Remediation trials for hydrocarbon-contaminated sludge from a soil washing process: evaluation of bioremediation technologies

AI-assisted systematic review on remediation of contaminated soils with PAHs and heavy metals

This systematic review addresses soil contamination by crude oil, a pressing global environmental issue, by exploring effective treatment strategies for sites co-contaminated with heavy metals and polycyclic aromatic hydrocarbons (PAHs). Our study aims to answer pivotal research questions: (1) What are the interaction mechanisms between heavy metals and PAHs in contaminated soils, and how do these affect the efficacy of different remediation methods? (2) What are the challenges and limitations of combined remediation techniques for co-contaminated soils compared to single-treatment methods in terms of efficiency, stability, and specificity? (3) How do various factors influence the effectiveness of biological, chemical, and physical remediation methods, both individually and combined, in co-contaminated soils, and what role do specific agents play in the degradation, immobilization, or removal of heavy metals and PAHs under diverse environmental conditions? (4) Do AI-powered search tools offer a superior alternative to conventional search methodologies for executing an exhaustive systematic review? Utilizing big-data analytics and AI tools such as Litmaps.co, ResearchRabbit, and MAXQDA, this study conducts a thorough analysis of remediation techniques for soils co-contaminated with heavy metals and PAHs. It emphasizes the significance of cation-π interactions and soil composition in dictating the solubility and behavior of these pollutants. The study pays particular attention to the interplay between heavy metals and PAH solubility, as well as the impact of soil properties like clay type and organic matter on heavy metal adsorption, which results in nonlinear sorption patterns. The research identifies a growing trend towards employing combined remediation techniques, especially biological strategies like biostimulation-bioaugmentation, noting their effectiveness in laboratory settings, albeit with potentially higher costs in field applications. Plants such as Medicago sativa L. and Solanum nigrum L. are highlighted for their effectiveness in phytoremediation, working synergistically with beneficial microbes to decompose contaminants. Furthermore, the study illustrates that the incorporation of biochar and surfactants, along with chelating agents like EDTA, can significantly enhance treatment efficiency. However, the research acknowledges that varying environmental conditions necessitate site-specific adaptations in remediation strategies. Life Cycle Assessment (LCA) findings indicate that while high-energy methods like Steam Enhanced Extraction and Thermal Resistivity - ERH are effective, they also entail substantial environmental and financial costs. Conversely, Natural Attenuation, despite being a low-impact and cost-effective option, may require prolonged monitoring. The study advocates for an integrative approach to soil remediation, one that harmoniously balances environmental sustainability, cost-effectiveness, and the specific requirements of contaminated sites. It underscores the necessity of a holistic strategy that combines various remediation methods, tailored to meet both regulatory compliance and the long-term sustainability of decontamination efforts.

A new simpler and reliable method for determining mineral oil in sewage sludge: Influence of biogenic compounds for the quantitative analysis of C10-C40 hydrocarbons

The characterization of organic contaminants in sewage sludge is a fundamental step to address the relevant most appropriate management practice. In this perspective, C10-C40 hydrocarbon content was considered in Italy a crucial parameter to be considered, in spite of its irrelevance in the literature. The very complex mixture of organic substances of both biogenic and anthropogenic origin the sludge is made up of makes sewage sludge a matrix of uniqueness nature, and the analytic determination of hydrocarbon content through conventional procedures may be subjected to overestimation. In this work, optimization of two conventional protocols for the determination of mineral oil (EN14039 and IRSA CNR gravimetric method) were run with attention to anthropogenic compounds potentially affecting the C10-C40 mineral hydrocarbons determination. Effects from the first manipulations of sewage sludge samples to extraction procedure and clean-up operations were investigated. A new simple procedure was set up and tested on 30 samples from different wastewater treatment plants (WWTPs). Through a simple extraction with hexane (12 mL per 2 g of dried sludge, acidified with HCl conc.) at room temperature for 2 h, followed by a clean-up on Florisil column (10 mL-2 g) a confident determination of C10-C40 were obtained with respect to conventional optimized procedures. Variability within the range 0.06-9.49% was calculated with respect to the average value determined using three different methods, with an average value of 2.48 ± 2.37%, demonstrating the robustness of the determination. Up to 3% of the total hydrocarbons were identified as naturally occurring, namely terpenes, squalenes and deoxygenized sterols, passed through the clean-up Florisil column. A significant incidence (up to 75%) of the final overall C10-C40 content was found to be related to the C10-C20 component, originally present in the commercial polyelectrolytes in emulsion, widely used for conditioning before mechanical dewatering.

