The role of pH, electrodes, surfactants, and electrolytes in electrokinetic remediation of contaminated soil

Electrokinetic remediation has, in recent years, shown great potential in remediating polluted environments. The technology can efficiently remove heavy metals, chlorophenols, polychlorinated biphenyls, phenols, trichloroethane, benzene, toluene, ethylbenzene, and xylene (BTEX) compounds and entire petroleum hydrocarbons. Electrokinetic remediation makes use of electrolysis, electroosmosis, electrophoresis, diffusion, and electromigration as the five fundamental processes in achieving decontamination of polluted environments. These five processes depend on pH swings, voltage, electrodes, and electrolytes used in the electrochemical system. To apply this technology at the field scale, it is necessary to pursue the design of effective processes with low environmental impact to meet global sustainability standards. It is, therefore, imperative to understand the roles of the fundamental processes and their interactions in achieving effective and sustainable electrokinetic remediation in order to identify cleaner alternative solutions. This paper presents an overview of different processes involved in electrokinetic remediation with a focus on the effect of pH, electrodes, surfactants, and electrolytes that are applied in the remediation of contaminated soil and how these can be combined with cleaner technologies or alternative additives to achieve sustainable electrokinetic remediation. The electrokinetic phenomenon is described, followed by an evaluation of the impact of pH, surfactants, voltage, electrodes, and electrolytes in achieving effective and sustainable remediation.The University of Pretoria, Sedibeng Water Chair in Water Utilisation Engineering, RandWater Chair in Water Utilisation and National Research Foundation.https://www.mdpi.com/journal/moleculesam2023Chemical Engineerin

Biosurfactant facilitated emulsification and electro-osmotic recovery of oil from petrochemical contaminated soil

Petroleum industries are burdened with the problem of handling petroleum products, petroleum waste products and refinery byproducts such as large quantities of oil waste. Improper management of these products and their wastes present an environment hazard when they end up in the atmosphere, water and land due to their hazardous constituents. An evaluation to determine the possibility of enhancing the electrokinetic process by application of a biosurfactant producing strain for remediation of petroleum contaminated soil through oil recovery and hydrocarbon degradation was studied at a bench scale. A DC powered electrokinetic reactor consisting of electrode/electrolyte compartments and a medium chamber was used under voltage variations of 10 V and 30 V with an electrode spacing of 185 mm. Biosurfactant with its producing microbes and biosurfactant free cells were introduced in the soil chamber after which the reactor was left to run for 10 days under the electric field. The technology was able to achieve the highest oil recovery of 75.15 % from the soil in 96 hours at 30 V. The microorganisms were able to survive under the electric field there by leading to further reduction of the carbon content in the reactor.The National Research Foundationhttp://www.aidic.it/cetam2020Chemical Engineerin

Evaluation of the toxicity of a rhamnolipid biosurfactant for its application in the optimization of the bio-electrokinetic remediation of petrochemical contaminated soil

The combination of bioremediation, biosurfactants and electrokinetic remediation as a hybrid system was evaluated for the possibility of enhancing the removal of petrochemical hydrocarbons from contaminated soil as a sustainable and effective replacement for ineffective conventional remediation methods in an optimized manner. To begin with, the toxicity of the biosurfactant was determined by examining the effect of the biosurfactant on plant growth and microbial growth. The independent effect of biosurfactant concentration, voltage, the distance between electrodes and multifactor interactions on the bio-electrokinetic remediation of petrochemical contaminated soil using a bench-scale electrokinetic system were then evaluated. The results revealed that the rhamnolipid biosurfactant did not have any observable inhibition effects on the growth of the test bacteria in 5 days since the growth under test solutions of 0 mg/L, 10 mg/L, 50 mg/L and 100 mg/L did not have any significant differences. On the other hand, the biosurfactant affected root elongation and germination of the three test vegetables. Still, SDS had more substantial adverse effects represented by extremely low values of germination index as compared to the biosurfactant. The bio-electrokinetic remediation of soil revealed that a combination of the highest voltage of 30 V, the lowest electrode spacing of 185 mm and the highest biosurfactant concentration of 84 g/L had the highest microbial growth of 11.52 CFU/mL and hydrocarbon removal of 92% as compared to other configuration combinations. Microbial growth and hydrocarbon removal were mainly affected by voltage and biosurfactant concentration as the independent variables.https://www.sciencedirect.com/journal/cleaner-engineering-and-technologyhj2023Chemical Engineerin

