Petroleum Refinery Wastewater Research Articles

Nano-pumice derived from pumice mine waste as a low-cost electrode catalyst for microbial fuel cell treating edible vegetable oil refinery wastewater for bioenergy generation and reuse

This study aimed to assess nano-pumice (NP) from pumice mining waste as a local, cost-effective anode catalyst in microbial fuel cells (MFCs) for treating edible vegetable oil refinery wastewater (EVORW) and generating bioenergy. Pumice mining waste was converted into nano in three stages: crushing up to ≤3 cm, reducing the size of the previous step particles to 150 μm and converting the previous step particles to <100 nm. Nano-pumice prepared was coated on the carbon cloth (CC) to increase anode surface area of MFC. Two MFCs were utilized, with MFC-1 serving as a control and MFC-2 incorporating a CC electrode coated with nano-pumice. The surface morphology, elemental and chemical composition, and textural characterization of CC, pumice, NP, and CC coated with NP were analyzed using FE-SEM, EDX, XRF, and BET techniques. MFC-2 achieved a maximum power density of 30±4W/m³ at a current density of 55±5A/m³. The MFC-1 reached a maximum power density of 18±4W/m³ at a current density of 35±6A/m³. In MFC-2, the EVORW treatment achieved maximum removals of COD (94 ± 2 %), NH4+-N (85 ± 4 %), TP (76 ± 5 %), SO42− (68 ± 6 %), TSS (81 ± 2 %), and TDS (73 ± 1 %). MFC-1 achieved removal efficiencies of 66 ± 3 % for COD, 57 ± 6 % for NH4+-N, 48 ± 3 % for TP, 45 ± 3 % for SO42−, 65 ± 3 % for TSS, and 61 ± 1 % for TDS. MFC-2 power density rose significantly, reaching 61 ± 3 % (1.6 times) higher than MFC-1and it also demonstrated a superior ability to improve raw wastewater quality compared to MFC-1. The MFC with the CC/NP anode exhibited both excellent power production and high COD removal efficiency, making nano-pumice a suitable anode catalyst for MFC applications.

The Degradation of Furfural from Petroleum Refinery Wastewater Employing a Packed Bubble Column Reactor Using O3 and a CuO Nanocatalyst

Furfural is one of the main pollutant materials in petroleum refinery wastewater. This work used an ozonized bubble column reactor to remove furfural from wastewater. The reactor applied two shapes of packing materials and two dosages of CuO nanocatalyst (0.05 and 0.1 ppm) to enhance the degradation process. The results indicated that adding 0.1 ppm of nanocatalyst provided an efficient rate of furfural degradation compared to that of 0.05 ppm. Also, the packing materials enhanced the furfural degradation significantly. As a result, the contact area between the gas and liquid phases increased, and a high furfural removal efficiency was achieved. It was found that the CuO nanocatalyst generated more (OH•) radicals. At a treatment time of 120 min and an ozone flow of 40 L/h, the furfural degradation recorded values of 80.66 and 78.6% at 10 and 20 ppm of initial concentration, respectively. At 60 ppm, the degradation efficiency did not exceed 74.16%. Furthermore, the kinetic study indicated that the first-order mechanism is more favorable than the second-order mechanism, representing the furfural degradation with a correlation factor of 0.9837. Finally, the furfural reaction can be achieved successfully in a shorter time and at low cost.

Harnessing microbial synergy: A comprehensive evaluation of consortia-mediated bioremediation strategies for petroleum refinery wastewater treatment

