Shift in microbial group during remediation by enhanced natural attenuation (RENA) of a crude oil-impacted soil: a case study of Ikarama Community, Bayelsa, Nigeria

Optimizing nano-sized oxygen bubble application for prolonged aerobic degradation of BTEX in contaminated groundwater

This study investigates the use of nano-sized oxygen bubbles (NOBs) to enhance BTEX (benzene, toluene, ethylbenzene, xylene) biodegradation in groundwater. Optimized NOBs, averaging 155 nm and at a concentration of 6.59 × 10⁸ bubbles/mL, were found to provide sustained oxygen release with a half-life of approximately 50 days. Laboratory column experiments demonstrated that NOBs released up to 380% more oxygen than initially injected, significantly boosting BTEX degradation. The repeated injection of NOBs increased the volume of trapped bubbles within soil pores, enhancing long-term oxygen release efficiency by expanding the available gas phase within the porous matrix. NOB treatment resulted in markedly lower effluent BTEX concentrations and elevated gene expression linked to BTEX-degrading enzymes. This mechanism supports the sustainability of NOBs as an oxygen source, maintaining aerobic conditions over extended periods. Compared to traditional oxygen sources, NOBs improve oxygen solubility without introducing secondary pollutants, offering a novel in situ remediation strategy for urban groundwater contamination, thereby supporting long-term monitored natural attenuation (MNA).

Challenges and opportunities for low-carbon remediation in the Niger Delta: Towards sustainable environmental management

There is increasing demand for low-carbon remediation strategies for reducing greenhouse gas emissions and promoting sustainable development in the management of environmental contamination. This trend is within the broader context of sustainable remediation strategies that balance environmental, economic, and social aspects. This article critically reviewed existing literature to evaluate and compare various low-carbon remediation methods, such as bioremediation, phytoremediation, in situ chemical oxidation, soil vapour extraction, and electrokinetic remediation, to identify suitable techniques for the remediation of oil-contaminated sites in the Niger Delta region of Nigeria. We analysed the UK sustainable remediation frameworks (SuRF-UK) to glean lessons for the Nigerian context. Our findings indicate that bioremediation and phytoremediation are particularly promising low-carbon remediation technologies for the Niger Delta region due to their cost-effectiveness and adaptability to local conditions. We proposed a framework that deeply considers opportunities for achieving multiple goals including effective remediation and limited greenhouse gas emissions while returning net social and economic benefit to local communities. The proposed framework will help decision makers to implement effective remediation technologies that meet sustainability indices, integrates emissions considerations return net environmental benefit to local communities. There is a need for policymakers to establish and enforce policies and regulations that support sustainable remediation practises, build the capacity of stakeholders, invest in research and development, and promote collaboration among stakeholders to create a regulatory environment that supports sustainable remediation practises and promotes environmental sustainability in the region. This study provides insights for achieving low-carbon remediation in regions addressing land contamination by different contaminants and facilitates the adoption of remediation technologies that consider contextual socio-economic and environmental indices for sustainable development.

Bioremediation of an industrial soil contaminated by hydrocarbons in microcosm system, involving bioprocesses utilizing co-products and agro-industrial wastes

The present study describes practical implication of bioaugmentation and biostimulation processes for bioremediation of an industrial soil chronically contaminated by hydrocarbons. For this purpose, biomass production of six autochthonous hydrocarbon-degrading bacteria were evaluated as inoculum of bioaugmentation strategy, by testing carbon and nitrogen sources included co-products and agro-industrial waste as sustainable and low-cost components of the growth medium. Otherwise, biostimulation was approached by the addition of optimized concentration of nitrogen and phosphorus. Microcosm assays showed that total hydrocarbons (TH) were significantly removed from chronically contaminated soil undergoing bioremediation treatment. Systems Mix (bioaugmentation); N,P (biostimulation) and Mix + N,P (bioaugmentation and biostimulation) reached higher TH removal, being 89.85%, 91.00%, 93.04%, respectively, comparing to 77.83% of system C (natural attenuation) at 90 days. The increased heterotrophic aerobic bacteria and hydrocarbon degrading bacteria counts were according to TH biodegrading process during the experiments. Our results showed that biostimulation with nutrients represent a valuable alternative tool to treat a chronically hydrocarbon-contaminated industrial soil, while bioaugmentation with a consortium of hydrocarbon degrading bacteria would be justified when the soil has a low amount of endogenous degrading microorganisms. Furthermore, the production of inoculum for application in bioaugmentation using low-cost substrates, such as industrial waste, would lead to the development of an environmentally friendly and attractive process in terms of cost-benefit.

Innovative Culturomic Approaches and Predictive Functional Metagenomic Analysis: The Isolation of Hydrocarbonoclastic Bacteria with Plant Growth Promoting Capacity

Innovative culturomic approaches were adopted to isolate hydrocarbonoclastic bacteria capable of degrading diesel oil, bitumen and a selection of polycyclic aromatic hydrocarbons (PAH), e.g., pyrene, anthracene, and dibenzothiophene, from a soil historically contaminated by total petroleum hydrocarbons (TPH) (10,347 ± 98 mg TPH/kg). The culturomic approach focussed on the isolation of saprophytic microorganisms and specialist bacteria utilising the contaminants as sole carbon sources. Bacterial isolates belonging to Pseudomonas, Arthrobacter, Achromobacter, Bacillus, Lysinibacillus, Microbacterium sps. were isolated for their capacity to utilise diesel oil, bitumen, pyrene, anthracene, dibenzothiphene, and their mixture as sole carbon sources. Pseudomonas, Arthrobacter, Achromobacter and Microbacterium sps. showed plant growth promoting activity, producing indole-3-acetic acid and expressing 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase activity. In parallel to the culturomic approach, in the microbial community of interest, bacterial community metabarcoding and predictive functional metagenomic analysis were adopted to confirm the potentiality of the isolates in terms of their functional representativeness. The combination of isolation and molecular approaches for the characterisation of a TPH contaminated soil microbial community is proposed as an instrument for the construction of an artificial hydrocarbonoclastic microbiota for environmental restoration.

Polycyclic Aromatic Hydrocarbons: Sources, Toxicity, and Remediation Approaches

Polycyclic aromatic hydrocarbons (PAHs) are widespread across the globe mainly due to long-term anthropogenic sources of pollution. The inherent properties of PAHs such as heterocyclic aromatic ring structures, hydrophobicity, and thermostability have made them recalcitrant and highly persistent in the environment. PAH pollutants have been determined to be highly toxic, mutagenic, carcinogenic, teratogenic, and immunotoxicogenic to various life forms. Therefore, this review discusses the primary sources of PAH emissions, exposure routes, and toxic effects on humans, in particular. This review briefly summarizes the physical and chemical PAH remediation approaches such as membrane filtration, soil washing, adsorption, electrokinetic, thermal, oxidation, and photocatalytic treatments. This review provides a detailed systematic compilation of the eco-friendly biological treatment solutions for remediation of PAHs such as microbial remediation approaches using bacteria, archaea, fungi, algae, and co-cultures. In situ and ex situ biological treatments such as land farming, biostimulation, bioaugmentation, phytoremediation, bioreactor, and vermiremediation approaches are discussed in detail, and a summary of the factors affecting and limiting PAH bioremediation is also discussed. An overview of emerging technologies employing multi-process combinatorial treatment approaches is given, and newer concepts on generation of value-added by-products during PAH remediation are highlighted in this review.