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Chromium (Cr) contamination is one of the main pollution issues in the soils of tanning industries. Nevertheless, it is unclear how tannery organics affect the movement and transformation of Cr in soil. Column leaching tests were carried out to investigate the impact of various tannery organics, such as phenol, dyes, and surfactants on Cr mobility in tannery soil. The cumulative release of Cr from the soil was less in the presence of tannery organics than that from the non-tannery organics treated group. This suggests that the tannery organics enhanced the fixing of Cr in the soil. Cr was poured from the top of the soil column in the form of Cr (III) solution for leaching, and the concentration of Cr decreased with the increase of soil depth regardless of the presence of tannery organic matter. After leaching, the residual Cr concentration in the soil was 59%−78% of the total Cr concentration. The potential risk of Cr in the soil/groundwater system decreased in the presence of the tannery organics, which decreased the bioavailability of Cr and increased the percentage of Cr in residual state. Understanding the relationship between Cr migration and tannery organics in soil is helpful for soil environment risk assessment of tannery site. [ABSTRACT FROM AUTHOR]

Electro-Fenton process could remove pollutant in in tannery industry wastewater. The objectives of this is used to know the effect of electro-Fenton on, ammonia (NH3), chromium (III) (Cr(III), total suspended solid (TSS), biological oxygen demand (BOD), and chemical oxygen demand (COD) removal in tannery wastewater treatment. The voltage variation used to trigger the electro-Fenton reaction was 6 V, 8 V, and 10 V. Observation time at 0, 30, 60, 90, and 120 mins was used to see changes in the sample. The results obtained are electro-Fenton method has an effective time of 30 mins to removal efficiency of 60.7%, 32.9%, 72.8%, 53.4%, and 53.4% for NH3, Cr(III), TSS, BOD, and COD respectively. Pollution from tannery effluent can be eliminated to a sufficient extent using the electro-Fenton technique. [ABSTRACT FROM AUTHOR]

The tannery industry produces one of the worst contaminants, and unsafe disposal in nearby waterbodies and landfills has become an imminent threat to public health, especially when the resulting multidrug-resistant bacteria and heavy metals enter community settings and animal food chains. In this study, we have collected 10 tannery wastewater (TWW) samples and 10 additional non-tannery wastewater (NTW) samples to compare the chemical oxygen demand (COD), pH, biological oxygen demand (BOD), dissolved oxygen (DO), total dissolved solids (TDS), chromium concentration, bacterial load, and antibiotic resistance profiles. While COD, pH, and chromium concentration data were previously published from our lab, this part of the study uncovers that TWW samples had a significantly higher bacterial load, compared to the non-tannery wastewater samples (5.89 × 104 and 9.38 × 103 cfu/mL, respectively), higher BOD and TDS values, and significantly lower DO values. The results showed that 53.4, 46.7, 40.0, and 40.0% of the TWW isolates were resistant to ceftriaxone, erythromycin, nalidixic acid, and azithromycin, respectively. On the other hand, 20.0, 30.0, 50.0, and 40.0% of the NTW isolates were resistant to the same antibiotics, respectively. These findings suggest that the TWW isolates were more resistant to antibiotics than the NTW isolates. Moreover, the TWW isolates exhibited higher multidrug resistance than the NTW isolates, 33.33, and 20.00%, respectively. Furthermore, spearman correlation analysis depicts that there is a negative correlation between BOD and bacterial load up to a certain level (r = − 0.7749, p = 0.0085). In addition, there is also a consistent negative correlation between COD and bacterial load (r = − 0.7112, p = 0.0252) and TDS and bacterial load (r = − 0.7621, p = 0.0104). These findings suggest that TWW could pose a significant risk to public health and the environment and highlight the importance of proper wastewater treatment in tannery industries. [ABSTRACT FROM AUTHOR]

There is a pressing demand for the introduction of environmentally safe technologies for the industries that supply the basic needs of industrialized societies. Advanced Oxidation Processes may become one of the answers to these uprising pollution management problems in the near future. The present investigation aimed to reduce the refractory organics present in the biologically treated (Activated Sludge Process) tannery effluent using Photocatalysis. The optimum time, pH, dosage of H2O2, and mass of NPAC required for the effective treatment using photocatalysis were found to be 60 mins, 8, 0.2 mg.L-1, and 1g. 100 mL-1, respectively. Although the efficiency of homogeneous photocatalysis was found to be higher than that of heterogeneous photocatalysis, the biodegradability was higher in the latter, with a value of 0.26. The experimental results have proved that photocatalysis could be a promising technology to reduce the refractory organics present in the tannery effluent. [ABSTRACT FROM AUTHOR]

Gelatin-based aerogel (G-Aerogel) from untanned proteinaceous solid wastes was applied as an adsorbent in batch and fixed-bed column systems to remove acid red 97 (AR97) from water. Adsorption was evaluated as a function of pH, adsorbent mass, contact time, temperature, and initial dye concentration. Maximum removal of AR97 was achieved at pH 3 after about 4 h. The pseudo-second-order equation provided the best adsorption kinetic model. The adsorption of AR97 onto G-Aerogel was best described with the Langmuir model, and the maximum adsorption capacity was about 196 mg·g−1. A thermodynamic study showed an exothermic and spontaneous adsorption process. It was also demonstrated that G-Aerogel can be reused several times. The column study showed that breakthrough and saturation times decreased with increasing initial AR97 concentration. Thomas and Yoon-Nelson kinetic models were applied to the experimental data to predict the breakthrough curves and determine the characteristic parameters of column adsorption. Practical Applications: Tannery solid wastes composed mainly of collagen are very abundant and constitute a material that should be valorized. In this study, we examined the transformation of untanned proteinaceous wastes into a biomaterial [Gelatin-based aerogel (G-Aerogel)] of environmental interest. The results demonstrated the promise of this material for dye adsorption because of its advantages in terms of its ease of preparation, its containing functional groups that are able to attract dye, its ability to be reused several cycles, and its high adsorption capacity. In addition to studying adsorption in static mode, we also studied dynamic adsorption, because the common industrial practice is to pass water to be treated through a column packed with an adsorbent, allowing the transport of the pollutant from the liquid to the solid. In summary, G-Aerogel can be applied as an environmentally friendly and efficient adsorbent for the removal of dyes from contaminated water. [ABSTRACT FROM AUTHOR]

