Emerging organic contaminants in the soil-plant-receptor continuum: transport, fate, health risks, and removal mechanisms.

There is a lack of comprehensive reviews tracking emerging organic contaminants (EOCs) within the soil-plant continuum using the source-pathway-receptor-impact-mitigation (SPRIM) framework. Therefore, this review examines existing literature to gain insights into the occurrence, behaviour, fate, health hazards, and strategies for mitigating EOCs within the soil-plant system. EOCs identified in the soil-plant system encompass endocrine-disrupting chemicals, surfactants, pharmaceuticals, personal care products, plasticizers, gasoline additives, flame retardants, and per- and poly-fluoroalkyl substances (PFAS). Sources of EOCs in the soil-plant system include the land application of biosolids, wastewater, and solid wastes rich in EOCs. However, less-studied sources encompass plastics and atmospheric deposition. EOCs are transported from their sources to the soil-plant system and other receptors through human activities, wind-driven processes, and hydrological pathways. The behaviour, persistence, and fate of EOCs within the soil-plant system are discussed, including sorption, degradation, phase partitioning, (bio)transformation, biouptake, translocation, and bioaccumulation in plants. Factors governing the behaviour, persistence, and fate of EOCs in the soil-plant system include pH, redox potential, texture, temperature, and soil organic matter content. The review also discusses the environmental receptors of EOCs, including their exchange with other environmental compartments (aquatic and atmospheric), and interactions with soil organisms. The ecological health risks, human exposure via inhalation of particulate matter and consumption of contaminated food, and hazards associated with various EOCs in the soil-plant system are discussed. Various mitigation measures including removal technologies of EOCs in the soil are discussed. Finally, future research directions are presented.

Detection and Quantification of Bisphenol A in Surface Water Using Absorbance-Transmittance and Fluorescence Excitation-Emission Matrices (A-TEEM) Coupled with Multiway Techniques.

In the present protocol, we determined the presence and concentrations of bisphenol A (BPA) spiked in surface water samples using EEM fluorescence spectroscopy in conjunction with modelling using partial least squares (PLS) and parallel factor (PARAFAC). PARAFAC modelling of the EEM fluorescence data obtained from surface water samples contaminated with BPA unraveled four fluorophores including BPA. The best outcomes were obtained for BPA concentration (R2 = 0.996; standard deviation to prediction error's root mean square ratio (RPD) = 3.41; and a Pearson's r value of 0.998). With these values of R2 and Pearson's r, the PLS model showed a strong correlation between the predicted and measured BPA concentrations. The detection and quantification limits of the method were 3.512 and 11.708 micro molar (µM), respectively. In conclusion, BPA can be precisely detected and its concentration in surface water predicted using the PARAFAC and PLS models developed in this study and fluorescence EEM data collected from BPA-contaminated water. It is necessary to spatially relate surface water contamination data with other datasets in order to connect drinking water quality issues with health, environmental restoration, and environmental justice concerns.

A clay-coal fly ash based dual hydraulic-reactive liner for controlling acid mine drainage.

Hydraulic liners are used to restrict hazardous leachates such as acid mine drainage (AMD) from entering the hydrogeological system. In this study, we hypothesized that: (1) a compacted mix ratio of natural clay and coal fly ash with a hydraulic conductivity of at most 1 × 10- 8 ms- 1 can be achieved, and (2) mixing clay and coal fly ash in the right proportion can result in increased contaminant removal efficiency of a liner system. The effects of adding coal fly ash to clay on the mechanical behavior, contaminant removal efficiency, and saturated hydraulic conductivity of the liner were investigated. All clay:coal fly ash specimen liners with less than 30% coal fly ash had significantly (p < 0.05) lower cohesion stress values, and were discarded without further tests. Saturated hydraulic conductivity values showed no significant effect (p > 0.05) on the results of clay:coal fly ash (7:3) specimen liners and compacted clay liner. The clay:coal fly ash mix ratios of 8:2 and 7:3 significantly (p < 0.05) reduced the leachate concentration of Cu, Ni, and Mn. The pH of AMD increased from an average of 2.14 to 6.80 after permeating through a compacted specimen of mix ratio 7:3. Overall, the 7:3 clay to coal fly ash liner showed superior pollutant removal capacity and its mechanical and hydraulic properties were comparable to compacted clay liners. This laboratory scale investigation emphasizes potential limitations with column scale evaluation of liners and provides new information on the application of dual hydraulic reactive liners for engineered hazardous waste disposal systems.