Research progress of bio-slurry remediation technology for organic contaminated soil

Bio-slurry remediation technology, as a controllable bioremediation method, has the significant advantage of high remediation efficiency and can effectively solve the problems of high energy consumption and secondary pollution of traditional organic pollution site remediation technology. To further promote the application of this technology in the remediation of organically polluted soil, this paper summarizes the importance and advantages of bio-slurry remediation technology compared with traditional soil remediation technologies (physical, chemical, and biological). It introduces the technical infrastructure and its technological processes. Then, various factors that may affect its remediation performance are discussed. By analyzing the applications of this technology to the remediation of typical organic pollutant-(polycyclic aromatic hydrocarbons(PAHs), polychlorinated biphenyls(PCBs), total petroleum hydrocarbons(TPH), and pesticide) contaminated sites, the following key features of this remediation technology are summarised: (1) the technology has a wide range of applications and can be used in a versatile way in the remediation projects of various types of organic-contaminated soil sites such as in clay, sand, and high organic matter content soil; (2) the technology is highly controllable. Adjusting environmental parameters and operational conditions, such as nutrients, organic carbon sources (bio-stimulation), inoculants (bio-augmentation), water-to-soil ratio, etc., can control the remediation process, thus improving the restoration performance. To sum up, this bio-slurry remediation technology is an efficient, controllable and green soil remediation technology that has broad application prospects.

Organic wastes bioremediation and its changing prospects

Increasing inappropriate anthropogenic activities and industrialization have resulted in severe environmental pollution worldwide. Their effective treatment is vital for general health concerns. Depending on the characteristics of pollutants, the severity of pollution may differ. For sustainable treatment of polluted environments, bioremediation is accepted as the most efficient, economical, and environmentally friendly method hence largely preferred. However, every bioremediation technique has its own unique advantages and limitations due to its defined applications criteria. In bioremediation, microorganisms play a decisive role in detoxification by degrading, mineralizing and accumulating various forms of harmful and biodegradable pollutants from the surroundings and transforming them into less lethal forms. Bioremediation is performed ex-situ or in-situ, based on location of polluted site as well as characteristics, type and strength of the pollutants. Furthermore, the most popular methodologies for bioremediation include bioaugmentation, biostimulation, bioattenuation among others which depend on the prevailing environmental factors into the microbial system. Implementing them appropriately and effectively under ex-situ or in-situ method is extremely important not only for obtaining efficient treatment but also for the best economic, environmental, and social impacts. Therefore, this review aims to analyze various bioremediation methods for organic pollutants remediation from soil/sediments and wastewater, their strength, limitation, and insights for the selection of appropriate bioremediation techniques based on nature, types, degree, and location of the pollution. The novelty aspect of the article is to give updates on several key supporting technologies which have recently emerged and exhibited great potential to enhance the present bioremediation efficiency such as nanobubble, engineered biochar, mixotrophic microalgae, nanotechnology etc. Moreover, amalgamation of these technologies with existing bioremediation facilities are significantly changing the scenario and scope of environmental remediation towards sustainable bioremediation.

Plant contribution to the remediation of PAH-contaminated soil of Dagang Oilfield by Fire Phoenix

Pot experiments were conducted to evaluate plant contribution during remediation of the polycyclic aromatic hydrocarbons (PAH)-contaminated soil of Dagang Oilfield by Fire Phoenix (a mixture of Festuca L.). The results showed that Fire Phoenix could grow in soil contaminated by high and low concentrations of PAHs. After being planted for 150 days, the total removal rate of six PAHs in the high and low PAH concentrations was 80.36% and 79.79%, significantly higher than the 58.79% and 53.29% of the unplanted control group, respectively. Thus, Fire Phoenix can effectively repair the soil contaminated by different concentrations of PAHs. In high concentrations of PAHs, the results indicated a positive linear relationship between PAH absorption in tissues of Fire Phoenix and the growth time in the early stage. In contrast, the contents of PAHs were just slightly increased in the late period of plant growth. The main factor for the dissipation of PAHs was plant-promoted biodegradation (99.04%-99.93%), suggesting a low contribution of PAH uptake and transformation (0.07%-0.96%). The results revealed that Fire Phoenix did not remove the PAHs in the soil by accumulation but promoted PAH dissipation in the soil by stimulating the microbial metabolism in the rhizosphere.

