques without hampering the environment. Hence, the present literature survey mainly concentrates on the various wastewater treatment techniques and their advantages. Moreover, the focus of the study was to describe the methods for the reduction of environmental waste and effective utilization of recycled water with zero wastewater management techniques. The alternative methods for the reduction of textile waste are also covered in this investigation. Finally, this paper also suggests utilization of solid wastes after treatment of wastewater in other sectors like construction for the preparation of low-grade tiles and or bricks by replacing the cement normally used in their manufacturing.

Textile dye biodecolourization and ammonium removal over nitrite in aerobic granular sludge sequencing batch reactors

Biodecolourization of azo dye and removal of ammonium by aerobic granular sludge (AGS) was investigated under different growth conditions. AGS not previously exposed to azo dye was able to effectively decolourize azo dye under anaerobic and microaerophilic conditions. Azo dye, total organic carbon and ammoniacal nitrogen removal efficiencies of 89-100%, 79-95% and 92-100%, respectively, were achieved in the AGS reactor operated for 80days under microaerophilic conditions. Removal of carbon, nitrogen and phosphorus was not impacted by azo dye loading. Azo dye, organic carbon and ammonium were majorly removed in the anoxic period wherein bulk dissolved oxygen was ranged from 0.5 and <0.08mgL^-1. Removal of 60mgL^-1 NH₄⁺-N was associated only with smaller amounts of nitrite build-up (∼5mgL^-1 NO₂^--N) and negligible nitrate concentrations. Profiles of nitrogen compounds in individual sequencing batch reactor cycles supported the occurrence of ammonium removal over nitrite pathway. Bacterial community analysis showed enrichment of specific microorganisms capable of decolourizing azo dyes in the dye-decolourizing AGS. Dye decolourization and nutrient removal by AGS under microaerophilic conditions is a novel finding and can be further developed for treating textile wastewaters onsite or after dilution with sewage.

Effect of quinoid redox mediators on the aerobic decolorization of azo dyes by cells and cell extracts from Escherichia coli

It is widely accepted that the addition of redox mediators increases the decolorization rates of azo dyes by bacterial strains under anaerobic conditions. However, little information exists about whether quinoid redox mediators can enhance the performance of aerobic azo dye decolorization. In the present study, quinone-mediated decolorization of different azo dyes by whole cells and cell extracts from the Escherichia coli strain CD-2 under aerobic conditions were investigated. The results demonstrated that reduction rates of different azo dyes were greatly increased when quinone compounds were used as redox mediators. Compared with menadione, 2-hydroxy-1,4-naphthoquinone (lawsone) was more effective at aiding azo dye degradation and the optimum concentration for lawsone is 0.1 mM. Strain CD-2 and the anthraquinone were co-immobilized by entrapment in different polymeric matrices. The co-immobilized beads exhibited good catalytic activity for azo dye degradation and kept stable during successive repeated experiments. The mechanism of the quinone-mediated reduction showed that although whole cells incubated with quinones could significantly increase the rate of decolorization of azo dyes, the quinone compounds did not directly promote azoreductase activity. According to the survey, this is the first report to confirm that the addition of quinoid redox mediators to bacteria increased decolorization under aerobic conditions.

Methylene blue biosorption by pericarp of corn, alfalfa, and agave bagasse wastes

