Accumulation of heavy metals in Spinacia oleracea irrigated with paper mill effluent and sewage

Performance evaluation of gravity-driven bioreactor (GDB) for simultaneous treatment of black liquor and domestic wastewater

A lab-scale gravity-driven bioreactor (GDB) was designed and constructed to evaluate the simultaneous treatment of black liquor and domestic wastewater. The GDB was operated with a mixture of black liquor and domestic wastewater at a ratio of 1:1 and maintained at an average organic loading rate of 1235 mg-COD/L-Day. The wastewater was fed to the primary sedimentation tank at a flow rate of approximately 12 mL/min and subsequently passed through serially connected anaerobic and aerobic chambers with the same flow rate. Each wastewater sample was allowed to undergo a hydraulic retention time of approximately 72 h, ensuring effective treatment. The GDB was actively operated for nine samples (W1-W9) at a weekly frequency. The entire process was conducted within the workstation's ambient temperature range of 30-35 °C to sustain microbial activity and treatment efficiency in an open environment. The performance of the GDB was evaluated in terms of various pollution indicators, including COD, BOD5, lignin removal, TDS, TSS, EC, PO43-, SO42-, microbial load (CFU/mL and MPN index), total nitrogen, and color reduction. The results showed that the GDB achieved promising treatment efficiencies: 84.5% for COD, 71.80% for BOD5, 82.8% for TDS, 100% for TSS, 74.71% for E.C., 67.25% for PO43-, 81% for SO42-, and 69.36% for TN. Additionally, about 80% reduction in lignin content and 57% color reduction were observed after the treatment. The GDB substantially reduced microbial load in CFU/mL (77.98%) and MPN (90%). This study marks the first to report on wastewater treatment from two different sources (black liquor and domestic wastewater) using a simple GDB design. Furthermore, it highlights the GDB's potential as a cost-effective, environmentally friendly, and efficient solution for wastewater treatment, with no need for supplementary chemical or physical agents and zero operational costs.

Accumulation risk and source apportionment of heavy metals in different types of farmland in a typical farming area of northern China

The types of land used for farmland can greatly influence the source and accumulation risk of heavy metals in soil. However, the apportioning quantitatively the source of soil heavy metals has been studied insufficiently, especially in terms of different types of farmland. In this study, a total of 252 soil samples were taken from dry land, paddy fields and greenhouse fields in the Jinyuan district of Taiyuan city, China, to assess the accumulation risk of heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb and Zn). The results were then integrated, and source apportionment was evaluated by geospatial analysis, multivariate statistical analysis and positive matrix factorization (PMF). Cr, Cd and Hg were the dominant pollutants in the studied area. Accumulation risk by Cd and Cu was more severe in greenhouse fields than in dry land or paddy fields, whereas As, Hg and Pb had relatively higher accumulation in paddy fields than in dry land or greenhouse fields. Hg was derived mainly from coal combustion by atmospheric precipitation for the three types of farmland. Long-term irrigation using sewage is the main reason for the accumulation of Cu and Ni in dry land soil, Cu and Zn in paddy field soil and Zn in greenhouse soil. Cd in dry land, Cd and Pb in paddy fields and Cd, Cu, Ni and Pb in greenhouse fields were primarily added to soil through fertilization. Sewage irrigation and fertilization were the dominant sources of heavy metals for paddy field (31.3%) and greenhouse field (33.1%), respectively.

Phytoremediation Potential of Crop Plants in Countering Nickel Contamination in Carbonation Lime Coming from the Sugar Industry

