Assessment of industrial wastewater for potentially toxic elements, human health (dermal) risks, and pollution sources: A case study of Gadoon Amazai industrial estate, Swabi, Pakistan

Fe Crystalline Phases in Fe/C Composites Modulated the Selective Adsorption of Pb(II) from Industrial Wastewater with Cd(II): An Electronic-Scale Perspective

Fe oxide or Fe0-based materials display weak removal capacity for Pb(II), especially in the presence of Cd(II), and the electronic-scale mechanisms are not reported. In this study, Fe3C(220) modified black carbon (BC) [Fe3C(220)@BC] with high adsorption and selectivity for Pb(II) from industrial wastewater with Cd(II) was developed. The quantitative experiment suggested that Fe species accounted for 80.5-100 and 18.4-33.8% of Pb(II) and Cd(II) removal, respectively. Based on X-ray absorption near-edge structure analysis, 57.3% of adsorbed Pb2+ was reduced to Pb0; however, 61.6% of Cd2+ existed on Fe3C@BC. Density functional theory simulation unraveled that Cd(II) adsorption was attributed to the cation-π interaction with BC, whereas that of Pb(II) was ascribed to the stronger interactions with different Fe phases following the order: Fe3C(220) > Fe0(110) > Fe3O4(311). Crystal orbital bond index and Hamilton population analyses were innovatively applied in the adsorption system and displayed a unique discovery: the stronger Pb(II) adsorption on Fe phases was mediated by a combination of covalent and ionic bonding, whereas ionic bonding was mainly accounted for Cd(II) adsorption. These findings open a new chapter in understanding the functions of different Fe phases in mediating the fate and transport of heavy metals in both natural and engineered systems.

The effect of quorum sensing on cadmium- and lead-containing wastewater treatment using activated sludge: Removal efficiency, enzyme activity, and microbial community

Quorum sensing (QS) is prevalent in activated sludge processes; however, its essential role in the treatment of heavy metal wastewater has rarely been studied. Therefore, in this study, acyl homoserine lactone (AHL)-mediated QS was used to regulate the removal performance, enzyme activity, and microbial community of Cd- and Pb-containing wastewater in a sequencing batch reactor (SBR) over 30 cycles. The results showed that exogenous AHL strengthened the removal of Cd(II) and Pb(II) in their coexistence wastewater during the entire period. The removal of NH4+-N, total phosphorus, and chemical oxygen demand (COD) was also enhanced by the addition of AHL despite the coexistence of Cd(II) and Pb(II). Meanwhile, the protein content of extracellular polymeric substances was elevated and the microbial metabolism and antioxidative response were stimulated by the addition of AHL, which was beneficial for resistance to heavy metal stress and promoted pollutant removal by activated sludge. Microbial sequencing indicated that AHL optimized the microbial community structure, with the abundance of dominant taxa Proteobacteria and Unclassified_f_Enterobacteriaceae increasing by 73.9% and 59.2% maximally, respectively. This study offers valuable insights into the mechanisms underlying Cd(II) and Pb(II) removal as well as microbial community succession under AHL availability in industrial wastewater.

Isotopic insights and integrated analysis for heavy metal levels, ecological risks, and source apportionment in river sediments of the Qinghai-Tibet Plateau

The research was carried out to examine the pollution characteristics, ecological risk, and origins of seven heavy metals (Hg, As, Pb, Cu, Cd, Zn, and Ni) in 51 sediment samples gathered from 8 rivers located on the Qinghai-Tibet Plateau (QTP) in China. The contents of Hg and Cd were 5.0 and 1.1 times higher than their background values, respectively. The mean levels of other measured heavy metals were below those found naturally in the local soil. The enrichment factor showed that the study area exhibited significantly enriched Hg with 70.6% sampling sites. The Cd contents at 19.6% of sampling sites were moderately enriched. The other sampling sites were at a less enriched level. The sediments of all the rivers had a medium level of potential ecological risk. Hg was the major ecological risk factor in all sampling sites, followed by Cd. The findings from the positive matrix factorization (PMF) analysis shown agricultural activities, industrial activities, traffic emissions, and parent material were the major sources. The upper, middle, and low reaches of the Quanji river had different Hg isotope compositions, while sediments near the middle reaches were similar to the δ202Hg of the industrial source. At the upstream sampling sites, the Hg isotope content was very close to the background level. The results of this research can establish a strong scientific sound to improve the safety of the natural circumstances of rivers on the QTP.