The presence of dyes in effluent is a matter of concern due to their toxicologic and aesthetical effects. In this research, locally available agro-industrial wastes (Zea mays pericarp, ZMP; Agave tequilana bagasse, ATB; and Medicago sativa waste, MSW) were used as alternative low-cost adsorbents for the removal of methylene blue (MB) from aqueous solutions. The adsorbents were characterized physically and chemically by Fourier transform infrared, scanning electron microscopy, potentiometric titrations, and N2 physisorption. MB adsorption experiments were carried out in batch systems and experimental data were used to calculate the adsorption isotherm model parameters (Langmuir, Freundlich, and Temkin) and the adsorption kinetic model parameters (pseudo-first- and pseudo-second-order models). MB-loaded biosorbents were desorbed with deionized water, ethanol (10% and 50% v/v), hydrochloric acid (0.01 and 0.05 N), and sodium hydroxide (0.1 N) at room temperature, and the best eluent was used in various adsorption-desorption cycles. The selected agricultural wastes can be considered as promising adsorbents for dye uptake from water since they exhibit considerable MB adsorption capacity (MSW 202.6 mg g(-1), ATB 156.2mg g(-1), and ZMP 110.9mg g(-1)), but it is lower than that reported for activated carbon; however, the biosorbents show higher adsorption rate than powdered activated carbon. Furthermore, the adsorbents can be economically regenerated with HCl solutions and reused for seven adsorption-desorption cycles.

Study of bio-degradation and bio-decolourization of azo dye by Enterobacter sp. SXCR

The objective of this study was to evaluate the decolourization potential of textile dyes by a relatively newly identified bacteria species, Enterobacter sp. SXCR which was isolated from the petroleum polluted soil samples. The bacterial strain was identified by 16S rRNA gene sequence analysis. The effects of operational conditions like initial dye concentration, pH, and temperature were optimized to develop an economically feasible decolourization process. The isolate was able to decolourize sulphonated azo dye (Congo red) over a wide range (0.1-1 gl(-1)), pH 5-9, and temperature 22-40 degrees C in static condition. Anaerobic condition with minimal salt medium supplemented with 2 gl(-1) glucose, pH 7 and 34 degrees C were considered to be the optimum decolourizing condition. The bacterial isolate SXCR showed a strong ability to decolourize dye (0.2 gl(-1)) within 93 h. The biodegradation was monitored by UV-vis, fourier transform infra-red spectroscopy (FTIR) spectroscopy and high performance liquid chromatography (HPLC). Furthermore, the involvement of azoreductase in the decolourization process was identified in this strain. Cells of Enterobacter cloacae were immobilized by entrapment in calcium-alginate beads. Immobilized bacterial cells were able to reduced azo bonds enzymatically and used as a biocatalyst for decolourization of azo dye Congo red. Michaelis-Menten kinetics was used to describe the correlation between the decolourization rate and the dye concentration.

Low-cost adsorbents from bio-waste for the removal of dyes from aqueous solution

Activated carbons (ACs) were developed from bio-waste materials like rice husk and peanut shell (PS) by various physicochemical activation methods. PS char digested in nitric acid followed by treatment at 673 K resulted in high surface area up to ∼585 m(2)/g. The novelty of the present study is the identification of oxygen functional groups formed on the surface of activated carbons by infrared and X-ray photoelectron spectroscopy and quantification by using temperature programmed decomposition (TPD). Typical TPD data indicated that each activation method may lead to varying amounts of acidic and basic functional groups on the surface of the adsorbent, which may be a crucial factor in determining the adsorption capacity. It was shown that ACs developed during the present study are good adsorbents, especially for the removal of a model textile dye methylene blue (MB) from aqueous solution. As MB is a basic dye, H(2)O(2)-treated rice husk showed the best adsorption capacity, which is in agreement with the acidic groups present on the surface. Removal of the dye followed Langmuir isotherm model, whereas MB adsorption on ACs followed pseudo-second-order kinetics.

Microbial community structures in mixed bacterial consortia for azo dye treatment under aerobic and anaerobic conditions

Thirteen pure strains that possessed high methyl red (MR)-decolorizing ability were isolated from dye-contaminated water. Each isolate was identified by 16S rDNA sequencing. The results reveal that all of the isolated strains were facultative anaerobic bacteria. Two novel bacterial consortia (AE and AN), which could decolorize MR under aerobic and anaerobic conditions, respectively, were developed. Azo dye decolorization rate was significantly higher with the use of consortia compared to that with the use of individual strains. Both of the consortia can decolorize different azo dyes effectively in a short time, and tolerate MR with high concentrations. To provide further insight into the microbial diversity of the bacteria consortia under aerobic and anaerobic conditions, polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analyses were performed. PCR-DGGE profiles revealed that the microbial community had changed significantly with varying initial concentrations of MR. Phylogenetic analysis indicated that microbial populations in the aerobic compartment belong to Klebsiella, Buttiauxella and Bacillus, whereas Klebsiella, Escherichia, Bacillus and Clostridium were present in the anaerobic compartment. Klebsiella, which was the majority genus in both of the consortia, may play an important role in azo dye removal.