The growing global demand for energy has led to the expansion of oil and gas industries, putting our environment at risk of pollution. The unregulated discharge of petroleum refinery wastewater (PRW), accidental spills, and ineffective policies have led to severe contamination and increased environmental and health consequences making management and mitigation a priority for everyone. This study evaluated the performance of two biological treatment methods - free-cell microbial consortium and immobilized microbial system - in the remediation of PRW using physicochemical, 2,6-dichlorophenollindophenol (DCPIP), Gas chromatography (GC) and Fourier-transform infrared spectroscopy (FTIR) techniques. The effectiveness of the two microbial consortia in reducing concentrations of polycyclic aromatic hydrocarbons (PAHs) and heavy metals (HMs) in the wastewater was compared to determine the most efficient method for treating PRW. The physicochemical result revealed cocktails of contaminants while Alcaligenes faecalis strain SLW6 and strain IAM 12369, and Providencia vermicola strain OP1, showed high degradative capacities. The immobilized and free-cell microbial systems significantly reduced the concentrations of PAHs, and HMs pollutants in the wastewater, with the former showing slightly better removal efficiencies for PAHs (92.97 % vs 87.34 %), heavy metals (99.17 %), and oil weight reduction (87.76 % vs 82.25 %) after the 28-day biodegradation period respectively. GC and FTIR analyses confirmed the formation of various degraded products, demonstrating the microbial consortia's effectiveness in degrading complex organic compounds. The findings highlight the potential of microbial consortia-mediated remediation as an eco-friendly and sustainable approach for treating PRW, contributing to protecting water resources and promoting sustainable practices in the petroleum industry.

Treatment of Petroleum Refinery Wastewater by Activated Carbon Assisted Electrocoagulation Process

Treatment of Petroleum Refinery Wastewater by Activated Carbon Assisted Electrocoagulation Process

A comprehensive study on the effects of electrocoagulation integrated in a membrane bioreactor treating sunflower oil refinery wastewater on treatment performance, biological properties, and fouling behavior.

This study evaluated the effects of electrocoagulation integrated in a laboratory-scale membrane bioreactor (MBR), namely EC-MBR, on the treatment performance, activated sludge morphological characterization, and membrane fouling of MBR treating actual sunflower oil refinery wastewater. The EC-MBR system exhibited significantly higher chemical oxygen demand (COD) and oil and grease (O&G) removal efficiency compared to the MBR system. Additionally, both systems achieved excellent turbidity removal, with a percentage above 99%. The membrane fouling rate was higher in the EC-MBR system compared to the MBR system. Despite the decrease in the soluble microbial product (SMP) and extracellular polymeric substance (EPS) concentration in the EC-MBR system, especially their protein fraction, the significant increase in MLSS and carbohydrates/protein ratio, and the decrease in the mixed liquor and the cake layer particles size were the main membrane fouling factors. The membrane fouling resistance distribution showed that the EC-MBR system had a higher percentage of pore blocking resistance compared to the MBR. FTIR analysis identified a greater proportion of carbohydrate compounds in the cake layer of the EC-MBR system. SEM images revealed dense microbial clusters, mainly rod- and oval-shaped bacteria, in the EC-MBR system. Furthermore, EDX analysis detected elements such as Ca, K, O, Al, and P in both systems, with the EC-MBR system showing a higher Al content. The EC-MBR system showed low energy consumption (0.431kWhm-3) and total operating costs ($0.90m-3), showcasing its effectiveness and affordability for sustainable wastewater management.

Preparation, characterization, and application of chitosan-silver nanoparticles for Cu(II) and Zn(II) removal from oil refinery wastewater

Copper and zinc stand as one of the most alarming contaminants, presenting a formidable challenge in the realm of drinking water across numerous countries. To deal with this challenge, the sequestration of copper and zinc by adsorption has been extensively investigated in the solid media. Here, an adsorbent system based on a natural polymer - chitosan with physical cross-linking using silver nanoparticles is investigated for high binding, to get a new modified adsorbents (CS/AgNPs) that used these metal ions from simulated oil refinery wastewater. The adsorption mechanism is extensively studied via FTIR, zeta potential, dynamic light scattering (DLS), EDS, SEM, and BET. The prepared adsorbents (CS/AgNPs) have a bigger surface area than pristine chitosan that expanded from 4.74 to 36.34 m2/g, respectively. The prepared CS/AgNPs showed stronger adsorption ability than pristine chitosan attributable to its permeable structure and expanded surface area. In batch experiments, the Langmuir adsorption isotherms revealed that the highest uptake removal amount for Copper (II) and zinc (II) onto CS/AgNPs are 110.67 and 92.13 mg/g, correspondingly. These findings indicate that CS/AgNPs show a great potential as a proficient and selective materials for eliminating copper and zinc ions from aqueous solutions.