The phytoremediation potential of four crop species cultivated on carbonation lime coming from the sugar industry with water-soluble nickel (Ni) exceeding the Italian legal limit of 10 µg L^-1 was assessed. Two autumn-winter species (spinach and canola) were tested with and without the addition of bentonite in a greenhouse experiment in order to overcome prolonged unfavourable weather conditions. Two spring-summer species (sunflower and sorghum) were grown in outdoor boxes. Plant species were selected among crops of interest for phytoremediation and their rotation throughout the year enable to maintain a permanent vegetation cover. Nickel concentration in different plant tissues and the concentrations of soluble and bioavailable Ni in lime were measured. In the greenhouse study, soluble Ni decreased below the legal limit in all the tests, and the combined effect of bentonite and plants reduced Ni in lime mainly in the bioavailable fraction. Spinach and sunflower emerged to be more suitable for phytoextraction than canola and sorghum, because of the higher concentration of the metal in the epigeal portions. The results from the outdoor experiment highlighted that sorghum has a good phytostabilisation potential since its ability to accumulate Ni mainly at the root level and to attract a significant amount of bioavailable Ni in the rhizosphere. This study arose from a real scenario of environmental contamination and investigated the potential of different approaches on the bioremediation of a specific industrial waste product.

Airborne foliar transfer of PM bound heavy metals in Cassia siamea: A less common route of heavy metal accumulation

In order to investigate possible foliar transfer of toxic heavy metals, concentrations of Cd, Pb, and Fe were measured in samples of: Cassia siamea leaves (a common tree) Cassia siamea foliar dust, nearby road dust, and soil (Cassia siamea tree roots) at six different sites in/around the Bilaspur industrial area and a control site on the university campus. Bilaspur is located in a subtropical central Indian region. The enrichment factor (EF) values of Pb and Cd, when derived using the crustal and measured soil Fe data as reference, indicated significant anthropogenic contributions to Pb and Cd regional pollution. Based on correlation analysis and scanning electron microscopy (SEM) observations, it was evident that Pb and Cd in foliar part of Cassia siamea were largely from airborne sources. The SEM studies of leaf confirmed that leaf morphology (epidermis, trichome, and stomata) of Cassia siamea helped accumulate the toxic metals from deposited particulate matter (PM). There is a line of evidence that the leaf of Cassia siamea was able to entrap PM in respirable suspended particulate matter (RSPM) range (i.e., both in fine and coarse fractions). The overall results of this study suggest that Cassia siamea can be a potential plant species to control the pollution of PM and PM-bound metals (Pb and Cd) in affected areas.

Phytoremediation potential of a novel fern, Salvinia cucullata, Roxb. Ex Bory, to pulp and paper mill effluent: Physiological and anatomical response

The study was conducted with an aim to remediate effluent from a pulp and paper mill, after treating it for 28 days with an aquatic fern, Salvinia cucullata. The effluent had high BOD, COD, TS, TSS, TDS, P, hardness and chloride, and several heavy metals (Cd, Cu, Cr, Ni, Pb, Mg, Mn, Fe and Zn) above national limits. However, the plant survived a wide range of effluent concentrations (25%, 50%, 75% and 100%, v/v), and flourished well, particularly at 25% (v/v), resisted membrane injury and generation of H2O2 and O2, showed better growth and induced all the major antioxidant enzymes. The plants also induced lipid peroxidation. Most of the elemental profiles were higher than the toxic levels stipulated for plants, indicating tolerance to metal. In fact, barring Fe, for Cr, Cu, Pb, Zn, Mg and P, at all the effluent doses, and for Cd, Ni and Mn, up to 75% (v/v) effluent, greater concentrations were observed in leaf than in root. This plant was more suited for nutrient removal, as it effectively reduced BOD, Zn, Fe, Ni, Mg, P and increased dissolve oxygen. Further, pH, hardness, chloride, TS and Mn was reduced optimally by 25-50% (v/v) treatments. SEM revealed prominent structural damages from 50 to 100% treatments. Presence of Pb as well as Fe in the EDX peaks were observed in the cortex rather than in the root vascular zone. This plant could be suggested to be an effective phytoremediator of multi-contaminant effluent with maximum benefit at low doses (25-50%, v/v).

