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Environmental Business Review | Wednesday, January 10, 2024
Emerging as eco-friendly solutions to environmental challenges, five green technologies are revolutionising remediation practices worldwide.
FREMONT, CA: Integrating innovative technologies plays a pivotal role in pursuing a more sustainable future and reshaping environmental remediation practices. Five green technologies have emerged as transformative forces in this endeavour, offering eco-friendly solutions to address pollution and restore ecosystems. Remedial technologies are numerous. However, they can be broadly divided into in-situ and ex-situ techniques.
In-situ approaches address pollution directly at the site and in the configuration of contaminated land; nevertheless, the latter requires element extraction and excavation to be treated at the surface later. Land and groundwater contamination often stems from oil spills and improper disposal of high-risk materials. It is crucial to have a comprehensive understanding of hazardous waste disposal practices to prevent contamination.
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Thermal Desorption
This method of ex-situ heat treatment uses the various melting points of materials to extract impurities from the solid soil, sludge, or filter cake matrix. It is not the same as the incineration method, which damages the soil by heating the polluted material to a dangerous temperature.
It consists of two parts: a collection chamber and a thermal desorber. The earth that has been dug out is heated inside a container. When heated, certain semi-volatile organic compounds (SVOCs) and volatile organic compounds (VOCs) become vapours. For VOC, the temperature range is 200 to 600 °F, while for SVOC, it is 600 to 1000 °F. After evaporating, these vapours gather in a gas collection chamber. Usually, additional heat treatment is used to eliminate the gathered organic vapours and turn them into water and carbon dioxide. It is possible to recycle and reuse other elements. The soil may be sent to another location for more thorough treatment if it contains substances like metals that do not evaporate.
Surfactant Enhanced Aquifer Remediation (SEAR)
Also called solubilisation and recovery entails pumping trash out of an extraction point and injecting a chemical solution throughout the contaminated zone. Several injection and extraction stations are typically utilised to cover a sizable contaminated area. The fundamental goal of the SEAR process is to remove as much contamination as possible with the least amount of chemicals while preserving hydraulic control, waste, and chemical diffusion.
The substances that are injected are known as surfactants or hydrocarbon mitigation agents. These substances significantly increase organic pollutants' (like oil's) solubility in aqueous media. They also lessen the interfacial tension (IFT), which makes it easier for two immiscible liquids to mix. The impact of a surfactant in the presence of unidentified sources of soil pollution is simulated by numerical modelling. Additionally, it shows how flooding occurs at the location under various hydrogeologic circumstances.
In-Situ Oxidation
Chemical oxidants are employed in this technique to convert dangerous pollutants into less damaging ones. Oxidants include potassium permanganate, ozone gas, hydrogen peroxide, and persulfates. It is also possible to pump ambient air or pure oxygen gas to promote the growth of aerobic microorganisms, which progressively consume organic pollutants.
A chemical reaction occurs when oxidants are pumped through the contaminated area, producing generally safe byproducts. Ozone is a potent oxidant that is rarely employed since it is found in gaseous form. Increasing the rate of oxidation is a common purpose for catalysts. For example, an iron catalyst is added with hydrogen peroxide to increase the mixture's reactivity. ISCO has the potential to generate sufficient heat to allow pollutants to evaporate and rise to the surface, making extraction of the contaminants easier.
Soil Vapor Extraction and Air Sparging
Physical treatment methods for in situ soil remediation in the vadose zone (unsaturated state) include air sparging and SVE. The mechanisms underlying these procedures, which bring contaminated vapour from below the surface for further treatment, are incompatible. SVE uses a vacuum to extract vapours from soil above the water table, whilst air is pumped during the air-sparging process to remove pollutants from groundwater and moist soil below the water table.
Nanoremediation
Nanoparticles are heralded as the technology of the future. They are extensively used in computers, medicine, and other industries. With significant testing and research conducted for wastewater treatment and sediment cleanup, nano remediation has become a popular technique for treating groundwater in recent years. Even the use of nanoparticles to eliminate toxicity from gasses is being investigated by scientists. Through direct injection or a pump-and-treat method, tiny particles are injected into the contaminated soil and groundwater nanoremediation area. Because of their huge surface area-to-volume ratio, nanoparticles are very reactive.
Through redox processes, they break down organic pollutants and can even immobilise hazardous metals like arsenic, mercury, and lead. Nano Zero-Valent Iron (nZVI) has been employed in most soil and groundwater commercial remediation field operations. Due to their tiny size, they can occupy minuscule gaps on the surface of the pollutant and stay suspended like colloids, facilitating the spread of the contaminant and enabling more cleanup.
Government and relevant authorities typically provide funding and assistance for environmental remediation. Pollution of surface soil and groundwater is a severe health danger, but the cleanup process also puts receptors (humans) at further risk. Although it is a sustainable method of revitalising high-quality natural resources, staying away from the project site while it is in progress is strongly advised.
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