Significant Reduction In COD Research Articles

A new electro-active bacterium, Paraclostridium sp. AKS46, converts waste efficiently into electricity in microbial fuel cell

Microbial fuel cell (MFC) has gained importance for its ability to convert waste into energy. Exoelectrogens are the essential component of MFC that plays an important role in determining the efficiency of MFC. Therefore, the current study aimed at isolating efficient exoelectrogen(s) with significant biodegradation ability. Based on iron reduction ability, the current study isolated a bacterium that exhibited a high level of current generation and significant COD reduction (58–70%) of the medium/waste used in MFC. The maximum current density achieved in the 80 ml capacity of two electrodes MFC by the new isolate was 632 mA/m2. The ribotyping analysis identified this isolate as a member of the Paraclostridium genera and named Paraclostridium sp. AKS46. Further study revealed that this new isolate is capable of forming a biofilm on the anode, and the result showed a positive correlation of this biofilm formation with the current generation. Field emission-scanning electron microscopy (SEM), energy dispersive X-ray-SEM, Fourier transform infrared spectroscopy, gas chromatography-mass spectroscopy, and high-performance liquid chromatography analysis of the AKS46 reveal multiple electron transfer routes to the electrode surface. Furthermore, this new isolate was found to be capable of utilizing diverse carbon sources and thus generated current efficiently using different household wastes in MFC. Hence, the present study isolated an efficient exoelectrogen, Paraclostridium sp. AKS46, which can generate a high level of electricity with a significant reduction of COD of diverse wastes. Thus the new isolate has the potential to be used in MFC for sustainable development.

Water Quality Improvement by Wild Bacilli Isolated from Marine Environments

Huge feed volume and shrimp density loading in the intensive shrimp culture decreased water quality. Ammonia and nitrite, which are toxic substances, are occurred from feed and shrimp excretion. Bacillus and related genera (class Bacilli) are bacteria capable of transforming ammonia to nitrite and then nitrite to nitrate by nitrification. In this study, wild marine Bacilli were isolated from samples collected from seagrass beds Andaman Sea, Thailand. Bacilli strains were obtained by using the heat-shock method. Three bacilli bacteria were consisting of Bacillus sp. BC02 (DNA-based), Bacillus sp. BC05 (morphology-based) and Virgibacillus sp. BC06 (DNA-based) was obtained. This study aims to investigate these isolates in shrimp wastewater improvement compared with the commercial seed of Bacillus spp. product (PM-1). Seven wastewater treatments were separately tested by adding different formulas of bacteria. Each treatment was added for 1% (w/v) of 107 CFU/mL density and incubated for 7 days. Treatment of BC02+BC05 showed a significant TSS decrease (66.56%) and produced the highest nitrate concentration. The highest increase of OTP (84.97%) was found in the treatment of BC02+BC05+BC06. PM-1 product has presented the best BOD lessening (54.35%) and showed a non-significant reduction of ammonia (98.60%) with the highest nitrite (0.685 ± 0.009 mg/L) at the end of the experiment. Virgibacillus (BC06) has resulted in the highest significant reduction of COD (60.39%). Thus, it might be summarized that three marine isolates of Bacillus, Virgibacillus, and commercial PM-1 product have excellent potential to improve wastewater quality with no significant diferent. Marine Bacilli can be substitution used for commercial PM-1 products.

Mixotrophic denitrification processes in basalt fiber bio-carriers drive effective treatment of low carbon/nitrogen lithium slurry wastewater