Polycarbonate ultrafiltration membrane modified with Mg–Al-layered double hydroxide nanoparticles for treatment of petroleum refinery wastewater

Polycarbonate ultrafiltration membrane modified with Mg–Al-layered double hydroxide nanoparticles for treatment of petroleum refinery wastewater

Micro-particle-clay aided microporous support for removal of hydrocarbon toxicity from petroleum refinery wastewater in single-slope solar distillation

The removal of toxic hydrocarbon pollutants is not sustainable via conventional treatment technology. This research investigates the feasibility of a solar distillation (SSD) system to eliminate soluble hydrocarbon salts, stubborn organics, and separation of oil emulsion from petroleum refinery wastewater (PRW). The PRW collected from the petroleum refinery facility and hydrophilic micro-particle clay (MP-clay) samples were characterized following the ASTM and SEM techniques. The treatment process for the removal of total dissolved salts (TDS), biological oxygen demand (BOD), and separation of oil emulsion was monitored in the SSD still using MP-clay aided microporous filter support, at varying MP-clay concentrations (0.5–3.5 mg/L), pH (6.6–7.3), temperature (27–80 0C), and exposure time (1–18hrs) respectively. The results showed MP-clay as self-assembled monolayers on microporous support with a 98 % reduction in BOD concentration under optimum conditions: pH of 7.3, contact time of 9 hours, and MP-clay concentration of 3.2 mg/L. The TDS concentration decreased by 94 % at the optimal exposure time (15hrs) and temperature (48 0C) in SSD still. The investigation also examined the recyclability of MP-clay for oil content accumulation and water separation. The findings demonstrated MP-clay on reuse retained 90.5 % of its activity in water separation and established MP-clay can be operated to the optimum of 3 cycles, each lasting 60 minutes. After this period, reactivity loss becomes severe owing to lipase leakage and substrate obstruction. The research findings will help harness solar energy for environmentally friendly and cost-effective PRW remediation.

Bioremediation of petroleum refinery wastewater using Bacillus subtilis IH-1 and assessment of its toxicity.

Environmental contamination from petroleum refinery operations has increased due to the rapid population growth and modernization of society, necessitating urgent repair. Microbial remediation of petroleum wastewater by prominent bacterial cultures holds promise in circumventing the issue of petroleum-related pollution. Herein, the bacterial culture was isolated from petroleum-contaminated sludge samples for the valorization of polyaromatic hydrocarbons and biodegradation of petroleum wastewater samples. The bacterial strain was screened and identified as Bacillus subtilis IH-1. After six days of incubation, the bacteria had degraded 25.9% of phenanthrene and 20.3% of naphthalene. The treatment of wastewater samples was assessed using physico-chemical and Fourier-transform infrared spectroscopy analysis, which revealed that the level of pollutants was elevated and above the allowed limits. Following bacterial degradation, the reduction in pollution parameters viz. EC (82.7%), BOD (87.0%), COD (80.0%), total phenols (96.3%), oil and grease (79.7%), TKN (68.8%), TOC (96.3%) and TPH (52.4%) were observed. The reduction in pH and heavy metals were also observed after bacterial treatment. V. mungo was used in the phytotoxicity test, which revealed at 50% wastewater concentration the reduction in biomass (30.3%), root length (87.7%), shoot length (93.9%), and seed germination (30.0%) was observed in comparison to control. When A. cepa root tips immersed in varying concentrations of wastewater samples, the mitotic index significantly decreased, suggesting the induction of cytotoxicity. However, following the bacterial treatment, there was a noticeable decrease in phytotoxicity and cytotoxicity. The bacterial culture produces lignin peroxidase enzyme and has the potential to degrade the toxic pollutants of petroleum wastewater. Therefore the bacterium may be immobilised or directly used at reactor scale or pilot scale study to benefit the industry and environmental safety.

