Treatment of wastewater from petroleum industry: current practices and perspectives

Unlocking the transcriptional profiles of an oily waste-degrading bacterial consortium

This study investigates the transcriptional profile of a novel oil-degrading microbial consortium (MC1) composed of four bacterial isolates from Brazilian oil reservoirs: Acinetobacter baumannii subsp. oleum ficedula, Bacillus velezensis, Enterobacter asburiae, and Klebsiella pneumoniae. Genomic analysis revealed an enrichment of genes associated with xenobiotic degradation, particularly for aminobenzoate, atrazine, and aromatic compounds, compared to reference genomes. The consortium demonstrated superior growth and complete oil degradation relative to individual strains. Transcriptional profiling during growth on oil indicated that key subsystems involved membrane transport, stress response, and dehydrogenase complexes, crucial for hydrocarbon uptake. Notably, genes for degrading aromatics, naphthalene, and chloroalkanes were significantly expressed during the initial oil growth phase. The dominant gene expressed was alkane 1-monooxygenase, particularly in the late growth phase. While A. baumannii exhibited the highest transcriptional activity, B. velezensis showed lower activity despite possessing numerous hydrocarbon degradation genes. The synergistic interactions among strains, confirmed by complementary gene expression patterns, position MC1 as a promising bioremediation agent for hydrocarbon-contaminated environments. However, more than collaboration, competition for nutrient uptake and resistance to stress drive gene expression and adaptation in the presence of oil as the carbon source.

Bioremediation petroleum wastewater and oil-polluted soils by the non-toxigenic indigenous fungi

Soil and wastewater samples contaminated by petroleum-related industries were collected from various locations in Saudi Arabia, a country known for its vast oil reserves. The samples were analyzed for their physicochemical properties, including the presence of metals, petroleum hydrocarbons, and aromatic compounds. A total of 264 fungal isolates were analyzed and categorized into eight groups of Aspergillus (194 isolates) and four groups of Penicillium (70 isolates). The potential of these fungal groups to grow in oil or its derivatives was investigated. Two isolates, Aspergillus tubingensis FA-KSU5 and A. niger FU-KSU69, were utilized in two remediation experiments-one targeting wastewater and the other focusing on polluted soil. The FA-KSU5 strain demonstrated complete removal of Fe3+, As3+, Cr6+, Zn2+, Mn2+, Cu2+ and Cd2+, with bioremediation efficiency for petroleum hydrocarbons in the wastewater from these sites ranging between 90.80 and 98.58%. Additionally, the FU-KSU69 strain achieved up to 100% reduction of Co2+, Ba2+, B3+, V+, Ni2+, Pb2+ and Hg2+, with removal efficiency ranging from 93.17 to 96.02% for aromatic hydrocarbons after 180 min of wastewater treatment. After 21 days of soil incubation with Aspergillus tubingensis FA-KSU5, there was a 93.15% to 98.48% reduction in total petroleum hydrocarbons (TPHs) and an 88.11% to 97.31% decrease in polycyclic aromatic hydrocarbons (PAHs). This strain exhibited the highest removal rates for Cd2+ and As3+ followed by Fe3+, Zn2+, Cr6+, Se4+ and Cu2+. Aspergillus niger FU-KSU69 achieved a 90.37% to 94.90% reduction in TPHs and a 95.13% to 98.15% decrease in PAHs, with significant removal of Ni2+, Pb2+ and Hg2+, followed by Co2+, V+, Ba2+ and B3+. The enzymatic activity in the treated soils increased by 1.54- to 3.57-fold compared to the polluted soil. Although the mixture of wastewater and polluted soil exhibited high cytotoxicity against normal human cell lines, following mycoremediation, all treated soils and effluents with the dead fungal biomass showed no toxicity against normal human cell lines at concentrations up to 500 µL/mL, with IC50 values ≥ 1000 µL/mL. SEM and IR analysis revealed morphological and biochemical alterations in the biomass of A. tubingensis FA-KSU5 and A. niger FA-KSU69 when exposed to petroleum effluents. This study successfully introduces non-toxigenic and environmentally friendly fungal strains play a crucial role in the bioremediation of contaminated environments. Both strains serve as low-cost and effective adsorbents for bio-remediating petroleum wastewater and oil-contaminated soil. Heavy metals and hydrocarbons, the primary pollutants, were either completely removed or reduced to permissible levels according to international guidelines using the dead biomass of FA-KSU5 and FA-KSU69 fungi. Consequently, the environments associated with this globally significant industry are rendered biologically safe, particularly for humans, as evidenced by the absence of cytotoxicity in samples treated with A. tubingensis FA-KSU5 and A. niger FA-KSU69 on various human cell types.

Agri-food waste biosorbents for volatile organic compounds removal from air and industrial gases - A review

Approximately 1.3 billion metric tons of agricultural and food waste is produced annually, highlighting the need for appropriate processing and management strategies. This paper provides an exhaustive overview of the utilization of agri-food waste as a biosorbents for the elimination of volatile organic compounds (VOCs) from gaseous streams. The review paper underscores the critical role of waste management in the context of a circular economy, wherein waste is not viewed as a final product, but rather as a valuable resource for innovative processes. This perspective is consistent with the principles of resource efficiency and sustainability. Various types of waste have been described as effective biosorbents, and methods for biosorbents preparation have been discussed, including thermal treatment, surface activation, and doping with nitrogen, phosphorus, and sulfur atoms. This review further investigates the applications of these biosorbents in adsorbing VOCs from gaseous streams and elucidates the primary mechanisms governing the adsorption process. Additionally, this study sheds light on methods of biosorbents regeneration, which is a key aspect of practical applications. The paper concludes with a critical commentary and discussion of future perspectives in this field, emphasizing the need for more research and innovation in waste management to fully realize the potential of a circular economy. This review serves as a valuable resource for researchers and practitioners interested in the potential use of agri-food waste biosorbents for VOCs removal, marking a significant first step toward considering these aspects together.

Microbial communities in petroleum refinery effluents and their complex functions

Petroleum refinery effluents (PRE) are a significant cause of pollution. It contains toxic compounds such as total petroleum hydrocarbons (TPH), and polycyclic aromatic hydrocarbons (PAHs), as well as heavy metals. They show a huge threat facing the aquaculture habitats, human health, and the environment if they are not treated before discharging into the environment. Physical and chemical procedures are used to treat hydrocarbon pollution in PRE, but these techniques often result in the formation of hazardous by-products during the remediation process. However, PRE contains various microbial communities, including bacteria, yeast, microalgae, and fungi. The bioremediation and biodegradation of oil contaminants are the primary functions of these microbial communities. However, these microorganisms can perform various additional functions including but not limited to heavy metals removal, production of biosurfactants, and nitrogen fixation. This review contributes to the comprehension of natural microbial communities and their complex functions in petroleum refinery effluents. Understanding microbial communities would facilitate the advancement of innovative biotechnology aimed at treating PRE, improving bioremediation processes, and potentially transforming PRE into valuable bio-products. Moreover, it assists in determining the most effective bioaugmentation strategy to enhance biodegradation and bioremediation in PRE. The review highlights the potential for sustainable green approaches using microbial communities to replace toxic chemical therapies and expensive physical treatments in the future.