Lithium battery slurry wastewater was successfully treatedby using basalt fiber (BF) bio-carriers in a biological contact oxidation reactor. This resulted in a significant reduction of COD (93.3 ± 0.5 %) and total nitrogen (77.4 ± 1.0 %) at 12 h of HRT and dissolved oxygen (DO) of 0–1 mg/L. The modified Stover-Kincannon model indicated that the total nitrogen removal rate was 4.462 kg/m3/d in R-BF while the substrate maximum specific reaction rate (qmax) in the Monod model was 0.323 mg-N/mgVSS/d. A stable internal environment was established within the bio-nest. Metataxonomic analysis revealed the presence of denitrification and decarbonization bacteria, combined heterotrophic nitrification-aerobic denitrification bacteria, nitrite-oxidizing bacteria, and ammonia-oxidizing bacteria. Functional analysis displayed changes related to (aerobic)chemoheterotrophy, nitrogen respiration, nitrate reduction, respiration/denitrification of nitrite, and nitrate in R-BF. The study proposes a novel approach to achieve denitrification for the treatment of lithium slurry wastewater at low C/N conditions.

Synergistic role of bacterial consortium (RKS-AMP) for treatment of recalcitrant coloring pollutants of textile industry wastewater

In this study, a bacterial consortium (RKS-AMP) was developed, which showed 99.28% decolorization of RCPs with significant reduction in COD (88.77%), BOD (93.99%), TOC (72.53%), phenol (85.90%) within 15 h at 30 ± 2 °C, pH 7, inoculum size (10%), salt concentration (1%), static condition in presence of glucose and yeast extract as carbon and nitrogen source, respectively. It also removed 72.35% of (Cr), 79.09% of (Cd), 65.88% (As) and Pb (83.87%) at same conditions. During RCPs treatment, lignin peroxidase (LiP), manganese peroxidase (MnP) and laccase enzyme activities were also recorded indicating that these enzymes are involved in RCPs degradation. The RCPs present in TIWW and their metabolites produced during the treatment process were identified by FT-IR and GC–MS analysis. In addition, the toxicity studies showed that metabolites of RCPs allowed 100–90% seed germination with significant improvement in root length, shoot length and biomass production in Vigna radiata and Vigna mungo indicating that the developed bacterial consortium (RKS-AMP) was effective in degradation and detoxification of RCPs. Thus, this newly developed bacterial consortium (RKS-AMP) can be used effectively in degradation and detoxification of textile industry wastewater pollutants.

Unhairing of bovine hide using wastewater from Merox unit of oil refinery: techno-environmental aspect.

The effluent generated by Merox unit of oil refinery was used instead of freshwater for bovine hide unhairing because of its proper composition and alkalinity. The effect of temperature, treatment period, sodium sulfide (Na2S), and calcium carbonate (CaCO3) dosage was investigated on unhairing efficiency using lutrom (unhairing slurry) prepared from the Merox effluent (effluent-based lutrom). Under similar operating conditions and chemicals' dosage, the effluent-based lutrom resulted in a higher efficiency (98.6%) than water-based lutrom (67.3%) indicating faster unhairing kinetics for the former lutrom. Moreover, an acceptable swelling (48%) and suitable mechanical properties were also observed. The experimental strategy can save 50 to 67% toxic chemicals and 100% of water consumption in unhairing, which is equivalent to US$ 34 per ton of hide, leading to zero discharge from Merox unit. Recycling of effluent-based lutrom after 3 consecutive runs was associated with a significant reduction in COD (55.6kg/t hide) and BOD5 (11.6kg/t hide) load. The effluent-based and conventional lutroms, before and after unhairing, were treated with ozone under moderate conditions. The FTIR results indicated a high-quality and low costly pelt benefits from the integration of wastewater treatment units of both industries in an environment-friendly manner.

Treatment of septic tank effluent using sequencing batch reactor along with the incorporation of rice husk and Bael pericarp as a natural adsorbent in reducing BOD and COD

The generation of liquid forms of waste has rapidly shown its hike in the presently expanding world. This quantification hugely includes the day today’s secretion of the human excreta into the septic tanks that are commonly found in every household. Proper treatment and disposal of faecal waste, once the septic tank is full, becomes challenging for every resident and local bodies. The primary contaminants found in the Septic Tank Effluents (STE) include many disease-causing pathogens, faecal coliform bacteria, detergents and toxic gases. The Sequencing Batch Reactor (SBR) takes its position when treating any waste, which contains a high amount of organic content. In this study, the characteristics, namely COD and BOD of STE samples collected from different locations of the semi-urban area at the outskirt of a town were analyzed. The STE samples treated using SBR mainly to reduce COD and BOD concentration found to be in higher concentration beyond the permissible limit. The same samples subjected to contact with adsorbents such as rice husk and powdered form of dried Bael (Aegle marmelos) outer shell. Results showed a good reaction with the adsorbents and found a significant reduction in COD and BOD concentration.