Modeling the antifouling properties of atomic layer deposition surface-modified ceramic nanofiltration membranes.

This work investigates the enhancement of antifouling properties of ceramic nanofiltration membranes by surface modification via atomic layer deposition (ALD) of TiO2. Feed solutions containing bovine serum albumin (BSA), humic acid (HA) and sodium alginate (SA) were used as model foulants. The classic fouling mechanism models and the modified fouling indices (MFI) were deduced from the flux decline profiles. Surface roughness values of the ALD coated and uncoated membranes were 63 and 71 nm, respectively, while the contact angles were 34.2 and 59.5°, respectively. Thus, coating increased the water affinity of the membrane surfaces and consequently improved the anti-fouling properties. The MFI values and the classic fouling mechanism correlation coefficients for cake filtration for the ALD coated and the uncoated membrane upon SA fouling were 42,963 (R2 = 0.82) and 143,365 sL-2 (R2 = 0.98), respectively, whereas the correlation coefficients for the combined foulants (SA + BSA + HA) were 267,185 (R2 = 0.99) and 9569 sL-2 (R2 = 0.37), respectively. The study showed that ALD can effectively enhance the antifouling properties of ceramic membranes.

Occurrence, behavior, and human exposure and health risks of potentially toxic elements in edible mushrooms with focus on Africa.

Understanding the occurrence, behavior, and fate of potentially toxic elements (PTEs) in the substrate-mushroom-human nexus is critical for assessing and mitigating their human health risks. In this review, we (1) summarized the nature, sources, and biogeochemical behavior of PTEs in the substrate-mushroom systems; (2) discussed the occurrence, exposure, and human health risks of PTEs in mushrooms with emphasis on African geological hotspots such as metalliferous and highly mineralized substrates; (3) developed a 10-step conceptual framework for identifying, assessing, and mitigating the human health risks of PTEs in mushrooms, and highlight future directions. High human exposure risks potentially exist in Africa due to the following: (1) widespread consumption of mushrooms from various metalliferrous and highly mineralized substrates such as serpentines and mine waste dumps, (2) inadequate and poorly enforced environmental health and food safety regulations and policies, (3) limited environmental and human health monitoring data, and (4) potential synergistic interactions among PTEs in mushrooms and human health stressors such as a high burden of human diseases and infections. Although the human health effects of individual PTEs are well known, scientific evidence linking human health risk to PTEs in mushrooms remains weak. A framework for risk assessment and mitigation, and future research directions are recommended.

PARAFAC model as an innovative tool for monitoring natural organic matter removal in water treatment plants.

The increase of fluorescent natural organic matter (fNOM) fractions during drinking water treatment might lead to an increased coagulant dose and filter clogging, and can be a precursor for disinfection by-products. Consequently, efficient fNOM removal is essential, for which characterisation of fNOM fractions is crucial. This study aims to develop a robust monitoring tool for assessing fNOM fractions across water treatment processes. To achieve this, water samples were collected from six South African water treatment plants (WTPs) during winter and summer, and two plants in Belgium during spring. The removal of fNOM was monitored by assessing fluorescence excitation-emission matrices datasets using parallel factor analysis. The removal of fNOM during summer for South African WTPs was in the range 69-85%, and decreased to 42-64% in winter. In Belgian WTPs, fNOM removal was in the range 74-78%. Principal component analysis revealed a positive correlation between total fluorescence and total organic carbon (TOC). However, TOC had an insignificant contribution to the factors affecting fNOM removal. Overall, the study demonstrated the appearance of fNOM in the final chlorinated water, indicating that fNOM requires a customised monitoring technique.

Fundamental fouling mechanisms of dissolved organic matter fractions and their implications on the surface modifications of ceramic nanofiltration membranes: insights from a laboratory scale application.

