Sanjeev K. Singh

Bioaccumulation and phyto-translocation of arsenic, chromium and zinc by Jatropha curcas L.: Impact of dairy sludge and biofertilizer

The present study was planned to remediate the metalloid and metal contaminated soil by using non-edible and economic plant species Jatropha curcas L. The experiment was conducted on pots to improve the survival rate, metal tolerance and growth response of the plant on soil; having different concentrations of arsenic, chromium and zinc. The soil was amended with dairy sludge and bacterial inoculum (Azotobacter chroococcum) as biofertilizer. The results of the study showed that the bioaccumulation potential was increased with increase in metalloid and metal concentration in soil system. Application of dairy sludge significantly reduces the DTPA-extractable As, Cr and Zn concentration in soil. The application of organic amendment stabilizes the As, Cr and Zn and reduced their uptake in plant tissues.

Bioremediation of multi-metal contaminated soil using biosurfactant — a novel approach

An unconventional nutrient medium, distillery spent wash (1:3) diluted) was used to produce di-rhamnolipid biosurfactant by Pseudomonas aeruginosa strain BS2. This research further assessed the potential of the biosurfactant as a washing agent for metal removal from multimetal contaminated soil (Cr-940 ppm; Pb-900 ppm; Cd-430 ppm; Ni-880 ppm; Cu-480 ppm). Out of the treatments of contaminated soil with tap water and rhamnolipid biosurfactant, the latter was found to be potent in mobilization of metal and decontamination of contaminated soil. Within 36 hours of leaching study, di-rhamnolipid as compared to tap water facilitated 13 folds higher removal of Cr from the heavy metal spiked soil whereas removal of Pb and Cu was 9–10 and 14 folds higher respectively. Leaching of Cd and Ni was 25 folds higher from the spiked soil. This shows that leaching behavior of biosurfactant was different for different metals. The use of wastewater for production of biosurfactant and its efficient use in metal removal make it a strong applicant for bioremediation.

Adsorption—;Desorption Process Using Wood‐Based Activated Carbon for Recovery of Biosurfactant from Fermented Distillery Wastewater

Methods used for biosurfactant recovery include solvent extraction, precipitation, crystallization, centrifugation and foam fractionation. These methods cannot be used when distillery wastewater (DW) is used as the nutrient medium for biosurfactant production by Pseudomonas aeruginosa strain BS2, because recovery of biosurfactant by any of these methods imparts color to the biosurfactant. The biosurfactant has a nonaesthetic appearance with lowered surface active properties. These methods cannot be used for continuous recovery of biosurfactant during cultivation. Hence, a new downstream technique for biosurfactant recovery from fermented DW comprised of adsorption‐desorption processes using wood‐based activated carbon (WAC) was developed. This study involves batch experiments to standardize the factors affecting the rate of biosurfactant adsorption onto WAC. WAC was the most efficient adsorbent among various ones tested (i.e., silica gel, activated alumina and zeolite). The WAC (1% w v−1), equilibrium time (90 min), pH range of 5–10 and temperature of 40 °C were optimum to achieve 99.5% adsorption efficiency. Adsorption kinetics and intraparticle diffusion studies revealed the involvement of both boundary layer diffusion and intraparticle diffusion. The Langmuir adsorption isotherm of WAC indicated the formation of a monolayer coverage of the biosurfactant over a homogeneous carbon surface, while the Freundlich isotherm showed high adsorption at strong solute concentrations and low adsorption at dilute solute concentrations. WAC concentration of 4% w v−1 facilitated complete removal of the biosurfactant from collapsed foam (contained 5‐fold higher concentration of biosurfactant than was present in fermented DW). Biosurfactant adsorption was of chemisorption type. Acetone (polar solvent) was a specific viable eluant screened among various ones tested because it selectively facilitated maximum recovery, i.e., 89% biosurfactant from WAC. By acetone treatment, complete regeneration of WAC was feasible and WAC can be reused for biosurfactant recovery up to 3 cycles. The recovered biosurfactant showed improved surface‐active property (i.e., much lower critical micelle concentration value of 0.013 verses 0.028 mg mL−1 for biosurfactant recovered by classical methods). The reuse potential of WAC was assessed and results suggest that the carbon can be reused for three consecutive cycles for biosurfactant adsorption from fermented wastewater without any decrease in adsorption efficiency. Thus, this process forms a basis for continuous recovery of biosurfactant from fermented DW and concentrated foam. This process reduces the use of high cost solvent, avoids end product inhibition and minimizes product degradation.

