Biological Desulfurization of Tannery Effluent Using Hybrid Linear Flow Channel Reactors

The tanning process generates a saline effluent with high residual organics, sulfate and sulfide concentrations. The transition from a linear to circular economy requires reimagining of waste streams as potential resources. The organics in tannery effluent have the potential to be converted to renewable energy in the form of biogas if inhibitors to anaerobic digestion are removed. Hybrid linear flow channel reactors inoculated with culture-enriched halophilic sulfate reducing bacteria from saline environments were evaluated as a novel pretreatment step prior to anaerobic digestion for the concurrent removal of sulfur species and resource recovery (elemental sulfur and biogas). During continuous operation of a 4-day hydraulic retention time, the reactors were capable of near-complete sulfide oxidation (>97%) and a sulfate reduction efficiency of 60–80% with the formation of a floating sulfur biofilm containing elemental sulfur. Batch anaerobic digestion tests showed no activity on untreated tannery effluent, while the pretreated effluent yielded 130 mL methane per gram COD consumed.

Biodegradation of Tannic Acid, Chromium and Cadmium Present in Leather Industrial Effluents Using Microorganisms Isolated from Leather Industrial Sludge

The present work was aimed to isolate indigenous predominant adapted Bacterial strains from tannery waste which possess the ability to detoxify and degrade Tannic acid, Chromium and Cadmium from tannery effluent. Fifteen bacterial strains were isolated from tannery sludge samples out of which Paracoccus pantotrophus (Tannery Waste 15) and Bacillus velezensis (Tannery Waste 17) were found to be the most efficient isolates. Degradation of Tannic acid, Cadmium and Chromium were evaluated for the two selected isolates. Better degradation of heavy metals was recorded in co-cultured media on day 7. From the study, it is evident that both P. pantotrophus and B. velezensis have has the ability to degrade tannic acid with maximum degradation on day 7 and absorbance was found to be 0.915 and 0.383 respectively. The strain P. pantotrophus showed better tannic acid degradation than B. velezensis. Better degradation was observed with co-culturing of both the strains with absorbance of 0.274. Optimal cadmium degradation was observed on day 7 with OD 2.013 and 1.709 for B. velezensis and P. pantotrophus respectively. P. pantotrophus showed better cadmium degradation when compared to B. velezensis. Chromium degradation was maximum on day 7 and absorbance was 2.096 for P. pantotrophus and 0.560 for B. velezensis. The isolates recorded an acceptable reduction in the concentration of Tannin, Chromium and Cadmium in tannery effluent. The results of this showed that the isolates reduced the concentration of Tannin, Chromium and Cadmium present in the raw tannery effluent and suggest that the organisms can be used as a possible treatment of tannery effluents. Keywords: Bio-degradation, Bacillus velezensis, Paracoccuspantotrophus, Chromium, Cadmium, Tannic acid, Tannery effluent.

Assessing the potential of Khayasenegalensis in phytoremediation of heavy metals under borehole water and tannery effluent irrigation

Khayasenegalensis was planted on soil irrigated with tannery effluent and borehole water for duration of three months. Plant samples were collected after harvest and soil samples were collected before planting and after harvesting. Atomic Absorption Spectroscopy (AAS) was used to determine the concentration of heavy metals in the planting media and plant tissues. The aim was to establish the phytoremediation potential of Khayasenegalensis under these conditions. After harvesting, a noticeable decrease in the concentrations of Cd, Cr, Cu Ni, Pb and Zn in the media was observed from the initial values. The highest levels of Cd (5.53±0.56mg/kg), Cr (13.99±0.82mg/kg), Pb(10.6110.61±0.57mg/kg, Ni (8.33±2.78mg/kg)and Zn(25.72±0.00 mg/kg) accumulation were found in the roots, whereas the highest Cu (7.29±1.80mg/kg) concentrations was observed in the shoot. The roots of Khayasenegalensis were found to be suitable for the phytostabilization heavy metals in both the tannery effluent and borehole water irrigated media. In addition, Cd, Cr, Cu, Ni and Pb mainly accumulated in the Khayasenegalensisroots. The results of translocation factors (TF) and bioconcentration factors (BCF) of Khayasenegalensis for heavy metals revealed that Khayasenegalensis is an excluder plant for Cd, Cr, Pb, Ni and Zn and a potential accumulator plant for Cu serving as an ideal remediation plant for this metal. Furthermore, the increasing heavy metal contents in soil that have been irrigated with tannery effluent resulted in the accumulation of these metals inKhayasenegalensis.