This work reports on the fundamental factors influencing inter-foulant and foulant-membrane interactions during simulated dissolved organic matter removal using ceramic nanofiltration. Fouling tests were performed using sodium alginate (SAL), humic acid (HA) and bovine serum albumin (BSA) as model foulants. Fouling potentials of each foulant and their mixtures were investigated using feed solutions containing fixed concentrations of K+, Na+, Mg2+ and Ca2+ with a total ionic strength of 10 mM. The impact of modification by atomic layer deposition on fouling mitigation was also assessed. The flux decline in the first 100 min for single foulants was 4.16 × 10-2, 2.69 × 10-2 and 1.60 × 10-2 Lm-2 for SAL, HA and BSA, respectively. These results demonstrated that for the single foulants, deposition on the membrane surface in the early stages of filtration was primarily governed by membrane-foulant interactions. Interestingly, cake filtration was the least fouling mechanism in feed solutions composed of BSA and SAL (R2 = 0.519, 0.374 for BSA + SAL and BSA + SAL + HA, respectively) and the most favorable fouling mechanism of feed solution which included HA and SAL (R2 = 0.972). The water contact angle dropped from 58o to 35° after coating, thus improving its anti-fouling properties.

Biochar-based water treatment systems as a potential low-cost and sustainable technology for clean water provision.

Approximately 600 million people lack access to safe drinking water, hence achieving Sustainable Development Goal 6 (Ensure availability and sustainable management of water and sanitation for all by 2030) calls for rapid translation of recent research into practical and frugal solutions within the remaining 13 years. Biochars, with excellent capacity to remove several contaminants from aqueous solutions, constitute an untapped technology for drinking water treatment. Biochar water treatment has several potential merits compared to existing low-cost methods (i.e., sand filtration, boiling, solar disinfection, chlorination): (1) biochar is a low-cost and renewable adsorbent made using readily available biomaterials and skills, making it appropriate for low-income communities; (2) existing methods predominantly remove pathogens, but biochars remove chemical, biological and physical contaminants; (3) biochars maintain organoleptic properties of water, while existing methods generate carcinogenic by-products (e.g., chlorination) and/or increase concentrations of chemical contaminants (e.g., boiling). Biochars have co-benefits including provision of clean energy for household heating and cooking, and soil application of spent biochar improves soil quality and crop yields. Integrating biochar into the water and sanitation system transforms linear material flows into looped material cycles, consistent with terra preta sanitation. Lack of design information on biochar water treatment, and environmental and public health risks constrain the biochar technology. Seven hypotheses for future research are highlighted under three themes: (1) design and optimization of biochar water treatment; (2) ecotoxicology and human health risks associated with contaminant transfer along the biochar-soil-food-human pathway, and (3) life cycle analyses of carbon and energy footprints of biochar water treatment systems.

Conversion of post consumer waste polystyrene into a high value adsorbent and its sorptive properties for Congo Red removal from aqueous solution.

Using post-consumer waste polystyrene (WPS), a conjugated microporous polymer (CMP) was synthesised and activated into a sulphonic-group carrying resin (SCMP). The surface chemistry of the materials showed a decline in both the aromatic CH and aliphatic CH2 stretching vibrations confirming successful crosslinking. The synthesised polymers were thermally stable with decomposition temperatures above 300 °C, had surface heterogeneity, and BET surface areas of 752 and 510 m2/g, respectively. A distribution of pores ranging from meso- to micro-pores was comparable to other CMPs. The materials had maximum adsorption capacities of 500 and 357 mg/g for Congo Red (CR) on CMP and SCMP, respectively. Converting waste polystyrene to an adsorbent is a cost effective way of handling waste and simultaneously providing material for wastewater remediation.

Biochar production and applications in sub-Saharan Africa: opportunities, constraints, risks and uncertainties.