Fault Detection of Urban Wastewater Treatment Process Based on Combination of Deep Information and Transformer Network

As one of the hot issues of concerns during modern social development, the wastewater treatment process is acknowledged to be a process with complex biochemical reactions and susceptible to an external environment, featuring strong nonlinear and time correlation characteristics, which are difficult for traditional mechanism-based models to tackle. For many classical data-driven fault detection methods, a complete retraining process is necessary to monitor every new fault, and most of the current neural network-based strategies rarely achieve satisfactory monitoring accuracy or robustness either. Giving full consideration to the aforementioned problems, this article takes advantage of position encoding, residual connection, and multihead attention mechanism embedded in the Transformer structure to establish an effective and efficient wastewater treatment process fault detection model, where offline modeling and online monitoring are performed successively to achieve accurate detection of the faults. In the experimental part, the advantages of the proposed method are strongly verified through the simulation monitoring of 27 faults on the benchmark simulation model 1 (BSM1), where the false alarm rate (FAR) and miss alarm rate (MAR) of the established method are proved to be significantly lower than those of the compared state-of-the-art methods.

Entropy-weighted water quality index, hydrogeochemistry, and Monte Carlo simulation of source-specific health risks of groundwater in the Morava River plain (Serbia)

Population growth, urbanization, industry, floods, and agriculture globally degrade groundwater in river plains, necessitating action for its quality assessment and management. Hence, a comprehensive methodology, including hydrogeochemical facies (Piper, Gibbs), irrigation indices (SAR, Wilcox), entropy-weighted water quality index (EWQI), positive matrix factorization (PMF), and Monte Carlo simulation of source-specific health risks was used in this study to analyze groundwater in the Morava river plain (Serbia). The results revealed a prevalent Ca-Mg-HCO3 groundwater type, influenced by water-rock interactions. Although groundwater was found suitable for irrigation, only 66.7 % of the samples were considered drinkable. Agricultural activities, natural processes, and municipal wastewater were identified as primary pollution sources. The incremental lifetime cancer risk (ILCR) and hazard index (HI) threshold exceedance for adults and children ranged from 8.5 % to 39 % of the samples, with arsenic identified as the most risk-contributing contaminant. These findings provide valuable insights for researchers studying groundwater vulnerability in river plains.

Unlocking the secrets of soil microbes: How decades-long contamination and heavy metals accumulation from sewage water and industrial effluents shape soil biological health

Heavy metals contamination is posing severe threat to the soil health and environmental sustainability. Application of industrial and sewage waste as irrigation and growing urbanization and agricultural industry is the main reason for heavy metals pollution. Therefore, the present study was planned to assess the influence of different irrigation sources such as industrial effluents, sewage wastewater, tube well water, and canal water on the soil physio-chemical, soil biological, and enzymatic characteristics. Results showed that sewage waste and industrial effluents affect the soil pH, organic matter, total organic carbon, and cation exchange capacity. The highest total nickel (383.71 mg kg-1), lead (312.46 mg kg-1), cadmium (147.75 mg kg-1), and chromium (163.64 mg kg-1) were recorded with industrial effluents application. Whereas, industrial effluent greatly reduced the soil microbial biomass carbon (SMB-C), soil microbial biomass nitrogen (SMB-N), soil microbial biomass phosphorus (SMB-P), and soil microbial biomass sulphur (SMB-S) in the winter season at sowing time. Industrial effluent and sewage waste inhibited the soil enzymes activities. For instance, the minimum activity of amidase, urease, alkaline-phosphatase, β-glucosidase, arylsulphatase and dehydrogenase activity was noted with HMs contamination. The higher levels of metals accumulation was observed in vegetables grown in soil contaminated with untreated waste water and industrial effluent in comparison to soil irrigated with canal and tube well water. The mean increase in soil microbial parameters and enzyme activities was also observed in response to the change in season from winter to spring due to increase in soil mean temperature. The SMB-C, SMB-N, SMB-P and SMB-S showed significant positive correlation with soil enzymes (amidase, urease, alkaline-phosphatase, β-glucosidase, arylsulphatase and dehydrogenase). The heavy metals accumulation in soil is toxic to microorganisms and inhibits enzyme functions critical for nutrient cycling and organic matter decomposition and can disrupt the delicate balance of soil ecosystem and may lead to long-term damage of soil biological health.

