Reducing water pollution in textile value chain

Presented in this paper is a low-carbon assessment for wastewater treatment by a constructed wetland as ecological engineering. Systems accounting by combining process and input–output analyses is applied to track both direct and indirect GHG emissions associated with the wastewater treatment. Based on the detailed assessment procedures and the embodied GHG emission intensity database for the Chinese economy in 2007, the GHG emissions embodied in both the construction and operation stages of a pilot constructed wetland in Beijing are investigated in detail, with parallel calculations carried out for a cyclic activated sludge plant as a typical conventional wastewater treatment system for comparison.

With the overall embodied GHG emissions taken into account, the constructed wetland is shown to be remarkably less carbon intensive than the conventional wastewater treatment system, and the contrast in GHG emission structure is also revealed and characterized. According to the results, the ecological engineering of the constructed wetland is considered to be favorable for achieving the low-carbon goal.

This work involved the treatment of industrial wastewater from a nylon carpet printing plant which currently receives no treatment and is discharged to sea. As nylon is particularly difficult to dye, acid dyes are required for successful coloration and cause major problems with the plant's effluent disposal in terms of color removal. Granular activated carbon Filtrasorb 400 was used to treat a ternary solution of acid dyes and the process plant effluent containing the dyes in a fixed-bed column system.

One of the textile industries in Penang, Malaysia is experiencing high  concentration  of  COD  and  colour  in  the  final  effluent  after  biological  treatment  exceeding  the  standard  discharge  limit.  The  purpose  of  the  present  study was to investigate the suitability of using activated carbon (AC), limestone (LS)  and  mixture  of  both  (LS:AC)  as  low  cost  media  for  the  post-treatment  of  treated  effluent.  The  physico-chemical  treatment  adopted  in  this  study  is  preferred  over  the  other  methods  because  of  its  simplicity,  easy  maintenance  and  quality  control.  The result showed that limestone  and  activated  carbon  mixture  provides an alternative medium for removing COD and colour at a much lower cost as compared with activated carbon.

US-based SeaChange Technologies has put a new spin on the clean-up of textile effluent from dyeing and finishing with a new way to treat wastewater and sludge using vortex separation in a one-step process.Funded by Fashion for Good, the North Carolina start-up has recently completed a 3- month pilot-scale trial with Indian textile giant Arvind using its patented cyclonic separation technique to clean wastewater streams and highly concentrated sludge to reduce both chemical discharge and overall greenhouse gas emissions in the dyeing process.

This article makes an attempt to review the various waste minimisation techniques and possibilities that are available for the textile industry. The strategies and technologies discussed apply to all types of wastes such as hazardous materials, non-hazardous materials, water, energy, raw materials, all waste emissions, and other resources.

Some of the prominent techniques discussed include source reduction of waste, reducing water and chemical consumption, energy conservation, solid waste generation minimization and more.

This study evaluates the feasibility of water minimization and wastewater reuse for a wool finishing textile mill. The evaluation process is based upon a detailed analysis on water use, process profile and wastewater characterization, indicating a potential for 34% reduction in water consumption and for 23% of wastewater recovery for reuse.

Wastewater reuse requires treatment and results in a remaining wastewater stream with stronger characteristics and consequently more costly to treat. The feasibility includes technical considerations for appropriate treatment alternatives and related cost factors for water consumption, treatment for reuse and for discharge either to sewer or to receiving media.

Textile industries use large amounts of water in the processes of dyeing and processing of textile fibers, generating high volumes of wastewater containing dyes, surfactants, inorganic ions, wetting agents, among others. The main environmental impact of these effluents is related to the absorption of light into the water, which interferes with the photosynthesis of plants and algae. Therefore, it is relevant to have environmental planning aimed at the reuse of the water, increased removal of dyes, as well as reducing losses in the dyeing.

In this work, studies were undertaken to propose control measures so as to introduce the concepts of Cleaner Production (CP) in the textile sector. Data was collected in a company located in the catchment area of the river Doce, in Minas Gerais, and established the association of the relative advantages of conventional coagulation/flocculation with the combined use of Advanced Oxidation Processes (AOP). The proposed measures entail a decrease in the volume and characteristics of the refractory sludge generated and the possibility of recirculation of treated effluent. The need to develop pilot-scale experiments was identified, including monitoring of the acute toxicity of treated effluents.

In textile reactive dyeing, dyed fabrics have to be rinsed in the wash-off step several times to improve color fastness. Thus, the multiple rinsing processes drastically increase the freshwater consumption and also generate massive waste rinsing effluents. This paper addresses an innovative alternative to recycle the waste effluents to minimize freshwater consumption in the wash-off step. Accordingly, catalytic ozonation with a highly effective catalyst has been applied to remedy the waste rinsing effluents for recycling.

The carbon aerogel (CA) hosted bimetallic hybrid material was fabricated and used as the catalyst in the degradation of residual dyes in the waste rinsing effluents by ozonation treatments. The results indicate the participation of the catalyst significantly enhanced the removal percentage of chemical oxidation demand by 30%. In addition, it has been validated that waste effluents had been successfully reclaimed after catalytic ozonation. They could be additionally reused to reduce freshwater consumption in the wash-off step, but without sacrificing the color quality of corresponding fabrics in terms of color difference and colorfastness.

This study may be the first to report the feasibility of catalytic ozonation in minimization of freshwater consumption in the wash-off step in textile reactive dyeing.

This article presents a new approach, which is an intersection of advanced primary and secondary water treatment solutions, to meet challenge of to meet the challenges faced by the textile industry.