Chemidegradation of polychlorinated biphenyls from transformer oil wastewater

Polychlorinated biphenyls (PCBs) are toxic compounds which are persistent in nature capable of bioaccumulation in the food chain. PCBs have been used in transformer oil as heat resistant compounds on large scale. The effect of Fenton process on the degradation of PCB was examined in synthetic wastewater containing old transformer oil for 21 days. Fenton oxidation accomplished completely degradation of PCB, and its degradation mechanism was studied in relation to time. The effectiveness of Fenton process in PCBs degradation was studied after initial characterization of wastewater for all physicochemical parameters of wastewater. Wastewater containing PCBs was treated by Fenton process by which resulted in degradation of PCBs into aldehydes, alcohols and simpler acids such as benzene dicarboxylic acid, hexa-decanoic acid, propanoic acid, benzyl oxy tridecanoic acid, benzoic acid and stearic acid. Simpler chlorinated compounds identified were: hexane, 2-chloro and heptacosane, 1-chloro and silane, trichlorooctadecyl, 1-chloroeicosane, respectively. Other degradation products included: benzaldehyde,2,5-dimethyl, benzene,1-ethyl-3-methyl, benzaldehyde,3,4-dimethyl, benzene,1,2,4-trimethyl and benzaldehyde,2,4-dimethyl. There was a significant reduction in COD of wastewater from its initial value of 705–106 mg/L consequent to treatment. Fenton treatment may be an effective low-cost treatment to eliminate hazardous PCBs compounds.

Comparative efficacy of biogenic zinc oxide nanoparticles synthesized by Pseudochrobactrum sp. C5 and chemically synthesized zinc oxide nanoparticles for catalytic degradation of dyes and wastewater treatment.

Discharge of untreated textile wastewaters loaded with dyes is not only contaminating the soil and water resources but also posing a threat to the health and socioeconomic life of the people. Hence, there is a need to devise the strategies for effective treatment of such wastewaters. The present study reports the catalytic potential of biogenic ZnO nanoparticles (ZnO NPs) synthesized by using a bacterial strain Pseudochrobactrum sp. C5 for degradation of dyes and wastewater treatment. The catalytic potential of the biogenic ZnO NPs for degradation of dyes and wastewater treatment was also compared with that of the chemically synthesized ones. The characterization of the biogenic ZnO NPs through FT-IR, XRD, and field emission scanning electron microscopy (FESEM) indicated that these are granular agglomerated particles having a size range of 90-110nm and zeta potential of -27.41mV. These catalytic NPs had resulted into almost complete (> 90%) decolorization of various dyes including the methanol blue and reactive black 5. These NPs also resulted into a significant reduction in COD, TDS, EC, pH, and color of two real wastewaters spiked with reactive black 5 and reactive red 120. The findings of this study suggest that the biosynthesized ZnO NPs might serve as a potential green solution for treatment of dye-loaded textile wastewaters.