Sub-Saharan Africa (SSA) experiences soil degradation, food and livelihood insecurity, environmental pollution and lack of access to energy. Biochar has gained international research attention, but few studies have investigated the potential of biochar to address the challenges in SSA. This paper seeks to identify and evaluate generic potential opportunities and constraints associated with biochar application in sub-Saharan Africa using Zimbabwe as case study. Specific objectives were to; (1) identify and quantify feedstocks for biochar production; (2) review literature on the biochar properties, and evaluate its potential applications in agriculture, environmental remediation and energy provision, and (3) identify research gaps, risks and constraints associated with biochar technology. Biochar feedstocks in Zimbabwe were estimated to be 9.9 Mton yr(-1), predominantly derived from manure (88%) and firewood (10%). This will yield 3.5, 1.7 and 3.1 Mton yr(-1) of biochar, bio-oil and synthetic gas, respectively. Land application of the 3.5 Mton yr(-1) of biochar (≈63% C) would sequester approximately 2.2 Mton yr(-1) of soil carbon in Zimbabwe alone, while simultaneously minimizing the environmental and public health risks, and greenhouse gas emissions associated with solid organic wastes. Biochar potentially enhances soil and crop productivity through enhanced nutrient and soil moisture availability, amelioration of acidic soils and stimulation of microbial diversity and activity. Due to its excellent adsorption properties, biochar has potential applications in industrial and environmental applications including water and wastewater treatment, remediation and revegetation of contaminated soils and water. Biochar products have energy values comparable or higher than those of traditional biomass fuels; thereby making them ideal alternative sources of energy especially for poor households without access to electricity. Before the benefits of biochar can be realized in SSA, there is need to overcome multiple risks and constraints such as lack of finance, socio-economic constraints including negative perceptions and attitudes among both researchers and consumers, and environmental and public health risks. Therefore, there is need to conduct fundamental research to demonstrate the benefits of biochar applications, and develop policy framework and criteria for its production and subsequent adoption.

Adsorption of Zn(2+) and Ni(2+) in a binary aqueous solution by biosorbents derived from sawdust and water hyacinth (Eichhornia crassipes).

The Zn(2+) and Ni(2+) adsorption capacities of six biosorbents derived from water hyacinth (Eichhornia crassipes) (WH) and sawdust (SD) were investigated, with activated carbon as the control. The biosorbents were raw biomass (WH, SD), charred WH (BWH) and SD and sulphonated bio-chars of WH and SD. The effect of the initial solution pH and Zn(2+) and Ni(2+) concentrations on adsorption capacity was studied, and adsorption isotherms for Zn(2+) and Ni(2+) evaluated. The initial solution pH significantly influenced adsorption (p < 0.05) but the relationship was generally nonlinear. Zn(2+) suppressed Ni(2+) adsorption on all biosorbents. The adsorption capacities of the biosorbents were statistically (p ≤ 0.05) similar to or higher than that of activated carbon. The effects of pyrolysis and bio-char sulphonation on adsorption were inconsistent and dependent on biomass type; in most cases bio-char was a better biosorbent than the original biomass, while sulphonation resulted in less or comparable adsorption. Adsorption data obeyed at least one of three isotherms (linear, Langmuir and Freundlich) (r(2) = 0.90-0.995, p < 0.05). The study revealed that low-cost biosorbents may be used as alternatives to activated carbon in applications including selective separation of Zn(2+) from multi-metal ion solutions containing Ni(2+), and water and wastewater treatment.

An optimised and validated surrogate analyte A-TEEM-PARAFAC-PLS technique for detecting and quantifying the biological oxygen demand in surface water.

A 5-day test duration makes BOD5 measurement unsatisfactory and hinders the development of a quick technique. Protein-like fluorescence peaks show a strong correlation between the BOD characteristics and the fluorescence intensities. For identifying and measuring BOD in surface water, a simultaneous absorbance-transmittance and fluorescence excitation-emission matrices (A-TEEM) method combined with PARAFAC (parallel factor) and PLS (partial least squares) analyses was developed using a tyrosine and tryptophan (tyr-trpt) mix as a surrogate analyte for BOD. The use of a surrogate analyte was decided upon due to lack of fluorescent BOD standards. Tyr-trpt mix standard solutions were added to surface water samples to prepare calibration and validation samples. PARAFAC analysis of excitation-emission matrices detected the tyr-trpt mix in surface water. PLS modelling demonstrated significant linearity (R2 = 0.991) between the predicted and measured tyr-trypt mix concentrations, and accuracy and robustness were all acceptable per the ICH Q2 (R2) and ASTM multivariate calibration/validation procedures guidelines. Based on a suitable and workable surrogate analyte method, these results imply that BOD can be detected and quantified using the A-TEEM-PARAFAC-PLS method. Very positive comparability between tyr-trypt mix concentrations was found, suggesting that tyr-trypt mix might eventually take the place of a BOD-based sampling protocol. Overall, this approach offers a novel tool that can be quickly applied in water treatment plant settings and is a step in supporting the trend toward rapid BOD determination in waters. Further studies should demonstrate the wide application of the method using real wastewater samples from various water treatment facilities.