Development of energy efficient flower-shaped defective TiO2 materials for wastewater remediation of agro-industries and oil refineries

Wastewater containing high concentrations of phenolic compounds (PhCs), produced in large quantities by the world's expanding agro-industries and oil refineries, is one of the main polluters of rivers and streams. It is economically and technically reasonable to treat such wastewater using TiO2-based photocatalysis. But in order for photocatalysis to be used on a large scale, it must degrade PhCs efficiently while using less electrical energy (EE) and treating them at lower costs (t-cost). In this study, a modified hydrothermal method was used to produce the flower-shaped defective black TiO2 (BTNFs) from pre-prepared black TiO2 nanoparticles (BTNPs) as an energy saving strategy in wastewater remediation. The adsorption and photocatalytic performance, energy needs, and t-costs for both materials were examined for photodegradation of PhCs from simulated oil refinery wastewater (ORW), palm oil mill wastewater (POW), and olive oil mill wastewater (OMW). The findings revealed that BTNFs have improved properties which made them more effective in adsorption of PhCs and photocatalyzing their degradation. Combining photocatalysis and adsorption based on BTNFs led to an improved removal (49.75–98.40%) of PhCs depending on the wastewater matrix and reduced the EE consumption and t-cost by 8.96–23.86% for treating OMW, POW, and ORW.

Enhanced Nanofiltration Performance of the PVC/PVA Thin Film Membranes for Treatment of Petroleum Refinery Wastewater through Incorporation of Amino-functionalized SBA-15 Nanoparticles

Enhanced Nanofiltration Performance of the PVC/PVA Thin Film Membranes for Treatment of Petroleum Refinery Wastewater through Incorporation of Amino-functionalized SBA-15 Nanoparticles

Sequential oxidation-composting-phytoremediation treatment for the management of an oily sludge from petroleum refinery

Oily sludges are generated in large quantities in petroleum refinery wastewater treatment plants. Given their complex composition, they are classified as hazardous waste. Selecting a single treatment technique for their remediation is challenging.This work aims to assess the extent of composting followed by phytoremediation on an oily sludge from an API separator unit, pre-treated by chemical oxidation with alkaline activated persulfate (PS). 18% of total petroleum hydrocarbons (TPH) were determined by IR spectroscopy. The aliphatic hydrocarbon content was 4714 ± 250 ppm by GC-FID, and aromatics were not detectable, suggesting a high amount of non-chromatographable complex hydrocarbons. The density of generalist and hydrocarbon-degrading populations of the oily sludge estimated by quantitative polymerase chain reaction (qPCR) evidenced an autochthonous microbiota with hydrocarbon-degrading capacity. The oxidative treatment with PS removed 31% of the TPH determined by IR after 20 days. The significant reduction of the native bacterial community was counterbalanced by coupling a composting treatment. Co-composting the sludge with goat manure and oat straw produced, after a year, a 96% reduction in TPH content, regardless of the oxidative pretreatment. Organic matter transformation was evidenced by the decrease of dissolved organic carbon (DOC) and the variation in E4/E6 ratio. The matrices obtained of composting were used as substrates for phytoremediation for 4 months. Ryegrass seeds were planted in both PS-treated and untreated sludge substrates. The presence of the plant grown in the pre-oxidised and composted substrate resulted in a higher aerial biomass of ryegrass (67%), an increase in enzymatic activities, and higher concentration of DOC, although without evidence of additional dissipation of TPH.The dynamics of the bacterial communities of the different substrates generated during the biological treatment were analyzed by Illumina NovaSeq DNA sequencing of 16S rRNA amplicons. The findings mirrored a succession compatible with that described in contaminated matrices, but also in other non-contaminated ones.According to these findings, an organic matter transformation process occurred, which included the complex hydrocarbons of the oily sludge, resulting in an active substrate that promoted the retention of nutrients and water and provided the necessary support for plant development.