The methods for improving the biodegradability of oily sludge: a critical review

Biological degradation method, as an environmentally friendly, low-carbon, and clean pollution treatment technology, is widely used for the harmless disposal of oily sludge. The biodegradability of oily sludge with stable emulsification system, high oil, and water content is poor. Therefore, it is necessary to pre-treat the oily sludge to improve its biodegradability, including recover the petroleum resources and remove heavy metals and bio-toxic organic matters. This review systematically summarizes five oily sludge treatment methods and their influences on sludge biodegradability, including pyrolysis, chemical hot washing, solvent extraction, chemical oxidation, and hydrothermal. Pyrolysis at temperatures above 750 °C produces high molecular weight polycyclic aromatic hydrocarbons, chemical hot washing and chemical oxidation would cause secondary pollution, solvent extraction method could not be applied due to the high cost and high toxicity of the extractant, and the oil removal of hydrothermal method is inefficient. Additionally, the principles, advantages, and disadvantages of those treatments and the factors affecting microbial degradation were analyzed, which provide the development direction of pretreatment technology to improve the biodegradability of oily sludge.

Synergistic algal/bacterial interaction in membrane bioreactor for detoxification of 1,2-dichloroethane-rich petroleum wastewater

The study addressed the challenge of treating petroleum industry wastewater with high concentrations of 1,2-dichloroethane (1,2-DCA) ranging from 384 to 1654 mg/L, which poses a challenge for bacterial biodegradation and algal photodegradation. To overcome this, a collaborative approach using membrane bioreactors (MBRs) that combine algae and bacteria was employed. This synergistic method effectively mitigated the toxicity of 1,2-DCA and curbed MBR fouling. Two types of MBRs were tested: one (B-MBR) used bacterial cultures and the other (AB-MBR) incorporated a mix of algal and bacterial cultures. The AB-MBR significantly contributed to 1,2-DCA removal, with algae accounting for over 20% and bacteria for approximately 49.5% of the dechlorination process. 1,2-DCA metabolites, including 2-chloroethanol, 2-chloro-acetaldehyde, 2-chloroacetic acid, and acetic acid, were partially consumed as carbon sources by algae. Operational efficiency peaked at a 12-hour hydraulic retention time (HRT) in AB-MBR, enhancing enzyme activities crucial for 1,2-DCA degradation such as dehydrogenase (DH), alcohol dehydrogenase (ADH), and acetaldehyde dehydrogenase (ALDH). The microbial diversity in AB-MBR surpassed that in B-MBR, with a notable increase in Proteobacteria, Bacteroidota, Planctomycetota, and Verrucomicrobiota. Furthermore, AB-MBR showed a significant rise in the dominance of 1,2-DCA-degrading genus such as Pseudomonas and Acinetobacter. Additionally, algal-degrading phyla (e.g., Nematoda, Rotifera, and Streptophyta) were more prevalent in AB-MBR, substantially reducing the issue of membrane fouling.

Impact of pyrolysis process conditions on the structure of biochar obtained from apple waste

Biochar is an eco-friendly carbon material whose properties allow it to be used as a sorbent for wastewater treatment or soil remediation. The paper presents the results of research related to the pyrolysis process of apple waste after supercritical CO2 extraction with the simultaneous use of physical activation. The research assessed the influence of the temperature of the pyrolysis process and steam activation on the structural properties of the obtained biochar, i.e. specific surface, porous structure, and presence of functional groups. The results obtained confirmed that lower temperature pyrolysis produces biochar characterised by the presence of functional groups and ordered structure. On the other hand, high temperature pyrolysis with simultaneous steam activation determines microporosity and high values of the specific surface area. Taking into consideration pollutant sorption mechanisms (physical and chemical sorption), the obtained biochar materials can be used as sorbents in water and wastewater treatment.

Enhanced reduction of COD in water associated with natural gas production using iron-based nanoparticles

The natural gas production industry faces the problem of the proper disposal of produced water and its treatment with significantly advanced technologies to meet the minimum quality standard for irrigation activities, commercial purposes, and consumption by living organisms. This study describes an effective method for reducing the COD (chemical oxygen demand) content in formation water using different metal oxide nanoparticles such as iron oxide (FO), iron zinc oxide (FZO), and iron vanadium oxide (FVO) nanoparticles. These nanoparticles were synthesized and fully characterized using powder X-ray diffraction (XRD) analysis, Fourier transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, dynamic light scattering particle size (DLS) analysis and zeta potential analysis. The experimental results revealed that the maximum reduction of COD content was 42.18% using FVO nanoparticles with a dose of 3 g L-1 at 25 °C and pH = 6. Compared to commercial products [Redoxy and Oxy(OXYSORB)], the synthesized FO, FZO, and FVO nanoparticles demonstrated their superiority by achieving excellent results in decreasing the COD content of wastewater associated with natural gas production by more than 86%. This study introduces a promising technique for decreasing the COD content using metal oxide nanoparticles, which are eco-friendly, bio-safe, cheap, and nontoxic materials, and improving the quality of wastewater associated with natural gas production for its safe disposal through sewage and treatment plants.

The treatment of oily wastewater by thermo-responsive calcium alginate capsules immobilized Pseudomonas aeruginosa

A microfluidic strategy of smart calcium alginate (CA) capsules is presented to immobilize Pseudomonas aeruginosa to treat oil slicks effectively. The capsule wall is embedded with poly (N-isopropyl acrylamide) sub-microspheres as thermo-responsive switches. CA capsules, with a diameter of 3.26 mm and a thin wall thickness about 12.8 μm, have satisfying monodispersity, cavity structure, and dense surface structures. The capsules possess excellent encapsulation of bacteria, which are fixed in a restricted space and become more aggregated. It overcomes the disadvantages of a long fermentation production cycle, easy loss of bacteria, and susceptibility to shear effect. The smart CA capsules immobilized with bacteria treat model wastewater containing soybean oil or diesel and display favorable fermentation ability. The capsules can effectively treat oil slicks with high concentration, and it is an economical way for processing oily wastewater. PRACTITIONER POINTS: A thermo-responsive calcium alginate capsule was prepared by microfluidic strategy. Pseudomonas aeruginosa is environmentally friendly in treating oil slicks. The capsules, immobilized bacteria, treat oil slicks effectively. This study provides an economical way for processing different oily water.

Treatment of high-strength saline bilge wastewater by four pilot-scale aerobic moving bed biofilm reactors and comparison of the microbial communities

Four Pilot-scale Moving Bed Biofilm Reactors (MBBRs) were operated for the treatment of real, saline, bilge wastewater. The MBBRs were connected in pairs to create two system configurations with different filling ratios (20%, 40%) and were operated in parallel. The inflow organic loading rate (OLR) varied from 3.6 ± 0.2 to 7.8 ± 0.6 g COD L-1 d-1, salinity was >15 ppt and three hydraulic residence times (HRTs) were tested 48, 30 and 24 h. In both systems, the first-stage bioreactors (R1 and R3) eliminated the higher part of the organic load (57%-65%). The second-stage bioreactors (R2 and R4) removed an additional fraction (18%-31%) of the organic load received by the effluent of R1 and R3, respectively. The microbial communities of the influent wastewater, suspended, and attached biomass were determined using 16S rRNA gene amplicon sequencing analysis. The evolution of the microbial communities was investigated and compared over the different operational phases. The microbial communities of the biofilm presented higher diversity and greater stability in composition over time, while the suspended biomass exhibited intense and rapid changes in the dominance of genera. Proteobacteria, Bacteroidetes and Firmicutes were highly present in the biofilm. The genera Celeribacter, Novispirillum, Roseovarius (class: Alphaproteobacteria) and Formosa (class: Flavobacteriia) were highly present during all operational phases. Principal Component Analysis (PCA) was used to identify similarities between samples, exhibiting high relation of samples according to the series of the bioreactor (1st, 2nd).