Photoelectrocatalytic treatment of recalcitrant compounds and bleach stage pulp and paper mill effluent using Au-TiO2 nanotube electrode

A simple anodization technique has been adopted for the synthesis of Au doped TiO2 nanotubes (Au/TiO2NTs) electrode. The physicochemical properties of Au/TiO2NTs electrodes have been studied using FE-SEM, Raman spectroscopy, FTIR, XRD, and UV–vis DRS analysis techniques and, compared with un-doped TiO2NTs electrodes. The optimization of process parameters has been carried out for the photoelectrocatalytic (PEC) degradation of 4-CG (4-Chloroguaiacol) under batch-mode experiments. Au/TiO2 nanotube electrodes showed 84% degradation efficiency in 6 h under optimized conditions viz. 0.15 mM Au loading, 0.08 g L−1 electrolyte concentration, 0.03 A current and pH 3 under UV light irradiations. The degradation of 4-CG was validated with the quantification of generated •OH and degradation intermediates/by-products during the batch-mode PEC treatment. The PEC process was observed to be more efficient for degrading and mineralizing 4-CG when compared to PC and EC processes, individually. PEC degradation of 4-CG has also been assessed in recirculation mode to study the feasibility of synthesized Au/TiO2NTs electrodes to treat large volume of contaminant polluted wastewater. For the feasibility of industrial scale applications, pulp and paper mill effluent was subjected to the PEC degradation under recirculation mode using Au/TiO2NTs electrodes and significant reduction in COD and TOC values were observed. Overall, the cost of electrical energy consumption was computed for all the batch and recirculation-mode PEC treatment of 4-CG as well as real pulp and paper mill effluent.

Application of advanced oxidation process combining anaerobic granular sludge on refractory industrial wastewater treatment

An AOPs of Fe/C micro-electrolysis (FCME) and Fenton oxidation (FO) was combined with anaerobic granular sludge (AGS) to treat recalcitrant pharmaceutical wastewater in this study. The AOPs showed significant COD reduction during both FCME and FO. For influent COD=9000∼11000mg/L, the pretreatment effluent COD could reach below 5500mg/L under 0.6% H2O2 adding condition. And the B/C of pharmaceutical wastewater was improved from 0.11 to 0.37. The subsequent AGS treatment in EGSB got a COD removal rate of 87.1%. The extracellular polymeric substance (EPS) and mean diameter detection demonstrated high stability of EGSB. AOPs with AGS is supposed to be a better option for recalcitrant wastewater treatment process.

Multistage fluidized bed bioreactor for dye decolorization using immobilized polyurethane foam: A novel approach

A multistage fluidized bed bioreactor (M-FBBR) was developed for Congo Red (CR) dye removal using Polyurethane foam (PUF)-immobilized Bacillus subtilis. The active surface area for microbial growth and biological interaction are important factors to be considered for immobilization mediated decolorization. In the present study, the active surface area can be improved in the reactor in two ways, (i) by avoiding the accumulation of PUF on the top surface of reaction volume and (ii) by providing free moving foams in larger number. To achieve this, existing FBBR was modified by introducing a porous stainless steel box (PSSB), which is autoclavable, custom made, and cost-effective. To elucidate this, dye decolorization studies were conducted in both FBBR and M-FBBR. The enhanced CR dye removal was observed in M-FBBR. Further, optimization study for M-FBBR approach showing the maximum CR dye removal (92%), was obtained at a dye concentration of 100 mg/L, PUF weight- 5 g, pH-8, and glucose concentration- 4 g/L respectively. Extensive mineralization has been performed for synthetic and real textile wastewater (RTW), and the significant COD reduction (86.6%, 90.15%) and TOC reduction (57.54%, 69.13%) were observed for synthetic wastewater and RTW respectively.

Remediation of textile bleaching effluent by bacterial augmented horizontal flow and vertical flow constructed wetlands: A comparison at pilot scale