Electrocoagulation is one of the emerging water treatment solutions capable of handling the varying wastewater characteristics of textile industry effluent. This advanced technology utilizes the advantages and functions of conventional flotation, coagulation, and electrochemistry in water and wastewater treatment to optimize contaminant removal in an environmentally sustainable and cost efficient way.Electrocoagulation is one of the emerging water treatment solutions capable of handling the varying wastewater characteristics of textile industry effluent. This advanced technology utilizes the advantages and functions of conventional flotation, coagulation, and electrochemistry in water and wastewater treatment to optimize contaminant removal in an environmentally sustainable and cost efficient way.

This specialized solution provides companies with new and existing wastewater treatment systems the opportunity to optimize their current treatment process, adding dependability, reducing operating & maintenance cost, sludge disposal costs, and the mitigation of environmental concerns relating to toxic non biodegradable solids sludge disposal.

Advanced electrocoagulation water treatment solutions can provide value in several aspects of the textile wastewater treatment process. These aspects include primary pretreatment to remove/reduce non biodegradable, toxic compounds and color prior to a biological process or as a polishing pretreatment for specific contaminants such as colloidal organics, minerals, or microbiological contaminants prior to ultrafiltration (UF) or reverse osmosis desalination (RO) systems.

The study investigates the performance of chitosan and microorganism towards treatment of textile wastewater by using aeration & flocculation process. Chitosan is found from chitin by deacetylation. Flocculation and the process are done using Jar test experiment. The effect of dosage, reduction of COD, reduction of BOD and color of textile wastewater is studied. The results obtained found that chitosan is very effective for reduction of COD, BOD and color.

Environmental  management  projects  require  economic  integrated  approach  including  the  combination  of  in–process, in–plant and end–of–pipe treatment modules to comply with environmental regulations.

The main objectives of this study to management and control of liquid and solid wastes in the industry as well as find a sustainable solution for the textile industrial wastewater in order to comply with the National Regulatory Standards governed by the ministerial decree for wastewater discharge into public sewage network to protect the environment as well as selecting the wastewater streams that need to be treated prior to its discharge, identifying  the  different  possible  treatment  trains  for  the  wastewater,  conducting  treatability  analysis  for investigating  the  feasibility  of  each  of  the  identified  trains,  selecting  the  most  suitable  treatment  train,  and developing  the  basic  design  for  the  selected  treatment  train.

The  study  is  conducted  through  very  precise characterization of the wastewater produced from the final effluent during the working shifts and application of appropriate  treatment  options  for  the  end-of-pipe  using  different  treatment  techniques  in  order  to  protect water resources from contamination.

An effluent treatment technique adapted to the dyes must eliminate them completely in order to avoid the formation of more dangerous by-products than the initial compounds and more particularly to prevent the formation of carcinogenic products. Conventional methods of treatment do not meet this expectation.

The objective of this study is the development of a new biological approach which is more suitable in terms of cost-effectiveness, pollutant removal efficiency, and recyclability and inexpensive, effective, and eco-friendly (biodegradable) for the treatment of effluents of the textile industry. To our knowledge, this is the first report on the textile effluent treatments using peptides. This technology will be based on the best binding affinity of textile dyes on peptides synthesized via a solid-phase peptide synthesis (SPPS) technique.

The objective of this study was development of a new biological method for the treatment of textile industry effluents, which is cheaper, more profitable, and eco-friendly. This method is essentially based on the synthesis of dye-fixing peptides. The use of peptides synthesized via a solid-phase synthesis to fix a reference textile dye like “Cibacron blue” (CB) and the performance analysis of binding assays were the main objectives of this study. For this reason, two peptides P1 (NH2-C-G-G-W-R-S-Q-N-Q-G-NH2) and P2 (NH2-C-G-G-R-R-Y-Q-P-D-S-NH2) binding with the CB dye were synthesized by the solid-phase peptide synthesis (SPPS) technique. The obtained results showed significant fixation yields of CB-peptides of 91.5% and 45.9%, respectively, and consequently, their interesting potential as a tool for a new biochemical method in the pollution prevention of textile wastewater.

The reduced natural waters and the large amount of wastewater produced by textile industry necessitate an effective water reuse treatment. In this study, a combined two-stage water reuse treatment was established to enhance the quality and recovery rate of reused water. The primary treatment incorporated a flocculation and sedimentation system, two sand filtration units, an ozonation unit, an ultrafiltration (UF) system, and a reverse osmosis (RO) system. The second treatment included an ozonation unit, a sand filtration unit, and UF and RO systems. The color removal rate increased with the increasing ozone dosage, and the relational expression between the ozone dosage and color removal rate was fitted. Ozonation greatly reduced the color by 92.59 and 97.27 times during the primary and second ozonation stages, respectively. RO had the highest removal rate. The combined processes showed good performance in water reuse treatment.

Microalgal biodiesel has emerged as an environment friendly alternative to the existing fossil fuels. The commercial production of this biodiesel is still challenging due to several technical and economic issues, which span from mass cultivation of microalgae to the biodiesel production. Mass cultivation is the most critical step in terms of water and nutrient requirement. Industrial wastewater such as textile wastewater (TWW) is a cheap source for water, which additionally contains necessary nutrients (phosphate, nitrates, micronutrients etc.) and organic dyes (potential carbon source) for algae cultivation. The application of microalgae for biodiesel production employing a single objective strategy is not sustainable.

Microalgae can be effectively employed to bioremediate TWW (dyes and nutrients removal) and to produce biodiesel from grown microalgae. This process integration (bioremediation-biodiesel production) can potentially improve biodiesel production and wastewater treatment. However, this process coupling needs to be thoroughly investigated to identify and optimize critical process factors (algal species, cultivation and harvesting methods, bioremediation mechanism etc.).