Imidazolate framework material for crude oil removal in aqueus media: Mechanism insight

Considerable amount of produced water discharged by the oil industry contributes to an environmental imbalance due to the presence of several components potentially harmful to the ecosystem. We investigated the factors influencing the adsorption capacity of Zinc Imidazolate Framework-8 (ZIF-8) in finite bath systems for crude oil removal from petroleum extraction in synthetic produced water. ZIF-8, experimentally obtained by solvothermal method, was characterized by XRD, FTIR, TGA, BET and its point of zero charge (pHpcz) was determined. Synthesized material showed high crystallinity, with surface area equal to 1558 m2 g-1 and thermal stability equivalent to 400 °C. Adsorption tests revealed, based on the Sips model, that the process takes place in a heterogeneous system. Additionally, intraparticle diffusion model exhibited multilinearity characteristics during adsorption process. Thermodynamic investigation demonstrated that adsorption process is spontaneous and exothermic, indicating a physisorption phenomenon. These properties enable the use of ZIF-8 in oil adsorption, which presented an adsorption capacity equal to 452.9 mg g-1. Adsorption mechanism was based on hydrophobic interactions, through apolar groups present on ZIF-8 structure and oil hydrocarbons, and electrostatic interactions, through the difference in charges between positive surface of adsorbent and negatively charged oil droplets.

Recent advances in microbial engineering approaches for wastewater treatment: a review

In the present era of global climate change, the scarcity of potable water is increasing both due to natural and anthropogenic causes. Water is the elixir of life, and its usage has risen significantly due to escalating economic activities, widespread urbanization, and industrialization. The increasing water scarcity and rising contamination have compelled, scientists and researchers, to adopt feasible and sustainable wastewater treatment methods in meeting the growing demand for freshwater. Presently, various waste treatment technologies are adopted across the globe, such as physical, chemical, and biological treatment processes. There is a need to replace these technologies with sustainable and green technology that encourages the use of microorganisms since they have proven to be more effective in water treatment processes. The present review article is focused on demonstrating how effectively various microbes can be used in wastewater treatment to achieve environmental sustainability and economic feasibility. The microbial consortium used for water treatment offers many advantages over pure culture. There is an urgent need to develop hybrid treatment technology for the effective remediation of various organic and inorganic pollutants from wastewater.

A comprehensive review on immobilized microbes - biochar and their environmental remediation: Mechanism, challenges and future perspectives

The environment worldwide has been contaminated by toxic pollutants and chemicals through anthropogenic activities, industrial growth, and urbanization. Microbial remediation is seen to be superior compared to conventional remediation due to its low cost, selectivity towards particular metal ions, and high efficiency. One key strategy in enhancing microbial remediation is employing an immobilization technique with biochar as a carrier. This review provides a comprehensive summary of sources and toxic health effects of hazardous water pollutants on human health and the environment. Biochar enhances the growth and proliferation of contaminant-degrading microbes. The combined activity of biochar and microbes in eliminating the contaminants has gained the researcher's interest. Biochar demonstrates its biocompatibility by fostering microbial populations, the release of enzymes, and protecting the microbes from the acute toxicity of surrounding contaminants. The current review complies with the immobilization technique and remediation mechanisms of microbes in pollutant removal. This review also emphasizes the combined utilization, environmental adaptability, and the potential of the combined effect of immobilized microbes and biochar in the remediation of contaminants. Challenges and future outlooks are urged to commercialize the immobilized microbes-biochar interaction mechanism for environmental remediation.

Exploring the potential of Diplosphaera mucosa VSPA for the treatment of petroleum effluent with simultaneous lipid production

The discovery of unexplored, robust microalgal strains will assist in treating highly polluted industrial effluent, including petroleum effluent. In the current analysis, a newly isolated microalgal strain, Diplosphaera mucosa VSPA, was used to treat petroleum effluent in a lab-scale raceway bioreactor. Its treatment efficiency was compared with a well-known species, Chlorella pyrenoidosa. The D. mucosa VSPA strain proliferated in petroleum effluent at a high growth rate, with final biomass, and lipid concentrations reaching 6.93 g/L and 2.72 g/L, respectively. Treatment efficiency was calculated based on the final removal efficiency of ammonium nitrogen, phosphate phosphorus, and chemical oxygen demand, which was more than 90%. Control experiments suggested that the maximum removal of pollutants from petroleum effluent was due to microalgae growth. Some growth models, including the Gompertz, Logistic, Stannard, Richard, and Schnute, were used to simulate the experimental data, verifying the results. Good fitting of all models was obtained, with the R2 value reaching more than 0.90. The development of a suitable model can help in decreasing the efforts required for the scale-up of the process.

Molecularly imprinted polymers (MIPs) as efficient catalytic tools for the oxidative degradation of 4-nonylphenol and its by-products

Water pollution is a current global concern caused by emerging pollutants like nonylphenol (NP). This endocrine disruptor cannot be efficiently removed with traditional wastewater treatment plants (WTPs). Therefore, this work aimed to evaluate the adsorption influence of molecularly imprinted polymers (MIPs) on the oxidative degradation (ozone and ultraviolet irradiations) of 4-nonylphenol (4-NP) and its by-products as a coadjuvant in WTPs. MIPs were synthesized and characterized; the effect of the degradation rate under system operating conditions was studied by Box-Behnken response surface design of experiments. The variables evaluated were 4-NP concentration, ozone exposure time, pH, and MIP amount. Results show that the MIPs synthesized by co-precipitation and bulk polymerizations obtained the highest retention rates (> 90%). The maximum adsorption capacities for 4-NP were 201.1 mg L-1 and 500 mg L-1, respectively. The degradation percentages under O3 and UV conditions reached 98-100% at 120 s of exposure at different pHs. The degradation products of 4-NP were compounds with carboxylic and ketonic acids, and the MIP adsorption was between 50 and 60%. Our results present the first application of MIPs in oxidation processes for 4-NP, representing starting points for the use of highly selective materials to identify and remove emerging pollutants and their degradation by-products in environmental matrices.