Behaviors and mechanism of acid dyes sorption onto diethylenetriamine-modified native and enzymatic hydrolysis starch

In this paper, different starches were modified by diethylenetriamine. The native starch reacted with diethylenetriamine giving CAS, whereas the enzymatic hydrolysis starch was modified by diethylenetriamine producing CAES. Adsorption capacities of CAES for four acid dyes, namely, Acid orange 7 (AO7), Acid orange 10 (AO10), Acid green 25 (AG25) and Acid red 18 (AR18) have been determined to be 2.521, 1.242, 1.798 and 1.570 mmol g(-1), respectively. In all cases, CAES has exhibited higher sorption ability than CAS, and the increment for these dyes took the sequence of AO7 (0.944 mmol g(-1))>AO10 (0.592 mmol g(-1))>AR18 (0.411 mmol g(-1))>AG25 (0.047 mmol g(-1)). Sorption kinetics and isotherms analysis showed that these sorption processes were better fitted to pseudo-second-order equation and Langmuir equation. Chemical sorption mechanisms were confirmed by studying the effects of pH, ionic strength and hydrogen bonding. Thermodynamic parameters of these dyes onto CAES and CAS were also observed and it indicated that these sorption processes were exothermic and spontaneous in nature.

Biosorption of Remazol Black B dye (Azo dye) by the growing Aspergillus flavus

In the present study, an attempt was made for the removal of Remazol Black B dye (azo dye) by using Aspergillus Flavus during its growth. Biosorption of the azo dye by growing fungi was investigated in batch reactors as a function of initial concentration of dye (25-1000 mg/L), inoculum concentration (5-20%), and pH (2.5-6.5). The total biomass concentration decreased from 6.3 g/L to 1.44 g/L by increasing the dye concentration from 0 to 1000 mg/L. The dye uptake increased from 4.37 to 233 mg/g of dried biomass by increasing initial concentration of dye from 25 to 1000 mg/L. The nearly complete removal of dye was found at initial concentration upto 250 mg/L and at pH 4.5 which was used as working pH value for removal of dye in all the batch studies. The removal of Chemical Oxygen Demand (COD) was found to be 90% at 100 mg/L initial concentration of dye. The experiments were also performed with wastewater from textile industry with an aim to examine the potential of fungal biomass for the removal of dyes from wastewater under actual field conditions. The maximum dye removal was obtained at 30° C temperature (87%) in presence of 1 % glucose concentration (89%) and 10 % inoculum concentration (91%) after 96 hours from textile wastewater. The surface of the biosorbent before and after the sorption of the dye was examined by FTIR and SEM analysis.

Acid violet 7 and its biodegradation products induce chromosome aberrations, lipid peroxidation, and cholinesterase inhibition in mouse bone marrow

INTRODUCTION

Acid violet 7 (AV7), mostly used in food, paper, cosmetic, and especially in textile industries, was degraded by Pseudomonas putida mt-2 at concentrations up to 200 mg/l.

MATERIALS AND METHODS

In this study, toxicity of AV7, before and after biodegradation, was evaluated in vivo, in mouse bone marrow, by assessing the percentage of cells bearing different chromosome aberrations, membrane lipid peroxidation, and acetylcholinesterasic activity inhibition. The studies included same conditions for animal treatment, corresponding to increasing doses by intraperitoneal (ip) injection.