Although the origin of leather industry in Hunan Province and even the whole country was earlier, the chrome tanning rules of modern China's new tannery began in Tianjin in 1898, while it appeared later in Hunan in the early period of Republic of China. Under the impetus of saving the country by industry and the movement of domestic products in the early 20th century, Hunan leather industry was initially developed. Especially in the 1920s, even under the influence of political turmoil, the joint-stock management appeared in the Hunan tannery industry while some tanneries temporarily stopped production or closed down, the industry showed the development trend of coexistence of machines and manual workshops. After the outbreak of the War of Resistance against Japanese Aggression in 1931, especially after the fall of Nanjing, Shanghai and other important cities for leather industry, with the inward migration of population and factories and the promotion of wartime economic construction, Hunan leather industry, like other textiles, showed an abnormally prosperous developing trend. At the same time, from the perspective of the comprehensive development of China's leather industry in the Republic of China, there were many characteristics in Hunan's leather industry such as insufficient raw materials, lower technological level and strong dependence on raw materials. [ABSTRACT FROM AUTHOR]

This article presents the results of a study on the current state and evaluation of the Polish tanning industry, focusing on its production characteristics. The research sample included 220 companies that were contacted to gather in- formation about their operations. Some of these companies have been suspended, liquidated, or have changed their business profiles. Approximately 30 % confirmed that they are still active in leather manufacturing, indicating that the Polish tanning industry is experiencing a process of deindustrialization. Surveys conducted in 20 companies revealed that Polish tanneries operate on national, European, and global scales. Most of them are micro or small enterprises with annual revenues of up to PLN 5 million. The primary factor defining their competitiveness is the high quality of the products and services they offer. They mainly process calfskin and cowhides sourced from Poland and abroad, primarily for the footwear sector. Polish tanneries are aware of global trends, including the industry's shift towards ecological practices, the adoption of modern technologies, and the introduction of innovations. Given the current challenges facing the Polish tanning industry, it is essential to take action to improve the health of this sector of the economy. [ABSTRACT FROM AUTHOR]

The study investigates the potential of anaerobic co-digestion (AcoD) as a sustainable solution for managing putrescible organic waste generated by leather processing. Three experiments were conducted to assess the impact of various tannery wastes, pretreatment methods, and waste combinations on methane production. Experiment 1 demonstrated that co-digesting tannery wastewater primary sludge (TWPS) and fleshings significantly increased methane yield compared to digesting TWPS alone, though the addition of chromium- and vegetable-tanned leather wastes decreased yield. Experiment 2 explored TWPS pretreatment methods and found that ultrasonic pretreatment increased soluble chemical oxygen demand (SCOD) but did not significantly improve methane yield, suggesting that pretreatment may not be necessary. Experiment 3 revealed that increasing the proportion of fleshings to TWPS resulted in higher methane yield, ranging from 226.52 mL/gVS with 6% fleshings to 395.71 mL/gVS and 538.34 mL/gVS with 12% and 20% of fleshings, respectively. Additionally, this increase in fleshings also led to a reduction in digester volume. These findings highlight the importance of AcoD in addressing both environmental and economic challenges in the leather industry. [ABSTRACT FROM AUTHOR]

Digested sludge wasted by tanneries is rich in nutrients and trace elements however, the presence of toxic metals restricts their use in agriculture. The present study explores the possible application of tannery sludge amendment for the cultivation of an energy crop, Hibiscus cannabinus. The toxicity of various sludge amendments (25, 50, 75, and 100%, w/w) was examined during early seedling growth, followed by metal accumulation potential by performing pot experiments. Chemical characterization revealed the presence of Cr (709.6), Cu (366.43), Ni (74.6), Cd (132.71), Pb (454.8) µg.g-1 in tannery sludge beside N (2.1%), P 3.8 & K 316.96 (kg.hec-1.) respectively. Germination of H. cannabinus exposed to sludge extracts ranged between 80 to 95%; Relative seed germination, 81.33 to 84.43%. Relative root growth, 0.9 to 1.16 cm; and germination index, 95 to 110%. It was found that sludge extracts have not caused adverse effects on seed germination and early seedling growth. Heavy metal accumulation was observed as follows: Ni (3.37, 2.38, 1.46 & 0.90 mg.kg-1) > Pb (10.59, 10.15, 5.26, & 2.84 mg.kg-1) > Cu (2.34, 2.24, 0.97 & 0.24 mg.kg-1) > Cd (2.31, 1.19, 1.33 & 1.12 mg.kg-1) > Cr (1458, 1136.12, 601.73 & 211.6 mg.kg-1) in 100, 75, 50, & 25% sludge amended soil, respectively. The bio-concentration pattern of metals was found to be in the order of root > leaf > stem. The findings of the present study give direction for the eco-friendly and cost-effective management of tannery sludge. Further, H. cannabinus can be used for the restoration of metal-contaminated agricultural land, however, results need to be corroborated with field trials. [ABSTRACT FROM AUTHOR]

Scarcity of water is becoming a big issue. Most of the water is used in industrial sectors including pharmaceutical, food, textiles, leather, and cosmetics. Industrial effluent water is unable to treat and reuse due to their intricate nature. Effluent water contains synthetic azo dyes since they employ synthetic azo dyes as a major coloring agent. Existing approaches are ineffective in treating effluent containing synthetic azo dyes. Synthetic azo dyes containing effluent water can be treated biologically to overcome the drawbacks of physical and chemical processes. In this research work, novel organism was isolated from tannery effluent water. Isolated organisms were screened and selected for effective degradation of azo dyes. One such organism is Citrobacter freundii which effectively degrade the effluent water containing synthetic azo dyes and allowing it to reuse for variety of purpose. Phytotoxicity study of the treated water was carried out and the study confirms non toxicity nature of the treated water. In‐silico screening was carried out to test the interaction efficacy of enzymes such as Laccase, Azo reductase, and peroxidase which are responsible for effective dye degradation with synthetic azo dyes. In silico studies showed better interactions between synthetic azo dyes and enzymes. This is the novel report on showing the effective degradation of synthetic azo yellow dye by using C. freundii isolated from tannery effluent. [ABSTRACT FROM AUTHOR]

The present study explores the partial replacement of clay by the addition of tannery sludge (TS) and glass in brick preparation. Bricks were prepared with varying weight percentages of TS (9%, 18%, and 27%) along with glass powder (10%) and fired at different temperatures (900, 950, and 1000 °C). Water absorption, compressive strength, weight loss on ignition, volumetric shrinkage, and bulk density of the bricks were found to be in the range of 12.3%–16.8%, 2.3–4.5 MPa, 4%–13.8%, 6%–11%, and 1600–1850 kg/m3, respectively. Heavy metal leaching was observed to be within the limits of United States Environmental Protection Agency 1311 for the prepared bricks. The addition of TS resulted in a decrease of physical and mechanical properties of the bricks due to the decomposition of organic and inorganic compounds. However, the presence of glass powder compensates for the effect of TS by fusion and densification process. The results indicate that hybrid addition of TS and glass can partially replace clay in brick production and effectively immobilize heavy metals. [ABSTRACT FROM AUTHOR]