Surfactant-supported organoclay for removal of anionic food dyes in batch and column modes: adsorption characteristics and mechanism study

This study aimed to create CTAB-modified bentonite organoclay (Bt@CTAB) by mixing the naturally occurring mineral bentonite (Bt) with the cationic surfactant cetyltrimethylammonium bromide (CTAB). Elemental analysis, N2 adsorption–desorption isotherm, scanning electron microscopy (SEM), FTIR spectroscopy, XRD, and thermogravimetric (TGA) analysis have been employed to analyze both the unmodified Bt and the Bt@CTAB organoclay. The dye sorption onto Bt@CTAB organoclay was investigated in the batch and column modes using aqueous solutions of anionic food dyes, viz., Sunset yellow FCF (E110), Azorubine (E122), and Ponceau 4R (E124) (individually or in a mixture). Experimental variables affecting the adsorption process, such as initial dye concentration, contact time, temperature, pH, and adsorbent dose, are evaluated. From the kinetic investigations, the adsorption of E110, E122, and E124 dyes well matched the pseudo-second-order kinetic model. E110 and E122 dyes adsorption onto Bt@CTAB attained equilibrium in 120 min while attained in 240 min for E124. The investigated food dyes were expected to achieve maximum adsorption efficiencies at concentration of 100 ppm of (E110 and E124) and 150 ppm of (E124), an adsorbent dosage of 0.4 gL−1, and an initial pH 5. In addition, Langmuir model best fits the sorption isotherm data, with the maximum adsorption capacity at 303 K being 238 mg/g, 248.75 mg/g, and 358.25 mg/g for E110, E122, and E124, respectively. The Bt@CTAB organoclay can be regenerated up to the 4th cycle successfully. The thermodynamic studies revealed the spontaneous and exothermic nature of the adsorption of these anionic dyes onto Bt@CTAB organoclay. The prepared cationic Bt@CTAB organoclay was successfully applied for the removal of E110, E122, and E124 from real water samples, synthetic effluents, and colored soft drinks with a recovery (R%) higher than 95%. The plausible adsorption mechanism of E110, E122, and E124 onto Bt@CTAB organoclay is proposed to be due to electrostatic interaction and hydrogen bond formation. Finally, the present study shows that Bt@CTAB organoclay may be employed efficiently and effectively to remove anionic food dyes from a wide range of real water and colored soft drinks.

Prediction of Hazardous Effect of Heavy Metals of Point-Source Wastewater on Fish (Anabas cobojius) and Human Health

Aquatic ecosystems are exceedingly contrived due to industrial dispenses, as a huge amount of toxicants especially heavy metals are released, causing drastic effects on aquatic lives and the human body. This study was performed to assess the quality of point-source industrial wastewater at varying percentage levels and their subsequent hazardous effect on fish (Anabas cobojius) and human health. The perceived value revealed that water quality parameters declined with the increase of wastewater concentration and trace metal evaluation index (TEI) ascertained a high level of water pollution due to Cr, Mn, Fe, Co, Ni, Cu, Zn, and As content for all percentages of wastewater. Concentration of wastewater and culture treatment duration largely impacted on fish mortality rate, body dis-pigmentation, mucus secretion rate, coagulation of mucus all over the body, and accumulation of heavy metals by fish samples. Metal pollution index (MPI) indicated low contamination of fish by the measured elements. Zn and Hg exceeded the threshold limit of target hazard quotient (THQ > 1) and contributed significantly to non-carcinogenic health implications for both the population group. Maximum hazard index in adults and children was observed to be 10.638 and 16.548 for 100% effluent at 96-h exposure period and the overall HI value manifested a very high to medium significant health effects regardless of age. Carcinogen Pb showed insignificant risk but Cr and Ni showed extremely high to medium-high risk for both the population group, and children were found more vulnerable receptors than adults. However, source of heavy metals in wastewater and fish samples stipulated anthropogenic sources.