This study has reviewed the status of TWW as a potential source of water and nutrients, role of different algal species in the bioremediation of TWW, different cultivation systems, harvesting and biodiesel production methods. It also suggests future research and development challenges for coupled textile wastewater treatment and microalgal biodiesel production.

In the early 1960’s, the Japanese company Nihon Chlorella was the first to make microalgae commercially available. Since then, the microalgae cultivation at industrial scale has grown and diversified significantly. Among the microalgae applications, bioremediation of textile wastewater is one the most promising technologies due to the simultaneous benefits: microalgae cultivation using textile wastewater as culture medium (bioremediation and CO2 mitigation) followed by microalgae lipid application (biodiesel production). Therefore, the aim of this work is to explore the potential business opportunities in using microalgae for bioremediation and wastewater treatment.

The study concludes that compared to physicochemical methods (ozonation, electrochemical destruction, activated carbon), biological methods (bioremediation using microalgae) show advantages in terms of cost effectiveness, easy scale up and mainly the potential to simultaneously carried out the bioremediation, CO2 mitigation and biosynthesize high-added value molecules. In addition, there is no consensus on the best microalgae cultivation system.

The aim of this article is to demonstrate the technical and economic feasibility of an integrated process for microbial treatment of dye(s) containing wastewater from textile effluent that evaluates the efficiency and effectiveness to meet the dye(s)’ maximum contaminant level. It covers the whole process of microbial treatment methods that are adopted for dye removal to make an eco-friendly system. The purpose of this treatment technology includes process modifications and engineering approaches. It comprises existing technologies with new advanced technologies at all stages of the process.

Apart from evaluating the reliability of technologies for small and large systems to make the system cost-effective, it also demonstrates the potential of genetically engineered microorganisms for their dye removing potential and feasible economics.

The textile wastewaters (TWWs) are one of the major sources of environmental pollution, due to the presence of various recalcitrant dyes. It is estimated that about 300,000 t of synthetic dyes are discharged in TWWs every year worldwide. Thus, untreated or incompletely treated TWWs cause harm to aquatic and terrestrial life. To avoid the negative impacts associated with the discharge of TWWs into the natural ecosystems, effective dye remediation processes are being developed.

Current methods of removing dyes from TWWs are generally regarded to be complex, expensive and energy demanding processes. Therefore, bioremediation of TWWs using microbial consortia has appeared as an emerging alternative for textile dyes removal. This chapter provides an updated literature on the application of microbial consortia in the treatment of TWWs, focusing on the mechanisms involved in dye biodegradation and the main interactions established between the consortia members and their influence on dye removal efficiencies.

Increasing concerns over discharge of untreated or partially treated textile wastewater have led many researchers to develop innovative, sustainable treatment systems. Current textile wastewater treatment system has its challenges in removing complex dyes such as Azo dyes. However, studies have shown that they can be biologically removed through a process called biodegradation. A wide variety of microorganisms (fungi, bacteria, and actinomycetes) growing in biological treatment systems are the biological agents for biodegradation. Microbial degradation is usually only meant for the complete mineralization of organic molecules. Besides, microbes can concentrate, accumulate, and absorb heavy metals inside cells or cell walls. This article provides inputs on the same.

The main factors affecting dye degradation are also broadly discussed. Microbial degradation of hazardous dyes is well known and currently being adopted as a better alternative for textile dye degradation. The enzymes produced by a range of microbes have a higher commercial importance and are also used for the degradation of a large class of pollutants or xenobiotics.

Current physical and chemical textile wastewater treatment processes have challenges owing to high cost and need for combination of technologies for the waste streams lacking homogeneity. Hence, sustainable cost effective biological methods are suggested which have been known to degrade pollutants completely. One such biological methods is phytoremediation which attempts to use plants and microbes associated with plant root systems to protect the environment by the removal of pollutants in the form of organic wastes. It is capable of treating pollutants of dye waste, which are derived from various sources. 

Different plants such as Tecoma stans var. angustata, Scirpus grossus, water hyacinth Eichhornia crassipes and aquatic plant Spirodela polyrrhiza have been discussed for their potential for dye degradation. A consortium of Petunia grandiflora and Gailardia grandiflora plants have also been established for their role in dye degradation.

Textile wastewater treatment is becoming a challenge for small and medium enterprises owing to lack of facilities, poor knowledge and financial problems. This case study analyses the potential of treating textile wastewater under biological aerobic or anaerobic conditions. Aerobic biodegradability was carried out using a closed bottle test, while anaerobic biodegradability was tested using Biochemical Methane Potential (BMP) test. 

The results showed that treating the textile wastewater aerobically can be a potential option as seen by 80-85% BOD removal, or approximately 12-13% BOD/COD removal compared to that of the theoretical value of 15% BOD/COD removal. While anaerobic digestion treatment indicates that a high COD concentration may inhibit the ability of microorganism consortia to degrade COD into biogas.

Biological approaches are the most prominent eco-friendly wastewater treatment systems, in which microalgae (Chlorella vulgaris, Chlorella pyrenoidosa, Spirogyra sp., Oscillatoria tenuisin and Scenedesmus sp.)  have risen to prominence due to their potential to simultaneously act on textile wastewater bioremediation,  CO2 mitigation  and produce high value-added molecules.