This study explores the potential of utilizing tannery sludge for short-chain fatty acids (SCFAs) production through fermentation, incorporating zeolites in the process. The study involved a mild thermal pretreatment of the sludge as well, aimed at enhancing the subsequent fermentation process by increasing the solubilization of the organic matter. Six thermophilic continuously stirred tank reactor runs with varying hydraulic retention times (HRT) and zeolite addition are conducted. Zeolites, known for their low cost and absorption properties, significantly impacted chromium concentrations. SCFA production levels remain relatively consistent across tests. However, the acidification efficiency, as reflected in the SCFAs/sCOD ratios, shows improvement in the presence of Chabazite. Specifically, the acidification efficiency is highest in test RB8 (0.92 COD/COD). This suggests that the addition of Chabazite enhances acidification efficiency in tannery sludge applications. The findings highlight zeolites' potential to absorb heavy metals and improve acidification efficiency, indicating promising practical applications for tannery sludge treatment. [ABSTRACT FROM AUTHOR]

Tannery sludge with high chromium content has been identified as hazardous solid waste due to its potential toxic effects. The safety disposal and valorization of the tannery sludge remains a challenge. In this study, the chromium stabilization mechanism was systematically investigated during chromium-rich tannery sludge was converted to biochar and the removal performance of the sludge biochar (SBC) for Cr(VI) from tannery wastewater was also investigated. The results showed that increase in pyrolysis temperature was conductive to the stabilization of Cr and significant reduction of the proportion of Cr(VI) in SBC. It was confirmed that the stabilization of chromium mainly was attributed to the embedding of chromium in the C matrix and the transformation of the chromium-containing substances from the amorphous Cr(OH) 3 to the crystalline state, such as (FeMg)Cr 2 O 5. The biochar presented high adsorption capacity of Cr(VI) at low pH and the maximal theoretical adsorption capacity of SBC produced at 800°C can reach 352 mg Cr(VI)/g, the process of which can be well expressed by Langmuir adsorption isotherm and pseudo second order model. The electrostatic effect and reduction reaction were dominantly responsible for the Cr(VI) adsorption by SBC800. Overall, this study provided a novel strategy for the harmless disposal and resource utilization for the solid waste containing chromium in leather industry. [Display omitted] [ABSTRACT FROM AUTHOR]

Industries play a substantial role in contaminating the freshwater sources. This study was performed to appraise the potential of biochar activated with 85% phosphoric acid was used as chemisorbent for the removal of Chromium III and VI (Cr III and VI)) and desorbed chromium was utilized for replacing the conventional basic chromium sulfate to ensure circular economy. In our previous studies, the factors for biosorption of Cr were optimized through Box–Behnken model under Response Surface Methodology. Batch adsorption studies revealed that the optimum conditions for maximum Cr (VI) biosorption by activated biochar is pH = 2, biosorbent dose: 1%, biosorbent size: 1 mm, solute concentration: 985 mg L−1 and reaction time 35 h. Based on these results a column experiments were carried out and flow rate was optimized as 0.5 ml m−1 where prominent "S" shaped breakthrough curves were noticed. The predicted values under Thomas model for the adsorption of Cr was 3827.2 µg g−1, which was in close agreement with experimental value of 3566.1 µg g−1. The percent Cr sorption varied from 70.05 to 88.75% in first cycle and showed decreasing trend in the subsequent cycles. The elutant 0.5 M H2SO4 desorbed 89.56% of chromium furthermore eluted chromium was utilized for leather tanning. Reusing of recovered chromium for tanning experiments does not alter the leather Tensile (240.82 kg cm−2) and tear strengths (32.41 kg mm−1). This study suggested that recovered chromium from biosorbent can be well utilized for leather tanning to attain the leather of equivalent qualities as that of conventional methods which could save 20–22% of the production cost besides defending the environment from Cr contamination. [ABSTRACT FROM AUTHOR]

Biodegradability is a crucial indicator to evaluate the sustainability of leather. Herein, a rapid method for biodegradation test in an aqueous medium by measuring biochemical oxygen demand was used to determine the biodegradability of leather from different tanning methods, tanning conditions and process stages. In addition, the difference in biodegradability between leather and leather-like synthetic materials were investigated. Chrome-free tanned leather showed higher degree of biodegradation and faster biodegradation rate than chrome tanned leather. Among them, leathers tanned with biomass-based tanning agents were much easier to biodegrade because the crosslinking network of tanned leather constructed with biomass was more susceptible to microbial attack. The enhancement of tanning effects through changing tanning methods and conditions (such as tanning agent dosage, pH and temperature) resulted in the decline of leather biodegradability. Future development of novel chrome-free tanning technologies should balance between these two aspects. The biodegradability of leather from tanning to post-tanning to finishing showed a stepwise decrease because various chemicals were applied and bound to leather during processing. Even so, finished leather still possessed significantly higher biodegradability compared to leather-like PU and microfiber synthetic materials, demonstrating superior environmental sustainability of natural leather. The results are expected to provide support for the evaluation of the ecological properties of leather and green upgrade of the leather industry. [ABSTRACT FROM AUTHOR]

Tannery effluent waste comprises various potentially toxic metals, including chromium (Cr) with varying acute or chronic toxicity. Cr(VI) is known to be a category‐A carcinogen. Reduction of toxic Cr(VI) to Cr(III), which has lesser bioavailability, is one of the mechanisms used by many microbes to withstand Cr(VI) toxicity in the contaminated effluents. Oxidoreductase (OXRs) reduces toxic Cr(VI) to Cr(III); hence a thorough understanding of the OXRs is important for developing a suitable strategy to minimize Cr(VI) toxicity. Therefore, the OXR‐encoding genes were sequenced using metagenomic DNA shotgun sequencing from the tannery effluent‐contaminated soil. Six OXR‐encoding genes were expressed in Escherichia coli, and OXR activity was confirmed by in situ quantitative assays. The six proteins were subjected to phylogenetic and evolutionary analysis. Further, detailed structural analysis of the two OXRs, namely, OXR3 and OXR8 with lowest and highest activity respectively, were investigated in silico for structural characteristics. The results revealed that both the proteins were soluble FMN‐linked oxidoreductases. Eight conserved active site residues (Pro24, Thr26, Ala59, Tyr139, His178, Tyr180, His219, Tyr221, Arg269, and Lys360) in the enzyme OXR3 were predicted. Similarly, nine conserved active site residues (Pro20, Thr22, Ala55, Glu97, His191, Tyr193, Arg241, Cys334, and Arg335) were predicted in OXR8. The tertiary structure of OXR8 was an aldolase TIM barrel structure, like Thermus scotoductus chromate reductase. Docking with FMN revealed the involvement of all the nine predicted active site residues in FMN binding with Pro20, Thr22, and Cys334 as the most important ones. [ABSTRACT FROM AUTHOR]