RESULTS

Results indicated that AV7 showed a significant ability to induce chromosome aberrations, lipid peroxidation, and acetylcholinesterase inhibitory effect. The toxicity of AV7 increased significantly after static biodegradation with P. putida mt-2 and totally disappeared after shaken incubation. In addition, the toxicity generated by the pure azo dye and the corresponding azoreduction metabolites (4'-aminoacetanilide (4'-AA) and 5-acetamido-2-amino-1-hydroxy-3,6-naphtalene disulfonic acid (5-ANDS)) were compared. 4'-AA and 5-ANDS would be responsible of static biodegradation medium toxicity. The present study demonstrates that P. putida mt-2, incubated under aerobic condition, has a catabolism which enables it to degrade AV7, and especially to completely detoxify the dye mixture.

Revealing interactive toxicity of aromatic amines to azo dye decolorizer Aeromonas hydrophila

This study attempted to combine chemostat pulse technique (CPT) and dose-mortality assessment in pursuit of quantitative rankings of toxicity of model aromatic amines (MAAs) in the presence of diazo dye reactive red 141 (or Evercion Red H-E7B; RR141) upon Aeromonas hydrophila. As known, bacterial decolorization performance of azo dyes is directly dependent upon both the characteristics of biochemical reactivity and biotoxicity of dyes and related aromatic amines towards color removal. Thus, the findings herein indicated that the relative toxicity series of MAAs were (1) ortho>para>MAA-free control>meta position (for isomeric aminophenols); (2) -OH>-SO(3)H>MAA-free control (-NH(2) at ortho position); (3) -COOH>MAA-free control>-OH (-NH(2) at meta position) through the CPT at 200mg/L MAAs. Comparison on results in higher levels of MAAs at 1000 mg/L almost showed parallel relative toxicity rankings at 200mg/L. Quantification using traditional plate count method also confirmed nearly similar trends for corresponding MAAs except 3-aminophenol, revealing the promising feasibility of CPT for the toxicity assessment in practical applications. In addition, dose-mortality analysis regularly used in toxicology was used to quantitatively determine toxicity rankings of MAAs. In conclusion, this study directly provided a kinetic model to quantify the relative toxicity ranking of MAAs in the presence of RR141. It could provide a feasible guideline for assessment on the toxicity or treatability of azo dyes and MAAs to A. hydrophila in wastewater treatment.

Jute stick powder as a potential biomass for the removal of congo red and rhodamine B from their aqueous solution

Jute stick powder (JSP) has been found to be a promising material for adsorptive removal of congo red (C.I. 22120) and rhodamine B (C.I. 45170) from aqueous solutions. Physico-chemical parameters like dye concentration, solution pH, temperature and contact time have been varied to study the adsorption phenomenon. Favorable adsorption occurs at around pH 7.0 whereas temperature has no significant effect on adsorption of both the dyes. The maximum adsorption capacity has been calculated to be 35.7 and 87.7mg/g of the biomass for congo red and rhodamine B, respectively. The adsorption process is in conformity with Freundlich and Langmuir isotherms for rhodamine B whereas congo red adsorption fits well to Langmuir isotherm only. In both the cases, adsorption occurs very fast initially and attains equilibrium within 60min. Kinetic results suggest the intra-particle diffusion of dyes as rate limiting step.

Removal of Acid Orange 7 from water by electrochemically generated Fenton's reagent

The removal of azo dye Acid Orange 7 (AO7) from water was investigated by the electro-Fenton technology using electrogenerated hydroxyl radicals (OH) which leads to the oxidative degradation of AO7 up to its complete mineralization. H(2)O(2) and Fe (II) ions are electrogenerated in a catalytic way at the carbon-felt cathode. AO7 decay kinetics and evolution of its oxidation intermediates were monitored by high-performance liquid chromatography. The absolute rate constant of AO7 hydroxylation reaction has been determined as (1.20+/-0.17)x10(10)M(-1)s(-1). The optimal current value for the degradation of AO7 was found as 300 mA. AO7 degradation rate was found to decrease by increase in Fe(3+) concentration beyond 0.1mM. Mineralization of AO7 aqueous solutions was followed by total organic carbon (TOC) measurements and found to be 92%. Based on TOC evolution and identification of aromatic intermediates, short-chain carboxylic acids and inorganic ions released during treatment, a plausible mineralization pathway was proposed.