Evaluating the potential of immobilized bacterial consortium for black liquor biodegradation

Two indigenous bacterial strains, Bacillus megaterium ETLB-1 (accession no. KC767548) and Pseudomonas plecoglossicida ETLB-3 (accession no. KC767547), isolated from soil contaminated with paper mill effluent, were co-immobilized on corncob cubes to investigate their biodegradation potential against black liquor (BL). Results exhibit conspicuous reduction in color and lignin of BL upto 913.46 Co-Pt and 531.45 mg l(-1), respectively. Reduction in chlorophenols up to 12 mg l(-1) was recorded with highest release of chloride ions, i.e., 1290 mg l(-1). Maximum enzyme activity for lignin peroxidase (LiP), manganese peroxidase (MnP), and laccase (LAC) was recorded as 5.06, 8.13, and 8.23 U ml(-1), respectively, during the treatment. Scanning electron microscopy (SEM) revealed successful immobilization of bacterial strains in porous structures of biomaterial. Gas chromatography/mass spectroscopy (GC/MS) showed formation of certain low molecular weight metabolites such as 4-hydroxy-benzoic acid, 3-hydroxy-4-methoxybenzaldehyde, ferulic acid, and t-cinnamic acid and removal of majority of the compounds (such as teratogenic phthalate derivatives) during the period of treatment. Results demonstrated that the indigenous bacterial consortium possesses excellent decolorization and lignin degradation capability which enables its commercial utilization in effluents treatment system.

Uptake and translocation of metals in different parts of crop plants irrigated with contaminated water from DEPZ area of Bangladesh

Metal contamination in arable soils and crops grown in and around an industrial area of Bangladesh were measured, and the transfer factor from soils to crops was calculated accordingly. The highest concentration was observed for Fe and the order of metal concentration was Fe > Zn > Cr > Pb > Cu > Ni > Cd in soils. Bioaccumulation and translocation of metals from roots to edible parts of the crop plants were varied for almost all elements studied. Absorption of metals was significantly more in the roots compared to other plant parts. Accumulation of all metals in the edible parts of the plants was compared with the recommended maximum tolerable levels proposed by the Joint FAO/WHO Expert Committee on Food Additives. Bioconcentration factors values based on dry weights were below one for all metals except Cu in the rice roots and decreased in the order of Cu > Zn > Fe > Pb > Ni > Cd > Cr.

Evaluation of biochemical and redox parameters in rats fed with corn grown in soil amended with urban sewage sludge

The increased production of urban sewage sludge requires alternative methods for final disposal. A very promising choice is the use of sewage sludge as a fertilizer in agriculture, since it is rich in organic matter, macro and micronutrients. However, urban sewage sludge may contain toxic substances that may cause deleterious effects on the biota, water and soil, and consequently on humans. There is a lack of studies evaluating how safe the consumption of food cultivated in soils containing urban sewage sludge is. Thus, the aim of this paper was to evaluate biochemical and redox parameters in rats fed with corn produced in a soil treated with urban sewage sludge for a long term. For these experiments, maize plants were grown in soil amended with sewage sludge (rates of 5, 10 and 20 t/ha) or not (control). Four different diets were prepared with the corn grains produced in the field experiment, and rats were fed with these diets for 1, 2, 4, 8 and 12 weeks. Biochemical parameters (glucose, total cholesterol and fractions, triglycerides, aspartate aminotransferase and alanine aminotransferase) as well the redox state biomarkers such as reduced glutathione (GSH), malondialdehyde (MDA), catalase, glutathione peroxidase and butyrylcholinesterase (BuChE) were assessed. Our results show no differences in the biomarkers over 1 or 2 weeks. However, at 4 weeks BuChE activity was inhibited in rats fed with corn grown in soil amended with sewage sludge (5, 10 and 20 t/ha), while MDA levels increased. Furthermore, prolonged exposure to corn cultivated in the highest amount per hectare of sewage sludge (8 and 12 weeks) was associated with an increase in MDA levels and a decrease in GSH levels, respectively. Our findings add new evidence of the risks of consuming food grown with urban sewage sludge. However, considering that the amount and type of toxic substances present in urban sewage sludge varies considerably among different sampling areas, further studies are needed to evaluate sludge samples collected from different sources and/or undergoing different types of treatment.