In this study, EC process using an aluminum anode, and EC-EO process using aluminum and mixed metal oxide, i.e., platinum-ruthenium dioxide-coated onto titanium (Al-Ti/Pt-RuO2) anode was used to understand the remove of phenolic syntan (PS) from synthetic tannery wastewaters. The operational conditions of the abovementioned electrochemical processes were optimized using Taguchi L16 method in terms of maximum removal of total organic carbon (TOC) and PS. At the optimum operating condition (current density = 14.25 mA/cm2, initial pH = 4, rotational speed = 70 rpm and initial PS amount = 0.25 g/L), the incomplete removal of TOC (83.93%) and PS (81.19%) was obtained in the EC process with the energy consumption of 0.135 kWh/g TOC remove and 0.056 kWh/g PS remove. In contrast, almost (≈100%) complete removal of the dissolved organic pollutant was observed in the EC-EO process with the energy consumption of 0.113 kWh/g TOC remove and 0.0453 kWh/g PS remove. The energy consumption per g TOC and PS removed was 0.135 and 0.056 kWh for the EC process, whereas 0.113 and 0.0453 kWh for the EC-EO process. The operating cost of the EC-EO process was estimated to be 1.39 USD/m3, which was lesser (-19.65%) than the operating cost of the EC process. Signal-to-noise ratio and ANOVA results showed that current density was the most influential parameter with the highest delta value and contribution ratio for TOC and PS removal in both the EC and EC-EO process. The UV/Vis and FT-IR analyses indicate that the highest removal of aromatic compounds was obtained in the EC-EO process compared to the EC process. FT-IR analyses confirmed that the PS was first degraded into a quinone functional group, which was further oxidized into carboxylic acid. [ABSTRACT FROM AUTHOR]

The aim of this article is to reduce the environmental harm caused by industrial solid waste, specifically tannery sludge, and enable its reutilization. This study prepared an alkali-activated tannery sludge–slag solidification product (ATSSP) with high mechanical properties using blast furnace slag and tannery sludge as raw materials. The response surface methodology (RSM) was used to optimize the product mix ratio. The hydration mechanism and solidification method of ATSSP for Cr in tannery sludge were studied using X-ray diffraction (XRD), scanning electron microscope-energy dispersive spectrometer (SEM-EDS), and Fourier transform infrared reflection (FT-IR). The results indicate that the compressive strength regression model established through RSM has high accuracy and credibility. When the ratio of activator to binder is 0.2174, the alkali activation modulus is 1.02, and the water-to-cement ratio is 0.37; the 28 d compressive strength of ATSSP can reach 71.3 MPa. The sulfate in tannery sludge can promote the secondary hydration reaction of slag, and the generated hydrated calcium silicate and calcite greatly improve the strength of the ATSSP. The reducing substances contained in slag can reduce Cr (VI) in tannery sludge to Cr (III) in the form of uvarovite. The total Cr and Cr (VI) precipitation concentrations of the product are far less than the specification requirements. [ABSTRACT FROM AUTHOR]

Electrocoagulation is an efficient treatment for the concurrent elimination organic and inorganic contaminants from tannery wastewater. The batch electrocoagulation investigations were carried out using mild steel and aluminium as sacrificial anodes and stainless steel as the cathode. Various operating constraints, such as the electrolyte pH, realistic current density, electrolysis time, effluent concentration and supporting electrolyte concentration were appraised to study their effects on electro-coagulation efficiency. The maximum Total Organic Carbon (TOC) removal has been observed was 90 % and 77 % under optimum operating conditions, and the maximum chromium removal has been recorded was 99 % and 90 % using mild steel and aluminium anodes respectively. The experimental data was also fitted with the first order kinetic model. The experimental data were investigated with the Langmuir and Freundlich adsorption isotherm models. The result shows that the experimental data fitted with the Langmuir isotherm model, with a rate of confidence of 0.98, using mild steel as an anode. The solid sludge and the liquid samples were characterized using the SEM (scanning electron microscopy) EDX (energy dispersive X-ray spectrometry), FT-IR (Fourier transform infrared spectrometer) and UV–Visible (Ultraviolet–visible spectroscopy) analyses. All experimental results show that mild steel was an efficient anode, for the instantaneous elimination of organic and inorganic contaminants from tannery wastewater. [ABSTRACT FROM AUTHOR]

The tannery wastewater from the tanning stage (TWT) comprises organic and Cr pollutants, which can adversely affect aquatic life and have carcinogenic effects. In this study, we investigated the performance of a Fenton-like process using commercial Nano-scale zero-valent iron (nZVI) for the simultaneous removal of Cr and organic matter from real TWT. We used an experimental design to select the principal operating parameters. A Plackett–Burman design identified variables for Cr-total and COD removal, followed by a central composite design (CC-D) to determine optimal variable levels. Finally, the response surface methodology (RSM) was used to find the optimum concentration of individual variables influencing Cr-total removal. Additionally, the effect of the leather-related, co-existing substances that influenced the efficiency of the process and the possibility of recycling nZVI were explored. The inclusion of nZVI was significantly more effective at removing both Cr-total and COD (97.3% ± 5.7% and 73.9% ± 9.1%, respectively), whereas the traditional Fenton process achieved lower removal rates (55.6% ± 10.0% for Cr-total and 34.8% ± 10.9% for COD). The optimal conditions for the Fenton-like process were nZVI/H2O2 = 1.05 w/w, and pH = 2.93. We obtained the best results during the first 5 min of the reaction, which increased after 48 h of agitation and subsequent neutralization. According to the results of four consecutive cycles, nZVI exhibited high reusability (97%) without compromising its adsorption potency. XPS analysis confirmed Cr removal through the adsorption mechanism on the nZVI surface. Hence, a Fenton-like process based on nZVI can be used as a promising alternative for treating organic and Cr wastewater. [ABSTRACT FROM AUTHOR]