Microalgae are known to remove dyes by adsorption, biodegradation, and bioconversion. They degrade dyes for nitrogen source by removing nitrogen, phosphorus, and carbon from wastewater; they can also help reduce eutrophication in the aquatic environment and are unique to sequestering higher amounts of carbon dioxide, one of the main contributors to the greenhouse gas effect.

Microbial wastewater treatment approaches are gaining prominence in textile industries owing to their advantages over physicochemical methods such as reduced need for complex plant facilities, reduced chemical requirements or sludge deposition and disposal and more. Further, microbes grown in dye contaminated sites have been shown to have a higher degree of waste treatment owing to their higher tolerance level and adapatability. This study isolates novel bacterial strains from the soil contaminated with textile wastewater that can effectively degrade local textile wastewater. It demonstrates the successful utilization of a pure culture of Bacillus licheniformis ZUL012 for the decolorization of local textile wastewater. 

The study showed evidence of a reduction in BOD, COD, TSS, TDS, and biosorption of metal ions in a varying magnitude. The removal efficiency in the level of pollutants and heavy metal biosorption could pave the way for the adoption of this bacterial sp for the treatment of textile wastewater on a large scale.

Constructed wetlands are cost-effective wastewater treatment alternatives that receive worldwide acceptance. This article gives us detailed inputs on wetlands, their types such as subsurface systems and hybrid systems, operations and challenges. It also discusses various case studies on the types of constructed wetlands.

The study, while not being carried out specifically for textile industry waste water treatment, suggests that the constructed wetlands could be a sustainable model for wastewater management. It shows that the technology can reduce contaminant load by an average of 75-80% for total suspended solids (TSS), chemical oxygen demand (COD), and biochemical oxygen demand (BOD). Treated water from the constructed wetlands could be recycled and used for a variety of purposes thereby resulting in reduction in operational costs, wastewater consumption, and environmental pollution, as well as increased profitability.

This article focuses on designing constructed wetlands for textile wastewater treatment, These technologies are gaining increased attention in recent times, owing to high efficiency, low cost and reduced sludge generation compared to conventional methods, Experiments were performed to remove the pH,  EC,  chloride, sulfate, phenols, BOD, and COD from the textile industrial effluent in constructed wetlands by using aquatic macrophytes Eichhornia crassipes. 

The results showed that the maximum removal percentage of various impurities like  EC, TDS,  chloride, sulfate, phenols, BOD, and  COD in a textile industry effluent were in the range of 85-90% for all parameters which shows that the technology could be a viable solution for sustainable treatment of textile waste water.

Plant based solutions have been emerging in the textile wastewater treatment methods, owing to challenges with conventional techniques. With wetland technology gaining prominence for sustainable wastewater treatment, this study focuses on an innovative, cost-effective, sustainable method called Floating treatment wetland (FTW). Here, FTWs vegetated with plants Phragmites australis and augmented with specific bacteria, were used to treat the dye-enriched synthetic effluent. 

Results showed that this bacterial augmented constructed wetlands or a hybrid system could have the potential to remove pollutants at a higher rate compared to other technologies, however, choice of plants and bacteria play a major role in enhancing efficiency of the process.

Biological treatments such as constructed wetlands are cheaper than the traditional methods for textile wastewater treatment, environmentally friendly and do not produce large amounts of sludge. In this study synthetic wastewater containing Acid Blue 113 (AB113) and Basic Red 46 (BR46) has been added to laboratory-scale vertical-flow constructed wetland systems, which have been planted with Phragmites australis (Cav.) Trin. ex Steud. (common reed). 

In experimental stages, wetlands used for bioremediation showed improved pollution absorption efficiency. However, challenges exist with varying seasons, higher efficiency during the summer and spring seasons, compared to autumn and winter, which suggests that more research into these solutions could make this technology viable irrespective of seasonal changes.

This study examines the potential reuse of textile effluent treatment plant (ETP) sludge in building materials. It studies the feasibility of lightweight bricks manufactured from ground soil, textile sludge, and coal ash.

It is said that the substitution of textile ETP sludge for cement, up to a maximum of 30%, may be possible in the manufacturing of non-structural building materials. The results of toxicity characteristic leaching procedure test show that the heavy metal concentrations in the leachates of the brick products are very low, which also satisfy the regulations. 

This article opens up a new opportunity for use of textile sludge as a biomass energy source. It discusses a case study where sewage sludge is used in optimizing the preparation of coal/sludge mixture for combustion in the existing fluid bed boilers in the Czech Republic. 

With proper treatment methods, there is a possibility of using bioremediation treated textile sludge in this similar application. The paper also discusses the possibilities of thermal usage of mechanically drained stabilized sewage sludge from the wastewater treatment plants in the boiler with circulating fluid layers. Results show that this method could be advantageous owing to reliable decomposition and the oxidation of the organic harmful elements and signi?cant sludge volume reduction. Another possibility of using the sludge is to lower its humidity and thus to improve the lower heating value, transportation and manipulation.

This study attempts to suggest electric incineration as a sustainable solution for textile sludge management through a case study.  The techniques are used for sludge volume reduction and destruction of the hazardous elements. 

The oven-dried samples can be powdered and mixed at various proportions with clay for making the ceramic products and also mixed with sand, cement, and aggregates for making blocks for the stabilization of heavy metals in sludge. Results show that sludge addition can improve the compressive strength of the blocks and ten percent sludge and 10-20% ash can be used as a cement replacement for block preparation.

This study presents a review of four sludge to energy recovery routes (anaerobic digestion, combustion, pyrolysis, and gasification) with emphasis on recent developments in research, as well as benefits and limitations of the technologies on economics and environmental impacts. Methodologies are discussed across various industries and their potential for use in textile industries.