Combination of online hollow fiber liquid phase microextraction with smartphone-based sensing for in situ formaldehyde assay in fabric and wastewater samples.

A miniaturized analytical methodology was introduced based on the combination of a direct and online hollow fiber microextraction method with smartphone color detection. The method was used for the determination of formaldehyde (target analyte) in fabric and wastewater samples. In this regard, two reagents including ammonium acetate buffer and acetylacetone were added to the formaldehyde samples to create a colored compound. The colored compound was extracted from the sample by using the hollow fiber liquid-phase microextraction method, the extracted phase was not taken out of the extraction box and was directly transferred into a specially designed detection cell, and a smartphone was applied forin-situ color sensing and data readout. This combination gathered the advantages of both state-of-the-art microextraction techniques and smartphone sensing. Formaldehyde, as a carcinogenic compound widely used in paint and clothing industries, was selected as a model test. Factors affecting extraction efficiency were investigated and optimized, including the type of organic solvents, reagent concentration, salt, pH, stirring speed, reaction temperature, and extraction time. The linear region of the method under optimal conditions was 40-1500µg L-1 for wastewater samples and 0.3-11.2mg kg-1 for fabrics. The limit of detection and limit of qualification were 13 and 40µg L-1, respectively. The relative standard deviations for concentrations of 100 and 1000µg L-1 were 6% and 4%, respectively. To evaluate the application of the method for real samples, types of fabric and two samples of oil refinery wastewater were selected. The relative recovery in real samples was 84-98%. The results of the analytical parameters of the method show that the developed method can be used as an efficient method to determine formaldehyde in real samples.

Optimization of coagulation-flocculation process for wastewater treatment from vegetable oil refineries using chitosan as a natural flocculant

Vegetable oil refinery wastewater (VORW) is a significant source of refractory pollutants necessitating efficient treatment prior to discharge. This study investigates the treatment of VORW via coagulation-flocculation using ferric chloride (FeCl3) as a coagulant and chitosan as a natural flocculant. Central Composite Design (CCD) is employed to optimize the treatment process and assess the interplay of experimental factors. The study evaluates turbidity, COD, and polyphenols as responses, with pH, FeCl3 concentration, chitosan dosage, and agitation time as independent factors.The results showed that the optimal conditions identified include pH 6, FeCl3 dosage of 1.6 g/L, chitosan dosage of 13.4 mg/L, and agitation time of 26 min, resulting in 100 % turbidity removal, 86 % COD reduction, and 90 % polyphenol removal. The analysis of variance indicated that the established models were significant and that they are characterized by a good fit (R2 in the order of 0.95, 0.96, and 0.96 for turbidity, COD, and polyphenols, respectively).These findings highlight the efficacy and sustainability of the coagulation-flocculation process with chitosan, offering a practical, rapid, and cost-effective solution for VORW treatment and environmental preservation.

Bioremediation of petroleum refinery wastewater by fungal stains isolated from the fishing harbour of Bizerte (Mediterranean Sea).

