Tannery Sludge Research Articles

Application of Heavy Metal Rich Tannery Sludge on Sustainable Growth, Yield and Metal Accumulation by Clarysage (Salvia sclarea L.)

A field experiment was conducted to evaluate the effective utilization of tannery sludge for cultivation of clarysage (Salvia sclarea) at CIMAP research farm, Lucknow, India during the year 2012–2013. Six doses (0, 20, 40, 60, 80, 100 tha−1) of processed tannery sludge were tested in randomised block design with four replications. Results revealed that maximum shoot, root, dry matter and oil yield were obtained with application of 80 tha−1of tannery sludge and these were 94, 113 and 61% higher respectively, over control. Accumulation of heavy metals (Cr, Ni, Fe, Pb) were relatively high in shoot portion of the plant than root. Among heavy metals, magnitude of chromium accumulation was higher than nickel, iron and lead in shoot as well as in root. Linalool, linalyl acetate and sclareol content in oil increased by 13,8 and 27% respectively over control, with tannery sludge application at 80 tha−1. Heavy metals such as chromium, cadmium and lead content reduced in postharvest soil when compared to initial status. Results indicated that clarysage (Salvia sclarea) can be grown in soil amended with 80 tha−1sludge and this can be a suitable accumulator of heavy metals for phytoremediation of metal polluted soils.

Effect of tannery sludge amended soil on glutathione activity of four aromatic crops: Tagetes minuta, Pelargonium graveolens, Ocimum basilicum and Mentha spicata

Glutathione (GSH) content in plants plays a vital role in protecting the plants against oxidative stress generated due to heavy metals (HMs) present in tannery sludge (TS). Aromatic plants were selected for the study because the final product essential oil does not contain even a trace amount of metal, so bio-magnification of HMs in food chain is avoided. Four aromatic plants which were studied in the experiments showed different response of GSH content and GR activity when subjected to different levels of TS. GSH activity increased and then decreased in Tagetes minuta, whereas in Ocimum basilicum and Mentha spicata GSH activity increased in all treatments and in Pelargonium graveolens GSH activity increased up to certain level and at 75:25 sludge and soil ratio and at 100% TS, no significant change was observed. Correlation study showed that glutathione reductase (GR) activity was highly correlated with GSH content. M. spicata contained a high concentration of GSH and GR activity as compared to the other plants.

Utilization of heavy metal-rich tannery sludge for sweet basil (Ocimum basilicum L.) cultivation.

Unlike food crops, essential oil-bearing crops in which the oil is extracted through hydro-distillation can be a suitable crop to be grown in heavy metal-polluted soils as the oil does not carry any heavy metal. In a field experiment conducted at CIMAP, Lucknow, India during 2011 and 2012, influence of six doses of tannery sludge viz 0, 10, 20, 30, 40, and 50 t ha(-1) were tested, taking sweet basil (Ocimum basilicum) as the test crop. Maximum herb yield was obtained with the application of sludge at 20 t ha(-1). While in root, accumulation of Cd and Pb increased significantly up to 20 t ha(-1), Cr accumulation increased with increasing the dose of tannery sludge reaching maximum at 50 t ha(-1). Essential oil yield of basil (Ocimum basilicum) was significantly affected due to sludge application. Quality of essential oil, in term of chemical constituents, however, was marginally influenced due to tannery sludge application.

Modelling aerobic stabilization of domestic and industrial sludge using a multi-component biomass model

The objective of the study was to investigate the achievable limits of aerobic sludge stabilization applied on waste-activated sludge generated in domestic, tannery, and pharmaceutical wastewater treatment plants. Stabilization study involved monitoring of conventional parameters and model evaluation of oxygen uptake rate and particulate components of waste sludge. Multi-component biomass approach was adopted based on death–regeneration mechanism. The results showed that sludge stabilization efficiency ranged between 25% and 30%, which was closely related to the fate of different particulate fractions of biomass, that is, viable biomass, hydrolysable particulates, and microbial metabolic products. Model calibration exercises yield in rate coefficient ranges of 0.18–0.32/day for biomass decay and 0.60–0.65/day for hydrolysis of non-biomass components. Degradation rates of particulate metabolic products were estimated as 0.035, 0.04, and 0.01/day for domestic, tannery, and pharmaceutical sludge, respectively. Relatively low degradation rates compared to conventional biological treatment processes confirmed reduced microbial activity in the course of aerobic stabilization.