Effect of varying current on Pseudomonas aeruginosa degradation of naphthalene

Polycyclic aromatic hydrocarbons are recognized as pollutants with carcinogenic, teratogenic, and mutagenic properties. Polycyclic aromatic hydrocarbons have therefore become priority pollutants that have attracted researchers' attention to developing remediation strategies. Numerous approaches, including physical, chemical, and biological strategies have been employed. But most of the techniques are associated with complexity issues, high cost and lack of scientific acceptance. Bioremediation making use of bacteria and fungi has also been researched extensively because of its cost effectiveness and environmental compatibility. But bioremediation of polycyclic aromatic hydrocarbons is associated with inefficiencies related to slow processes because of the recalcitrant, hydrophobic, and lipophilic properties of petroleum hydrocarbons. In this research, the possibility of enhancing the removal of naphthalene from contaminated water by the application of current was studied. The current of 1 A and 2 A was applied in an electrochemical cell inoculated with Pseudomonas aeruginosa. Total carbon removal was 87.33 %, 90.14 % and 80 % for 1 A, 2 A and when only biodegradation (0 A) was used respectively. The results showed that the application of current can enhance the degradation of naphthalene if the electrolytic current is not too high to affect cell membranes of the bacteria.http://www.aidic.it/cetam2023Chemical Engineerin

Feasibility study of atmospheric water harvesting augmented through evaporative cooling

The water harvesting potential of atmospheric water generators (AWGs) in high-altitude semiarid regions can be diminutive relative to the water generation capacity. Operational parameters for the dehumidification process can be augmented to increase atmospheric water in the defined zone available for harvesting. In this paper, the feasibility of augmenting the microclimates of AWGs at the point of air extraction through an evaporative cooling system (ECS) was investigated. Water yield and capacity utilisation were measured from two AWGs piloted on a plant in Ga-Rankuwa, South Africa. This was implemented between December 2019 and May 2021. The study revealed that although the ECS did impact the operating parameters through decreasing temperature and increasing relative humidity (p 0.05). Capacity utilisation of the AWGs remained below 50% after augmentation. Cooling efficiency of the ECS ranged between 1.4–74.5%. Energy expenditures of 0.926 kWh/L and 0.576 kWh/L for AWGs 1 and 2 were required under pristine conditions, respectively. Under the modified conditions, energy expenditure decreased to 0.855 kWh/L for AWG 1, but increased/L to 0.676 kWh for AWG 2. ECS is deduced to not be a feasible intervention for augmenting water harvesting potential for AWGs in this semiarid zone.The University of Pretoria and the Sedibeng Water in Water Utilisation Engineering.https://www.mdpi.com/journal/wateram2023BiochemistryChemical EngineeringGeneticsMicrobiology and Plant Patholog

Practical considerations for a TB controlled human infection model (TB-CHIM); the case for TB-CHIM in Africa, a systematic review of the literature and report of 2 workshop discussions in UK and Malawi