The present experimental set-up study of tannery fleshings with different inoculum batch sizes, was carried out for an hydraulic retention time of 50 days to check the capability of anaerobic digestion. Biogas production was between 10,102.5 and 14,505 ml/day. The firstorder and modified Gompertz models were calibrated using experimental data. For kinetic analysis of biogas production, modified Gompertz models and basic firstorder kinetics were employed. In each instance, the kinetic parameters, substrate biogas yield potential, maximal biogas production rate, lag phase time, coefficient of determination and root mean square error were calculated. The model parameters were estimated using the nonlinear regression approach made possible by IBM SPSS software 25.0. Both the models fitted/predicted the experimental data with over 99% accuracy (R2 = 0.990-0.999). [ABSTRACT FROM AUTHOR]

We introduce, and partially resolve, a conjecture that brings a three-centuries-old derangements phenomenon and its much younger two-decades-old analogue under the same umbrella. Our tools blend combinatorics and analysis in a medley incorporating Inclusion-Exclusion and Tannery's theorem. [ABSTRACT FROM AUTHOR]

Trivalent chromium (Cr(III)) is a contaminant with toxic activity. Its presence in waters and soils is usually related to industrial activities such as tanneries. The aim of this study was to compare the removal of Cr(III) in hydroponic solutions and tannery effluents using two floating macrophytes: Salvinia auriculata and Eichhornia crassipes. First, to determine the chromium removal capacity in solution and the bioaccumulation factor (BAF) in tissues of each plant, experiments were set up with contaminated solutions with Cr(III) concentrations of 2, 5, 10, 20, and 40 mg/L. Subsequently, both plant species were exposed to a primary tannery effluent contaminated with 12 mg/L of Cr(III) in order to study the removal capacity of organic and inorganic matter, as well as the acute toxicity in the water flea (Daphnia magna) and genotoxicity in zebrafish (Danio rerio). Tests carried out on nutrient solutions revealed that both plants have a high capacity for removing Cr(III) in solution. The BAF in tissues was higher in E. crassipes compared to S. auriculata. In the experiments with a tannery effluent, both species presented low nutrient and organic matter removal efficiency, but they showed good Cr(III) removal capacity, with average reduction values of 57% for S. auriculata and 54% for E. crassipes after 72 h of exposure. E. crassipes contributed most to the reduction in acute toxicity in D. magna, while S. auriculata did not show a similar effect. However, both plant species managed to reduce the genotoxicity marker in D. rerio when compared with the initial effluent and the control. [ABSTRACT FROM AUTHOR]

The Tannery Industry produces a massive amount of toxic effluent which needs to be treated properly. It contains high organic matter, suspended solids, and chromium which in turn can cause environmental problems. This study provides valuable insights into the potential of Moving Bed Biofilm Reactor (MBBR) and Activated Sludge Process (ASP) for treating tannery wastewater. It also highlights the importance of proper wastewater treatment in the tannery industry to mitigate environmental impacts. The batch analysis was conducted to find out removal efficiencies for Total Dissolved Solids (TDS), Chemical Oxygen Demand (COD), Biological Oxygen Demand (BOD5), Sulphide (S2-), Ammonia (NH4), Nitrate (NO3). Kaldness K1 bio-media was used with a 50% filling ratio in the laboratory setup of the MBBR and aeration was provided to both setups. The results for the MBBR system showed chromium removal of 95.4% with the obtained reduction of biochemical oxygen demand (BOD), chemical oxygen demand (COD), sulfide (S2-), and nitrate (NO3) 93.5%, 88.8%, 93.7%, and 97.09%, respectively. It indicates significant removal efficiencies for various pollutants in the tannery wastewater, suggesting the effectiveness of the MBBR system. [ABSTRACT FROM AUTHOR]

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This study assessed the effectiveness of integrating electrocoagulation, magnetic fields, and ozonation technologies to remove chemical oxygen demand (COD) and total suspended solids (TSS) from tannery wastewater. Furthermore, the effects of their key operating factors were determined. To achieve this goal, an electrocoagulation reactor coupled with a magnetic-field generator was used and the response surface methodology was applied through a Box-Behnken experimental design. Here, current intensity (I), treatment time (T), and ozone concentration (O3) are considered the influencing factors. Likewise, the removal percentages of COD and TSS serve as response indicators. The results indicate that T, I, and O3 are significant for the removal of COD and TSS at a confidence level of p-value < 0.05. For COD, the optimal operating conditions are I = 6.8 A, T = 30 min, and O3 = 10 mg/l; and for TSS, the optimal conditions are I = 5.72 A, T = 28 min, and O3 = 7.8 mg/l. These conditions yield removal efficiencies of 41.8% for COD and 97.9% for TSS. The findings suggest that integrating these technologies is a viable alternative for mitigating the pollution issues caused by the tannery industry. [ABSTRACT FROM AUTHOR]

Having across 450 tannery companies, Kanpur city has grown into an important tannery industrial area that is extremely harmful to the environment. Water and Soil pollution through the discharge of industrial effluents is causing severe problems. The contaminants include toxicants such as arsenic (As), chromium (Cr), cadmium (Cd), copper (Cu), iron (Fe), Mercury (Hg), lead (Pb) and zinc (Zn). The presence of heavy and transition metal significantly changes the water and soil characteristics. It has been considered one of the most polluted industrial wastes and contains high amounts of metals which are very toxic to plant, animal and soil. The present study deal with the survey of the tannery industrial area in Kanpur, Uttar Pradesh from month Mar 2020 to Feb 2021 to explore its earthworm's diversity and distribution in both qualitatively and quantitatively. Qualitatively earthworms' fauna included two genera belong to two different family's viz. Octochaetidae (Eutyphoeus waltoni) and (Metaphire posthuma Megascolecidae) commonly found in the study area. Of these, 01 taxa are native and one is exotic. Eutyphoeus waltoni species was the dominant species among three Shekhpur, Peundi and Sawaldas Ghat sites contributing 339, 465 and 662 respectively and Metaphire posthuma (exotic) species dominant three Shekhpur, Peundi and Maekupurwa sites contributing 48, 201 and 409, respectively. These surveys are important for environment because survey sites were irrigation by tannery treated water and untreated water use. So, the earthworm life cycle affected Finally, ecosystem more effected by industrial treated water uses in irrigation. [ABSTRACT FROM AUTHOR]