Biodegradation of petroleum refining industry oil sludge by microbial-assisted biocarrier matrix: process optimization using response surface methodology

Safe disposal of petroleum oil sludge generated from crude oil storage tank bottom is a major challenge for petroleum refineries across the globe. The presence of long chain hydrocarbons in petroleum oil sludge are known to have effects on the environment through bioaccumulation or biosorption. The present study was focused to develop a modified bioremediation process using hydrocarbonoclastic microbial-assisted biocarrier matrix (MABC) mediated through biosurfactants and biocatalysts for the efficient treatment of petroleum industrial oily sludge. The development of hydrocarbonoclastic microbial-assisted biocarrier matrix was confirmed by scanning electron microscopy analysis. The biocatalysts such as lipase, laccase, esterase and biosurfactant produced by MABC system were found to be 40 U/mg, 18 U/mg, 36 U/mg and 220 mg/g of oil sludge respectively using one variable at a time approach. Further, the response surface methodology was used to determine the optimum treatment conditions (Time, pH, Mass of biocarrier matrix and Amount of oil sludge) for the enhanced removal of total petroleum hydrocarbons (TPH) present in the oil sludge and TPH was degraded by 88.78% at Hydraulic Retention Time of 7 days. The biodegradation of oil sludge was confirmed using Gas Chromatography-Mass Spectrometry analysis.

Evaluating rhamnolipid-enhanced washing as a first step in remediation of drill cuttings and petroleum-contaminated soils

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Soil washing is an innovative approach to treatment of waste streams.

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Temperature has a significant effect on rhamnolipid enhanced soil washing.

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Drill cuttings and petroleum-impacted soil show similar optimum washing conditions.

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Maximum total petroleum hydrocarbon reduction in drill cuttings was 76.8%.

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Maximum total petroleum hydrocarbon reduction in soil was 58.5%.

Environmental pollution by petroleum hydrocarbons (PHCs) is a severe and widespread problem impacting human health and the environment. To combat this issue, innovative and sustainable treatment methods are required. This research study investigated rhamnolipid-enhanced washing of drill cuttings and petroleum-contaminated soil obtained from northeastern British Columbia in Canada. The efficiency of PHC reduction was analysed and quantified via a Gas Chromatography equipped with a Flame Ionization Detector. Optimum washing conditions for both drill cuttings and petroleum-contaminated soil were temperature of ∼23.5 °C (room temperature), rhamnolipid concentration of 500 mg/L, and a washing time of 30 min. The optimum stirring speed and solution-to-sample ratio for drill cuttings and petroleum-contaminated soil were 100 rpm; 1:1, and 200 rpm; 4:1 respectively. The maximum PHC reduction recorded for total petroleum hydrocarbon and PHC fractions – F2, F3 and F4 were 76.8%, 85.4%, 71.3% and 76.9% respectively for drill cuttings and 58.5%, 48.4%, 63.5% and 59.8% respectively for petroleum-contaminated soil. The results strongly suggest that soil washing is an effective step in the reduction of PHC and can be used as a first step in the treatment of drill cuttings and petroleum-contaminated soils.

FC. Soil Bioremediation Techniques

Soil pollution is rising rapidly due to the existence of pollutants or natural alterations in the soil. It makes the drinking water ineffective and unusable by the human beings. The major cause of the soil contamination is agricultural activities, industrial activities, and inadmissible disposal of waste in the soil. The most common pollutants to accumulate in the soil are petroleum hydrocarbons, solvents, pesticides, lead, and other heavy metals. The important technology to remediate the pollutants or contaminants in the soil is bioremediation. The utilization of bioremediation in the contaminated soil is increasing rapidly due to the presence of toxic pollutants. It is the most advanced technologies which make use of organisms to deteriorate the harmful compounds in order to prevent the soil pollution. The aim of the chapter is to describe the available bioremediation technologies and their application in removing the pollutants exist in the soil.

Enhanced biodegradation of hydrocarbons in petroleum tank bottom oil sludge and characterization of biocatalysts and biosurfactants