Ecotoxicological monitoring of potentially toxic elements contamination in Eucalyptus forest plantation subjected to long-term irrigation with recycled wastewater

Afforestation is an evergreen technology for restraining greenhouse gases (GHGs) emission and improving soil carbon sink in arid and semi-arid regions. Nonetheless, the long-term impact of woody forests irrigation using recycled wastewater resources remains inconclusive so far. For this purpose, the ecological risk benchmarks of potentially toxic elements (PTEs) were investigated on Eucalyptus forest plantation in order to gauge their bioavailability in the rhizospheric layer of Typic Torripsammentsoil and their accretion capacity in the biosphere. Water quality guidelines pointed to a moderate degree of restriction on use with elevated levels of PTEs. Notably, concentrations of As, B, Cd, Cr, Cu, Mn, Ni, V and Zn were above the permissible limits for irrigation. The geospatial mapping of PTEs concentration in soil pointed to elevated levels of most PTEs, particularly in the deforestated areas. Some of PTEs (Cd, Cu, Hg and Zn) showed values above the permissible limits. A spectrum of ecological risk indices showed considerable to high degree of contamination. Among PTEs, the water-soluble and exchangeable fractions showed high values of As, Cd and Hg (20.7, 17.2 and 11.0%, respectively). Sequential extraction showed variations among PTEs in their tendency to bind with different soil geochemical fractions: (i) carbonate (Cd, Zn and Cu), (ii) Fe-Mn oxides (Pb, Zn and Mn) and (iii) organic matter (B, Pb and Hg). Eight fungal species including Aspergillus flavus, Fusarium solani, Cephalosporimsp., Penicilliumsp., Rhizoctonia solani, Aspergillus niger, Botrytissp. and Verticilliumsp. were dominated in soil. Meanwhile, Agrobacteriumsp., phosphate solubilizing bacteria, nitrogen fixing bacteria and Escherichia coli were the dominant bacterial strains. Values of bioaccumulation index varied among PTEs, wherein B (5.15), Ni (1.98), Mn (1.62) and Cd (1.02) exhibited higher phytoextraction potentials. Other PTEs, however, exhibited values below 1.0 confirming their low phytoextraction potentials. Findings of this investigation, therefore, provide insights into biochemical signals of PTEs contamination in woody forest plantations and the urgent need to contextualize the large-scale utilization of recycled wastewater resources in such vulnerable areas.

Biofilm-based technology for industrial wastewater treatment: current technology, applications and future perspectives

The microbial community in biofilm is safeguarded from the action of toxic chemicals, antimicrobial compounds, and harsh/stressful environmental circumstances. Therefore, biofilm-based technology has nowadays become a successful alternative for treating industrial wastewater as compared to suspended growth-based technologies. In biofilm reactors, microbial cells are attached to static or free-moving materials to form a biofilm which facilitates the process of liquid and solid separation in biofilm-mediated operations. This paper aims to review the state-of-the-art of recent research on bacterial biofilm in industrial wastewater treatment including biofilm fundamentals, possible applications and problems, and factors to regulate biofilm formation. We discussed in detail the treatment efficiencies of fluidized bed biofilm reactor (FBBR), trickling filter reactor (TFR), rotating biological contactor (RBC), membrane biofilm reactor (MBfR), and moving bed biofilm reactor (MBBR) for different types of industrial wastewater treatment. Besides, biofilms have many applications in food and agriculture, biofuel and bioenergy production, power generation, and plastic degradation. Furthermore, key factors for regulating biofilm formation were also emphasized. In conclusion, industrial applications make evident that biofilm-based treatment technology is impactful for pollutant removal. Future research to address and improve the limitations of biofilm-based technology in wastewater treatment is also discussed.

Drinking water quality monitoring, assessment and management in Pakistan: A review

In this review, the importance of a robust frame work for drinking water quality monitoring, assessment and management has been discussed. This review presents the global overview of the drinking water quality, illuminating the global challenges of water supply system from catchment to consumers and briefly discussing appropriate regulatory frameworks and risk analysis tools. It also presents meticulous summaries of water reports released by the government and non-governmental organizations with special emphasis on health-based targets, proposed strategies related to preventive risk management (through water safety planning), environmental impact assessment (EIA), and independent surveillance in Pakistan. This paper reviews various studies published in national and international journals and reports, released by the government and non-governmental organizations, to provide a summary of the current knowledge with regards to the contemporary water quality management system that is still developing in the country. Role of agencies and their policies for water quality management and monitoring is one of the most important impact categories that has been covered in this review. The reviewed publications provide strong support for claims that impacts of unsafe water on health and economy of a country are very dangerous. Improved access to safe drinking water by a development-oriented strategy can have tangible improvements in socioeconomic status of a country.

