Manikant Tripathi

Strategies for Chromium Bioremediation of Tannery Effluent

Bioremediation offers the possibility of using living organisms (bacteria, fungi, algae,or plants), but primarily microorganisms, to degrade or remove environmental contaminants, and transform them into nontoxic or less-toxic forms. The major advantages of bioremediation over conventional physicochemical and biological treatment methods include low cost, good efficiency, minimization of chemicals, reduced quantity of secondary sludge, regeneration of cell biomass, and the possibility of recover-ing pollutant metals. Leather industries, which extensively employ chromium compounds in the tanning process, discharge spent-chromium-laden effluent into nearby water bodies. Worldwide, chromium is known to be one of the most common inorganic contaminants of groundwater at pollutant hazardous sites. Hexavalent chromium poses a health risk to all forms of life. Bioremediation of chromium extant in tannery waste involves different strategies that include biosorption, bioaccumulation,bioreduction, and immobilization of biomaterial(s). Biosorption is a nondirected physiochemical interaction that occurs between metal species and the cellular components of biological species. It is metabolism-dependent when living biomass is employed, and metabolism-independent in dead cell biomass. Dead cell biomass is much more effective than living cell biomass at biosorping heavy metals, including chromium. Bioaccumulation is a metabolically active process in living organisms that works through adsorption, intracellular accumulation, and bioprecipitation mechanisms. In bioreduction processes, microorganisms alter the oxidation/reduction state of toxic metals through direct or indirect biological and chemical process(es).Bioreduction of Cr6+ to Cr3+ not only decreases the chromium toxicity to living organisms, but also helps precipitate chromium at a neutral pH for further physical removal,thus offering promise as a bioremediation strategy. However, biosorption, bioaccumulation, and bioreduction methods that rely on free cells for bioremediation suffer from Cr6 toxicity, and cell damage. Therefore, immobilization of microbial cell biomass enhances bioremediation and renders industrial bioremediation processes more economically viable from reduced free-cells toxicity, easier separation of biosorbents from the tannery effluent, ability to achieve multiple biosorption cycles, and desorption (elution) of metal(s) from matrices for reuse. Thus, microbial bioremediation can be a cost competitive strategy and beneficial bioresource for removing many hazardous contaminants from tannery and other industrial wastes.

Strategies for Decolorization and Detoxification of Pulp and Paper Mill Effluent

The potential hazards associated with industrial effluents, coupled with increasing awareness of environment problems, have prompted many countries to limit the indiscriminate discharge of untreated wastewaters. The pulp and paper industry has been among the most significant of industrial polluters of the waterways, and therefore has been one of the industries of concern. The pulp and paper industry produces large quantities of brown/black effluent that primarily result from pulping, bleaching, and paper-making production stages. The dark color and toxicity of pulp-paper mill effluent comes primarily from lignin and its chlorinated derivatives (e.g., lignosulphonic acid, resins, phenols, and hydrocarbons) that are released during various processing steps of lignocellulosic materials. The color originates from pulping and pulp bleaching stages, while adsorbable organic halides (AOX) originates exclusively from chlorine bleaching. Discharge of untreated effluent results in increased BOD/COD, slime growth, thermal problems, scum formation, discoloration, loss of aesthetic quality and toxicity to the aquatic life, in the receiving waterbodies. The dark brow color of pulp-paper effluent is not only responsible for aesthetic unacceptability, but also prevents the passage of sunlight through colored waterbodies. This reduces the photosynthetic activity of aquatic flora, ultimately causing depletion of dissolved oxygen. The pulp-paper organic waste, coupled with the presence of chlorine, results in the generation of highly chlorinated organic compounds. These toxic constituents of wastewater pose a human health risk through long term exposure. via drinking water and\or through consumption of fish that can bioaccumulate certain pollutants from the food chain. Therefore, considerable attention has been focused by many countries on decolorization of paper mill effluents , along with reduction in the contaminants that pose human health or other environmental hazards. Various physicochemical remediation treatments in the pulp-paper industry are now used, or have been suggested, but often are not implemented, because of the high cost involved. More recently, the paper and pulp industry has been investigating the use of biological remediation steps to replace or augment current treatment strategies. Certain biological treatments offer opportunities to reduce cost (both capital and operating), reduce energy consumption, and minimize environmental impact. Two primary approaches may be effective to curtail release of toxic effluents: first, development of pulping and bleaching processes that emphasize improved oxygen delignification or biopulping, plus partial or complete replacement of chlorine treatment with hydrogen peroxide or with biobleaching; second, implementation of biological processing that involves sequential two-step anaerobic-aerobic or three-step aerobic-anaerobic treatment technologies at end of pipe. The selection of the specific process will depend upon the type of pollutants/toxicants/mutagens present in the effluent. The use of environmental-friendly technologies in the pulp and paper industry is becoming more popular, partly because of increasing regulation, and partly because of the availability of new techniques that can be used to economically deal with pollutants in the effluents. Moreover, biotechnology research methods are offering promise for even greater improvements in the future. The obvious ultimate goal of the industry and the regulators should be zero emission through recycling of industrial wastewater, or discharge of the bare minimum amount of toxicants or color.