Petroleum hydrocarbon removal from tank bottom oil sludge is a major issue due to its properties. Conventional physicochemical treatment techniques are less effective. Though the bioremediation is considered for the hydrocarbon removal from tank bottom oil sludge, the efficiency is low and time taking due to the low yield of biocatalysts and biosurfactants. The focal theme of the present investigation is to modify the process by introducing the intermittent inoculation for the enhanced biodegradation of hydrocarbons in the tank bottom oil sludge by maintaining a constant level of biocatalysts such as oxidoreductase, catalase, and lipase as well as biosurfactants. In addition, the heavy metal removal was also addressed. The microbial consortia comprising Shewanalla chilikensis, Bacillus firmus, and Halomonas hamiltonii was used for the biodegradation of oil sludge. One variable at a time approach was used for the optimum of culture conditions. The bacterial consortia degraded the oil sludge by producing biocatalysts such as lipase (80 U/ml), catalase (46 U/ml), oxidoreductase (68 U/ml) along with the production of lipoprotein biosurfactant (152 mg/g of oil sludge) constantly and achieved 96% reduction of total petroleum hydrocarbon. The crude enzymes were characterized by FT-IR and the biosurfactant was characterized by surface tension reduction, emulsification index, FT-IR, TLC, and SDS-PAGE. GC-MS and NMR also revealed that the hydrocarbons present in the oil sludge were effectively degraded by the microbial consortia. The ICP-OES result indicated that the microbial consortium is also effective in removing the heavy metals. Hence, bioremediation using the hydrocarbonoclastic microbial consortium can be considered as an environmentally friendly process for disposal of tank bottom oil sludge from petroleum oil refining industry.

Degradation of polycyclic aromatic hydrocarbons in soil mesocosms by microbial/plant bioaugmentation: Performance and mechanism

In order to study the degradation of polycyclic aromatic hydrocarbons (PAHs) in an aged and highly contaminated soil, four bioremediation strategies (indigenous microorganisms, microbial bioaugmentation with a PAH-degrading and bioemulsifier-producing strain, Rhodococcus ruber Em1, plant bioaugmentation with Orychophragmus violaceus and their combination) were compared and the enhanced degradation mechanism was investigated in soil mesocosms. Degradation rates over a period of 175 days showed that Em1 combined with Orychophragmus violaceus promoted a significant enhancement of PAHs degradation. In inoculated microcosms with Rhodococcus ruberEm1, mineralization reached a lower level in the absence than in the presence of plants. Elimination of PAHs was significantly enhanced (increased by 54.45%) in the bioaugmented mesocosms. Quantitative PCR indicated that copy numbers of linA and RHD-like gene (encoding PAH-ring hydroxylating dioxygenase) in the mesocosm with plant were three and five times higher than those in the mesocosm without plant, respectively. Transcript copy numbers of RHD-like gene and 16S rRNA gene of strain Em1 in mesocosm with plant were two and four times higher than those in the mesocosm without plant, respectively. Taken together, the results of this study show that plants or Rhodococcus ruber Em1 enhance total PAHs removal, moreover their effects are necessarily cumulative by combined strains and plants.

Giant reed growth and effects on soil biological fertility in assisted phytoremediation of an industrial polluted soil

Phytoremediation is a cost-effective "green technology" that uses plants to improve the soil properties of polluted sites, preventing the dispersion of pollutants and reducing the mobility of potentially toxic elements (PTEs) through their adsorption and accumulation by roots or precipitation within the root zone. Being highly tolerant to pollutants and other abiotic stresses, giant reed (Arundo donax L.) is a suitable biomass crop for phytoremediation of contaminated soils. We report the results of a two-year open-air lysimeter study aimed at assessing the adaptability of giant reed to grow on industrial substrates polluted by Pb and Zn and at testing commercial humic acids from leonardite as improvers of plant performance. We evaluated giant reed potential for: 1) biomass production for energy or biomaterial recovery; 2) PTE phytoextraction and 3) soil fertility restoration. Chemical fertility was monitored by measuring soil C while soil biological fertility was estimated by quantifying the abundance of bacterial functional genes regulating nitrogen fixation (nifH) and nitrification (amoA). Giant reed above-ground growth on the polluted soils was slightly lower (-16%) than on a non-polluted soil, with a preferential storage of biomass in the rhizome acting as a survival strategy in limiting growing conditions. Humic acids improved plant stress tolerance and production levels. As aerial biomass (shoots) did not accumulate PTEs, the plant in question can be used for bioenergy or biopolymer production. In contrast, below-ground biomass (rhizomes) accumulated PTEs, and can thus be harvested and removed from soil to improve phytoremediation protocols and also used as industrial biofuel. Giant reed growth increased the abundance of N-cycling bacteria and soil C in the rhizospheric soil, as well as reduced soil Pb and Zn EDTA extractable fraction.