Irrigation suitability, health risk assessment and source apportionment of heavy metals in surface water used for irrigation near marble industry in Malakand, Pakistan

Water is a vital, finite resource whose quantity and quality are deteriorating as the world population increases. The current study aims to investigate the concentration of heavy metals (HM) in surface water for irrigation purposes with associated human health risks and pollution sources near the marble industry in Malakand, Pakistan. Twenty-seven water samples were randomly collected and analyzed for HM concentration by inductively coupled plasma‒optical emission spectrometry (ICP‒OES). pH, electrical conductivity (EC), total dissolved solids (TDS), biological oxygen demand (BOD), and chemical oxygen demand (COD) were measured using standard methods of American Public Health Association (APHA). Irrigation suitability was assessed using specific water quality parameters. The associated health risks from ingestion and dermal exposure to heavy metals were calculated by USEPA health risk indices. Pollution sources and spatial distribution mapping were studied using compositional data analysis (CoDa) and the application of a geographic information system (GIS) to understand the changing behavior of heavy metals in surface waters. The concentrations of BOD (89%), COD (89%), Al (89%), Ca (89%), Cr (56%), Cu (78%), Fe (56%), K (34%) Mg (23%), Mn (56%), Na (89%), Ni (56%), P (89%), and Zn (11%) exceeded the safety limits of National Environmental Quality standards (NEQs) of Pakistan. The results of Kelly's ratio (KR) classified surface water as unsuitable for irrigation. The average daily doses (ADD, mg/kg/day) for Al, Cu, Cr, Fe, Mn, Ni, and Zn were higher in children than in adults. The hazard index (HI) for children and adults was above the threshold (HI > 1), indicating a significant risk of non-carcinogenic toxicity. The carcinogenic risk values for Cr and Ni were above the USEPA limit (1 × 10-6 to 1 × 10-4), suggesting a potential carcinogenic risk for the target population. Principal component analysis (PCA), biplot (CLR), and the CoDa-dendrogram allowed for the identification of elemental associations, and their potential source was anthropogenic rather than natural in origin. Regular monitoring and phytoremediation strategies are proposed to safeguard crops and human health.

Green effects of research and development on industrial waste reduction during the production phase: Evidence from China and policy implications

Maintaining public health requires a clean environment; however, some industrial wastes can damage the water, atmosphere, and living environment seriously. To promote green development, policy makers in China have developed and implemented strict environmental regulations to limit the pollutant emissions and improve the environmental quality. Industrial producers implement research and development (R&D) activities to gain more profits in competitive markets. A comprehensive understanding of the green effects of R&D on different industrial wastes could provide important policy recommendations, especially regarding the coordination of innovative and green developments. In this study, the author empirically analyzed the influence of R&D input, including the intramural expenditure on R&D and full-time equivalent of R&D personnel, on industrial wastes, including the discharge of chemical oxygen demand (COD) and ammonia nitrogen, emission of sulfur dioxide, nitrogen oxides, and particulate matter, and generation of common industrial solid and hazardous wastes, based on the data from Chinese industrial sectors for 2016-2020. The main findings of empirical analyses were robust and indicated that R&D activities significantly reduced the emissions of all three industrial waste gases and decreased the discharge of COD; however, in the case of China, the partial effects on the discharge of ammonia nitrogen and the industrial solid wastes were not statistically significant. The green effects of R&D on different industrial wastes may vary and generally depend on environmental regulations, with various limitations. The most viable policy recommendations indicate that by expanding and initiating the green effect of R&D on different industrial wastes, innovative and green developments are more likely to be achieved in a coordinated manner. Additionally, this can also support special R&D activities, with the added benefit of actively developing cleaner technology to treat pollutant emissions. Development, while maintaining a clean environment to ensure public health, could be more sustainable if innovative activities reduce the production of industrial wastes. This study analyzes the green effects of R&D on industrial waste and can serve as a viable framework for future studies on sustainable development.