The soil-microbe-plant resistome: A focus on the source-pathway-receptor continuum.

The One World, One Health concept implies that antibiotic resistance (AR) in the soil-microbe-plant resistome is intricately linked to the human resistome. However, the literature is mainly confined to sources and types of AR in soils or microbes, but comprehensive reviews tracking AR in the soil-microbe-plant resistome are limited. The present review applies the source-pathway-receptor concept to understand the sources, behaviour, and health hazards of the soil-microbe-plant resistome. The results showed that the soil-microbe-plant system harbours various antibiotic-resistance genes (ARGs), antibiotic-resistant bacteria (ARB), and mobile genetic elements (MGEs). Anthropogenic sources and drivers include soil application of solid waste, wastewater, biosolids, and industrial waste. Water-, wind-, and human-driven processes and horizontal gene transfer circulate AR in the soil-microbe-plant resistome. The AR in bulk soil, soil components that include soil microorganisms, soil meso- and macro-organisms, and possible mechanisms of AR transfer to soil components and ultimately to plants are discussed. The health risks of the soil-microbe-plant resistome are less studied, but potential impacts include (1) the transfer of AR to previously susceptible organisms and other resistomes, including the human resistome. Overall, the study tracks the behaviour and health risks of AR in the soil-plant system. Future research should focus on (1) ecological risks of AR at different levels of biological organization, (2) partitioning of AR among various phases of the soil-plant system, (3) physico-chemical parameters controlling the fate of AR, and (4) increasing research from low-income regions particularly Africa as most of the available literature is from developed countries.

Are earthworms the victim, facilitator or antidote of antibiotics and antibiotic resistance at the soil-animal-human interface? A One-Health perspective.

The transfer of antibiotics and antibiotic resistance (AR) to the soil systems poses ecological hazards to various organisms, including earthworms. Understanding the complex interactions between earthworms, antibiotics, and AR in the soil system requires a comprehensive assessment. Hence, the present review investigates the behaviour, fate, impacts, and mechanisms involved in the interaction of earthworms with antibiotics and AR. The antibiotics and AR detected in earthworms and their associated media, such as vermicompost, are presented, but several other antibiotics and AR widely detected in soils remain understudied. As receptors and bioassay organisms, earthworms are adversely affected by antibiotics and AR causing (1) acute and chronic toxicity, and (2) emergence of AR in previously susceptible earthworm gut microbiota, respectively. The paper also highlights that, apart from this toxicity, earthworms can also mitigate against antibiotics, antibiotic-resistant bacteria and antibiotic-resistance genes by reducing bacterial diversity and abundance. The behaviour and fate processes, including biodegradation pathways, biomarkers of antibiotics and AR in earthworms, are discussed. In addition, the factors controlling the behaviour and fate of antibiotics and AR and their interactions with earthworms are discussed. Overall, earthworms mitigate antibiotics and AR via various proximal and distal mechanisms, while dual but contradictory functions (i.e., mitigatory and facilitatory) were reported for AR. We recommend that future research based on the One-World-One-Health approach should address the following gaps: (1) under-studied antibiotics and AR, (2) degradation mechanisms and pathways of antibiotics, (3) effects of environmentally relevant mixtures of antibiotics, (4) bio-augmentation in earthworm-based bioremediation of antibiotics, (5) long-term fate of antibiotics and their metabolites, (6) bio-transfers of antibiotics and AR by earthworms, (7) development of earthworm biomarkers for antibiotics and AR, (8) application of earthworm-based bioremediation of antibiotics and AR, (9) cascading ecological impacts of antibiotics and AR on earthworms, and (10) pilot-scale field applications of earthworm-based bioremediation systems.

Emerging organic contaminants in drinking water systems: Human intake, emerging health risks, and future research directions.