Ecological and human health risk assessment of polycyclic aromatic hydrocarbons (PAH) in Tigris river near the oil refineries in Iraq

Recent Iraqi battles against ISIS in 2014 and 2015 resulted in the destruction or severe damage to several refineries' infrastructure. This, along with other factors, has led to the release and accumulation of a wide range of hazardous chemicals into the environment, for instance, polycyclic aromatic hydrocarbons (PAH). Thus, for the first time, a comprehensive 16 PAHs measurements campaign over the course of six months near the oil refineries along the Tigris River and its estuaries was investigated. The 16 PAHs concentrations in surface water and the sediments for the following oil refineries: Baiji, Kirkuk, Al-Siniyah, Qayyarah, Al-Kasak, Daura, South Refineries Company, and Maysan were examined. The overall findings indicated that the 16 PAHs concentrations ranged from 567.8 to 3750.7 ng/L for water and 5619.2-12795.0 ng/g for sediment. Water samples in South Refineries Company recorded the highest PAH concentrations while Baiji oil refinery registered the highest PAH concentrations in the sediment samples. The percentages of high molecular weight PAH (5-6 rings) in water and sediment samples were the highest, ranging from 49.41% to 81.67% and from 39.06% to 89.39% of total PAH for water and sediment, respectively. The majority of 16 PAHs measured in water and sediment samples of the Tigris River were derived from pyrogenic sources. Based on sediment quality guidelines (SQGs), most sites showed a possible effect range with occasional biological effects of most of the PAH concentrations in all sediments' samples. The calculated incremental lifetime cancer risk (ILCR) value was high risk with adverse health effects, including cancer.

Deep dewatering of refinery oily sludge by Fenton oxidation and its potential influence on the upgrading of oil phase

Highly efficient dewatering is essential to the reduction and reclamation disposal of oily sludge, which is a waste from the extraction, transportation, and refining of crude oil. How to effectively break the water/oil emulsion is a paramount challenge for dewatering of oily sludge. In this work, a Fenton oxidation approach was adopted for the dewatering of oily sludge. The results show that the oxidizing free radicals originated from Fenton agent effectively tailored the native petroleum hydrocarbon compounds into smaller organic molecules, hence destructing the colloidal structure of oily sludge and decreasing the viscosity as well. Meanwhile, the zeta potential of oily sludge was increased, implying the decrease of repulsive electrostatic force to realize easy coalescence of water droplets. Thus, the steric and electrostatic barriers which restrained the coalescence of dispersed water droplets in water/oil emulsion were removed. With these advantages, the Fenton oxidation approach derived the significant decrease of water content, in which 0.294 kg water was removed from per kilogram oily sludge under the optimal operation condition (i.e., pH value of 3, solid-liquid ratio of 1:10, Fe²⁺ concentration of 0.4 g/L and H₂O₂/Fe²⁺ ratio of 10:1, and reaction temperature of 50 °C). In addition, the quality of oil phase was upgraded after Fenton oxidation treatment accompanying with the degradation of native organic substances in oily sludge, and the heating value of oily sludge was increased from 8680 to 9260 kJ·kg^-1, which would facilitate to the subsequent thermal conversion like pyrolysis or incineration. Such results demonstrate that the Fenton oxidation approach is efficient for the dewatering as well as the upgrading of oily sludge.

Isotherm and Kinetic Study of Metal Ions Sorption on Mustard Waste Biomass Functionalized with Polymeric Thiocarbamate

The presence of high concentrations of metal ions in effluents resulting from industrial metal coatings is a well-known fact. Most of the time, such metal ions, once they reach the environment, significantly contribute to its degradation. Therefore, it is essential that the concentration of metal ions is reduced (as much as possible) before such effluents are discharged into the environment to minimize the negative impact on the quality of the ecosystems. Among all methods that can be used to reduce the concentration of metal ions, sorption is one of the most viable options due to its high efficiency and low cost. Moreover, due to the fact that many industrial wastes have sorbent properties, this method is in accordance with the principles of circular economy. Based on these considerations, in this study, mustard waste biomass (resulting from oil extraction) was functionalized with an industrial polymeric thiocarbamate (METALSORB) and used as a sorbent to remove Cu(II), Zn(II) and Co(II) ions from aqueous media. The best conditions for the functionalization of mustard waste biomass were found to be: mixing ratio biomass: METASORB = 1 g: 1.0 mL and a temperature of 30 °C. The experimental sorption capacities of functionalized sorbent (MET-MWB) were 0.42 mmol/g for Cu(II), 0.29 mmol/g for Zn(II) and 0.47 mmol/g for Co(II), which were obtained under the following conditions: pH of 5.0, 5.0 g sorbent/L and a temperature of 21 °C. The modeling of isotherms and kinetic curves as well as the analysis of the results obtained from desorption processes demonstrate the usefulness of this sorbent in the treatment of effluents contaminated with metal ions. In addition, tests on real wastewater samples highlight the potential of MET-MWB for large-scale applications.

Cu-based perovskite as a novel CWPO catalyst for petroleum refining wastewater treatment: Performance, toxicity and mechanism

For the first time, Cu-based perovskite oxides were used as catalysts to treat highly toxic and refractory petroleum refining wastewater based on catalytic wet peroxide oxidation (CWPO) technology. Perovskite La₂CuO₄ was synthesized by sol-gel method. A series of characterizations showed that the synthesized catalyst particles are tetragonal phase perovskite structure. The experimental results showed that under the conditions of catalyst dosage of 0.75 g, temperature of 100 ℃ and reaction time of 30 min, the COD removal rate was 89.58 %, the TOC removal rate was 87.38 %. The morphology and structure of the catalyst before and after the reaction proved that the catalyst has strong stability and catalytic activity. The components of raw water, Wet Air Oxidation (WAO) effluent and CWPO effluent were compared and analyzed by Gas Chromatography-Mass Spectrometry (GC-MS), and the possible mechanism and path of WAO and CWPO degradation of petroleum refining wastewater were further explored. The changes of Cu components in La₂CuO₄ before and after CWPO reaction and the transformation of lattice oxygen and adsorbed oxygen were analyzed by X-ray Photoelectron Spectroscopy (XPS). The involvement of Cu (Ⅱ) /Cu (Ⅰ) in the activation of H₂O₂ was speculated. Finally, the biotoxicity of raw water, WAO effluent and CWPO effluent was predicted. The results provide reference value for the application of catalyst La₂CuO₄ in various petrochemical wastewater.

VOCs absorption from gas streams using deep eutectic solvents - A review

Volatile organic compounds (VOCs) are one of the most severe atmospheric pollutants. They are mainly emitted into the atmosphere from anthropogenic sources such as automobile exhaust, incomplete fuel combustion, and various industrial processes. VOCs not only cause hazards to human health or the environment but also adversely affect industrial installation components due to their specific properties, i.e., corrosive and reactivity. Therefore, much attention is being paid to developing new methods for capturing VOCs from gaseous streams, i.e., air, process streams, waste streams, or gaseous fuels. Among the available technologies, absorption based on deep eutectic solvents (DES) is widely studied as a green alternative to other commercial processes. This literature review presents a critical summary of the achievements in capturing individual VOCs using DES. The types of used DES and their physicochemical properties affecting absorption efficiency, available methods for evaluating the effectiveness of new technologies, and the possibility of regeneration of DES are described. In addition, critical comments on the new gas purification methods and future perspectives are included.

Photocatalytic and Glucose Sensing Properties of ZnO-Based Nanocoating

Here, we report a simple and versatile synthesis of low-dimensional ZnO nanosheet (NS) arrays modified with Fe2O3 (hematite) to assemble photocatalytic coatings and non-enzymatic glucose sensors. Photocatalytic coatings made of widespread elements (zinc and iron) were tested for methylene blue (MB) dye decolorization under ultraviolet and visible (UV-vis) irradiation. A comparative study of unmodified and modified ZnO NS photocatalysts revealed a significant decrease in the dye concentration in 180 min when ZnO/Fe2O3 arrays were used. Size dependence efficiency of the hematite layer deposited onto ZnO is presented. A study of the sensitivity of biosensors made of ZnO nanostructures and ZnO/Fe2O3 nanocomposites for glucose detection showed an improvement in sensitivity with increased Fe2O3 thickness. The structure and morphology of low-dimensional coatings were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray analysis (EDX). The optical properties of nanoarrays showed a red shift of absorption after modifying ZnO with hematite layers, which holds good promise for expanding photocatalytic activity in the visible region.