Bioassay-based identification and removal of target and suspect toxicants in municipal wastewater: Impacts of chemical properties and transformation

Municipal wastewater contains numerous chemicals and transformation products with highly diverse physiochemical properties and intrinsic toxicity; thus, it is imperative but challenging to identify major toxicants. Herein, toxicity identification evaluation (TIE) was applied to identify major toxicants in a typical municipal wastewater treatment plant (WWTP). Impacts of chemical properties on the removal of contaminants and toxicity at individual treatment stages were also examined. The WWTP influent caused 100% death of Daphnia magna and zebrafish embryos, and toxicity characterization suggested that organics, metals, and volatiles all contributed to the toxicity. Toxicity identification based on 189 target and approximately one-thousand suspect chemicals showed that toxicity contributions of organic contaminants, metals, and ammonia to D. magna were 77%, 4%, and 19%, respectively. Galaxolide, pyrene, phenanthrene, benzo[a]anthracene, fluoranthene, octinoxate, silver, and ammonia were identified as potential toxicants. Comparatively, the detected transformation products elicited lower toxicity than their respective parent contaminants. In contrast, the analyzed contaminants showed negligible contributions to the toxicity of zebrafish embryos. Removal efficiencies of these toxicants in WWTP were highly related to their hydrophobicity. Diverse transformation and removal efficiencies of contaminants in WWTPs may influence the chemical compositions in effluent and ultimately the risk to aquatic organisms in the receiving waterways.

Making Pb Adsorption-Saturated Attapulgite with Excellent Photocatalysis Properties through a Vulcanization Reaction and Its Application for MB Wastewater Degradation

Attapulgite (AT) is a clay mineral with rich reserves in China, and it has good adsorption activity for Pb-containing wastewater. However, as a hazardous waste, the treatment of Pb adsorption-saturated attapulgite was quite difficult. In this work, through a simple vulcanization reaction, the waste Pb adsorption-saturated attapulgite (AT@Pb) was transformed into composite materials (AT@PbS) with good photocatalytic performance. After comprehensive material characterization (including XRD, TEM, XPS, and UV-Vis), the photocatalytic degradation performance and mechanism of AT@PbS for methylene blue (MB) were investigated. The results revealed that AT@PbS was a composite material of attapulgite nanorods (500-600 nm) and nanosquare PbS particles (80-100 nm). Additionally, AT@PbS displayed good visible light absorption, improved photo-electric properties, excellent photodegradation performance for MB, and recycling stability. Moreover, the energy band range of AT@PbS was about -0.043 V to 1.367 V. The photo-generated holes and their derived hydroxyl radicals were the main active species for MB degradation. This work not only provides a new approach to construct the composite photocatalyst, but also demonstrates the possibility of the comprehensive utilization of heavy metal adsorbents for wastewater degradation.

Characterization of drinking groundwater quality in rural areas of Inner Mongolia and assessment of human health risks

Groundwater is an important natural resource of drinking water in rural areas in Inner Mongolia, China. In this study, 4438 drinking groundwater samples were collected from the rural areas of 81 counties in Inner Mongolia, and were analyzed for 16 parameters, including pH, total hardness (TH), chemical oxygen demand (COD), total dissolved solids (TDS), sulfate (SO42-), chloride (Cl-), fluoride (F-), iron (Fe), manganese (Mn), arsenic (As), cadmium (Cd), hexavalent chromium (Cr), lead (Pb), aluminum (Al), cuprum (Cu), zinc (Zn). The groundwater quality was evaluated with water quality index (WQI) and human health risk assessment (HRA). Monte Carlo simulation were applied for the uncertainty and sensitivity analysis in the health risk assessment. The spatial map was employed based on the inverse distance weighted (IDW) interpolation technique. The results reveal that while the hazard quotient (HQ) suggests that the risk of single element contamination is feeble, the hazard index (HI) indicates a potential health risk for the local population. The observed cumulative carcinogenic risk (CCR) indicates a probable risks of carcinogenic health hazards in the study area. The sensitivity analysis revealed that daily ingestion rate (IR), exposure frequency (EF), and the concentrations of As, Mn, F-, and Cr are the most influential parameters for health hazards. The highly polluted areas are mainly distributed in the central and western regions of Inner Mongolia, including Xianghuangqi, New Barag Zuoqi, and Togtoh. It is observed that the groundwater may cause a potential health risk after long-term ingestion. The results of this study will contribute to groundwater management and protection in Inner Mongolia.