The study was conducted in order to explore the potential of fungi isolated from surface and bottom seawater collected from the fishing harbour of Bizerte on the bioremediation of industrial effluent (IE) contaminated by petroleum hydrocarbon. Among the 128 fungal isolates, 11 were isolated from surface seawater and 7 from bottom seawater, representing 18 taxa in total. The gas chromatography mass spectrometry (GC-MS) was used for the determination of hydrocarbon compounds in IE. An initial screening of fungal growth using six concentrations ranged between 20 and 70% (v/v) IE has allowed the identification of the optimal concentration for fungal growth as well as selection of species able to tolerate high amounts of hydrocarbon. Colorimetric test employing 2,6-dichlorophenol indophenol and gravimetric method was applied for the assessment of fungal growth using 20% EI. By checking the phylogenetic affiliation of the high-performing stains as identified using ITSr DNA sequence, a dominance of Ascomycetes was detected. Indeed, Aspergillus terreus and Penicillium expansum may degrade 82.07 and 81.76% of residual total petroleum hydrocarbon (TPH), respectively. Both species were collected from surface seawater. While, Aspergillus niger, Colletotrichum sp and Fusarium annulatum displayed comparable degradation rates 40.43%, 41.3%, and 42.03%, respectively. The lowest rate of degradation 33.62% was detected in Emericellopsis phycophila. All those species were isolated from bottom seawater, excepting A. niger isolated from surface water. This work highlighted the importance of exploring the potential of fungi isolated from the natural environment on the bioremediation of industrial effluent. Our results promoted the investigation of the potential of the high-performing isolates A. terreus and P. expansum on the bioremediation of IE at pilot-scale and then in situ.

Electrochemical preparation and characterization of a new configuration SnO2 anode and its application for treating petroleum refinery wastewater

In the present work, the feasibility of removing chemical oxygen demand (COD) from petroleum refiner wastewater (PRW) was examined through an anodic oxidation process using a SnO2-copper substrate anode in a prototype tubular batch electrochemical reactor. The SnO2 anode was prepared by cathodic deposition from a nitrate solution and characterized by techniques such as X-ray diffraction (XRD) and scanning electron microscopy (SEM). Effects of current density, [Sn2+]/[HNO3] molar ratio, and time on the properties of the prepared anode were investigated. The XRD results showed that main peaks corresponded to deposition of tetragonal SnO2. Besides, broad peeks were observed indicating that the deposits have a lower degree of crystallinity. The results confirmed that increasing current density higher than 10 mA/cm2 results in formation of a mixture of SnO2 and Sn deposits. Additionally, the results proved that [Sn2+]/[HNO3] molar ratio has the main effect on the electrodeposition process, where keeping this ratio lower than 0.33 is recommended to ensure pure SnO2 film deposition. The best conditions for electrodeposition of SnO2 as a compact film on a copper substrate were a current density of 10 mA/cm2, [Sn2+] of 25 mM, [HNO3] of 125 mM to make a molar ratio of 0.2, and 30 min to confirm the formation of deposits without cracks and having an atomic percent (Sn/O) of 20.6/65. The application of the prepared anode for removing of COD from PRW confirmed a good performance with a removal efficiency of 79 % at current density of 12 mA/cm2, pH of 7.8, and operating time of 150 min in which an energy consumption of 9.93 kWh/kg COD was required. The degradation of COD using the SnO2 electrode was found to obey a pseudo first-order kinetic. The application of anodic oxidation using the new configuration of the SnO2 anode can be considered an eco-friendly process for treating wastewater, featuring easy scale-up to an industrial scale at high removal efficiency and lower cost.

Comparative study of electrochemical oxidation system hybrid with photocatalytic system for the treatment of Al-Najaf petroleum refinery wastewater

Comparative study of electrochemical oxidation system hybrid with photocatalytic system for the treatment of Al-Najaf petroleum refinery wastewater

Three-dimensional Electrocoagulation Process Optimization Employing Response Surface Methodology that Operated at Batch Recirculation Mode for Treatment Refinery Wastewaters

The performance of a three-dimensional electrocoagulation process operated at a batch recirculation mode for treating petroleum refinery wastewater using aluminium as a sacrificial anode, stainless steel as a cathode, and granular activated carbon with metal impregnated carbon (GACMI (Al: Fe)) with mass ratio (2:1) as a third particle electrode was investigated. Effects of operating factors such as the applied voltage (15-30 v), flow rate (50-175 mL/min), pH (4-10), and GACMI dosage (5-10) g/L on the chemical oxygen demand removal were investigated. Using Box-Behnken design (BBD), a mathematical model relating the essential operational parameters to chemical oxygen demand (COD) reduction was constructed. Results showed that the effect of GACMI dosage on the efficiency of COD removal was the major one, where COD removal increased as GACMI dosage increased. However, increasing applied voltage would enhance the performance of the electrocoagulation reaction. Experimental chemical oxygen demand removal of 96.25 % was attained at the optimized conditions (applied voltage=27.7 v, flow rate=128 mL/min, pH=5.6, GACMI dosage= 8.7 g/L). BET-specific surface area, total pore volume, X-ray fluorescence (XRF), energy-dispersive X-ray spectroscopy (EDX), and scanning electron microscopy (SEM) were employed for the characterization of GACMI particle electrodes.