The effect of electron acceptors on biogas production from tannery sludge of a Mexican wastewater plant

Effluents from the leather processing generally are discharged into rivers or are used to irrigate farmland. The biogas production from the digestion of sludge produced could be used as alternative sources for energy and power generation. A study was carried out to examine the effects of various electron acceptor amendments on biogas production from Mexican tannery sludge. Two bench scale experiments were performed: The first experiment used different electron acceptors (nitrate, iron and sulfate) and three different levels for each variable (4.5, 9.0 and 13.5 mg/mL); in the second only urea was used as a nitrogen source with three carbon/nitrogen ratios (6.0, 8.0 and 11). It was found that the reactors with nitrate as electron acceptor (4.5 mg/mL) generated the most biogas (200 mL of biogas accumulated in 25 days). Similarly, the reactors with the lower ratio of carbon/nitrogen (6.0) produced larger biogas production (131.50 ± 19.1 mL of biogas) in a shorter period of time (9 days). The results also showed that the addition of glucose did not significantly influence the production of biogas.

Devitrification routes of a vitrified chromium-loaded ash

The devitrification routes of vitrified materials containing chromium-loaded ash were studied in this work. Chromium-loaded ash originates from the incineration of tannery sludge. Vitrification was applied using SiO2, Na2O and CaO. Three different batch compositions were studied with the relative proportions of SiO2 and Na2O kept constant, and varying proportions of chromium-loaded ash and CaO. All vitrified products were thermally treated in order to produce glass–ceramic materials, i.e. to induce devitrification. Thermal treatment temperatures were selected by application of differential thermal analysis. All products were characterized with X-ray diffraction, scanning electron microscopy and energy dispersive spectrometry. The resulting glass–ceramic products possessed different microstructures, i.e. composition, morphology and spatial distribution of separated ceramic phases, depending on the chromium-loaded ash content and thermal treatment temperature. The results show that a combination of differential thermal analysis with morphological, structural and elemental characterization methods renders microstructural tailoring and control of physical properties feasible.

CHROMIUM IN SOIL ORGANIC MATTER AND COWPEA AFTER FOUR CONSECUTIVE ANNUAL APPLICATIONS OF COMPOSTED TANNERY SLUDGE

Tannery sludge contains high concentrations of inorganic elements, such as chromium (Cr), which may lead to environmental pollution and affect human health The behavior of Cr in organic matter fractions and in the growth of cowpea (Vigna unguiculata L.) was studied in a sandy soil after four consecutive annual applications of composted tannery sludge (CTS). Over a four-year period, CTS was applied on permanent plots (2 × 5 m) and incorporated in the soil (0-20 cm) at the rates of 0, 2.5, 5.0, 10.0, and 20.0 Mg ha-1 (dry weight basis). These treatments were replicated four times in a randomized block design. In the fourth year, cowpea was planted and grown for 50 days, at which time we analyzed the Cr concentrations in the soil, in the fulvic acid, humic acid, and humin fractions, and in the leaves, pods, and grains of cowpea. Composted tannery sludge led to an increase in Cr concentration in the soil. Among the humic substances, the highest Cr concentration was found in humin. The application rates of CTS significantly increased Cr concentration in leaves and grains.

Potential of Biogas in Waste Activated Tannery Sludge by Anaerobic Co-Digestion

Potential of Biogas in Waste Activated Tannery Sludge by Anaerobic Co-Digestion

Utilization of phosphogypsum in tannery sludge stabilization and evaluation of the radiological impact.