Sub-Chronic Toxicity Evaluation of Tannery Waste Water to Clarias gariepinus Juveniles

This paper was conducted to investigate the sub-chronic toxicity of tannery effluents sourced from Challawa industrial estate Kano, Nigeria using Clarias gariepinus. The study covered physicochemical parameters, haematological, and biochemical stress enzymes assessments. The water quality results revealed mean value of Temperature (29.92±1.93oC), pH (8.14±0.85), DO (1.60±0.38mg/l), BOD (0.77±0.16mg/l), Salinity (7.75±0.60mg/l), Nitrate (1.19 ± 0.05mg/l) and Phosphate (16.48±0.85mg/l). After termination of 21 days sub-chronic test, haematological and biochemical changes analysed were generally considered significantly different (P<0.05) within the treatments. The haematological indices revealed a decrease and sudden increase in concentration of estimated values of PCV, Hb, RBC, MCHC and MCH, while WBC and MCV fluctuated. These may be attributed to stress, the duration of exposure and levels of pollutants in the effluent. Furthermore, oxidative stress enzymes followed an order of SOD > CAT > GSH. This could be due to level of pollutants in the effluent. The results of the data indicated tannery effluent to have a toxic effect on the experimented organism. The information calls for a more enrich toxicity testing that should involve wide range of organisms. It should entail reproductive aspects of the species, detail relationship and enhanced methodological procedures.

Effect of Process Parameters on the Adsorption of Chromium VI on a Packed Bed Column (PBC) using Vetiver (Vetiveria zizanioides)

The objective of this study is to evaluate the different process parameters on adsorption of chromium VI on a packed bed column using Vetiver (Vetiveria zizanioides) and to examine the effect of pH, Chemical Oxygen Demand (COD) and Biological Oxygen Demand (BOD) at a constant contact time of 10 minutes at a temperature of 40 ºC under two experimental conditions namely, tannery effluent with and without microwave treatment. The results revealed that microwave heating process had a higher impact on chromium (VI) adsorption than normal heating process. The pH values of microwave treated sample were found to be 6.65±0.65 when compared to normal heated sample where the pH was 4.62±0.72 when compared to the initial pH of effluent found to be 3.47±0.58. Further, a threefold reduction in BOD and COD values was observed in microwave treated vetiver sample which was around 86.73±1.43 and 107.90±2.82 mg/l respectively when compared to normal heated sample (250±1.45 and 200±2.65 mg/l respectively) and untreated effluent (780±2.53 and 920±3.86 mg/l respectively) which indicated the reduction of chromium VI present in the effluent water. It was also observed that the metal adsorption capacity of the vetiver powder and the adsorption characteristics were positively correlated with the FTIR and SEM analysis which confirmed the presence of chromium (VI) on the surface of vetiver.

Genetic Variability Screening of the Leptolyngbya Boryana with Expressed ChrR Gene for the Biotransformation of Cr (VI) to Cr (III) Reduction

Chromium is well known pollutant for its mutagenicity, and carcinogenicity in humans. Excessive uses of chromium in leather tanning industries, stainless-steel production, and wood preservatives have resulted as chromium contamination in soil and water. This investigation indicates the effective use of Leptolyngbya boryana as an eco-friendly option to overcome Chromium (VI) toxicity in tannery effluents. The main objective of this research was to find out ChrR gene and its variability in the context of Cr (VI) stress. This is a novel study in the relation of Leptolyngbya boryana. Industrial polluted soil samples were collected and processed according to the standard protocols for ChrR variation and 16S rRNA gene. DNA was isolated and amplified through PCR. Amplified DNA was sequenced and aligned with the known sequences. In this study a strong co-relation was established in the nucleotide sequences of ChrR and 16S rRNA genes. MIC was determined for Cr (VI) and pure strains of Leptolyngbya boryana were identified and isolated from soil. In the present study presence of ChrR gene variability was recorded in Leptolyngbya boryana which is a cyanobacterium in the soil of tannery effluent under Cr (VI) stressed condition and its gene variability was confirmed by sequencing. We can conclude that Leptolyngbya boryana strain could be eco-friendly option to overcome Chromium (VI) toxicity in tannery effluents.