Removal of COD from petroleum refinery wastewater by adsorption using activated carbon derived from avocado plant

In the present work, removing of COD from wastewater generated via Al-Diwanya petroleum refinery plant located in Iraq by adsorption with activated carbon (AC) derived from avocado seeds was successfully performed via a two-step approach. In the first step, AC was prepared from avocado seeds via impregnating with H3PO4 at 400 °C where effects of H3PO4 concentration and calcination time on the specific surface area of AC were studied. Additionally, properties of the prepared AC were examined by XRD, SEM, and FTIR to knowledge the features of the internal structure of AC. Results showed that the prepared AC has mesopores structure with pore diameters in the range between 30.07 and 50.8 µm. Increasing the weight percent of H3PO4 led to an increase in the specific surface area of AC to reach a maximum value beyond which a decrease in the specific surface area was happened with further increasing in H3PO4 percent. Increasing the time resulted in an increase in the AC specific surface area to reach a maximum value beyond which a decrease in specific surface area was happened. The best value of AC specific surface area was 436.6 m2/g which obtained at 70 %H3PO4 and 4 h. At the second step, the performance of the prepared AC in removing of COD by adsorption process was evaluated via studying the effects of three operating parameters, namely adsorbent dosage (1–5 g/L), pH (3–9), and shaking speed (100–400 rpm) on the removal of COD(RE%) using a response surface methodology (RSM). Increasing AC dosage led to an increase in RE% while increasing each of pH and shaking speed resulted in lowering RE%. The optimum conditions for higher RE% were AC dosage of 5 g/L, pH of 3, and shaking speed of 100 rpm in which a removal efficiency of 94.54 % was obtained. The degradation of COD with time was found to obey a second order kinetic confirming the chemisorption is the rate limiting step in the adsorption process.

The impact of ozone treatment on the removal effectiveness of various refractory compounds in wastewater from petroleum refineries

Large volumes of wastewater are generated during petroleum refining processes. Petroleum refinery wastewater (PRW) can contain highly toxic compounds that can harm the environment. These toxic compounds can be a challenge in biological treatment technologies due to the effects of these compounds on microorganisms. These challenges can be overcome by using ozone (O3) as a standalone or as a pretreatment to the biological treatment. Ozone was used in this study to degrade the organic pollutants in the heavily contaminated PRW from a refinery in Mpumalanga province of South Africa. The objective was achieved by treating the raw PRW using ozone at different ozone treatment times (15, 30, 45, and 60 min) at a fixed ozone concentration of 3.53 mg/dm3. The ozone treatment was carried out in a 2-liter custom-designed plexiglass cylindrical reactor. Ozone was generated from an Eco-Lab-24 corona discharge ozone generator using clean, dry air from the Afrox air cylinder as feed. The chemical oxygen demand, gas chromatograph characterization, and pH analysis were performed on the pretreated and post-treated PRW samples to ascertain the impact of the ozone treatment. The ozone treatment was effective in reducing the benzene, toluene, ethylbenzene, and xylenes (BTEX) compounds in the PRW. The 60-min ozone treatment of different BTEX pollutants in the PRW resulted in the following percentage reduction: benzene 95%, toluene 77%, m + p-xylene 70%, ethylbenzene 69%, and o-xylene 65%. This study has shown the success of using ozone in reducing the toxic BTEX compounds in a heavily contaminated PRW.