The study concludes that all the technologies considered require further research and development into co-utilization of sludge, operating condition optimization and effective technology scale-up for maximizing energy recovered while reducing cost and emissions.

Effluents from the textile industries contain reactive dye in a concentration range of 5-1500 mg/ L.  Physical  and  chemical methods  are effective  for  color removal  but  they require more energy  and  chemicals  than  biological  processes  and sometimes it causes pollution into solid or liquid side streams which requires additional treatment or disposal. Biological treatment, on the other hand, offers easy, cheaper, and effective alternatives for colour and toxicity removal of Azo dyes.

Number of microorganisms  like  bacteria, fungi, algae,  actinomycetes, and yeast possess dye decolorizing ability. This study suggests the utilization of microorganism consortia as they offer considerable advantages over pure cultures with higher  degrees  of biodegradation and  mineralization due  to synergistic metabolic activities of the microbial community. Consortia usually do not require sterile conditions and have greater stability towards changes in the prevailing conditions(pH, temperature and feed composition) compared to pure cultures.

About 70% of dyes used in textile industries are azo, a dye complex in structure. They are cost-effective and easy to use, which makes them the most popular synthetic dye. Conventional degradation systems have challenges with degrading azo dyes efficiently at lesser costs. Hence, the use of bacterial methods can be useful in degrading synthetic dyes, including azo dyes at less cost and higher efficiency. The use of microorganisms for biodegradation is convenient because it is versatile, has dynamic metabolisms, and has potential machinery of enzymes. Bioremediation is a non hazardous, cost-efficient, environment-friendly, and often more effective alternative to conventional methods for the treatment of textile waste.

This article reviews the contribution of different bacteria in the biodegradation of synthetic dyes and the factors influencing the performance of these bacteria. While various bacterial species have been employed since long such as Bacillus cereus, Bacillus subtilis, and Aeromonas hydrophila, due to advances in dye composition, the structure of azo dyes have become more complex which even kills the organisms in anoxic conditions. Recent research studies on cultures of Proteus mirabilis, Pseudomonas luteola, and Pseudomonas sp. have shown promising results for azo dye degradation under anoxic conditions.

Biologically synthesized iron nanoparticles are gaining increased attention due to their potential to degrade Azo dye’s  intermediate byproducts such as aromatic amines by various enzymes. These are successfully utilized for the elimination of hazardous and toxic wastes due to their catalytic, super-magnetic property and greater efficiency.This review article discusses the mechanism of the same.

The results suggest that iron nanoparticles are suitable for decolorization of textile effluents which is eco-efficient, less time consuming and an economic approach. Optimization of various parameters like temperature, pH, salinity and use of growth supplements such as yeast extract can further enhance the biodegradation activity.

Microbial fuel cells (MFCs) are a promising technology for the simultaneous treatment of wastewater and electricity production. With regard to azo-dye containing wastewater (e.g., from textile manufacturing), the dye may be fed via the anode chamber containing electrochemically active bacteria or via the cathode chamber containing laccase enzyme as catalyst for oxygen reduction. This study investigates the potential of the two approaches with regard to rate of decolourization of the dye (Acid orange 7), COD reduction and electricity production.

Results showed that anodic process had challenges with exposing the samples to atmosphere and that feeding azo dyes in cathode chambers of MFCs containing laccase is a better way of treating the dyes compared to the commonly used approach of feeding the dye in the anode chamber provided enzyme activity can be sustained.

Increasing needs for efficient treatment of textile azo dyes have led many researchers to identify novel microbial strains from niche natural environments, to test their potential for biodegradation. Scientists at India’s National Institute of Oceanography have identified a bacterium derived from marine sponges that can be used to break down potentially hazardous textile dyes in wastewater.

While using bacteria to break down textile dyes in wastewater is not new, the researchers isolated the bacteria Yangia pacifica from intertidal rocks off the coast of Goa and investigated its potential to break down azo dyes in an aqueous environment.  It is to be noted that bacteria from these regions have not been previously tested for their biodegradation potential. While the bacteria has been found to effectively decolourize the water samples with azo dyes, more research is needed to analyse their environmental impacts.

This article provides details on the discussions the University College London had with experts on the azo dye bioremediation needs. In a bid to further understand the industry requirements for an azo dye remediation project the team had discussions with The Ecological and Toxicological Association of Dyes and Organic Pigments Manufacturers (ETAD) in Basel, Switzerland.

The debate centred around three key themes which reflected the concerns of the public in relation to the development of genetically modified organisms and synthetic biology. (i) Are there better solutions to the problem available? (ii) Is it safe to use synthetic biology in the bioremediation of dyes? (iii) Whose responsibility is the problem?

Other experts present during the discussion were representatives from  Bezema and Huntsman Dyeing companies.

Azo dyes are xenobiotic compounds which have bioaccumulated in the environment as a consequence of escalated industrial improvement. These are hazardous in nature, possessing carcinogenic and mutagenic effects on human beings. The objective of this research was to isolate and find out azo dye (Reactive Orange-16) degrading potential of marine actinobacteria obtained from sediment samples of Port Blair, India.

Through various biochemical and molecular research, the isolate with highest potential of azo dye reduction was identified. Results showed that the marine isolated strain had the potential of decolorizing the dye to about 85% in 24 hours which suggests that the strain could have the potential to be used for large scale textile dye treatments.

Growing research developments to explore the potential of microbes for efficient treatment of textile wastewater and the dyes have resulted in several innovative approaches for the same. In this study, a bacterial consortium consisting of Providencia rettgeri strain HSL1 and Pseudomonas sp. SUK1 has been investigated for degradation and detoxification of structurally different azo dyes.