Fabric bleaching is one of the most widely used processes of the textile industry that also produces a significant amount of highly polluted wastewater. Previously, expensive and chemically extensive conventional remediation systems were used to treat bleaching effluent. Despite this, the potential of constructed wetlands (CWs) as a treatment system remains un-investigated. Furthermore, most research on the use of CWs for textile effluents are conducted at laboratory scale and therefore further research at field-scale is timely. This study compares the efficacy of bacterial augmented vertical flow constructed wetlands (VFCWs) and horizontal flow constructed wetlands (HFCWs) for the remediation of textile bleaching wastewater at pilot scale. To this end, CWs macrocosms of 1000 L water capacity were planted with Phragmites australis and inoculated with bacterial strains possessing pollutant degradation and plant growth-promoting traits. The results showed that both variants of CWs were effective in attenuating pollutants from the wastewater; however, the performance of HFCWs exceeded that of the VFCWs for almost every pollutant measure undertaken. For HFCWs, a significant reduction in COD (89%), BOD (91%), TOC (96%), and toxicity was achieved in a period of 72 h during the first month of operation. Bacterial inoculation in CWs further improved the system's performance and these bacteria also exhibited persistence in the rhizoplane (43%), root interior (56%) and shoot interior (29%) of P. australis. This study, therefore, suggests that the bacterial augmented HFCWs is a suitable approach for industrial scale textile bleach wastewater treatment.

UV/H2O2/Ferrioxalate Based Integrated Approach to Decolorize and Mineralize Reactive Blue Dye: Optimization Through Response Surface Methodology

Abstract The decolorization and mineralization of Reactive Blue 222 dye was studied using UV/H2O2/ferrioxalate approach in combination with Pleorotus ostreatus. The dye was decolorized by UV/H2O2/ferrioxalate based advanced oxidation process (AOP) at different levels of process variables dye concentration, catalyst dose, pH, reaction time and resultantly, 80% decolorization was achieved. Pleorotus ostreatus treatment enhanced the dye degradation up to 92% at optimum levels of pH, temperature, inoculum size, carbon and nitrogen sources at specific concentration. Response Surface Methodology (RSM) was employed for optimization under face-centered central composite design (CCD). Although both treatments were found efficient for the removal of dye, but on applying the integrated approach, 96% dye removal was obtained which led to complete degradation of the dye. FTIR analysis confirmed the degradation of dye into low mass compounds. The water quality assurance parameters were measured to assess the mineralization efficiency. A significant reduction in COD (94%) and TOC (92%) were found when dye was degraded integrated approach. A phytotoxicity analysis on Pisum sativum plant revealed the non-toxic behavior of metabolites produced. Results revealed that the integrated approach is highly promising for the decolorization and mineralization of the Reactive Blue 222 dye and is also extendable to treat the dye in textile wastewater.

Trial of a new escape panel concept to reduce cod catches in a mixed demersal fishery

The species selectivity of demersal fishing gear in mixed whitefish fisheries needs to be improved for vessels with limited cod (Gadus morhua) quota which are encountering increasing abundances of cod in some areas of the North Sea, particularly around Shetland. Based on the known behavioural characteristics of cod within a demersal trawl, a new escape panel concept was designed and tested using an alternate haul methodology aboard a 12 m trawler. A modified (henceforth “experimental”) net was made by incorporating an upwardly inclined panel connected to a horizontal middle panel that extends back over and beyond a large mesh escape panel in the lower side of the net extension. The results of 22 paired comparative hauls are presented which demonstrated the relative selectivity of the experimental net by reference to a control net. Catch rate data showed a significant reduction in cod in the experimental net by an estimated 81% (p < 0.001). Importantly, no significant differences in the catches of other main target species were recorded between the two nets. The results indicated that the escape probability of cod increased for larger fish, whereas no significant length effects were found for haddock (Melanogrammus aeglefinus) or plaice (Pleuronectes platessa). Further research and development is recommended to evaluate the escape panel concept in commercial conditions and to optimise this promising method for vessels in the mixed demersal fishery.