Few earlier reviews on emerging organic contaminants (EOCs) in drinking water systems (DWS) focused on their detection, behaviour, removal and fate. Reviews on multiple exposure pathways, human intake estimates, and health risks including toxicokinetics, and toxicodynamics of EOCs in DWS are scarce. This review presents recent advances in human intake and health risks of EOCs in DWS. First, an overview of the evidence showing that DWS harbours a wide range of EOCs is presented. Multiple human exposure to EOCs occurs via ingestion of drinking water and beverages, inhalation and dermal pathways are discussed. A potential novel exposure may occur via the intravenous route in dialysis fluids. Analysis of global data on pharmaceutical pollution in rivers showed that the cumulative concentrations (µg L-1) of pharmaceuticals (mean ± standard error of the mean) were statistically more than two times significantly higher (p = 0.011) in South America (11.68 ± 5.29), Asia (9.97 ± 3.33), Africa (9.48 ± 2.81) and East Europe (8.09 ± 4.35) than in high-income regions (2.58 ± 0.48). Maximum cumulative concentrations of pharmaceuticals (µg L-1) decreased in the order; Asia (70.7) had the highest value followed by South America (68.8), Africa (51.3), East Europe (32.0) and high-income regions (17.1) had the least concentration. The corresponding human intake via ingestion of untreated river water was also significantly higher in low- and middle-income regions than in their high-income counterparts. For each region, the daily intake of pharmaceuticals was highest in infants, followed by children and then adults. A critique of the human health hazards, including toxicokinetics and toxicodynamics of EOCs is presented. Emerging health hazards of EOCs in DWS include; (1) long-term latent and intergenerational effects, (2) the interactive health effects of EOC mixtures, (3) the challenges of multifinality and equifinality, and (4) the Developmental Origins of Health and Disease hypothesis. Finally, research needs on human health hazards of EOCs in DWS are presented.

Characterization of natural organic matter in South African drinking water treatment plants: Towards integrating ceramic membrane filtration.

This work presents the first comprehensive investigation of natural organic matter (NOM) fraction removal using ceramic membranes in South Africa. The rate of removal of bulk NOM (measured as UV254 and DOC % removal), the biodegradable dissolved organic carbon (BDOC) fraction, polarity-based fractions, and fluorescent dissolved organic carbon (FDOM) fractions was investigated from water abstracted from drinking water treatment plants (WTPs) in South Africa. Further, mechanisms of ceramic membrane fouling by waters of South Africa were studied. Ceramic membranes removed more than 80% DOC from samples from coastal WTPs, whereas for inland plants, the removal was between 60% and 75% of DOC. FDOM was removed to at least 80% regardless of the site of the plant. The BDOC removal by the ceramic membranes was above 85%. The hydrophobic fraction was the most amenable to removal by ceramic membranes regardless of the site of sample abstraction (above 60% for all sites). The freshness index (ß:α) correlated strongly to UV254 removal (R2 = 0.96), thus UV254 removal can serve as a proxy for the susceptibility to removal of such class of NOM by ceramic membranes. This investigation demonstrated that ceramic membranes could be a valuable technology if integrated into the existing WTPs. PRACTITIONER POINTS: The removal of bulk parameters by ceramic membrane was greater than unit conventional processes used in all the sampled water treatment plants. The hydrophobic polarity-based fraction of NOM was the most amenable to removal by ceramic membranes regardless of the site of the WTP. Polarity-based fractions, aromaticity, and initial DOC had a combined influence on the removal of organic matter by ceramic membranes as explained by principal component three.

Regeneration of dye-saturated activated carbon through advanced oxidative processes: A review.

Activated carbon (AC) is a porous carbon-rich material that is widely used to remove pollutants, such as synthetic dyes, from contaminated water. Although quite efficient, the use of this technology is limited to the ability of the AC to be regenerated and/or reused. Conventional regeneration procedures are inefficient, requiring the development and/or implementation of new approaches. Advanced Oxidative Processes (AOP) have unique properties that result in high efficiency in wastewater treatment. The use of these technologies in the regeneration of AC has gained considerable prominence due to the ability to remove organic pollutants concentrated in the AC. During this process, the oxidizing species produced interact with the substrates adsorbed on the AC, in a non-selective way, mineralizing them and/or reducing their recalcitrance. Although widely used in wastewater treatment, few reviews focus on the use of AOP as AC regeneration technology, causing an insufficient exchange of information and ideas for strategic development in this area. Therefore, in this review, the authors present an overview of the use of some AOP (Photolysis, Peroxidation, Fenton reaction and Advanced electrochemical oxidative processes) when applied in regeneration of dye-saturated AC, including the mechanisms involved in the different processes, the general aspects that affect individual processes and the different methods established to quantify the effectiveness of regeneration.