The consortium showed 98-99 % decolorization of all the selected azo dyes viz. Reactive Black 5 (RB 5), Reactive Orange 16 (RO 16), Disperse Red 78 (DR 78) and Direct Red 81 (DR 81) within 12 to 30 h under microaerophilic, sequential aerobic/microaerophilic and microaerophilic/aerobic processes.

As biodegradation under sequential microaerophilic/aerobic process completely detoxifies all the selected textile azo dyes, further efforts should be made to implement such methods for large scale dye wastewater treatment technologies.

This article proposes the use of white rot fungi for degrading azo dyes in textile industries. It uses three white rot fungi species - Trametes versicolor, Pleurotus ostreatus, and Pleurotus pulmonarius for the fermentation process. A maximum degradation percentage of 63.0% was achieved at 17 days of incubation with T. versicolor strain.

The study concludes that T. versicolor can be a candidate for large-scale fermentation due to its versatility against changes in the evaluated variables, which allow it to achieve efficient BR46 degradation. It is therefore a suitable species to develop an efficient and low-cost strategy with a positive environmental impact for the bioremediation of xenobiotic compounds such as synthetic dyes.

Dyes like malachite green, nigrosin, and basic fuchsin are complex to get degraded by conventional methods owing to high costs and process efficiency challenges. These can be treated using fungal isolates such as Aspergillus niger, and Phanerochaete chrysosporium, isolated from dye effluent soil. This article provides details on the same. 

The isolates were studied in three different biodegradation methods namely, agar overlay and liquid media methods, stationary and shaking methods.

Higher decolorization was observed under shaking conditions by P. chrysosporium and A. niger, which could be due to better oxygenation of the fungus and regular contact of secreted enzymes with dye molecules to decolorize it, moreover agitation also helps the fungus to grow better. The performance of A. niger and P. chrysporium in the biodegradation of textile dyes of different chemical structures suggests and reinforces the potential of these fungi for environmental decontamination.

Azo dyes are complex textile dyes which do not get easily treated by physical and chemical methods owing to process and economic limitations. A wide range of aerobic and anaerobic bacteria such as Pseudomonas sp., Bacilus subtilis, Geobacillus sp., Escherichia coli, Rhabdobacter sp., Enterococcus sp., Staphylococcus sp., Corneybaterium sp., Lactobacillus sp., etc. have hence been extensively explored and reported for resulting good biodegradation of azo dyes in  a bacterial consortia.

Enzymatic breakdown of industrial azo dyes, with commonly used enzymes such as azoreductase and laccase are reported to have a great potential. Microbial enzymes have several advantages compared to other sources such as low cost raw material, less maintenance cost, simple downstream processing, etc. While the production cost is higher for enymes, operational costs are lower by operating under lower temperature and pressure.

With growing concerns over improper disposal of azo dyes from textile wastewater and their adverse environmental effects, many researchers are working to develop biological solutions for their sustainable treatment. This study focuses on analysing the potential of three bacterial strains for complete degradation of azo dyes. The isolated bacterial strains Pseudomonas putida, Pseudomonas aeruginosa and Bacillus subtilis are very effective in reducing dyes such as Blue RR, Black B, Red RR, and Yellow R.

Each of these bacterial strains were optimal and efficient for a particular type of dye discussed above. The strains could also be used in consortia to efficiently remove the dyes. On an average all three strains show a decolorization rate of above 90%.

Biological techniques for textile wastewater treatment are being extensively researched owing to their advantages over traditional techniques. Several innovations are being tried out to enhance the efficiency of these systems. One such approach in the case of use of microbial strains is the utilization of microorganism consortia which offer considerable advantages over the use of pure cultures in the degradation of synthetic textile dyes. Higher degrees of biodegradation and mineralization can be achieved due to synergistic metabolic activities of the microbial community. Consortia usually do not require sterile conditions and have greater stability towards changes in the prevailing conditions (pH, temperature and feed composition) compared with pure cultures.

Various microbial consortia have been proved as a better solution due to the synergetic action of bacterias. Microbes including Rhizopus oryzae, Cyathus bulleri, Coriolus versicolour, Funalia trogii, Laetiporus sulphureus, Streptomyces sp., Trametes versicolour work good in such conditions.

Biodegradation activities of land environment based microorganisms and their enzymes azoreductase, laccase, and other associated enzymes on azo dyes are well known. However, little is known about the biodegradation genes and azo dye degradation genes residing in sediments from coastal and estuarine environments. Unlike laccase genes, azoreductase (Azor), and naphthalene degrading genes which are ubiquitous in the coastal and estuarine environments have the property to reduce azo dyes naturally. This article explores the potential opportunities on the same.

The study shows that inland river discharges have a higher influence on the occurrence and abundance of azo dye degrading genes in the nearshore environments and these could enable the use of indigenous microorganisms for remediating textile effluent contaminated sites.

This article attempts to develop a novel membrane bioreactor with photocatalyst to improve the efficiency of conventional bioreactor systems for textile wastewater treatment. The photocatalytic membrane bioreactor is made of a mild steel rectangular reactor of the photocatalytic unit and polyethersulfone submerged hollow fiber membrane bioreactor unit. Graphene oxide incorporation has shown better results in decolorization and degradation.

Results showed that the COD removal efficiency of 48% was attained with photocatalysis, and the removal efficiency was further increased up to 76% when integrated with membrane bioreactor. The color removal efficiency after photocatalysis was 25% further increased up to 70% with MBR.  The study concludes that complete total suspended solids ((TSS) removal can be achieved with this hybrid system.