Bioremediation techniques-classification based on site of application: principles, advantages, limitations and prospects

Environmental pollution has been on the rise in the past few decades owing to increased human activities on energy reservoirs, unsafe agricultural practices and rapid industrialization. Amongst the pollutants that are of environmental and public health concerns due to their toxicities are: heavy metals, nuclear wastes, pesticides, green house gases, and hydrocarbons. Remediation of polluted sites using microbial process (bioremediation) has proven effective and reliable due to its eco-friendly features. Bioremediation can either be carried out ex situ or in situ, depending on several factors, which include but not limited to cost, site characteristics, type and concentration of pollutants. Generally, ex situ techniques apparently are more expensive compared to in situ techniques as a result of additional cost attributable to excavation. However, cost of on-site installation of equipment, and inability to effectively visualize and control the subsurface of polluted sites are of major concerns when carrying out in situ bioremediation. Therefore, choosing appropriate bioremediation technique, which will effectively reduce pollutant concentrations to an innocuous state, is crucial for a successful bioremediation project. Furthermore, the two major approaches to enhance bioremediation are biostimulation and bioaugmentation provided that environmental factors, which determine the success of bioremediation, are maintained at optimal range. This review provides more insight into the two major bioremediation techniques, their principles, advantages, limitations and prospects.

Remediation of phenanthrene contaminated soils by nonionic-anionic surfactant washing coupled with activated carbon adsorption

Batch experiments were conducted to investigate the performance of nonionic-anionic mixed surfactants and their recovery through activated carbon. The solubilization capabilities of mixed surfactants toward phenanthrene (PHE) were reduced by addition of anionic surfactant to the mixed systems. Results showed that sorption of Triton X-100 (TX100) onto soil decreased with increasing mass fraction of sodium dodecyl sulfate (SDS) in the mixed surfactant solutions. Soil contaminated with PHE at 200 mg/kg was washed with different surfactant concentrations at various mass ratios of nonionic-anionic mixed surfactant. Experiments with low-concentrations of mixed surfactants revealed that removal efficiencies for PHE-contaminated soil close to the individual higher nonionic surfactant concentration can be achieved. Overall performance considering both soil washing and surfactant recovery steps is apposite when an TX100:SDS mass ratio of 8:2 at 3 g/L is used.

Influence of inocula with prior hydrocarbon exposure on biodegradation rates of diesel, synthetic diesel, and fish-biodiesel in soil

To achieve effective bioremediation within short warm seasons of cold climates, microbial adaptation periods to the contaminant should be brief. The current study investigated growth phases for soil spiked with diesel, Syntroleum, or fish biodiesel, using microbial inocula adapted to the specific substrates. For modeling hydrocarbon degradation, multi-phase first order kinetics was assumed, comparing linear regression with nonlinear parameter optimization of rate constants and phase durations. Lag phase periods of 5 to >28d were followed by short and intense exponential growth phases with high rate constants (e.g. from kFish=0.0013±0.0002 to kSyntr=0.015±0.001d(-1)). Hydrocarbon mineralization was highest for Syntroleum contamination, where up to three times higher cumulative CO2 production was achieved than for diesel fuel, with fish biodiesel showing initially the slowest degradation. The amount of hydrocarbons recovered from the soil by GC-MS decreased in the order fish biodiesel>diesel>Syntroleum. During initial weeks, biodegradation was higher for microbial inocula adapted to a specific fuel type, whereby the main effect of the inoculum was to shorten the lag phase duration; however, the inoculum's importance diminished after daily respiration peaked. In conclusion, addition of an inoculum to increase biodegradation rates was not necessary.

Pilot scale ex-situ bioremediation of heavily PAHs-contaminated soil by indigenous microorganisms and bioaugmentation by a PAHs-degrading and bioemulsifier-producing strain

This study aims at the remediation of heavily PAH-contaminated soil containing 375 mg of total PAHs per kilogram dry soil. Pilot scale bioremediation experiments were carried out by three approaches with contaminated soil from abandoned sites of Beijing Coking Plant using outdoor pot trials. The first approach was bioaugmentation with a bacterial strain which degrades PAH and produces bioemulsifier, the second approach comprised of biostimulation of indigenous microorganisms with supplementing nutrients and the last approach involved the combination of both biostimulation and bioaugmentation. An on-site land farming group was set as a control in which the total PAHs and 4-6 ring-PAHs were reduced by 23.4% and 10.1%, respectively after 175 days. Meanwhile, in the first approach group, the total PAHs and 4-6 ring-PAHs were reduced by 26.82% and 35.36%, respectively; in the second approach group both percentages were 33.9% and 11.0%, respectively; while in the third approach group, these pollutants were reduced by 43.9% and 55.0%, respectively. The results obtained suggested that biostimulation and bioaugmentation combined could significantly enhance the removal of PAHs in the contaminated soil.