Comparative assessment upon dye removal capability of indigenous bacterial strains from Lanyang Plain in northeast Taiwan

This study provides a first attempt from a geological and ecological perspective to look forward isolations of indigenous strains with the decolorization capability from the most biodiverse region in Taiwan for dye-laden wastewater treatment. Serial selections were conducted by a specific use of the fungicide nystatin and model azo dye C.I. reactive red 141 (RR141) during isolation. Several bacterial strains with the excellent capability of azo dye decolorization were predominantly isolated from river water and mud samples of Lanyang River Basin. Phase-curve profiles indicated that azo dye decolorization was found to be non-growth associated for both mixed cultures and isolated pure strains. The color removal efficiency of the mixed culture was nearly 10-fold to that of Pseudomonas luteola at ca. 600mgL(-1) RR141, indicating a promising feasibility of isolated cultures to be applicable for practical treatments. The decolorization performance of unacclimated and acclimated pure cultures was at most 20% and 70-80% to that of the mixed cultures, respectively. It might suggest that combined interactions among decolorizers were crucial for the optimal color removal. According to the results of physiological and 16S rRNA gene sequence examinations, the isolated strains should belong to Aeromonas species (very likely A. hydrophila).

The testing of several biological and chemical coupled treatments for Cibacron Red FN-R azo dye removal

Several biological and chemical coupled treatments for Cibacron Red FN-R reactive azo dye degradation have been evaluated. Initially, a two-stage anaerobic-aerobic biotreatment has been assessed for different dye concentrations (250, 1250 and 3135 mg l(-1)). 92-97% decolourisation was attained during the anaerobic digestion operating in batch mode. However, no dissolved organic carbon (DOC) removal neither biogas production was observed during the process, indicating that no methanogenesis occurred. Additionally, according to Biotox and Zahn-Wellens assays, the anaerobically generated colourless solutions (presumably containing the resulting aromatic amines from azo bond cleavage) were found to be more toxic than the initial dye as well as aerobically non-biodegradable, thus impeding the anaerobic-aerobic biological treatment. In a second part, the use of an advanced oxidation process (AOP) like photo-Fenton or ozonation as a chemical post-treatments of the anaerobic process has been considered for the complete dye by-products mineralisation. The best results were obtained by means of ozonation at pH 10.5, achieving a global 83% mineralisation and giving place to a final harmless effluent. On the contrary, the tested photo-Fenton conditions were not efficient enough to complete oxidation.

Variability of enzyme system of Nocardioform bacteria as a basis of their metabolic activity

The present review describes some aspects of organization of biodegradative pathways of Nocardioform microorganisms, first of all, with respect to their ability to degrade aromatic compounds, mostly methylbenzoate, chlorosubstituted phenols, and chlorinated biphenyls and the intermediates of their transformation: 4-chlorobenzoate and para-hydroxybenzoate. Various enzyme systems induced during degradation processes are defined. The ability of microorganisms to induce a few key enzymes under the influence of xenobiotics is described. This ability may increase the biodegradative potential of strains allowing them to survive in the changing environment or demonstrate to some extent the unspecific response of microorganisms to the effect of toxicants. Nocardioform microorganisms responsible for degradation of such persistent compounds as polychlorinated biphenyls, polyaromatic hydrocarbons, chlorinated benzoates and phenols and other xenobiotics are characterized. The possibility of using Nocardioform microorganisms in some aspects of biotechnology due to their ability to produce some compounds important for industry is also estimated.