A study on the efficiency of the sequential batch reactor on the reduction of wastewater pollution from oil washing

Industrial pollution discharges from washing fuel oils pose severe problems for the environment, particularly for the marine environment receiving these discharges. This work evaluates the biological treatment performance of wastewater (90 m³/h) rich in organic matter with low biodegradability using a sequential batch reactor (SBR) on a laboratory scale. The test using SBR was carried out for 25 days on a continuous cycle of 24 h (30 min of filling, 17 h of aeration, 4 h of anoxia, 2 h of settling, and 30 min of emptying). The feasibility of alternative sources of microorganisms from urban wastewater. The performance of the batch sequencing reactor was evaluated using turbidity, total suspended solids, chemical oxygen demand (COD), biological oxygen demand (BOD), ammonium, nitrate, and phenol as indicators. The results obtained showed that the COD/BOD ratio and the pollutant load vary from one campaign to another. The removal efficiency of COD, BOD, TSS (Total suspended solids), ammonium, nitrate, and phenol varies from 81%, 91%, 72%, 100%, 52%, and 63%. Thus, SBR-type treatment could be an interesting way to reduce pollution due to its simplicity, less space occupation, low energy consumption, and not requiring highly qualified personnel.

Outstanding Separation Performance of Oil-in-Water Emulsions with TiO2/CNT Nanocomposite-Modified PVDF Membranes

Membrane filtration is an effective technique for separating micro- and nano-sized oil droplets from harmful oil-contaminated waters produced by numerous industrial activities. However, significant flux reduction discourages the extensive application of this technology; therefore, developing antifouling membranes is necessary. For this purpose, various titanium dioxide/carbon nanotube (TiO₂/CNT) nanocomposites (containing 1, 2, and 5 wt.% multi-walled CNTs) were used for the modification of polyvinylidene fluoride (PVDF) ultrafilter (250 kDa) membrane surfaces. The effects of surface modifications were compared in relation to the flux, the filtration resistance, the flux recovery ratio, and the purification efficiency. TiO₂/CNT_2% composite modification reduced both irreversible and total filtration resistances the most during the filtration of 100 ppm oil emulsions. The fluxes were approximately 4-7 times higher compared to the unmodified PVDF membrane, depending on the used transmembrane pressure (510, 900, and 1340 L/m²h fluxes were measured at 0.1, 0.2, and 0.3 MPa pressures, respectively). Moreover, the flux recovery ratio (up to 68%) and the purification efficiency (95.1-99.8%) were also significantly higher because of the surface modification, and the beneficial effects were more dominant at higher transmembrane pressures. TiO₂/CNT_2% nanocomposites are promising to be applied to modify membranes used for oil-water separation and achieve outstanding flux, cleanability, and purification efficiency.

The collaborative monitored natural attenuation (CMNA) of soil and groundwater pollution in large petrochemical enterprises: A case study

A large in-service petrochemical enterprises in Northeast China was taken as the research object, and the Collaborative Monitored Natural Attenuation (CMNA) for soil and groundwater pollution was carried out to remedy combined pollution and reduce environmental risks. The pollutants distributions were obtained based on detailed regional investigation (Mar. 2019), and feature pollutants in soil and groundwater were then screened. The spatiotemporal variations of feature pollutants and relative microbial responses were explored during the CMNA process. Furthermore, the CMNA efficiency of the contaminated site at initial stage was evaluated by calculation of natural attenuation rate constant. The results showed that the feature pollutants in soil were 2,2',5,5'-tetrachlorobiphenyl (2,2',5,5'-TCB) and petroleum hydrocarbons (C₁₀∼C₄₀), and the feature pollutant in groundwater was 1,2-dichloroethane (1,2-DCA). The concentrations of all feature pollutants decreased continuously during four years of monitoring. Feature pollutants played a dominant role in the variability of microbial species both in soil and groundwater, increasing the relative abundance of petroleum tolerant/biodegradation bacteria, such as Actinobacteria, Proteobacteria and Acidobacteriota. The average natural attenuation rate constant of 2,2',5,5'-TCB and C₁₀∼C₄₀ in soil was 0.0012 d^-1 and 0.0010 d^-1, respectively, meeting the screening value after four years' attenuation. The average natural attenuation rate constant of 1,2-DCA was 0.0004 d^-1, which need strengthening measures to improve the attenuation efficiency.

Technological advancements in valorisation of industrial effluents employing hydrothermal liquefaction of biomass: Strategic innovations, barriers and perspectives

Hydrothermal liquefaction (HTL) is identified as a promising thermochemical technique to recover biofuels and bioenergy from waste biomass containing low energy and high moisture content. The wastewater generated during the HTL process (HTWW) are rich in nutrients and organics. The release of the nutrients and organics enriched HTWW would not only contaminate the water bodies but also lead to the loss of valued bioenergy sources, especially in the present time of the energy crisis. Thus, biotechnological as well as physicochemical treatment of HTWW for simultaneous extraction of valuable resources along with reduction in polluting substances has gained significant attention in recent times. Therefore, the treatment of wastewater generated during the HTL of biomass for reduced environmental emission and possible bioenergy recovery is highlighted in this paper. Various technologies for treatment and valorisation of HTWW are reviewed, including anaerobic digestion, microbial fuel cells (MFC), microbial electrolysis cell (MEC), and supercritical water gasification (SCWG). This review paper illustrates that the characteristics of biomass play a pivotal role in the selection process of appropriate technology for the treatment of HTWW. Several HTWW treatment technologies are weighed in terms of their benefits and drawbacks and are thoroughly examined. The integration of these technologies is also discussed. Overall, this study suggests that integrating different methods, techno-economic analysis, and nutrient recovery approaches would be advantageous to researchers in finding way for maximising HTWW valorisation along with reduced environmental pollution.

The role of TiO2 NPs catalyst and packing material in removal of phenol from wastewater using an ozonized bubble column reactor

Phenol is present as a highly toxic pollutant in wastewater, and it has a dangerous impact on the environment. In the present research, the phenol removal from wastewater has been achieved using four treatment methods in a bubble column reactor (treatment by ozone only, using packed bubble column reactor with ozone, utilizing ozone with TiO2 NPs catalyst in the reactor without packing, and employing ozone with TiO2 NPs in the presence of packing). The effects of phenol concentration, ozone dosage, TiO2 NPs additions, and contact time on the phenol removal efficiency were determined. It was found that at a contact time of 30 min, the phenol removal was 60.4, 74.9, 86.0, and 100% for the first, second, third, and fourth methods, respectively. The results indicated that the phenol degradation method using catalytic ozonation in a packed bubble column with TiO2 NPs is the best treatment method. This study demonstrated the advantages of using packing materials in a bubble column reactor to enhance the mass transfer process in an ozonation reaction and then increase the phenol removal efficiency. Also, the presence of TiO2 NPs as a catalyst improves the ozonation process via the production of hydroxyl routs. Additionally, the reaction kinetics of ozonation reaction manifested that the first order model is more applicable for the reaction. Eventually, the packed bubble column reactor in the presence of TiO2 NPs catalyst provided a highperformance removal of phenol with a high economic feasibility.