Nowadays tannery waste is a matter of concern because if it used as livestock feed, it could cause health hazards to humans. Therefore, this study was conducted to know the generation rates, utilization, disposal method of tannery solid wastes (TSWs), and inclusion level of it into the poultry feed. Moreover, this study determined the physical and chemical parameters of interest including moisture content, crude protein (CP) levels, and the presence of heavy metals such as chromium (Cr) and lead (Pb) in the poultry feeds that were sold in the studied area. For these purposes, a field survey was conducted with twenty tannery industries. Broiler feed samples were procured from multiple farmers situated in the Savar area of Dhaka. The feed source was classified into two categories, namely registered and unregistered feed mills. According to the study, wet blue trimmings was generated in 3.84% that was used as an ingredient of poultry feed. In addition, 55% of tanneries landfilled their waste, while 30% of them sold it for poultry feed. The utilization of TSWs in poultry feed production in this country was limited to a maximum of 1.314% of the total annual production. Besides, the CP% was determined in the range of 24.24 - 13.32 % and 18.15 - 11.01 % for broiler starters and growers, respectively, where lower CP content was found only in unregistered feed mills. Trace amounts of Cr and Pb were identified in each of the feed samples at very low concentrations. In conclusion, it can be stated that the percentage of tannery solid wastes mixed poultry feed was generated in negligible amounts and the registered companies' feed was found normal in all aspects of the quality tested in the study. [ABSTRACT FROM AUTHOR]

In this study, COD, turbidity, total nitrogen, phosphate, sulphate, oil-grease and chromium removals from wastewaters taken from a local tannery using the electrocoagulation process were examined and the most suitable parameters for the electrocoagulation system were tried to be determined. Soluble iron plate electrodes were used as electrodes in the experiments. As a result of the studies carried out, the most suitable initial pH in uncontrolled pH was determined as pH = 4 and for controlled pH as pH = 5. In studies, the most suitable current density for iron electrodes was determined as 1.2 mA cm−2. Even if the increase in current density increased the amount of dissolved Fe, it negatively affected the removal efficiency. In addition, the turbidity of the wastewater was removed in 30 minutes, phosphate in 20 minutes and chromium in 15 minutes by 100%. During 60 minutes of operation, while 62.91% of TN, 87.8% of oil-grease were removed, sulphate was removed at the rate of 54.78%. In the studies, 1st and 2nd order kinetic equations for COD removal were examined and it was determined that removal kinetic is more suitable for 2nd order kinetics. [ABSTRACT FROM AUTHOR]

The leather-making process necessitates large amounts of water and consequently generates tons of liquid waste as leather tannery wastewater (TWW) is disposed of directly in the open environment. Open disposal of untreated TWW into the natural environment causes an accumulation of various polluting compounds, including heavy metals, dyes, suspended solids inorganic matter, biocides, oils, tannins, and other toxic chemicals. It thus poses potential hazards to the environment and human health. This study primarily focuses on providing in-depth insight into the characteristics, treatment strategies, and regulatory frameworks for managing TWW in leather processing industries. Different technologies of conventional physico-chemical (equalization, coagulation, and adsorption), advanced approaches (Fenton oxidation, ozonation, cavitation), thermo-catalytic and biological treatments available to treat TWW, and their integrative approaches were also highlighted. This review also sheds light on the most frequently applied technologies to reduce contaminant load from TWW though there are several limitations associated with it such as being ineffective for large quantities of TWW, waste generation during treatment, and high operational and maintenance (O&M) costs. It is concluded that the sustainable alternatives applied in the current TWW technologies can minimize O&M costs and recirculate the treated water in the environment. The exhaustive observations and recommendations presented in this article are helpful in the industry to manage TWW and recirculate the water in a sustainable manner. [ABSTRACT FROM AUTHOR]

In this study, the effects of the pH of tannery wastewater obtained from a local leather processing factory on the removal of COD and turbidity, and cost of theelectrocoagulation process was investigated. Studies were carried out under two different operatingconditions. The highest COD removal efficiency was obtained as 83.5% when the initial pH was set to 3, while the energy consumption at this pH was found to be 3.88 kwh m−3. In studies where pH was kept constant, the highest removal efficiency obtained was 83.33% at pH = 5. In this case, the energy consumption was determined as 2.44 kWh m−3. The total cost of the system was calculated as 1.0899 $ m−3 under controlled pH conditions and 0.8761 $ m−3with uncontrolled pH. Studies show that the COD removal kinetics are more suited to 2nd degree kinetics. The highest removal rate for uncontrolled pH was k2 = 0.0791 L g−1 min−1 at pH = 3. The highest rate for controlled pH was k2 = 0.0397 L g−1 min−1 at pH = 5. [ABSTRACT FROM AUTHOR]

This present study depicts the successful employment of fixed-bed column for total chromium removal from tannery wastewater in dynamic mode using sodium alginate-powdered marble beads (SA–Marble) as adsorbent. The SA–Marble composite beads prepared were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and Brunauer, Emmett and Teller (BET) method. The adsorption process performance of this bio-sorbent was examined in batches and columns for real effluent (tannery wastewater). After 90 min, the total chromium removal efficiency could be kept above 90% in the batch experiment. The adsorption kinetics fit better with the pseudo-second-order model, indicating the chemisorption process and the adsorption capacity of about 67.74 mg g−1 at 293 K (C0 = 7100 mg L−1) was obtained. Additionally, dynamic experiments indicate that the total chromium removal efficiency could be maintained above 90% after 120 min at 293 K and 60 min at 318 and 333 K; it's an endothermic but rapid process. The effects of two adsorption variables (Temperature and time) were investigated using central composite design (CCD), which is a subset of response surface methodology (total Cr, COD, sulfate, and total phosphorus percentage removal). This work paves a new avenue for synthesizing SA–Marble composite beads and provides an adsorption efficiency of total chromium removal from tannery wastewater. Highlights: Powder marble coated in sodium-alginate beads (SA–Marble) was prepared & characterized, A reactor with a fixed bed was employed for the dynamic removal of total Cr from tannery wastewater, A capacity of 67.74 mg g−1 at 293 K (C0=7100 mg L-1) allows 90% total Cr removal after 90mn, Pseudo-II-order model simulates well the total Cr endothermic rapid chemisorption process, COD, SO2-4, and TP good removal suggest its use as a successful tannery wastewater treatment. [ABSTRACT FROM AUTHOR]