Revealing characteristics of mixed consortia for azo dye decolorization: Lotka-Volterra model and game theory

This study provides a novel explanation to put forward, in Lotka-Volterra competition model and game theory, interspecific competition in bioaugmentation using constructed mixed consortia for azo dye decolorization. As mixed cultures are regularly used in industrial dye-laden wastewater treatment, understanding species competition of mixed consortia is apparently of great importance to azo dye decolorization. In aerobic growth conditions, Escherichia coli DH5alpha owned a growth advantage to out-compete Pseudomonas luteola due to preferential growth rate of DH5alpha. However, in static decolorization conditions DH5alpha surrendered some proportion of its advantage (i.e., a decrease in its competitive power for metabolite stimulation) to enhance color removal of P. luteola for total coexistence. In aerobic growth, DH5alpha had its growth advantage to exclude P. luteola for dominance (i.e, conflict strategy) according to competitive exclusion principle. In static decolorization conditions, as the removal of a common dye threat was crucial to both species for survival, both species selected cooperation strategy through metabolite stimulation of DH5alpha to enhance effective decolorization of P. luteola for long-term sustainable management. This analysis of game theory clearly unlocked unsolved mysteries in previous studies.

Uptake of cationic dyes from aqueous solution by biosorption onto granular kohlrabi peel

A new, low cost, locally available biomaterial was tested for its ability to remove cationic dyes from aqueous solution. Granules prepared from kohlrabi peel had been utilized as a sorbent for uptake of three cationic dyes, methylene blue (MB), neutral red (NR) and acridine orange (AO). The effects of various experimental parameters (e.g., dye concentration, particle size, initial pH, contact time and other factors) were investigated and optimal experimental conditions were ascertained. Above the value of initial pH 4, three dyes studied could be removed effectively. The isothermal data fitted the Langmuir model in the case of NR sorption and the Freundlich model for all three dyes sorption. The biosorption processes followed the pseudo-first-order rate kinetics. The results in this study indicated that kohlrabi peel was an attractive candidate for removing cationic dyes from the dye wastewater.

Biosorption of Reactive Blue 4 dye by native and treated fungus Phanerocheate chrysosporium: Batch and continuous flow system studies

The native and treated fungal biomass of Phanerocheate chrysosporium was used for the biosorption of a textile dye (i.e., Reactive Blue 4). In the batch system, the biosorption equilibrium time was about 4 h and the maximum dye uptake on all the tested fungal biomass preparations was observed at pH 3.0. The dye uptake capacities of the biosorbents at 600 mg L(-1) dye concentration were found to be 132.5, 156.9, 147.6 and 81.1 mg g(-1) for native and heat-, acid- and base-treated dry fungal preparations, respectively. The dye uptake capacity order of the fungal preparations was found as heat-treated>acid-treated>native>base-treated. The Langmuir, Freundlich and Temkin adsorption models were used for the mathematical description of the biosorption equilibrium. The Freundlich and Temkin models were able to describe the biosorption equilibrium of Reactive Blue 4 on native and treated fungal preparations. The dye biosorption on the fungal biomass preparations followed Ritchie kinetic model. Biosorption of the dye from aqueous solution was also investigated in a continuous flow system. The maximum biosorption capacity of the heat-treated fungal biomass P. chrysosporium was 211.6 mg (g dry biomass)(-1) at an initial dye concentration of 600 mg L(-1) and at a flow rate of 20 mL h(-1).

Decolorisation, biodegradation and detoxification of benzidine based azo dye

The present study deals with the decolorisation, biodegradation and detoxification of Direct Black-38, a benzidine based azo dye, by a mixed microbial culture isolated from an aerobic bioreactor treating textile wastewater. The studies revealed a biotransformation of Direct Black-38 into benzidine and 4-aminobiphenyl followed by complete decolorisation and biodegradation of these toxic intermediates. From cytotoxicity studies, it was concluded that detoxification of the dye took place after degradation of the toxic intermediates by the culture.