Treating textile effluents involve an increased energy consumption and hence higher costs for any factory. Energy efficiency is the key to reducing energy costs in an effluent treatment plant. This article suggests a microbial fuel cell-membrane bioreactor integrated system which combines the advantages of the individual systems, by simultaneously treating wastewater and recovering energy. 

Microbial fuel cells (MFCs) are devices that use bacteria as catalysts to oxidize various substrates and recover electricity. An MFC–membrane bioreactor (MBR) integrated design appears to be more attractive in terms of costs and footprint. The system favors a better utilization of the oxygen in the aeration tank of MBR by the MFC biocathode and enables high quality effluent treatment.

This study attempts to explore a novel membrane reactor technique for improved textile wastewater treatment at reduced costs. The novel reactor called Self-Forming Dynamic Membrane Coupled Bioreactor (SFD-MBR), uses coarse pore-sized material to separate solid and liquid in biorreactors, which offers some advantages when compared to membrane bioreactor using micro-/ultrafiltration membranes. 

It has good effluent quality under steady-state conditions and shows good resilience to extreme organic loading conditions. It also has a higher tendency to mesh clogging when compared to the traditional MBR. It also leads to higher solid retention times which results in a more stable biological process at a steady state, which positively affects the filtration performance. Studies reveal that over 97% of dye removal has been achieved with industry experiments.

This article provides an overview of the phytoremediation technique, together with information concerning its specific application to the leather industry using reed beds.

Phytoremediation takes advantage of the nutrient utilisation processes of the plant to take in water and nutrients through roots, transpire water through leaves, and act as a transformation system to metabolise organic compounds, such as oil and pesticides. Alternatively they may absorb and bio-accumulate toxic trace elements, including heavy metals such as lead, cadmium and selenium. Heavy metals are closely related to the elements plants use for growth.

Phytoremediation is an affordable technology that is most useful when contaminants are within the root zone of the plants (top three to six feet of the soil). For sites with contamination spread over a large area as in leather industries and tanneries, this may be the only economically feasible technology. The advantages of Reed bed system is that they require less maintenance, minimal chemicals and power and the sludge generation is also safe to the environment and can be easily disposed according to the legislations.

BLC is developing reed bed technology for leather effluent treatment in co-operation with the company ARM Ltd.

Phytoremediation dominates over microbial and other physico-chemical methods of textile wastewater treatment because of cost effectiveness, safety, easiness to manage due to the autotrophic system of larger biomass requiring little nutrient inputs and more.

A lot of advancement has been progressed in the utilization of plants for cleaning up textile wastewater. This article provides details of various phytoremediation techniques available for the removal of different contaminants from textile wastewater. It also provides the list of plant species that have shown effective results when used in the textile wastewater treatment. 

The study suggests that root morphology and depth are critical characterisitcs to be noted for effective phytoremediation and terrestrial plants are more likely to be effective due to their large root systems compared to aquatics. Some examples for terrestrial plants include Indian nustard which has the ability to accumulate metals and radionuclides and sunflower. In the aquatic plants, duckweed has found to be an effective phytoremediator.

Lemnion Green Solutions Pvt. Ltd. is an Indian company providing tailor -made plant based wastewater treatment systems. They have expertise in utilising duckweed systems, wetland development and ecological floating beds for water treatment, aesthetic improvement and ecological restoration.

According to them, Duckweed based wastewater treatment, as well as ecological floating beds, are able to treat high nitrogenous waste containing water. Duckweed can tolerate the eutrophic condition making diatoms while the floating beds treat the nitrogenous water.

They also claim that duckweed-based wastewater treatment systems on integration with ‘Micro-era’ culture enhances the sludge digestion efficiency.

Treatment of textile effluents by using solar driven plants through phytoremediation is an eco-friendly, and cost-effective approach. In this regard, researchers have identified the potential of various plants including some decorative plants for effective textile dye removal. Various decorative plants can also be used for the treatment of textile wastewater with constructed wetlands.

Among different categories of plants, aquatic macrophytes appear to be more appropriate and successful for the treatment of effluent, of which, this study focuses on the potential for macroalgae C. vulgaris explored for treatment of textile effluent of different concentrations and treatment performance measured via various water quality parameters.

The results reveal that they have the potential to remove 95% of dyes in 24 hours. Further, they could efficiently reduce BOD, COD, pH, EC, and TDS of the 10-50% of concentrated textile effluent within 120 h of treatment, thus enabling an opportunity for its use in large scale textile effluent treatments.

Phytorestore is a French market leader in phytoremediation technologies. The plants involved in the process provide just an anchor while the bacteria attached to the roots play a major role in removing pollution. The contaminants are digested or, in the case of heavy metals that cannot be broken down, trapped by the plant fibres. The choice of vegetation – grass, reeds, bamboo, irises, maize, sorghum, willow, poplar – depends on their ability to break down or sequester pollutants.

Plant-based methods have many advantages. They generally cost less than conventional processes, particularly with respect to operating costs. However, space and time requirements are critical to enable effective absorption of pollutants from the contaminated sites.

Growing research developments to explore the potential of microbes for efficient treatment of textile wastewater and the dyes have resulted in several innovative approaches for the same. In this study, a bacterial consortium consisting of Providencia rettgeri strain HSL1 and Pseudomonas sp. SUK1 has been investigated for degradation and detoxification of structurally different azo dyes.