Growth responses and metal accumulation capabilities of woody plants during the phytoremediation of tannery sludge.

Five woody plants species (i.e. Terminalia arjuna, Prosopis juliflora, Populus alba, Eucalyptus tereticornis and Dendrocalamus strictus) were selected for phytoremediation and grow on tannery sludge dumps of Common Effluent Treatment Plant (CETP), Unnao (Uttar Pradesh), India. Concentration of toxic metals were observed high in the raw tannery sludge i.e. Fe-1667>Cr-628>Zn-592>Pb-427>Cu-354>Mn-210>Cd-125>Ni-76 mg kg(-1) dw, respectively. Besides, physico-chemical properties of the raw sludge represented the toxic nature to human health and may pose numerous risks to local environment. The growth performances of woody plants were assessed in terms of various growth parameters such as height, diameter at breast height (DBH) and canopy area of plants. All the plant species have the capabilities to accumulate substantial amount of toxic metals in their tissues during the remediation. The ratio of accumulated metals in the plants were found in the order Fe>Cr>Mn>Pb>Zn>Cu>Cd>Ni and significant changes in physico-chemical parameters of tannery sludge were observed after treatment. All the woody plants indicated high bioconcentration factor for different metals in the order Fe>Cr>Mn>Ni>Cd>Pb>Zn>Cu. After one year of phytoremediation, the level of toxic metals were removed from tannery sludge up to Cr (70.22)%, Ni (59.21)%, Cd (58.4)%, Fe (49.75)%, Mn (30.95)%, Zn (22.80)%, Cu (20.46)% and Pb (14.05)%, respectively.

Effect of amendment on phytoextraction of arsenic by Vetiveria Zizanioides from soil

The present study was undertaken to evaluate the growth response of Vetiveria zizanioides amended with organic amendments to arsenic (As) in contaminated soils and its ability to sequester As. The test results indicate that the plants exhibited high tolerance to As in the soils and their normal growth continued even though As concentration reached 500 mg/kg. However, when As concentrations in soils were in the range of 1000∼2000 mg/kg the plants could not survive no matter whether the soils were amended. The accumulation of As in roots (185.4 mg/kg) was higher than that in shoots (100.6 mg/kg). The As level in the contaminated soil was reduced from 500 mg/kg to 214 mg/kg after six months of As phytoextraction. Microbial population was not affected in the As contaminated soil amended with dairy sludge, mycorrhizae and Azotobacter.

Biochemical changes in plant leaves as a biomarker of pollution due to anthropogenic activity.

The air pollution due to anthropogenic activities seriously affected human life, vegetation, and heritage as well. The vegetation cover in and around the city mitigates the air pollution by acting as a sink for pollution. An attempt was made to evaluate biochemical changes occurred in four selected plant species, namely Azadirachta indica, Mangifera indica, Delonix regia, and Cassia fistula of residential, commercial, and industrial areas of Nagpur city in India. It was observed that the correlated values of air pollutants and plant leaves characteristics alter foliar biochemical features (i.e., chlorophyll and ascorbic acid content, pH and relative water content) of plants due to air pollution. The changes in air pollution tolerance index of plants was also estimated which revealed that these plants can be used as a biomarker of air pollution.

Potential of New Microbial Isolates for Biosurfactant Production using Combinations of Distillery Waste with other Industrial Wastes

In the present study, combinations of Distillery Waste (DW) with other industrial wastes viz. curd Whey Waste (WW), Fruit Processing Waste (FPW) and Sugar Industry Effluent (SIE) were evaluated to replace the use of water that was reported earlier for biosurfactant production from 1: 3 diluted distillery waste by using four new bacterial cultures BS-A, BS-J, BS-K and BS-P, isolated from soil collected from a distillery unit. These isolates have the potential to produce biosurfactant from these individual wastes and in their combinations. Highest biomass and biosurfactant yields with higher reduction in the Chemical Oxygen Demand (COD), total sugars, nitrogen and phosphate levels were obtained in 1:1:1 proportion of DW+WW+FPW followed by DW+WW+ SIE and individual wastes. The combinations of wastes improved the yields of biosurfactants by 18-41% and reduced COD of the combined wastes by 76-84.2%. Total sugars, nitrogen and phosphate levels reduced in the range of 79-86%, 58-71% and 45-59%, respectively. Among the four microbial isolates tested, BS-J and BS-P were the efficient biosurfactant producers and were identified as Kocuria turfanesis and Pseudomonas aeruginosa based on the 16S rDNA sequence and phylogenetic analyses. Benefits derived by using combined distillery waste with other wastes are improved production of biosurfactant as resource and saving precious water and the costly nutrients with concomitant reduction in pollution load of the wastes.