Potential use of waste foundry sand in dual process (photocatalysis and photo-Fenton) for the effective removal of phenazone from water: Slurry and fixed-bed approach

In this study, degradation of a pharmaceutical drug, Phenazone (PNZ) has been carried out via heterogeneous photocatalysis, photo-Fenton and in-situ dual process (photocatalysis + photo-Fenton) in suspension and fixed-mode under artificial UV-A as well as under natural solar radiations. Waste material such as foundry sand (FS) was exploited as a supplement for iron in case of photo-Fenton reaction. The distinct processes including photocatalysis and photo-Fenton were found to be competent for the degradation of PNZ as both processes revealed an almost 90–95% removal of PNZ after 180 min of UV irradiations. The degradation was improved to a great extent with remarkable reduction in treatment time of PNZ to almost 105 min when these two individual processes were combined together within the same unit. An almost 14% synergy of dual process over distinct processes was obtained. For fixed-bed studies, TiO2 immobilized hollow circular composite disc already containing FS was utilized which yielded an almost 96% reduction in the concentration of PNZ after 4 h of solar irradiations. The disc was recycled 10 times and its stability and activity was confirmed through XRD, SEM/EDS, and DRS. The mineralization of PNZ was confirmed through significant reduction in COD and generation of anions during the treatment process. The transformation products were examined through GC-MS analysis. The novel technique of in-situ dual process especially in fixed-mode visualized in this study by employing renewable energy and durable catalyst can represent a viable solution to various industries for the treatment of wastewater comprising of bio-recalcitrant pollutants.

TREATABILITY OF OPIUM ALKALOID INDUSTRY WASTEWATERS BY ANAEROBIC PROCESSES

The effluents from alkaloid industry contain high levels of organic matter, alkalinity, salinity, color and sulphate. The treatment of this complex industrial wastewater was attempted in two stages anaerobic reactors. The effects of COD, conductivity, pH, alkalinity, sulphate and TKN on anaerobic treatment were evaluated. When the reactors were fed with original wastewater, VFA’s were accumulated in the presence of 25,794 mg/L COD and 30.2 mS/cm conductivity of the raw opium wastewater even at OLR of 1-3 kgCOD/m3day. However, stepwise dilution was applied and COD removal of 90% was achieved at OLR of 7-8kgCOD/m3day as the conductivity and COD were reduced to 20 mS/cm 20,000 mg/L, respectively. Based on the findings of this study, highly concentrated wastewaters of opium alkaloid industry wastewaters can be treated with anaerobic digestion and significant reduction of COD can be achieved.

Detoxification of real pharmaceutical wastewater by integrating photocatalysis and photo-Fenton in fixed-mode

The applications of novel Fe-TiO2 composite capable of incorporating in-situ dual effect (photocatalysis and photo-Fenton) have been studied for the treatment of real pharmaceutical effluent using batch and continuous reactors. The treatment time was reduced to a great extent using these novel composite beads along with significant reduction in COD (83%). Coagulation using FeCl3 as a coagulating agent was used as a pre-treatment step prior to in-situ dual process. The parametric optimization in case of in-situ dual process was carried out in batch mode under artificial UV-A irradiations. The biodegradability index (BOD5/COD) of wastewater became 0.71 from 0.172 after 5 h of treatment via in-situ dual process. The intermediates present in the real wastewater before and after the treatment process, were carefully identified through GC–MS analysis based on which a tentative degradation mechanism for the treatment of pharmaceutical wastewater has been proposed. The treated wastewater was found to be completely non-toxic as confirmed through cyto-toxicity as well as acute toxicity analysis. The field-scale applications of fixed-bed in-situ dual process using Fe-TiO2 composite beads were validated from successful treatment (∼80% COD reduction) of real wastewater (5 L) in less than 120 min in a pilot-scale once-though cascade reactor under natural solar irradiations. Moreover, Fe-TiO2 composite beads represented an outstanding recyclability efficiency (>70 recycles) without depicting any significant reduction in their activity as confirmed through various characterization techniques.