The current global trend towards increasingly stringent environmental standards and efforts for efficient utilization and re-use of available by-products and/or wastes, favors the use of low-cost sorbent materials for the treatment of heavy metal-contaminated solid wastes. In this study, the stabilization of tannery sludge, produced from the physicochemical and biological treatment of tannery wastewaters, was examined by the addition of phosphogypsum (PG) at a ratio of 1:1. Characterization of the tannery sludge leachates showed high amounts of chromium which exceeded the acceptable level for disposal in non-hazardous waste landfills, while the dissolved organic carbon (DOC) concentrations exceeded the limits for disposal in landfills for hazardous wastes, according to the EU Decision 2003/33/EC. Leachates of the waste stabilized with PG presented chromium and DOC concentrations below the regulation limits for disposal in landfills for non-hazardous wastes. Moreover, mixing PG with tannery sludge resulted in a stabilized waste with reduced radioactivity.

Soil microbial properties after 5 years of consecutive amendment with composted tannery sludge.

Composting has been recognised an alternative method to tannery sludge recycling and afterwards to be used in agriculture. As the tannery sludge contains salts and chromium, the application of composted tannery sludge (CTS) should be performed carefully to minimise negative effects on soil microbial properties. Therefore, this study evaluated the effects of 5-year repeated CTS amendment on soil microbial biomass (SMB) and enzyme activities in a tropical soil. CTS was applied during 5 years at 0, 2.5, 5, 10 and 20 Mg ha(-1), and at the fifth year, the microbial biomass C (MBC) and N (MBN), basal and substrate-induced respiration (SIR), metabolic quotient (qCO₂) and dehydrogenase (DHA) and fluorescein diacetate (FDA) hydrolysis were determined in the soil samples. Soil MBC and MBN showed the highest values with the amendment of 5 Mg ha(-1) CTS. Soil respiration increased with the increase in CTS rates, while SIR showed the highest values with the amendment of 0, 2.5 and 5 Mg ha(-1) CTS. DHA activity showed the highest values with the amendment up to 2.5 Mg ha(-1), while FDA hydrolysis increased up to the rate of 5 Mg ha(-1) CTS. The results show that after 5 years of permanent amendment of CTS, soils amended with 2.5 Mg ha(-1) have SMB and enzymatic activities similar to those in unamended soil.

Short communication. Growth and nodulation of cowpea after 5 years of consecutive composted tannery sludge amendment

Tannery industry releases high amounts of tannery sludge which are currently composted and used in agricultural soils. The consecutive amendment of such composted tannery sludge (CTS) may affect soil microrganisms, such as rhizobia. In this study, we evaluated the effects of 5-year repeated CTS amendment on growth, nodulation, and yield of cowpea (Vigna unguiculata L.) CTS was applied in different amounts (0, 2.5, 5, 10 and 20 Mg/ha) to a sandy soil. Amendment of CTS increased soil pH, electrical conductivity (EC), sodium and chromium content. Plant growth, nodulation, N accumulation, and cowpea yield increased up to 10 Mg/ha; however, above this rate, these variables decreased. After 5 years of CTS amendment, the increase in soil chemical properties, particularly EC and Na content, exerted negative effects on the growth, nodulation, and yield of cowpea.

Phytoextraction capacity of Pelargonium graveolens L’Hér. grown on soil amended with tannery sludge – Its effect on the antioxidant activity and oil yield

The metal accumulation potential of Pelargonium graveolens L’Hér. grown with various amendments of heavy metal (HM) rich tannery sludge (TS) was studied. Root accumulated more metals followed by leaves and stem. At 50:50 ratio of TS and soil, translocation factor (TF) for Cd, Co, Ni, Pb and Cr were 0.77, 0.74, 1.09, 0.81 and 0.70, respectively. Chlorophyll a, chlorophyll b, carotenoid content and biomass of plant were high at 50:50 ratio of sludge and soil. Maximum oil content was observed at the same ratio of sludge and soil. No detectable amount of metal was found in the oil of P. graveolens. Citronellol, geraniol (C/G) ratio was close to 1 at 50:50 ratio of TS and soil, which is considered to be the best oil quality and most preferred by the industries. HMs present in TS increased oxidative stress in plant resulting in increased level of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), proline and melondialdehyde (MDA) at all ratios of TS and soil as compared to control. At 100% TS without soil antioxidant activity decreased which indicated that high concentration of HMs impaired the oxygen scavenging function. Translocation factor emphasized that 50:50 ratio of TS and soil were suitable for extraction of various metals without affecting the oil yield of P. graveolens. So, this plant can be suggested as a good candidate to be grown in metal polluted soil vis-à-vis for phytostabilization of metals.