Background: Tuberculosis (TB) remains a major challenge in many domains including diagnosis, pathogenesis, prevention, treatment, drug resistance and long-term protection of the public health by vaccination. A controlled human infection model (CHIM) could potentially facilitate breakthroughs in each of these domains but has so far been considered impossible owing to technical and safety concerns. Methods: A systematic review of mycobacterial human challenge studies was carried out to evaluate progress to date, best possible ways forward and challenges to be overcome. We searched MEDLINE (1946 to current) and CINAHL (1984 to current) databases; and Google Scholar to search citations in selected manuscripts. The final search was conducted 3rd February 2022. Inclusion criteria: adults ≥18 years old; administration of live mycobacteria; and interventional trials or cohort studies with immune and/or microbiological endpoints. Exclusion criteria: animal studies; studies with no primary data; no administration of live mycobacteria; retrospective cohort studies; case-series; and case-reports. Relevant tools (Cochrane Collaboration for RCTs and Newcastle-Ottawa Scale for non-randomised studies) were used to assess risk of bias and present a narrative synthesis of our findings. Results: The search identified 1,388 titles for review; of these 90 were reviewed for inclusion; and 27 were included. Of these, 15 were randomised controlled trials and 12 were prospective cohort studies. We focussed on administration route, challenge agent and dose administered for data extraction. Overall, BCG studies including fluorescent BCG show the most immediate utility, and genetically modified Mycobacteria tuberculosis is the most tantalising prospect of discovery breakthrough. Conclusions: The TB-CHIM development group met in 2019 and 2022 to consider the results of the systematic review, to hear presentations from many of the senior authors whose work had been reviewed and to consider best ways forward. This paper reports both the systematic review and the deliberations

Underpinning Sustainable Vector Control through Informed Insecticide Resistance Management

Background: There has been rapid scale-up of malaria vector control in the last ten years. Both of the primary control strategies, long-lasting pyrethroid treated nets and indoor residual spraying, rely on the use of a limited number of insecticides. Insecticide resistance, as measured by bioassay, has rapidly increased in prevalence and has come to the forefront as an issue that needs to be addressed to maintain the sustainability of malaria control and the drive to elimination. Zambia’s programme reported high levels of resistance to the insecticides it used in 2010, and, as a result, increased its investment in resistance monitoring to support informed resistance management decisions. Methodology/Principal Findings: A country-wide survey on insecticide resistance in Zambian malaria vectors was performed using WHO bioassays to detect resistant phenotypes. Molecular techniques were used to detect target-site mutations and microarray to detect metabolic resistance mechanisms. Anopheles gambiae s.s. was resistant to pyrethroids,DDT and carbamates, with potential organophosphate resistance in one population. The resistant phenotypes were conferred by both target-site and metabolic mechanisms. Anopheles funestus s.s. was largely resistant to pyrethroids and carbamates, with potential resistance to DDT in two locations. The resistant phenotypes were conferred by elevated levels of cytochrome p450s. Conclusions/Significance: Currently, the Zambia National Malaria Control Centre is using these results to inform their vector control strategy. The methods employed here can serve as a template to all malaria-endemic countries striving to create a sustainable insecticide resistance management pla

May Measurement Month 2018: a pragmatic global screening campaign to raise awareness of blood pressure by the International Society of Hypertension

Aims Raised blood pressure (BP) is the biggest contributor to mortality and disease burden worldwide and fewer than half of those with hypertension are aware of it. May Measurement Month (MMM) is a global campaign set up in 2017, to raise awareness of high BP and as a pragmatic solution to a lack of formal screening worldwide. The 2018 campaign was expanded, aiming to include more participants and countries. Methods and results Eighty-nine countries participated in MMM 2018. Volunteers (≥18 years) were recruited through opportunistic sampling at a variety of screening sites. Each participant had three BP measurements and completed a questionnaire on demographic, lifestyle, and environmental factors. Hypertension was defined as a systolic BP ≥140 mmHg or diastolic BP ≥90 mmHg, or taking antihypertensive medication. In total, 74.9% of screenees provided three BP readings. Multiple imputation using chained equations was used to impute missing readings. 1 504 963 individuals (mean age 45.3 years; 52.4% female) were screened. After multiple imputation, 502 079 (33.4%) individuals had hypertension, of whom 59.5% were aware of their diagnosis and 55.3% were taking antihypertensive medication. Of those on medication, 60.0% were controlled and of all hypertensives, 33.2% were controlled. We detected 224 285 individuals with untreated hypertension and 111 214 individuals with inadequately treated (systolic BP ≥ 140 mmHg or diastolic BP ≥ 90 mmHg) hypertension. Conclusion May Measurement Month expanded significantly compared with 2017, including more participants in more countries. The campaign identified over 335 000 adults with untreated or inadequately treated hypertension. In the absence of systematic screening programmes, MMM was effective at raising awareness at least among these individuals at risk