Sustainable treatment of dye wastewater by recycling microalgal and diatom biogenic materials: Biorefinery perspectives

Discharge of untreated or partially treated toxic dyes containing wastewater from textile industries into water streams is hazardous for environment. The use of heavy metal(s) rich dyes, which are chemically active in azo and sulfur content(s) has been tremendously increasing in last two decades. Conventional physical and chemical treatment processes help to eliminate the dyes from textile wastewater but generates the secondary pollutants which create an additional environmental problem. Microalgae especially the diatoms are promising candidate for dye remediation from textile wastewater. Nanoporous diatoms frustules doped with nanocomposites increase the wastewater remediation efficiency due to their adsorption properties. On the other hand, microalgae with photosynthetic microbial fuel cell have shown significant results in being efficient, cost effective and suitable for large scale phycoremediation. This integrated system has also capability to enhance lipid and carotenoids biosynthesis in microalgae while simultaneously generating the bioelectricity. The present review highlights the textile industry wastewater treatment by live and dead diatoms as well as microalgae such as Chlorella, Scenedesmus, Desmodesmus sp. etc. This review engrosses applicability of diatoms and microalgae as an alternative way of conventional dye removal techniques with techno-economic aspects.

Prospective review on bioelectrochemical systems for wastewater treatment: Achievements, hindrances and role in sustainable environment

Bioelectrochemical systems (BESs) are a relatively new arena for producing bioelectricity, desalinating sea water, and treating industrial effluents by removing organic matter. Microbial electrochemical technologies (METs) are promising for obtaining value-added products during simultaneous remediation of pollutants from wastewater. The search for more affordable desalination technology has led to the development of microbial desalination cells (MDCs). MDC combines the operation of microbial fuel cells (MFC) with electrodialysis for water desalination and energy generation. It has received notable interest of researchers in desalination and wastewater treatment because of low energy requirement and eco-friendly nature. Firstly, this article provides a brief overview of MDC technology. Secondly, factors affecting functioning of MDC and its applications have been accentuated. Additionally, challenges and future outlook on the development of this technology have been delineated. State-of-the-art information provided in this review would expand the scope of interdisciplinary and translational research.

Experimental and optimization studies on phycoremediation of dairy wastewater and biomass production efficiency of Chlorella vulgaris isolated from Ganga River, Haridwar, India

Dairy wastewaters (DWW) are rich in several pollutants, including high biochemical oxygen demand (BOD) and chemical oxygen demand (COD), and their unsafe disposal may cause damage to the environment. In this study, Chlorella vulgaris (identified as NIES:227 strain based on 28s rRNA sequencing) was isolated from the freshwater habitat of the Ganga River at Haridwar, India, and further tested for its efficacy in treating DWW. The phycoremediation experiments were conducted using three different DWW concentrations (0, 50, and 100%), operating temperatures (20, 25, and 30 °C), and light intensities (2000, 3000, and 4000 lx) using response surface methodology. Results showed that after 16 days of experiments, a significant (P < 0.05) reduction in BOD (96.65%) and COD (87.50%) along with a maximum biomass production of 1.757 g/L was achieved using 57.72% of dairy industry wastewater, 24.16 °C of reactor temperature, and 3874.51 lx of light intensity. The RSM models had coefficient of determination (R²) values above 0.9459 with a minimum difference between measured and predicted responses. Therefore, the findings of this study suggest that the isolated C. vulgaris can be effectively used to treat dairy wastewater along with significant production of algal biomass which can be further used for the generation of low-cost biofuel and other materials.

Investigation of Dioctyl Sodium Sulfosuccinate in Demulsifying Crude Oil-in-Water Emulsions

This research investigated the performance of dioctyl sodium sulfosuccinate (DSS), a double-chain anionic surfactant, in breaking crude oil-in-water emulsions. The response surface methodology was used to consider the effect of the DSS concentration, oil concentration, and shaking time on demulsification efficiency and obtain optimum demulsification conditions. Further single-factor experiments were conducted to investigate the effects of salinity, crude oil conditions (fresh and weathered), and gravity separation settling time. The results showed that DSS efficiently demulsified stable emulsions under different oil concentrations (500-3000 mg/L) within 15 min shaking time. Increasing DSS concentration to 900 mg/L (critical micelle concentration) increased the demulsification efficiency to 99%. DSS not only improved the demulsification efficiency but also did not impede the demulsifier interfacial adsorption at the oil-water interface due to the presence of the double-chain structure. The low molecular weight enables the homogeneous distribution of DSS molecules in the emulsion, leading to a high demulsification efficiency within 15 min. Analysis of variance results indicated the importance of considering the interaction of oil concentration and shaking time in demulsification. DSS could reduce the total extractable petroleum hydrocarbons in the separated water to <10 mg/L without gravity separation and could achieve promising demulsification performance at high salinity (36 g/L) and various concentrations of fresh and weathered oil. The demulsification mechanism was explained by analyzing the microscopic images and the transmittance of the emulsion. DSS could be an efficient double-chain anionic surfactant in demulsifying stable oil-in-water emulsions.

Free-living amoebae in an oil refinery wastewater treatment facility

Free Living Amoebae (FLA) are ubiquitous microorganisms reported from harsh environmental conditions. Oil refinery facilities consume vast volumes of water during their processes, generating a large amount of wastewater. The present study aimed to evaluate the wastewater treatment process in an oil refinery wastewater treatment facility (ORWWTF) for the presence of FLA. Water samples were collected from an oil refinery wastewater (ORWW) for nine months. After recording physical-chemical features, samples were cultivated onto non-nutrient agar (NNA). The discriminative fragments of the ribosomal RNA (rRNA) gene were amplified and sequenced to characterize the isolated FLA. Phylogenetic tree, and network analysis were employed to evaluate genetic relationships. The thermo- and osmotolerant tests were performed on the isolated FLA. Twenty-five (32.9%) samples were positive for FLA cultivation. Acanthamoeba spp., Vahlkampfiids, and Vermamoeba spp. were detected, of which Acanthamoeba species were predominant. There was no statistical correlation between pH, NH₃, PO₄, H₂S, and TDS with the presence of FLA. A statistical correlation between the presence of FLA and the type of wastewater treatment plants (WWTPs) was significant (P-value = 0.011). All Acanthamoeba spp. isolates belonged to the genotypes T4 (17/21; 80.95%) and T11 (4/21; 19.05%). Vahlkampfiids were Naegleria spp., (7/10; 70%), Tetramitus aberdonicus (1/10; 10%), Learamoeba spp., (1/10; 10%), and Vahlkampfia spp., (1/10; 10%). All three Vermamoeba spp. were V. vermiformis. The ORWW contains toxic materials, and a few microorganisms can stay active in these environments. This is the first study which isolates FLA from such super harsh conditions. For the first time, T. aberdonicus, and Learamoeba spp., were isolated from oily wastewater. Our findings signify the concern due to the distribution of potentially pathogenic FLA to downstream lands via treated wastewater that may be released after treatment processing.