The consortium showed 98-99 % decolorization of all the selected azo dyes viz. Reactive Black 5 (RB 5), Reactive Orange 16 (RO 16), Disperse Red 78 (DR 78) and Direct Red 81 (DR 81) within 12 to 30 h under microaerophilic, sequential aerobic/microaerophilic and microaerophilic/aerobic processes.

As biodegradation under sequential microaerophilic/aerobic process completely detoxifies all the selected textile azo dyes, further efforts should be made to implement such methods for large scale dye wastewater treatment technologies.

Azo dyes are xenobiotic compounds which have bioaccumulated in the environment as a consequence of escalated industrial improvement. These are hazardous in nature, possessing carcinogenic and mutagenic effects on human beings. The objective of this research was to isolate and find out azo dye (Reactive Orange-16) degrading potential of marine actinobacteria obtained from sediment samples of Port Blair, India. 

Through various biochemical and molecular research, the isolate with highest potential of azo dye reduction was identified. Results showed that the marine isolated strain had the potential of decolorizing the dye to about 85% in 24 hours which suggests that the strain could have the potential to be used for large scale textile dye treatments.

This articles provides details on the discussions the University College London had with experts on the azo dye bioremediation needs. In a bid to further understand the industry requirements for an azo dye remediation project the team had discussions with The Ecological and Toxicological Association of Dyes and Organic Pigments Manufacturers (ETAD) in Basel, Switzerland.

The debate centred around three key themes which reflected the concerns of the public in relation to the development of genetically modified organisms and synthetic biology. (i) Are there better solutions to the problem available? (ii) Is it safe to use synthetic biology in the bioremediation of dyes? (iii) Whose responsibility is the problem?

Other experts present during the discussion were representatives from  Bezema and Huntsman Dyeing companies.

Increasing needs for efficient treatment of textile azo dyes have led many researchers to identify novel microbial strains from niche natural environments, to test their potential for biodegradation. Scientists at India’s National Institute of Oceanography have identified a bacterium derived from marine sponges that can be used to break down potentially hazardous textile dyes in wastewater.

While using bacteria to break down textile dyes in wastewater is not new, the researchers isolated the bacteria Yangia pacifica from intertidal rocks off the coast of Goa and investigated its potential to break down azo dyes in an aqueous environment.  It is to be noted that bacteria from these regions have not been previously tested for their biodegradation potential. While the bacteria has been found to effectively decolourize the water samples with azo dyes, more research is needed to analyse their environmental impacts.

Microbial fuel cells (MFCs) are a promising technology for the simultaneous treatment of wastewater and electricity production. With regard to azo-dye containing wastewater (e.g., from textile manufacturing), the dye may be fed via the anode chamber containing electrochemically active bacteria or via the cathode chamber containing laccase enzyme as catalyst for oxygen reduction. This study investigates the potential of the two approaches with regard to rate of decolourization of the dye (Acid orange 7), COD reduction and electricity production. 

Results showed that anodic process had challenges with exposing the samples to atmosphere and that feeding azo dyes in cathode chambers of MFCs containing laccase is a better way of treating the dyes compared to the commonly used approach of feeding the dye in the anode chamber provided enzyme activity can be sustained.

Biologically synthesized iron nanoparticles are gaining increased attention due to their potential to degrade Azo dye’s  intermediate byproducts such as aromatic amines by various enzymes. These are successfully utilized for the elimination of hazardous and toxic wastes due to their catalytic, super-magnetic property and greater efficiency.This review article discusses the mechanism of the same.

The results suggest that iron nanoparticles are suitable for decolorization of textile effluents which is eco-efficient, less time consuming and an economic approach. Optimization of various parameters like temperature, pH, salinity and use of growth supplements such as yeast extract can further enhance the biodegradation activity. 

About 70% of dyes used in textile industries are azo, a dye complex in structure. They are cost-effective and easy to use, which makes them the most popular synthetic dye. Conventional degradation systems have challenges with degrading azo dyes efficiently at lesser costs. Hence, the use of bacterial methods can be useful in degrading synthetic dyes, including azo dyes at less cost and higher efficiency. The use of microorganisms for biodegradation is convenient because it is versatile, has dynamic metabolisms, and has potential machinery of enzymes. Bioremediation is a non hazardous, cost-efficient, environment-friendly, and often more effective alternative to conventional methods for the treatment of textile waste.

This article reviews the contribution of different bacteria in the biodegradation of synthetic dyes and the factors influencing the performance of these bacteria. While various bacterial species have been employed since long such as Bacillus cereus, Bacillus subtilis, and Aeromonas hydrophila, due to advances in dye composition, the structure of azo dyes have become more complex which even kills the organisms in anoxic conditions. Recent research studies on cultures of Proteus mirabilis, Pseudomonas luteola, and Pseudomonas sp. have shown promising results for azo dye degradation under anoxic conditions.

Effluents from the textile industries contain reactive dye in a concentration range of 5-1500 mg/ L.  Physical  and  chemical methods  are effective  for  color removal  but  they require more energy  and  chemicals  than  biological  processes  and sometimes it causes pollution into solid or liquid side streams which requires additional treatment or disposal. Biological treatment, on the other hand, offers easy, cheaper, and effective alternatives for colour and toxicity removal of Azo dyes. 

Number of microorganisms  like  bacteria, fungi, algae,  actinomycetes, and yeast possess dye decolorizing ability. This study suggests the utilization of microorganism consortia as they offer considerable advantages over pure cultures with higher  degrees  of biodegradation and  mineralization due  to synergistic metabolic activities of the microbial community. Consortia usually do not require sterile conditions and have greater stability towards changes in the prevailing conditions(pH, temperature and feed composition) compared to pure cultures.