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Recent past has witnessed to increase in environmental pollution because of rapid urbanization and industrialization. Various organic and inorganic toxicants are present in tannery effluents such as metals and other xenobiotic compounds which cause imbalance to the ecosystem having carcinogenic effects threaten plants, human, and animals’ health. Chromium is one of the major pollutants discharged from tanneries, is highly toxic, mutagenic, and carcinogenic in nature. There are several remedial measures for the removal of such toxicants. Physicochemical approaches remove the pollutants but they are not cost-effective and eco-friendly. Microorganisms based treatment of toxic chemicals either in liquid or solid system is one of the most economic, effective, environment friendly, robust, and sustainable remediation strategy. Several microbes of different physicochemical orientation and plants may selectively be employed for such remedial measure of any type of toxic chemicals of industrial effluent. This chapter discusses the recent advances and challenges in bioremediation methods of tannery wastewater.

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.

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.

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 energ...

In 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.

A native Bacillus cereus isolate has been employed, for the first time, for simultaneous decolorization, dechlorination of chloroorganics, and Cr(6+) remediation from the real tannery effluent. Most of the physicochemical variables in 3:1 diluted effluent were well above the standard prescribed limits, which decreased substantially upon microbial treatment. The extent of bioremediation was better in diluted (3:1) as compared to undiluted effluent supplemented with nutrients and augmented with B. cereus isolate. Maximum growth, effluent decolorization (42.5 %), dechlorination (74.1 %), and Cr(6+) remediation (34.2 %) were attained with 4.0 % (v/v) inoculum, 0.8 % glucose, and 0.2 % ammonium chloride in 3:1 diluted effluent at natural pH (8.1) within 72 h of incubation. The efficiency of bioremediation in a bioreactor was higher as compared to a flask trial during 72 h of incubation: decolorization (47.9 %) was enhanced by 5.4 %, dechlorination (77.4 %) by 3.3 %, and Cr(6+) removal (41.7 %) by 7.5 % at an initial color of 286 Pt-Co units and initial concentration of 62 mg chloride ions and 108 mg l(-1) Cr(6+). Immobilized biomass of Pseudomonas putida and B. cereus coculture enhanced the extent of Cr(6+) remediation (51.9 %) by 10.2 % compared to the bioreactor trial. Chromate reductase activity and reduced Cr directly correlated and were mainly associated with soluble fraction of B. cereus plus effluent natural microflora. The GC-MS analyses revealed the formation of metabolites such as acetic acid and 2-butenoic acid in bacterially treated effluent. The supplementation of nutrients along with B. cereus augmentation is required for efficient effluent bioremediation.

It is the first report in which a novel psychrotrophic Pseudomonas putida SKG-1 strain was evaluated for simultaneous bioremediation of pentachlorophenol and Cr(6+) under various cultural and nutritional conditions. Pentachlorophenol (PCP) dechlorination products, bacterial structure, and functional groups were characterized by gas chromatography and mass spectrometry (GC-MS), scanning electron microscope and energy dispersive X-ray spectroscopy (SEM-EDS), and Fourier-transform infrared (FTIR) techniques. The strain was extremely tolerant to excessively higher individual concentration of PCP (1,400 mg l(-1)) and Cr(6+) (4,300 mg l(-1)). Increasing concentration of PCP and Cr(6+) exerted inhibitory effect on bacterial growth and toxicants' removal. The strain exhibited growth, and concomitantly remediated both the pollutants simultaneously over a broad pH (7.0-9.0) and temperature (28-32 °C) range; maximum growth, PCP dechlorination (87.5%), and Cr(6+) removal (80.0%) occurred at optimum pH 8.0 and 30 °C (from initial PCP 100 mg l(-1) and Cr(6+) 500 mg l(-1)) under shaking (150 rpm) within 72 h incubation. Optimization of agitation (125 rpm) and aeration (0.4 vvm) in bioreactor further enhanced PCP dechlorination by ~10% and Cr(6+) removal by 2%. A direct correlation existed between growth and bioremediation of both the toxicants. Among other heavy metals, mercury exerted maximum and cobalt minimum inhibitory effect on PCP dechlorination and Cr(6+) removal. Chromate reductase activity was mainly associated with the supernatant and cytosolic fraction of bacterial cells. GC-MS analysis revealed the formation of tetrachloro-p-hydroquinone, 2,4,6-trichlorophenol, and 2,6-dichlorophenol as PCP dechlorination products. FTIR spectrometry indicated likely involvement of carbonyl and amide groups in Cr(3+) adsorption, and SEM-EDS showed the presence of chromium on P. putida surface. Thus, our promising isolate can be ecofriendly employed for biotreatment of various industrial wastes contaminated with high PCP and Cr(6+) concentrations.

Pollution of the environment by toxic metals results largely from industrial activities, although sources such as agriculture and sewage disposal also contribute to some extent (Nriagu and Pacyna 1989). Toxic metallic species, once mobilized into the environment, tend to persist, circulate, and eventually accumulate at different trophic levels in members of the food chain. Ultimately, metal pollutants pose a serious threat to the environment, and affect plants, animals, and humans (Olson and Foster 1956; Reidske 1956; Sauter et al. 1976; Levis and Bianchi 1982; Mance 1987; Xing and Okrent 1993). Metal pollutants eventually affect ecosystem function, and impose an economic and public health burden. The problems associated with wastewater disposal in developing countries can generally be attributed to lack of adequate treatment/management policies, coupled with ineffective legislation on the part of entrusted governmental agencies (The Environmental Protection Act 1991; Oboh and Aluyor 2008). Environmental awareness has grown among consumers and industrialists in recent decades, and more recently has culminated in legal constraints being imposed on emissions; such constraints have increasingly become more strict necessitating cost-effective emission control (Gadd and White 1993).

The bacterial strains resistant to pentachlorophenol (PCP) and hexavalent chromium [Cr(VI)] were isolated from treated tannery effluent of a common effluent treatment plant. Most of the physico-chemical parameters analyzed were above permissible limits. Thirty-eight and four bacterial isolates, respectively were found resistant to >50 μg/ml concentration of [Cr(VI)] and the same level of PCP. Out of the above 42 isolates, only one was found simultaneously tolerant to higher levels of both PCP (500 μg/ml) and Cr(VI) (200 μg/ml), and hence was selected for further studies. To the best of our knowledge, this is the first report in which a native bacterial isolate simultaneously tolerant to such a high concentrations of Cr(VI) and PCP has been reported. The culture growth was best at 0.4% (w/v) glucose as an additional carbon source and 0.2% (w/v) ammonium chloride as a nitrogen source. The growth results with cow urine as a nitrogen source were comparable with the best nitrogen source ammonium chloride. The isolate exhibited resistance to multiple heavy metals (Pb, As, Hg, Zn, Co & Ni) and to antibiotics nalidixic acid and polymixin-B. The efficacy of bacterial isolate for growth, PCP degradation (56.5%) and Cr(VI) bioremediation (74.5%) was best at 48 h incubation. The isolate was identified as Bacillus sp. by morphological and biochemical tests. The 16S rDNA sequence analysis revealed 98% homology with Bacillus cereus. However, further molecular analysis is underway to ascertain its likelyhood of a novel species.