The screening of emerging micropollutants in wastewater in Sol Plaatje Municipality, Northern Cape, South Africa.

Although pollutants pose environmental and human health risks, the majority are not routinely monitored and regulated. Organic pollutants emanate from a variety of sources, and can be classified depending on their chemistry and environmental fate. Classification of pollutants is important because it informs fate processes and apposite removal technologies. The occurrence of emerging contaminants (ECs) in water bodies is a source of environmental and human health concern globally. Despite being widely reported, data on the occurrence of ECs in South Africa are scarce. Specifically, ECS in wastewater in the Northern Cape in South Africa are understudied. In this study, various ECs were screened in water samples collected from three wastewater treatment plants (WWTPs) in the province. The ECs were detected using liquid chromatography coupled to high resolution Orbitrap mass spectrometry following Oasis HLB solid-phase extraction. The main findings were: (1) there is a wide variety of ECs in the WWTPs, (2) physico-chemical properties such as pH, total dissolved solids, conductivity, and dissolved organic content showed reduced values in the outlet compared to the inlet which confirms the presence of less contaminants in the treated wastewater, (3) specific ultraviolet absorbance of less than 2 was observed in the WWTPs samples, suggesting the presence of natural organic matter (NOM) that is predominantly non-humic in nature, (4) most of the ECs were recalcitrant to the treatment processes, (5) pesticides, recreational drugs, and analgesics constitute a significant proportion of pollutants in wastewater, and (6) NOM removal ranged between 35 and 90%. Consequently, a comprehensive database of ECs in wastewater in Sol Plaatje Municipality was created. Since the detected ECs pose ecotoxicological risks, there is a need to monitor and quantify ECs in WWTPs. These data are useful in selecting suitable monitoring and control strategies at WWTPs.

Biochars as media for air pollution control systems: Contaminant removal, applications and future research directions.

Biochars are low-cost and renewable biomaterials with several applications, including soil amendment, mitigation of greenhouse gas emissions, and removal of both inorganic and organic contaminants in aqueous systems. An increasing body of recent evidence indicates that biochars can also remove gaseous chemical contaminants, such as those occurring in industrial flue gases. However, unlike other applications such as in agroecosystems, soil amendments, and aquatic systems, comprehensive reviews on biochar applications in the field of air pollution control are still lacking. The current paper examined existing evidence to understand the nature of contaminants, particularly the gaseous ones, potential applications, constraints, and future research needs pertaining to biochar applications in air pollution control. The preparation of biochars and their functionalized derivatives, and the properties influencing their capacity to remove gaseous contaminants are summarized. The removal capacity and mechanisms of various organic and inorganic gaseous contaminants by biochars are discussed. Evidence shows that biochars effectively remove metal vapours, particularly elemental mercury (Hg0), acidic gases (H2S, SO2, CO2), ozone, nitrogen oxides (NOx), and organic contaminants including aromatic compounds, volatile organic compounds, and odorous substances. The mechanisms for the removal of gaseous contaminants, including; adsorption, precipitation, and size exclusion were presented. Potential industrial application domains include remediation of gaseous emissions from incinerators, waste-to-energy systems, kilns, biomass and coal-fired boilers/cookers, cremation, smelters, wastewater treatment, and agricultural production systems including livestock husbandry. These industrial applications, coupled with the renewable, low-cost and sustainable nature of biochars, point to opportunities to further develop and scale up the biochar technology in the air pollution control industry. However, the biochar-based air filter technology still faces several challenges, largely stemming from constraints and several knowledge gaps, which were highlighted. Hence, further research is required to address these constraints and knowledge gaps before the benefits of the biochar-based air filters are realized.