Simple Summary: Several large tanneries operate in Saudi Arabia. The tanneries produce more than 15,000 pieces of leather per day and 200 metric tons of wastewater per day. Leather manufacturing is a highly polluting activity throughout the world, and in many places, it is not known how efficient the wastewater treatments in the factories are. This was found to be the case in Saudi Arabia, where we revealed insufficient treatments in all four of the factories that we studied. We propose here an additional biological treatment using a bacterial–fungal consortium. Bacteria and fungi were isolated from tannery wastewaters, and their collagenase and gelatinase activities were measured to discover their potential to clean tannery wastewater. Different single bacteria and fungi and their consortia were used in the experiment to find the most suitable species for the treatment. The treatment appeared to be efficient, reducing almost all parameters to below the environmental regulation limit for wastewater discharge to the environment in Saudi Arabia. Environmental pollutants such as toxic heavy metals and oxygen-demanding solids are generated by leather manufacturing. In most tanneries, wastewaters are treated with physico-chemical methods but overly high levels of pollutants remain in surface waters. The efficiency of tanning wastewater treatment with conventional techniques was evaluated in four tanneries in Saudi Arabia. It was observed that the wastewaters contained high amounts of pollutants, needing further treatment. We isolated microorganisms from the wastewaters and carried out experiments to treat the effluents with different bacteria, fungi, and their consortia. We hypothesized that a consortium of microorganisms is more efficient than the single microorganisms in the consortium. The efficiency of five single bacterial and five fungal species from different genera was tested. In a consortium experiment, the efficiency of nine bacterial–fungal consortia was studied. The bacterium Corynebacterium glutamicum and the fungus Acremonium sp. were the most efficient in the single-microbe treatment. In the consortium treatment, the consortium of these two was the most efficient at treating the effluent. The factory wastewater treatment reduced total dissolved solids (TDS) from 1885 mg/L to 880 mg/L. C. glutamicum treatment reduced TDS to 150 mg/L and Acremonium sp. to 140 mg/L. The consortium of these two reduced TDS further to 80 mg/L. Moreover, the factory treatment reduced BOD from 943 mg/L to 440 mg/L, C. glutamicum to 75 mg/L, and Acremonium sp. 70 mg/L. The consortium reduced BOD further to 20 mg/L. The total heavy-metal concentration (Cd, Cr, Cu, Mn, and Pb) was reduced by the factory treatment from 43 μg/L to 26 μg/L and by the consortium to 0.2 μg/L. The collagen concentration that was studied using hydroxyproline assay decreased from 120 mg/L to 39 mg/L. It was shown that the consortium of the bacterium C. glutamicum and the fungus Acremonium sp. was more efficient in reducing the pollutants than the single species. The consortium reduced almost all parameters to below the environmental regulation limit for wastewater discharge to the environment in Saudi Arabia. The consortium should be studied further as an additional treatment to the existing conventional tannery wastewater treatments. [ABSTRACT FROM AUTHOR]

The leather industry has long grappled with environmental challenges associated with waste disposal. One ton of wet-salted hides or skins generates approximately 650 kg of solid waste. The majority of trims and hair waste remain underutilized, with hair often discarded or used inefficiently. We initiated the creation of a retanning agent devoid of formaldehyde by utilizing discarded tannery trimmings, with the goal of promoting a circular economy approach in the leather processing industry in our sustainability efforts. Optimal hydrolysis conditions were determined, involving an alkaline (3.75% w/w NaOH) pre-treatment followed by thermal hydrolysis at 100 °C for 5 hours, effectively maximizing the use of trimmings. Similar treatments were applied to hair waste, particularly red sheep hair, yielding successful hydrolysis. Keratin hydrolysate-g-methacrylic acid (KH-g-MA) copolymers were synthesized through in situ polymerization, employing hydrolysates in a redox system. Characterization was carried out using dynamic light scattering and Fourier transform infrared spectroscopy. These newly developed copolymers were applied as retanning agents in the leather industry, enhancing leather qualities such as fullness, grain tightness, and color brightness. Moreover, they improved leather mechanical strength and reduced the need for post-tanning chemicals. This innovative approach not only addresses solid waste issues but also contributes to greener leather processing, thereby fostering a more sustainable environmental landscape. [ABSTRACT FROM AUTHOR]

The main polluting source of heavy metal contamination of water is the leather tanning industry, which uses chrome powder and discharges it into the nearby ecosystem. In this investigation, chromium-resistant bacterial strains were isolated and characterized from tannery effluent. Based on morphological and biochemical characterization, the predominant sporulating Bacillus sp. was isolated and identified as Bacillus subtilis based on 16S rRNA gene sequencing. Chromium degradation by the bacterial strain was evaluated using the flask culture method at three different concentrations (300, 600, and 900 µg/ml) of Cr (VI), and the reduction potential of the isolated bacterium was analyzed by Atomic Absorption Spectrophotometry. A maximum reduction of approximately 78% was found at 24 hrs of incubation at pH 7 and at a constant temperature of 30°C. More than 50% of the Cr(VI) was decreased in 24 hours when the Cr(VI) concentration varied from 300 to 900 g/ml. FTIR analysis showed the involvement of hydroxyl and amine groups in chromium adsorption. As an outcome, this strain could be a promising bioagent for the environmentally friendly elimination of toxic Cr(VI) from polluted environments. [ABSTRACT FROM AUTHOR]

Metal pollution in rivers from untreated industrial and domestic wastewater is a major issue in economically developing countries worldwide. The Awash River Basin in Ethiopia is one of those rivers that faces rising heavy metal concentrations due to poor wastewater management and loose law enforcement controlling effluent discharge into rivers. In this study, surface water and wastewater samples were collected within the Awash River Basin, with metals analysis using ICP-MS techniques. Acute toxicity of water was determined using new molecular biosensor technology based on engineered luminescent bacteria. A multi-branch Integrated Catchment Model (INCA) for metals, including Arsenic, Cadmium, Chromium, Copper, Lead, Manganese, and Zinc was applied to the Awash River Basin to simulate the impact of tannery discharge on the river water pollution levels and to evaluate a set of treatment scenarios for pollution control. Results show that all samples from tannery wastewater have high levels of metals, such as Chromium and Manganese with high levels of toxicities. River water samples from upper Awash near Addis Ababa showed elevated concentrations of heavy metals due to the untreated wastewater from the dense population and a large number of industries in that area. The modeling scenarios indicate that improved wastewater management will reduce the metal concentration significantly. With a 50% reduction in effluent concentrations, the mean concentrations of heavy metals (such as Chromium) over two years would be able to reach 20 to 50% reduction in river water samples. [ABSTRACT FROM AUTHOR]

Pyrolysis in an inert atmosphere is a widely applied route to convert tannery wastes into reusable materials. In the present study, the Cr(III) conversion into the toxic hexavalent form in the pyrolyzed tannery waste referred to as KEU was investigated. Ageing experiments and leaching tests demonstrated that the Cr(III)–Cr(VI) inter-conversion occurs in the presence of air at ambient temperature, enhanced by wet environmental conditions. Microstructural analysis revealed that the Cr-primary mineral assemblage formed during pyrolysis (Cr-bearing srebrodolskite and Cr-magnetite spinel) destabilized upon spray water cooling in the last stage of the process. In the evolution from the higher to the lower temperature mineralogy, Cr is incorporated into newly formed CrOOH flakes which likely react in air forming extractable Cr(VI) species. This property transforms KEU from an inert waste to a hazardous material when exposed to ordinary ambient conditions. [ABSTRACT FROM AUTHOR]