Incineration of tannery sludge under oxic and anoxic conditions: Study of chromium speciation

A tannery sludge, produced from physico-chemical treatment of tannery wastewaters, was incinerated without any pre-treatment process under oxic and anoxic conditions, by controlling the abundance of oxygen. Incineration in oxic conditions was performed at the temperature range from 300°C to 1200°C for duration of 2h, while in anoxic conditions at the temperature range from 400°C to 600°C and varying durations. Incineration under oxic conditions at 500°C resulted in almost total oxidation of Cr(III) to Cr(VI), with CaCrO4 to be the crystalline phase containing Cr(VI). At higher temperatures a part of Cr(VI) was reduced, mainly due to the formation of MgCr2O4. At 1200°C approximately 30% of Cr(VI) was reduced to Cr(III). Incineration under anoxic conditions substantially reduced the extent of oxidation of Cr(III) to Cr(VI). Increase of temperature and duration of incineration lead to increase of Cr(VI) content, while no chromium containing crystalline phase was detected.

Utilização de lodo de curtume como substrato alternativo para produção de mudas de café conilon

A pecuaria bovina brasileira representa grande fonte de renda e investimentos dos setores publicos e privados, sendo que apos o abate, o destino dos couros para curtumes ocasiona a geracao de uma quantidade expressiva de residuos na forma de lodos, tornando-se assim um problema ambiental para os curtumes em muitos estados brasileiros que nao dispoe de legislacoes para destinacao correta desse residuo. Desta forma, o aproveitamento dos lodos dos curtumes na agricultura apresenta-se como uma solucao tecnicamente viavel, devido as elevada quantidades de nutrientes minerais disponiveis no lodo, como o calcio, enxofre, magnesio e nitrogenio, alem da materia orgânica. Este trabalho, portanto, tem como objetivo avaliar a influencia de diferentes concentracoes de lodo de curtume desidratado para a producao de mudas de cafe conilon em comparacao a adubacao convencional. O experimento foi montado na forma de blocos casualizados composto de cinco tratamentos, sendo quatro proporcoes de lodo desidratado (10, 20, 30 e 40% de lodo) e um substrato convencional de producao de mudas de cafe conilon. Para este experimento, foram avaliadas as caracteristicas biometricas das mudas, sendo observado que a adubacao convencional apresentou melhor desenvolvimento das mudas avaliadas, no entanto, pode-se observar que os tratamentos com as concentracoes a 20 e notadamente a 30% de lodo de curtume desidratado no substrato nao apresentaram diferencas significativas para a maioria das caracteristicas avaliadas em relacao ao tratamento com adubacao convencional, demonstrando assim seu potencial de uso no substrato de mudas.

Atributos químicos de um cambissolo e crescimento de mudas de eucalipto após adição de lodo de curtume contendo cromo