Visible-light-induced water reduction reaction for efficient hydrogen production by N-doped In2Ga2ZnO7 nanoparticle decorated on RGO sheets

This work presents an efficient in situ chemical method for constructing graphene-based N-doped In2Ga2ZnO7 nanocomposites (RGO/N-IGZ) for the production of hydrogen (H2) under visible-light irradiation. Well-anchored N-doped IGZ nanoparticles on RGO sheets were successfully obtained by the hydrothermal route that was employed. Several crystallographic, microscopic, and spectroscopic methods (XRD, DRUV-vis, PL spectra, TRPL analysis, XPS, TEM, and photoelectrochemical and photostability measurements) were adopted to study the robust photocatalytic activity of all the synthesised photocatalysts. A DRS study revealed that doping an IGZ nanoparticle with N reduced its band gap (Eg) from 2.50 eV to 2.34 eV and, furthermore, the introduction of RGO into the N-IGZ nanoparticle altered its Eg to 2.29 eV. The loading amount of RGO in an N-IGZ nanoparticle played a crucial role in enhancing the photocatalytic H2-producing ability of the N-IGZ nanoparticle. In the absence of a co-catalyst, a loading of RGO of only 2 wt% in N-IGZ enabled the production of the highest amount of H2, i.e. 726 μmol h−1, under visible-light irradiation. The superior photocatalytic activity of the 2RGO/N-IGZ nanocomposite in comparison with that of neat N-IGZ nanoparticles was demonstrated by correlation with the results obtained from BET surface area analysis, TEM, PL, TRPL, and photocurrent and photostability measurements, which concluded by showing better charge separation in the 2RGO/N-IGZ nanocomposite. 2RGO/N-IGZ exhibited low PL intensity, a longer average decay time (the values of for N-IGZ and 2RGO/N-IGZ were 2.11 and 7.11 ns, respectively), high photocurrent generation (42 times greater than that of N-IGZ), a large surface area and the production of the highest amount of H2 under visible-light irradiation without using any co-catalyst.

Enhanced Biodegradation of Mobil Oil Hydrocarbons by Biosurfactant Producing Bacterial Consortium in Wheat and Mustard Rhizosphere

Hydrocarbon fuels are one of the most common global environmental pollutants which cannot be easily degraded owing to their hydrophobic nature. The present study involves the degradation of hydrocarbons by biosurfactant producing bacterial consortia. In this study, results showed 73.66% and 75.80% degradation of 2% mobil oil hydrocarbons in contaminated soil by biosurfactant producing bacterial consortium with wheat (Triticum aestivum) and mustard (Brassica juncea) crops, respectively. Therefore, it indicates that the developed bacterial consortium are capable for the effective degradation of mobil oil hydrocarbons in wheat and mustard rhizosphere and hence can be employed effectively for the degradation of mobil oil hydrocarbons in oil contaminated soils. Phthalate esters formed during the degradation can be used for industrial applications like PVC softening.

Utilisation of municipal solid waste as an amendment for reclamation of coal mine spoil dump.

Mine spoil dumps generated due to mining activities pose drastic physico-chemical and biological constraints for sustainable vegetation. Thus an eco-friendly and cost-effective Microbe Assisted Phytoremediation (MAP) is adopted for reclamation of coalmine spoil dumps. The results indicate that MAP is also an excellent tool for fast restoration and productivity of wastelands, 95?99% plants survival rate, provides CO2 sinks, generating fuel, fibre, food, fodder, medicines, etc. Thus, the MAP aids the mining industries in converting the negative impacts of the degraded ecosystem into a source of revenue in a short span and opens a new avenue to implement the technology in different types of wastelands.