Approaching electrodes configurations in bio-electrokinetic deoiling of petrochemical contaminated soil

The expeditious growth of the petroleum industry and its products in the last three decades has led to increased pollution of soil which is of great concern considering the effects it poses to the environment. Oil waste usually considered as hazardous due to its composition presents the same problems as other petroleum-based products to the environment. An electrokinetic reactor with an inoculum of biosurfactant producing bacteria was studied at a bench scale with different electrode spacing configurations. A DC powered electrokinetic reactor consisting of electrode/electrolyte compartments, and a matrix chamber was operated under a constant voltage of 30 V with configurations of fixed electrodes spacing’s of 335 mm, 260 mm,185 mm and continuous approaching electrodes at 335 mm, 260 mm and 185 mm. The biosurfactant producing microbes and cell-free biosurfactant were introduced in the matrix chamber after which the reactor was left to run for 10 days under the electric field. The electroosmotic flow, electrical current, pH and biodegradation of the hydrocarbons in the soil were observed and assessed. The current in the reactor was highest with the least electrode distance of 185 mm. The increase in current led to a directly proportional increase in the electroosmotic flow towards the cathode leading to the increased coalescence of the oil from the soil as compared to the other electrode distances. The analysis of the results showed a reduction in the total carbon content in the soil with viable oil recovery rates for all the electrode distances with 185 mm being the most effective. The viable cell counts in the reactor showed significant growth of the bacteria in the first 6 days under the applied voltage of 30 V enabling the biodegradation of the petrochemical pollutants by the strain for all the four different electrode configurations.The National Research Foundation (NRF_DST).http://www.aidic.it/cetam2020Chemical Engineerin

Application of biosurfactants and pulsating electrode configurations as potential enhancers for electrokinetic remediation of petrochemical contaminated soil

The remediation of soil contaminated with petrochemicals using conventional methods is very di cult because of the complex emulsions formed by solids, oil, and water. Electrokinetic remediation has of recent shown promising potential in the removal of organics from contaminated media as calls for further improvement of the technology are still made. This work investigated the performance of electrokinetic remediation of soil contaminated with petrochemicals by applying fixed electrode configurations and continuous approaching electrode configurations. This was done in combination with bioremediation by inoculating hydrocarbon degrading bacteria and biosurfactants with the aim of obtaining an improved method of remediation. The results obtained show that the biosurfactant produced by the hydrocarbon degrading bacteria Pseudomonas aeruginosa was able to enhance oil extraction to 74.72 2.87%, 57.375 3.75%, and 46.2 4.39% for 185 mm fixed electrodes, 335-260-185 mm continuous approaching electrodes, and 335 mm fixed electrode configurations, respectively. By maintaining high current flow, the 335-260-185mmcontinuous approaching electrodes configuration enhanced electroosmotic flow (EOF) on every event of electrodes movement. The fixed electrode configuration of 185 mm provided amiable pH conditions for bacterial growth by allowing quick neutrality of the pH due to high EOF as compared to the 335 mm fixed electrodes configuration. After 240 h, the carbon content in the soil was reduced from 0.428 0.11 mg of carbon/mg of the soil to 0.103 0.005, 0.11355 0.0006, and 0.1309 0.004 for 185 mm, 335-260-185 mm, and 335 mm, respectively. The application of biosurfactants and continuous approaching electrodes reduced the energy expenditure of electrokinetic remediation by enhancing the decontamination process with respect to time.Rand Water and the National Research Foundation (NRF) of South Africhttp://www.mdpi.com/journal/sustainabilityam2021Chemical Engineerin