O processo de curtimento do couro gera resíduos com potencial de uso como corretivo e fertilizante, no entanto alguns de seus constituintes são tóxicos quando presentes em elevado teor no solo, o que limita sua utilização nos sistemas de produção. O objetivo deste trabalho foi avaliar as alterações nos atributos químicos de um Cambissolo Húmico e o crescimento e teor de Cr em clones de Eucalyptus urophylla após a adição de doses de lodo de curtume (LCT). O experimento foi realizado em casa de vegetação, no período de março a julho de 2009. Os tratamentos consistiram da adição de doses de lodo de curtume (0; 1,5; 3,0; 4,5; e 6,0 g dm-3) ao solo, que recebeu, de forma complementar, calcário e adubação NPK em dose única. O pH, a condutividade elétrica, a relação de adsorção de sódio e a porcentagem de sódio trocável, relacionadas com a salinidade do solo, aumentaram com o incremento das doses do lodo de curtume, porém os valores observados ficaram abaixo dos níveis salinos. O teor de Cr solúvel no solo, extraído pela água, decresceu linearmente com o aumento das doses de LCT, correlacionando-se negativamente com o pH do solo. O aumento da dose do LCT proporcionou incremento na altura dos clones de Eucalyptus urophylla em até 11,5% em relação à testemunha. A produção de massa das raízes secas decresceu, em média, 28,3%, em relação à testemunha, com a maior dose (6 g dm-3). As plantas de eucalipto, em todos os tratamentos, continham o Cr somente no sistema radicular, e, quanto maior a dose de LCT, maior o teor desse metal nas raízes.

Impact of plant growth promoting Pseudomonas monteilii PsF84 and Pseudomonas plecoglossicida PsF610 on metal uptake and production of secondary metabolite (monoterpenes) by rose-scented geranium (Pelargonium graveolens cv. bourbon) grown on tannery sludge amended soil

Bacterial strains PsF84 and PsF610 were isolated from tannery sludge polluted soil, Jajmau, Kanpur, India. 16S rRNA gene sequence and phylogenetic analysis confirmed the taxonomic affiliation of PsF84 as Pseudomonas monteilii and PsF610 as Pseudomonas plecoglossicida. A greenhouse study was carried out with rose-scented geranium (Pelargonium graveolenscv. bourbon) grown in soil treated with tannery sludge in different proportions viz. soil: sludge ratio of 100:0, 25:75, 50:50, 75:25 and 0:100 to evaluate the effects of bacterial inoculation on the heavy metal uptake. The isolates solubilized inorganic phosphorus and were capable of producing indole acetic acid (IAA) and siderophore. The isolate PsF84 increased the dry biomass of shoot by 44%, root by 48%, essential oil yield 43% and chlorophyll by 31% respectively over uninoculated control. The corresponding increase with the isolate PsF610 were 38%, 40%, 39% and 28%, respectively. Scanning electron microscopic (SEM) studies reveal that the Cr(VI) accumulation resulted in breakdown of vascular bundles and sequesters Cr(VI) in roots. The glandular trichomes (GT) were investigated using SEM studies as these glands are probably the main site of essential oil synthesis. Owing to its wide action spectrum, these isolates could serve as an effective metal sequestering and bioinoculants due to the production of IAA, siderophore and solubilization of phosphate for geranium in metal-stressed soil. The present study has provided a new insight into the phytoremediation of metal-contaminated soil.

Recovery of methane from tannery sludge: the effect of inoculum to substrate ratio and solids content

Anaerobic batch experiments were conducted at mesophilic temperatures to investigate the possibility of biogas recovery from tannery sludge originating from a tannery wastewater treatment process. According to preliminary findings, the highest biogas yield was obtained as 0.172 L biogas/g VSadded within an inoculum to substrate (I:S) ratio of 1:10 and at solids content of 10.6 %. The highest methane yield of 0.089 L CH4/g VSadded was achieved within an I:S ratio of 1:2 during the experiments. Relatively lower biogas and methane yields could be attributed to the low organic content of raw sludge cake. Potential inhibitors of anaerobic digestion, such as heavy metals, particularly chromium, chloride and sulfate available in raw sludge cake did not seem to influence the process adversely. Despite lower methane yields, it seemed possible to employ anaerobic digestion process for stabilization and energy recovery from tannery sludge, since the biogas obtained could further be used in the wastewater treatment plant as a source of energy. Co-digestion of tannery sludge with another type of substrate available (e.g., tannery solid wastes) can be an alternative to achieve higher biogas and methane yields considerably.