Advancements of sequencing batch reactor for industrial wastewater treatment: Major focus on modifications, critical operational parameters, and future perspectives

Industrial wastewater discharge has increased manifolds over the last few decades. Efficient industrial wastewater treatment is mandatory to meet stringent discharge regulations. Biological treatment systems, such as the sequencing batch reactor (SBR) are generally employed for domestic wastewater treatment. However, low infrastructure and energy requirements, as well as low footprint, make SBR a prominent technique to treat industrial wastewater. In the present review, the feasibility of SBR to treat wastewater generated from industries, such as textile, pulp and paper, pharmaceutical, tannery, etc., has been discussed. The factors affecting the treatment efficacy of the SBR in terms of organics and nutrient removal have also been investigated. It has been observed that the SBR system is effective for industrial wastewater treatment as it is easy to operate, resistant to shock loads, and can retain high biomass concentrations. The modifications to the conventional SBR, such as sludge granulation, the addition of bio-film carriers, and the incorporation of adsorbents, salt-tolerant microbes, and coagulants have been discussed. Further, various novel combinations of SBR with the other advanced treatment technologies, such as Fenton, membrane-based process, and electrochemical process have shown enhanced removal of various conventional and recalcitrant pollutants. The current review also accentuates the sustainability aspects of SBR technology to treat industrial wastewater which may be beneficial for researchers and engineers working in this field.

Evolution in mitigation approaches for petroleum oil-polluted environment: recent advances and future directions

Increasing petroleum consumption and a rise in incidental oil spillages have become global concerns owing to their aquatic and terrestrial toxicity. Various physicochemical and biological treatment strategies have been studied to tackle them and their impact on environment. One of such approaches in this regard is the use of microbial processes due to their being "green" and also apparent low cost and high effectiveness. This review presents the advancement in the physical and biological remediation methods and their progressive efficacy if employed in combination of hybrid modes. The use of biosurfactants and/or biochar along with microbes seems to be a more effective bioremediation approach as compared to their individual effects. The lacuna in research at community or molecular level has been overcome by the recent introduction of "-omics" technology in hydrocarbon degradation. Thus, the review further focuses on presenting the state-of-art information on the advancement of petroleum bioremediation strategies and identifies the research gaps for achieving total mitigation of petroleum oil.

Sustainable strategies for combating hydrocarbon pollution: Special emphasis on mobil oil bioremediation

The global rise in industrialization and vehicularization has led to the increasing trend in the use of different crude oil types. Among these mobil oil has major application in automobiles and different machines. The combustion of mobil oil renders a non-usable form that ultimately enters the environment thereby causing problems to environmental health. The aliphatic and aromatic hydrocarbon fraction of mobil oil has serious human and environmental health hazards. These components upon interaction with soil affect its fertility and microbial diversity. The recent advancement in the omics approach viz. metagenomics, metatranscriptomics and metaproteomics has led to increased efficiency for the use of microbial based remediation strategy. Additionally, the use of biosurfactants further aids in increasing the bioavailability and thus biodegradation of crude oil constituents. The combination of more than one approach could serve as an effective tool for efficient reduction of oil contamination from diverse ecosystems. To the best of our knowledge only a few publications on mobil oil have been published in the last decade. This systematic review could be extremely useful in designing a micro-bioremediation strategy for aquatic and terrestrial ecosystems contaminated with mobil oil or petroleum hydrocarbons that is both efficient and feasible. The state-of-art information and future research directions have been discussed to address the issue efficiently.

Bioremoval of some heavy metals from aqueous solutions by two different indigenous fungi Aspergillus sp. AHM69 and Penicillium sp. AHM96 isolated from petroleum refining wastewater

Myco-remediation of heavy metals using indigenous fungi of different petroleum refining areas in Egypt was applied. Among the physicochemical parameters determined in these refineries effluents, the highest levels of heavy metals were recorded for the most toxic heavy metals Fe³⁺ and Co²⁺. The fungal isolates under the isolation codes AHM69 and AHM96 isolated from the mycobiome of Mostorod and Tanta refineries, respectively showed the best bioremoval efficiency toward heavy metals from the real wastewater mixture and polycyclic aromatic hydrocarbons from aqueous solutions. Based on phenotypic and genotypic analysis they were identified as Aspergillus sp. AHM69 and Penicillium sp. AHM96. The optimum conditions for the best bioremoval of Fe³⁺ and Co²⁺ from aqueous solutions by Aspergillus sp. AHM69 were live biomass, temperature 45–55 °C, pH 4.5–5.0, contact time 180 min, metal concentration equal to 1000 and 400 mg/L of Fe³⁺ and Co²⁺ with live fungal biomass dose of 0.5% and 0.4% with Fe³⁺ and Co²⁺, respectively. Concerning to the biomass of Penicillium sp. AHM96, the optimum operation conditions for the best removal of Fe³⁺ and Co²⁺ were 45 °C, pH 5.0 and 400 mg/L of Fe³⁺ with 1.0% biosorbent dosage or 1000 mg/L of Co²⁺ with 0.5% biosorbent dosage for 180 min as process time. Furthermore, FTIR analysis showed masking, shifting, creating and absenting of different functional groups in the fungal biomass surface of AHM96 and AHM69 strains in the presence of Fe³⁺ and Co²⁺ compared to unloaded biomasses. Microscopy with Energy Dispersive X-ray analysis (SEM-EDX) indicated that the removal of Fe³⁺ and Co²⁺ by fungi AHM69 and AHM96 was via biosorption and bioaccumulation on the biomass surface. Our results suggested that in the near future, fungal treatment is likely to outperform and replace other chemical and biological treatments in industrial wastewater treatment for oil refining.

Current technologies and future perspectives for the treatment of complex petroleum refinery wastewater: A review

Petroleum refinery wastewater (PRW) is a complex mixture of hydrocarbons, sulphides, ammonia, oils, suspended and dissolved solids, and heavy metals. As these pollutants are toxic and recalcitrant, it is essential to address the above issue with efficient, economical, and eco-friendly technologies. In this review, initially, an overview of the characteristics of wastewater discharged from different petroleum refinery units is discussed. Further, various pre-treatment and post-treatment strategies for complex PRW are introduced. A segregated approach has been proposed to treat the crude desalting, sour, spent caustic, and oily wastewater of petroleum refineries. The combined systems (e.g., ozonation + moving bed biofilm reactor and photocatalysis + packed bed biofilm reactor) for the treatment of low biodegradability index wastewater (BOD₅/COD < 0.2) were discussed to construct a perspective map and implement the proposed system efficiently. The economic, toxicity, and biodegradability aspects are also introduced, along with research gaps and future scope.

Review of oilfield produced water treatment technologies

Produced water is the wastewater formed when water is brought from subsurface reservoirs during oil or gas extraction. Currently, produced water is mainly treated using conventional trains that contain adsorbates, membrane filters, phase separators and cyclones. This paper reviewed the detailed characteristics of oilfield-produced water and the assessment of multiple technologies at primary, secondary, and tertiary treatments stages. The effectiveness of the treatment technology from the production of waste, energy requirements, usage of chemicals and the treatment effect of contaminants has been discussed. Then a qualitative assessment was presented in terms of energy requirements, robustness, flexibility, waste generation, modularity, and mobility, which has become critical to the development and application prospects of any technology.