CTAB-modified carboxymethyl cellulose/bagasse cryogels for the efficient removal of bisphenol A, methylene blue and Cr(VI) ions: Batch and column adsorption studies

The simultaneous removal of organic and inorganic pollutants from water requires multifunctional adsorbents. Cryogels of carboxymethyl cellulose (CMC) and sugarcane bagasse (BG) were modified with cetyltrimethylammonium bromide (CTAB) micelles for the adsorption of methylene blue (MB), Cr(VI) ions and bisphenol A (BPA) separately, in binary or ternary aqueous mixtures. Batch adsorption studies of MB and Cr(VI) and BPA on the CMCBG-CTAB adsorbents indicated removal capacities of 100%, 70% and 95%, respectively. MB adsorbed as multilayers on the CMCBG walls by electrostatic interaction, whereas Cr(VI) and BPA adsorbed on the cationic CTAB micelles surface and hydrophobic core of CTAB micelles, respectively. The breakthrough curves obtained for pure adsorbates and their mixtures showed that the adsorption of Cr(VI) ions increased (i) ~ 3.5 times in binary mixture with BPA or in the ternary mixture, in comparison to pure Cr(VI) solution, and (ii) 1.4 times in binary mixture with MB molecules, due to synergistic effects. In the presence of Cr(VI) ions in binary or ternary mixtures, the adsorption of MB was dramatically reduced due to screening effects. The adsorption of BPA was not significantly affected by the presence of MB or Cr(VI). The adsorbents were recycled five times without significant efficiency loss.

Machine Learning Approach to Predict Quality Parameters for Bacterial Consortium-Treated Hospital Wastewater and Phytotoxicity Assessment on Radish, Cauliflower, Hot Pepper, Rice and Wheat Crops

Raw hospital wastewater is a source of excessive heavy metals and pharmaceutical pollutants. In water-stressed countries such as Pakistan, the practice of unsafe reuse by local farmers for crop irrigation is of major concern. In our previous work, we developed a low-cost bacterial consortium wastewater treatment method. Here, in a two-part study, we first aimed to find what physico-chemical parameters were the most important for differentiating consortium-treated and untreated wastewater for its safe reuse. This was achieved using a Kruskal–Wallis test on a suite of physico-chemical measurements to find those parameters which were differentially abundant between consortium-treated and untreated wastewater. The differentially abundant parameters were then input to a Random Forest classifier. The classifier showed that ‘turbidity’ was the most influential parameter for predicting biotreatment. In the second part of our study, we wanted to know if the consortium-treated wastewater was safe for crop irrigation. We therefore carried out a plant growth experiment using a range of popular crop plants in Pakistan (Radish, Cauliflower, Hot pepper, Rice and Wheat), which were grown using irrigation from consortium-treated and untreated hospital wastewater at a range of dilutions (turbidity levels) and performed a phytotoxicity assessment. Our results showed an increasing trend in germination indices and a decreasing one in phytotoxicity indices in plants after irrigation with consortium-treated hospital wastewater (at each dilution/turbidity measure). The comparative study of growth between plants showed the following trend: Cauliflower > Radish > Wheat > Rice > Hot pepper. Cauliflower was the most adaptive plant (PI: −0.28, −0.13, −0.16, −0.06) for the treated hospital wastewater, while hot pepper was susceptible for reuse; hence, we conclude that bacterial consortium-treated hospital wastewater is safe for reuse for the irrigation of cauliflower, radish, wheat and rice. We further conclude that turbidity is the most influential parameter for predicting bio-treatment efficiency prior to water reuse. This method, therefore, could represent a low-cost, low-tech and safe means for farmers to grow crops in water stressed areas.

Heavy Metals and Microbes Accumulation in Soil and Food Crops Irrigated with Wastewater and the Potential Human Health Risk: A Metadata Analysis