Bioelectricity Generation From Synthetic Wastewater Treatment in a Membrane-Less Microbial Fuel Cell Using Methylene Blue and/or Neutral Red as Mediators

Microbial fuel cells (MFCs) represent a new method for treating wastewaters and simultaneously producing electricity (renewable energy (bioelectricity)) as innovative technologies. Feasibility of using synthetic wastewater as a substrate for electricity generation using anaerobic sludge as a source of microorganisms was investigated after a short acclimatization period of less than 10 days. among two different kind substrate (methanol and acetic acid) Significant reduction in COD of synthetic wastewater by 63% and 75% was observed at initial COD=2743 mg/l and 2560 mg/l respectively in Methanol and Acetic Acid indicated effective wastewater treatment in batch experiments. The present article deals with the studies of a two chambered salt bridge (membrane-less) MFC anode chamber [(with mediator; plain graphite electrode; acidified by ortho-posphoric acid (pH≈6)]; cathode chamber (50mM potassium ferricyanide [K3Fe(CN)6] in phosphate buffer; pH ≈7.5; plain graphite electrode) in the presence of mediators. The effect of Methylene Blue (MB) and Neutral Red (NR) as electron mediators and microelements inoculated to anolyte chamber on the power generation in MFCs are reported. The best performance was obtained in the case of Acetic Acid. Using methylene blue (MB) (0.2mM) as the electron mediator, the maximum power density and current density of 61.718 mW/m2 and 92.530 mA/m2 were obtained respectively with CE of 3.94%, which are found to be very promising. The maximum power density and current density of 58.820 mW/m2 and 89.940 mA/m2 were obtained respectively with CE of 8.05%. In the most cases, results show that MB has more effective role than NR. Efforts are being made to improve the performance and reduce the construction and operating costs of MFCs.

Silver nanoparticle loaded silica adsorbent for wastewater treatment

Our aim was to prepare silver nanoparticle loaded silica adsorbent for the removal of pollutants and pathogens in wastewater. The pathogens were inactivated by silver nanoparticles loaded with silica by wet impregnation method. Fourier transform infrared spectroscopy, energy dispersive X-ray spectroscopy, and X-ray Diffraction studies confirmed the silver nanoparticle loaded on silica. Inductively coupled plasma atomic emission spectroscopy showed 0.6 mg/g silver nanoparticle in the prepared adsorbent. The prepared adsorbent has potential against Escherichia coli and was described through Chick, Chick-Watson and Homs inactivation kinetic models. Five-hundred (500) ppm concentration of the prepared adsorbent showed complete inhibition with the shouldering or lag curve of inactivation and the k′ values of 0.019 min−1. After treatment, tannery, dairy and canteen effluents showed significant COD reduction with maximum adsorption capacity of 145, 142 and 69 mg/g visa versa. Regeneration of the spent adsorbent used alkali washing and reused up to three cycles.

Low-Cost Biodegradation and Detoxification of Textile Azo Dye C.I. Reactive Blue 172 byProvidencia rettgeriStrain HSL1

Present study focuses on exploitation of agricultural waste wheat bran (WB) as growth medium for degradation of textile azo dye C.I. Reactive Blue 172 (RB 172) using a single bacteriumP. rettgeristrain HSL1 (GenBank accession numberJX853768.1). The bacterium was found to completely decolorize 50 mg L−1of dye RB 172 within 20 h at 30 ± 0.2°C under microaerophilic incubation conditions. Additionally, significant reduction in COD (85%) and TOC (52%) contents of dye decolorized medium was observed which suggested its mineralization. Induction in the activities of azoreductase (159%) and NADH-DCIP reductase (88%) provided an evidence for reductive cleavage of dye RB 172. The HPLC, FTIR, and GC-MS analysis of decolorized products confirmed the degradation of dye into various metabolites. The proposed metabolic pathway for biodegradation of RB 172 has been elucidated which showed the formation of 2 intermediate metabolites, namely, 4-(ethenylsulfonyl) aniline and 1-amino-1-(4-aminophenyl) propan-2-one. The acute and phytotoxicity evaluation of degraded metabolites suggests that bacterial strain favors the detoxification of dye RB 172. Thus, WB could be utilized as a low-cost growth medium for the enrichment of bacteria and their further use for biodegradation of azo dyes and its derivatives containing wastes into nontoxic form.