Modified PVA membrane for separation of micro-emulsion

Release of liquefied hydrocarbons in domestic and industrial effluents, along with oil spills cause significant adverse effects on the soil, water, aquatic ecosystem, and humans. Thus, selective and cost-effective technology to address this challenge is highly desirable. Here, we report the fabrication of electrospun polyvinyl alcohol (PVA) membrane, modified with glutaraldehyde (GA) and a device thereof, for treatment of oil emulsions and recovery of precious fossil fuel. The modified PVA membranes are super-oleophobic with a high static underwater oil contact angle of 163 ± 3° for motor oil. Investigation of wetting properties suggests that the membrane can efficiently separate different oils such as sesame oil, motor oil, mustard oil, and sunflower oil from their emulsions. The motor oil emulsion with separation efficiency of >99% at an excellent permeate flux of 5128 L/m²·h·bar has been achieved. Thus, the prepared modified PVA membrane construes an easy solution for not only effective treatment of oily wastewater but also for oil recovery with high flux.

Antifouling BaTiO3/PVDF piezoelectric membrane for ultrafiltration of oily bilge water

Barium titanate/polyvinylidene fluoride (BaTiO₃/PVDF) piezoelectric membrane was successfully prepared and generated in-situ vibrations to reduce membrane fouling by applying alternating current (AC) signal for oily bilge water ultrafiltration. The effect of in-situ vibration on membrane fouling was investigated through changing in the excitation alternating voltage and its frequency, pH, crossflow rate. The results indicated that the piezoelectric membrane by applying AC signal remarkably alleviated the membrane fouling for bilge water ultrafiltration. The membrane fouling decreased with increasing the AC signal voltage. The final steady-state permeate flux from the piezoelectric membrane for bilge water ultrafiltration increased with the AC signal voltage, raising it by up to 63.4% at AC signal voltage of 20 V compared to that of the membrane without applying AC voltage. The high permeate flux was obtained at the resonant frequency of 220 kHz. During the 50-h ultrafiltration of bilge water with the piezoelectric membrane excited at 220 kHz and 15 V, the permeate flux from the membrane was stable. The oil concentration in outflow from the piezoelectric membrane was below 14 ppm, which met the discharged level required by IMO convention. The total organic carbon removal rate in bilge water was over 94%.

A review of application and development of combustion technology for oil sludge

Oil sludge is a typical hazardous waste in the petrochemical and electric power industry. It has complex components and special properties, and has serious hazards to humans, plants, water, and soil. Therefore, how to realize the effective disposal of oil sludge has become an urgent issue to be solved worldwide. Among the existing oil sludge treatment approaches, combustion has been considered to be a promising technology to realize the large-scale industrial application. In the present work, the characteristics of oil sludge were described in detail. The application and development of oil sludge combustion technology were critically summarized and discussed, including factors affecting combustion, drying process, combustion characteristics, synergistic treatment technology, and formation and control of secondary pollution. Besides, the development of combustion equipment, and integrated thermal treatment technology for oil sludge were prospected. This work can be used for guiding the industrial disposal of oil sludge.

Systematic and quantitative analysis of two decades of anodic wastewater treatment in bioelectrochemical reactors

Wastewater treatment is generally performed using energy-intensive processes, such as activated sludge. Improving energy efficiency has become one of the main challenges for next-generation wastewater treatment plants. Bioelectrochemical systems (BES) have been attracting attention because they take advantage of the chemical energy contained in wastewater while enabling the valorization of effluents: either with electrical energy (microbial fuel cells) or with useful chemicals (microbial electrolysis cells). Bioelectrochemical wastewater treatment has been under investigation since the early 2000s and is now the subject of an abundant literature, which is most frequently focused on anodic COD removal. Comparing results obtained in different studies is particularly difficult with BES, because many different parameters (effluent characteristics, inoculation, design, and operation) may interact and because using real effluents results in high variability. To address this issue, data were retrieved from 1,073 articles that were selected objectively and with transparency. This systematic review evaluates the potential of anodic wastewater treatment, based on 4,579 experimental observations. Overall, BES has already shown satisfactory treatment capacity, with a median chemical oxygen demand removal of 72%. However, the median coulombic efficiency was only 18%, increasing this parameter offers the greatest opportunity for BES improvement.

Oily Wastewater Treatment: Methods, Challenges, and Trends

The growing interest in innovations regarding the treatment of oily wastewater stems from the fact that the oil industry is the largest polluter of the environment. The harm caused by this industry is seen in all countries. Companies that produce such wastewater are responsible for its treatment prior to disposal or recycling into their production processes. As oil emulsions are difficult to manage and require different types of treatment or even combined methods, a range of environmental technologies have been proposed for oil-contaminated effluents, such as gravity separation, flotation, flocculation, biological treatment, advanced oxidation processes, and membranes. Natural materials, such as biopolymers, constitute a novel, sustainable solution with considerable potential for oily effluent separation. The present review offers an overview of the treatment of oily wastewater, describing current trends and the latest applications. This review also points to further research needs and major concerns, especially with regards to sustainability, and discusses potential biotechnological applications.

The Formation, Stabilization and Separation of Oil–Water Emulsions: A Review

Oil–water emulsions are widely generated in industries, which may facilitate some processes (e.g., transportation of heavy oil, storage of milk, synthesis of chemicals or materials, etc.) or lead to serious upgrading or environmental issues (e.g., pipeline plugging, corrosions to equipment, water pollution, soil pollution, etc.). Herein, the sources, classification, formation, stabilization, and separation of oil–water emulsions are systematically summarized. The roles of different interfacially active materials–especially the fine particles–in stabilizing the emulsions have been discussed. The advanced development of micro force measurement technologies for oil–water emulsion investigation has also been presented. To provide insights for future industrial application, the separation of oil–water emulsions by different methods are summarized, as well as the introduction of some industrial equipment and advanced combined processes. The gaps between some demulsification processes and industrial applications are also touched upon. Finally, the development perspectives of oil–water treatment technology are discussed for the purpose of achieving high-efficiency, energy-saving, and multi-functional treatment. We hope this review could bring forward the challenges and opportunities for future research in the fields of petroleum production, coal production, iron making, and environmental protection, etc.

Operational parameters optimization for remediation of crude oil-polluted water in floating treatment wetlands using response surface methodology

The application of floating treatment wetlands (FTWs) is an innovative nature-based solution for the remediation of polluted water. The rational improvement of water treatment via FTWs is typically based on multifactorial experiments which are labor-intensive and time-consuming. Here, we used the response surface methodology (RSM) for the optimization of FTW's operational parameters for the remediation of water polluted by crude oil. The central composite design (CCD) of RSM was used to generate the experimental layout for testing the effect of the variables hydrocarbon, nutrient, and surfactant concentrations, aeration, and retention time on the hydrocarbon removal in 50 different FTW test systems planted with the common reed, Phragmites australis. The results from these FTW were used to formulate a mathematical model in which the computational data strongly correlated with the experimental results. The operational parameters were further optimized via modeling prediction plus experimental validation in test FTW systems. In the FTW with optimized parameters, there was a 95% attenuation of the hydrocarbon concentration, which was very close to the 98% attenuation predicted by the model. The cost-effectiveness ratio showed a reduction of the treatment cost up to $0.048/liter of wastewater. The approach showed that RSM is a useful strategy for designing FTW experiments and optimizing operational parameters.