Wastewater is actively used for irrigation of vegetable and forage crops in arid lands due to water scarcity and cost advantages. The objective of this review was to assess the effect of wastewater (mixture sources) reuse in irrigation on soil, crop (vegetable and forage crops), animal products, and human health. The metadata analysis of 95 studies revealed that the mean of toxic heavy metals including nickel (Ni), chromium (Cr), cadmium (Cd), lead (Pb), and zinc (Zn) in untreated wastewater were higher than the world standard limits in wastewater-irrigated regions. Although heavy metals in treated wastewater were within the standard limits in those areas, the concentration of those toxic elements (Pb, Cd, Ni, Cr, and As) exceeded the allowable limits in both soil and vegetables’ edible parts. In fact, the concentration of heavy metals in vegetables’ edible parts increased by 3–9 fold when compared with those irrigated with fresh water. Escherichia coli in wastewater-irrigated soil was about 2 × 106 (CFU g−1) and about 15 (CFU g−1) in vegetables’ edible parts (leaf, bulb, tuber and fruit) while the mean total coliforms was about 1.4 × 106 and 55 (CFU g−1) in soil and vegetables’ edible parts, respectively. For human health risk assessment, the estimated daily intake (EDI) and human health risk index (HRI) ranged from 0.01 to 8 (EDI and HRI > 1.0 associated with adverse health effects). Although the mean of EDI for heavy metals from wastewater-irrigated vegetables were less than 1, the HRI for Cd and Pb were above the limits for safe consumption. Overall, heavy metal levels in wastewater that used for irrigation of agricultural crops could be within the recommended levels by the world standards, but the long-term use of this reused water will contaminate soil and crops with several toxic heavy metals leading to potential carcinogenic risks to humans. Therefore, rigorous and frequent testing (wastewater, soil, and plant) is required in cultivated farms to prevent the translocation of heavy metals in the food chain.

Reliable environmental trace heavy metal analysis with potentiometric ion sensors - reality or a distant dream

Over two decades have passed since polymeric membrane ion-selective electrodes were found to exhibit sufficiently lower detection limits. This in turn brought a great promise to measure trace level concentrations of heavy metals using potentiometric ion sensors at environmental conditions. Despite great efforts, trace analysis of heavy metals using ion-selective electrodes at environmental conditions is still not commercially available. This work will predominantly concentrate on summarizing and evaluating prospects of using potentiometric ion sensors in view of environmental determination of heavy metals in on-site and on-line analysis modes. Challenges associated with development of reliable potentiometric sensors to be operational in environmental conditions will be discussed and reasoning behind unsuccessful efforts to develop potentiometric on-site and on-line environmental ion sensors will be explored. In short, it is now clear that solely lowering the detection limit of the ion-selective electrodes does not guarantee development of successful sensors that would meet the requirement of environmental matrices over long term usage. More pressing challenges of the properties and the performance of the potentiometric sensors must be addressed first before considering extending their sensitivity to low analyte concentrations. These are, in order of importance, selectivity of the ion-selective membrane to main ion followed by the membrane resistance to parallel processes, such as water ingress to the ISM, light sensitivity, change in temperature, presence of gasses in solution and pH and finally resistance of the ion-selective membrane to fouling. In the future, targeted on-site and on-line environmental sensors should be developed, addressing specific environmental conditions. Thus, ion-selective electrodes should be developed with the intention to be suitable to the operational environmental conditions, rather than looking at universal sensor design validated in the idealized and simple sample matrices.

Enhanced biodegradation of hydrophobic organic pollutants by the bacterial consortium: Impact of enzymes and biosurfactants

Hydrocarbons and their derivative compounds are recalcitrant in nature and causing adverse impacts to the environment and are classified as important pollutants. Removal of these pollutants from the atmosphere is a challenging process. Hydrophobic organic pollutants (HOPs) including crude oil, diesel, dotriacontane (C₃₂), and tetracontane (C₄₀) are subjected to the biodegradation study by using a bacterial consortium consist of Bacillus subtilis, Pseudomonas stutzeri, and Acinetobacter baumannii. The impact of pH and temperature on the biodegradation process was monitored. During the HOPs biodegradation, the impact of hydrocarbon-degrading extracellular enzymes such as alcohol dehydrogenase, alkane hydroxylase, and lipase was examined, and found average activity about 47.2, 44.3, and 51.8 μmol/mg^-1, respectively. Additionally, other enzymes such as catechol 1,2 dioxygenase and catechol 2,3 dioxygenase were found as 118 and 112 μmol/mg^-1 Enzyme as an average range in all the HOPs degradation, respectively. Also, the impact of the extracellular polymeric substance and proteins were elucidated during the biodegradation of HOPs with the average range of 116.90, 54.98 mg/L^-1 respectively. The impact of biosurfactants on the degradation of different types of HOPs is elucidated. Very slight changes in the pH were also noticed during the biodegradation study. Biodegradation efficiency was calculated as 90, 84, 76, and 72% for crude oil, diesel, C_32, and C₄₀, respectively. Changes in the major functional groups (CH, C-O-C, CO, =CH₂, CH₂, CH₃) were confirmed by FTIR analysis and intermediated metabolites were identified by GCMS analysis. The surface-active molecules along with the enzymes played a crucial role in the biodegradation process.