Advanced materials undergo a complex and lengthy process of maturation for scaling up and deployment, mainly due to the high cost of their precursors. Therefore, it is highly desirable to fabricate highly valuable advanced porous solid-state materials, with proven applicability, by sustainably combining organic and inorganic waste materials as precursors. This study successfully demonstrates the preparation of Cr-terephthalate Metal–Organic Frameworks (Cr-BDC MOFs) by combining metal salt and organic linker extracted from tannery effluent and waste plastic bottles. The waste from tanneries was used as the source of Cr(III), while terephthalic acid was obtained from the alkaline hydrolysis of plastic bottles. Appropriate extraction and assembly processes led to the functional Cr-BDC MOFs, MIL-101(Cr) and MIL-53(Cr). The prepared MOFs showed similar properties (surface area, hydrolytic and thermal stability, and water adsorption performance) to similar MOFs synthesized from pure commercial-grade precursors, as confirmed by N2 sorption, XRD, TGA, and water adsorption experiments. The advancements made in this study represent significant progress in overcoming the bottleneck of MOF production cost efficiency via applying sustainability principles and pave the way for easy scaling-up and maturation of MOF-based processes, for air dehumidification and water harvesting as a case study. [ABSTRACT FROM AUTHOR]

The major sources of aquatic pollution are tannery effluent from tannery industries. One of method for removing harmful metals from natural water and commercial refuse sources is biosorption of heavy metals. The chrome tannery wastewater sample was procured from State Industries Promotion Corporation of Tamil Nadu Ltd (SIPCOT). To isolate the metal-tolerant fungus with the ability to absorb heavier metal chromium, the gathered specimens were serially reduced. It offers a possible substitute for the traditional method of eliminating metals. The filtered fungal biomass Fusarium subglutinans and agro-waste biosorbent Hylocereus undatus are used to remove the Cr6+ which is present in tannery effluent. The atomic absorption spectrophotometer was used to ascertain the remaining Cr level in solution. The highest % elimination of Cr6+ for the mixed biosorbent was determined to be 98.67% at 50 mg/L starting Cr6+ content, 5 g biosorbent dose, pH 2.0, and 150 rpm agitation speed at room temperature. The optimal period for Cr6+ biosorption on the biosorbent was 60 min. Finding the biosorption process efficiency requires determining its balance. The equilibrium parameters were examined. The association coefficient (R2) for mixed biosorbent was discovered to be in the following order: Redlich-Peterson (0.9877) > Langmuir (0.8319) > Sips (0.7913) > Freundlich (0.5769). The findings indicated that mixed biosorbent had the capability to remove Cr6+, and the amount of Cr6+ removed from chrome tannery wastewater was determined to be 99.87%. The elimination of Cr6+ from chrome tannery wastewater is a practical, affordable, and environmentally beneficial procedure, according to the analysis of the processed effluent. [ABSTRACT FROM AUTHOR]

With the vigorous development of the leather industry, the environmental pollution problem originating from tannery wastewater is becoming increasingly serious, which can be solved by using advanced adsorption technology. As a biodegradable natural biomaterial, starch has a wide range of sources and has gradually become one of the best choices for preparing superabsorbent polymers. The excellent characteristics of starch‐based superabsorbent polymer make it widely applied in wastewater treatment. Therefore, this paper reviews the research progress of starch‐based superabsorbent polymer in recent years by removing metal ions and typical organic compounds from tannery wastewater. Firstly, the synthesis methods and characteristics of starch‐based superabsorbent polymers are discussed. Secondly, the main factors influencing the adsorption performance of starch‐based superabsorbent polymer have been introduced. Thirdly, the present situation of treating tannery wastewater with starch‐based superabsorbent polymer is summarized. Finally, some problems existing in the practical application of starch‐based superabsorbent polymer are proposed. Although starch‐based superabsorbent polymer shows excellent adsorption properties, there remain several issues such as recycling that needed to be addressed. This review is of benefit for the high‐value utilization of starch‐based superabsorbent polymers in reducing environmental pollution caused by tannery wastewater. [ABSTRACT FROM AUTHOR]

The disposal of tannery sludge (TNS) without treatment causes severe toxic metal contamination in the ecosystem and food chain. Hence, eco-friendly solid waste management is essentially needed for the tanneries. The aim of this study was to degrade the raw TNS into composted sludge using coir pith (CP) as an adsorbent for organic compounds and other pollutants and Nava Rasa Karaisal (NRK) as a consortium of microorganisms. The TNS treated with CP and NRK showed decolorization and a reduction in pH. After the treatment, the electrical conductivity decreased from 24.7 to 6.31 μS/cm; total dissolved solids (28.4 ppm), salinity (21.2 ppm) and dissolved oxygen (7.5 mg/L) in the untreated TNS were reduced to 10.9 ppm, 4.9 ppm, and 4.6 mg/L in the TNS+CP+NRK treatment, respectively. SEM analysis showed small, smooth-walled structures on the surface of composted TNS compared to rough textures on the untreated TNS. Energy-dispersive spectroscopy analysis showed a higher number of elements in NRK (16) than in untreated sludge (8). Four different bacteria and six fungi were dominant in the treated tannery waste. The effect of different dilutions (12.5%, 25%, 50%, 75%, and 100%) of treated TNS on seed germination of Vigna radiata L. was carried out to check the feasibility of using the treated TNS for plant irrigation and growth. The results showed maximum growth at lower concentrations (12.5% and 25%). The results indicated that TNS treatment using CP and NRK is a potential eco-friendly approach to remediating the sludge waste. [ABSTRACT FROM AUTHOR]

In this work, a UV/H2O2 system in real tannery wastewater was evaluated by an experimental design with optimal stage 2-level I-optimal reaction surface using Design Expert software to analyze the effects of temperature, pH, UV lamp power (W), and H2O2 concentration on COD removal and nitrification. It was found that pH and temperature were the variables that affected the process the most. It was found that an acidic pH of 4.5–5.5 and temperatures between 50 and 70 °C favored improved COD and ammonium oxidation. The process conditions—temperature 54.6 °C, pH 4, pW-UV 60 W and hydrogen peroxide 0.5—were confirmed in the next phase of the study using a one-way statistical analysis ANOVA. Under these conditions, the nitrite removal rate was 98.4%, ammonium 94.53%, chromium 92.3%, chlorides 62.4%, BOD 67.4%, COD 44.5%, and color 48%. [ABSTRACT FROM AUTHOR]