Response surface methodology for optimization of process variable for reactive orange 4 dye discoloration by Pseudomonas putida SKG-1 strain and bioreactor trial for its possible use in large-scale bioremediation

AbstractIn this study, Pseudomonas putida SKG-1 isolate employed earlier for pulp-/paper-mill effluent discoloration, was used for bioremediation of reactive orange 4 azo dye under varied cultural and nutritional conditions. The optimization through one-factor-at-a-time approach revealed maximum growth (A620 1.31) and dye discoloration (95.2%) at optimum temperature 35°C, pH 8.0, inoculum dose 5.0%, sucrose 0.7%, peptone 0.25%, and 50 mg reactive orange 4 dye L−1 within 72 h of incubation. Under response surface methodology (RSM; using Box–Behnken design) approach, the dye discoloration enhanced to 97.8% at reactive orange 4 concentration of 50 mg L−1, sucrose 0.7%, and peptone 0.28% during 72 h of incubation. In bioreactor trial, the maximum dye discoloration (98% within 60 h) was achieved in 12 h advance compared to RSMs trial.

Response Surface Modeling for Co-Remediation of Cr6+ and Pentachlorophenol by Bacillus cereus RMLAU1: Bioreactor Trial and Structural and Functional Characterization by SEM-EDS and FT-IR Analyses

ABSTRACT This is the first report on optimization of process variables for simultaneous bioremediation of pentachlorophenol (PCP) and Cr6+ employing traditional and response surface methodology (RSM). In a one-factor-at-a-time approach, the effect of PCP level exhibited maximum bacterial growth and Cr6+ (82%) and PCP (91.5%) removal at initial 100 mg PCP L−1 with simultaneous presence of 200 mg Cr6+ L−1 within a 36-h incubation. However, at varied Cr6+ concentrations, maximum growth and Cr6+ (97%) and higher PCP (59%) removal were achieved at 50 mg Cr6+ L−1 with simultaneous presence of 500 mg PCP L−1 within a 36-h incubation. The Box-Behnken design suggested 100% Cr6+ and 95% PCP remediation at 36 h under optimum conditions of 75 mg PCP and 160 mg Cr6+ L−1, pH 7.0, and 35°C; Cr6+ removal was further enhanced to 97% in bioreactor trial. Fourier transform infrared (FT-IR) analysis revealed the likely involvement of hydroxyl, amide, and phosphate groups in Cr3+ binding. Scanning electron microscopy and energy-dispersive x-ray spectroscopy (SEM-EDS) showed biosorption of reduced chromium on bacterial cell surface. This isolate can be employed for eco-friendly and effective in situ bioremediation of Cr6+ and PCP simultaneously.

Metagenomic approach towards bioprospection of novel biomolecule(s) and environmental bioremediation

Microorganisms have developed several physiological adaptations to survive within extreme ecological niches including environments contaminated with heavy metals, pesticides, polycyclic aromatic hydrocarbons, and nuclear wastes. Microorganisms in extreme habitat are potential source of “novel biomolecule(s)” such as whole microbial cells, extremozymes and extremolytes, significantly required for environmental, industrial, and red medical/pharmaceutical biotechnology. These novel biomolecule(s) are valuable resources and may help improve economic development. The scanty information about the factors governing the microbial growth within stressed Review Article Tripathi et al.; ARRB, 22(2): 1-12, 2018; Article no.ARRB.38385 2 environments is the major constraint in the recovery of novel biomolecule(s) from extreme habitats. Understanding the structure, metabolic capabilities, microbial physiology, and factors governing the composition and role of indigenous microorganism is the key to success of any study. In recent past the problems associated with classical cultivation techniques have been resolved by an emerging approach referred to as “metagenomics”. Metagenomic studies give an insight into details of the structure, metabolic and physiological capabilities of indigenous microbial communities. High-throughput sequencing technologies in conjunction with metagenomics has aided in the identification and characterization of novel culturable and uncultured microorganisms with unique capabilities. Metagenomic studies have been used for isolation and characterization of novel biomolecule(s) relevant for white, grey, and red biotechnologies. The major objective of this review is to discuss the applications of metagenomic approach for bioprospection of novel biomolecule(s) and environmental bioremediation.

Treatment and Recycling of Wastewater from Tannery

Tanneries are one of the most important industries of the world, but discharge toxic hexavalent chromium through their waste water into the environment beyond the permissible limit. Such waste water may cause significant damage to the agricultural lands and receiving water bodies due to its higher toxicity and high COD and BOD values and thus is a matter of global concern. To reduce the impact of discharged waste water on all living beings and the environment, several conventional physico-chemical treatment methods are developed to remediate metal polluted sites. However, these methods are costly due to use of non-regenerable materials, high operating cost and generate toxic sludge. Microbial bioremediation is a relatively cheaper and eco-friendly technique for the removal of heavy metals and chloroorganics from tannery waste water and thus has wider implications. Also, there is a chance to recover the economically valuable metal for reuse. Among various microbes, bacteria have proven to be very effective in removing Cr (VI) and pentachlorophenol from tannery waste water. The treated waste water can also be used for various non-potable purposes including agriculture and also during leather tanning. It will ultimately minimize water scarcity problem and will increase the productivity.

Mycoremediation: An Alternative Treatment Strategy for Heavy Metal-Laden Wastewater

Industrial wastewater containing heavy metals constitutes a major source of contamination in the environment. Remediation of toxic metals from wastewater has been a challenge since long. Several physicochemical techniques are used to detoxify metal polluted sites. However, these traditional techniques are cost prohibitive due to use of chemical compounds, expensive and release of secondary toxic solid waste. Biosorption is a metabolism-independent and cost-effective method for removal of toxic metals from discharged liquid waste. Application of fungal biomass as biosorbent for toxic metal remediation has gained interest because of high surface to volume ratio, enough availability, rapid biosorption/desorption efficiency, and cost competitiveness. This chapter presents an overview of heavy metal biosorption studies performed on few potential fungal sorbents.