Spatial distribution and the extent of heavy metal and hexavalent chromium pollution in agricultural soils from Jajmau, India

This study quantifies the extent of heavy metal pollution in the agricultural soils (57 samples) from Jajmau, Kanpur, India. Heavy metal concentrations (mg/kg) in agricultural soils, frequently irrigated with treated tannery effluent, are significantly higher: Cr 118–3142, Cr(VI): 2–87, Mn 341–821, Ni 24–47, Zn 78–427, V 73–110, Cd 2–13, Pb 15–69. Sludge embedded soil, mainly comprising of tannery sludge disposed in open ground, contains ~40,500 mg/kg Cr [and 1,400 mg/kg Cr(VI)], Zn (884), Cu (300), Cd (192), Pb (180) and Ni (68 mg/kg). Results show ~65 % of the total chromium is easily leachable from these soils under acidic conditions. Pollution assessment suggests that agricultural soils are highly polluted with Cr, Cu, Cd, Pb and Zn. Spatial distribution maps of heavy metals identifies specific areas that are heavily contaminated with Cr, Cu, Zn, Cd, Pb and Cr(VI), mostly along the length of the major canal constructed to distribute the treated tannery effluents. Principal component (PC) and cluster analysis suggest two principal components (or two clusters) that explain 83 % of data variability. PC1 positively correlates with Cr, Cu, Zn, Cr(VI), Pb, Cd and OM, which is attributed to anthropogenic activities, i.e. irrigation by treated tanneries effluent, open dumping of Cr sludge. PC2 strongly correlates with Fe, Ni, Co, V and Mn, which is attributed to weathering of parental materials. This study clearly reveals significant metal pollution including Cr(VI) pollution in Jajmau, which can lead to widespread soil and groundwater contamination.

Soil Microbial Biomass After Three-Year Consecutive Composted Tannery Sludge Amendment

Brazilian industry produces huge amounts of tannery sludge as residues, which is often disposed by landfilling or land application. However, consecutive amendment of such composted industrial wastes may cause shifts in soil microbial biomass (SMB) and enzyme activity. This study aimed to evaluate SMB and enzyme activity after 3-year consecutive composted tannery sludge (CTS) amendment in tropical sandy soils. Different amounts of CTS (0.0, 2.5, 5.0, 10.0, and 20.0 t ha−1) were applied to a sandy soil. The C and N contents of SMB, basal and substrate-induced respiration, respiratory quotient (qCO2), and enzyme activities were determined in the soil samples collected after CTS amendment for 60 d at the third year. After 3 years, significant changes were found in soil microbial properties in response to different CTS amounts applied. The organic matter and Cr contents significantly increased with increasing CTS amounts. SMB and soil respiration peaked following amendment with 10.0 and 20.0 t ha−1 of CTS, respectively, while qCO2 was not significantly affected by CTS amendment. However, soil enzyme activity decreased significantly with increasing CTS amounts. Consecutive CTS amendment for 3 years showed inconsistent and contrasting effects on SMB and enzyme activities. The decrease in soil enzyme activities was proportional to a substantial increase in soil Cr concentration, with the latter exceeding the permitted concentrations by more than twofold. Thus, our results suggest that a maximum CTS quantity of 5.0 t ha−1 can be applied annually to tropical sandy soil, without causing potential risks to SMB and enzyme activity.

Chromium, Cadmium, Nickel, and Lead in a Tropical Soil after 3 Years of Consecutive Applications of Composted Tannery Sludge

Agricultural use of tannery sludge (TS) may increase risks to soils. Thus, composting is recognized as one of the most suitable alternatives for TS recycling. Field experiments were carried out to evaluate the effects of composted tannery sludge (CTS) on chromium (Cr), cadmium (Cd), nickel (Ni), and lead (Pb) accumulation in soil after 3 years. Soil samples were collected 60 days after CTS application. After 3 years, The CTS increased Cr and Ni content, while Cd and Pb contents decreased. The third year, Cr contents showed linear increases as CTS rates were applied. The application of CTS, after 3 years, in the 2.5, 5, and 10 Mg ha−1 increased Cr significantly (140.7%, 159.7%, and 19%, respectively) and Ni (32%, 53%, and 43.8%, respectively) contents in the soil surface layer. This means that consecutive amendments of CTS increase Cr contents in the soil and plants.