Petroleum Wastewater Treatment Research Articles

Preparation of superparamagnetic AC/Fe3O4/TiO2 nanoparticles from magnetic waste oily petroleum sludge (MWOPS): comprehensive characterization, H2 production, design batch photoreactor, and treatment of oily petroleum wastewater (OPW) under UVA light

Preparation of superparamagnetic AC/Fe3O4/TiO2 nanoparticles from magnetic waste oily petroleum sludge (MWOPS): comprehensive characterization, H2 production, design batch photoreactor, and treatment of oily petroleum wastewater (OPW) under UVA light

Photocatalytic Oxidation Process for Petroleum Wastewater Treatment and The Possibility of Using Tapered Bubble Column (TBC): A Review

<p>The photocatalytic oxidation of organic and petroleum wastewater treatment is an advanced oxidation process (AOP) with several benefits. It operates at normal temperatures and pressure, is inexpensive, does not produce secondary waste, and us easily accessible. Many studies have employed bubble columns, slurry bubble columns, and three-phase fluidized reactors in the photocatalytic process for wastewater treatment. Pure TiO2 and Fe-doped TiO2 are considered the most promising catalysts. The aim of this work was to review the literature on the photocatalytic process for organic pollutants and petroleum wastewater (produced water) treatment, with a special focus on pure TiO2 and Fe-doped TiO2 as well as to study the possibility of using a tapered bubble column reactor for this treatment. A circulating upflow tapered bubble column reactor with a light lamp at the center facilitates the separation of the gas-liquid-solid phases with no dead zone in the photocatalytic process.</p>

Synthesis of Polyaluminum Chloride Coagulant from Waste Aluminum Foil and Utilization in Petroleum Wastewater Treatment

This work investigates the potential synthesis of cost-effective polyaluminum chloride (PACl) coagulant from waste household aluminum foil and utilization for treating petroleum wastewater (PWW), especially dissolved organic compounds (DOC, like octanol–water mixture) and nonsettleable suspended (NSS-kaolin) mineral particles. Based on the Standard Practice for Coagulation–Flocculation Jar Test, the efficiency of PACl for DOC and NSS removal was evaluated in relation to the effects of the operational parameters. The results demonstrated that the as-prepared PACl has an amorphous morphology with a Keggin-type e-Al13 molecular structure {Na[AlO4(OH)24(H2O)]·xH2O and good thermal stability up to 278 °C. PACl coagulant also exhibited a higher efficiency for NSS removal than DOC by around 1.5- to 1.9-fold under broad pH (5–7), while a higher acidic/alkaline pH disrupts the sweep floc formation. An increased PACl dosage (over 25 mg/L) also caused a decrease in the coagulation efficiency by 11.7% due to Al species’ transformation and pH depression (from 6.8 to 4.9) via increased PACl hydrolysis. With a fast rotating speed of 280 rpm for 2 min, the minimum dose of PACl (10–25 mg/L) can maximize the removal efficiency of NSS (~98%) and DOC (~69%) at pH 6.5 ± 0.5 and 35 °C after 30 min of settling time. Treating actual saline PWW samples (salinity up to 187.7 g/L) also verified the high efficacy of PACl coagulation performance in reducing the turbidity and dissolved hydrocarbons by more than 75.5% and 67.7%, respectively. These findings verify the techno-economic feasibility of the as-prepared PACl coagulant in treating PWW treatment at different salinity levels.

Efficient removal of naphthenic acids from real petroleum wastewater by natural pyrite activated persulfate system

The petroleum wastewater (PWW) contains a diverse range of recalcitrant organic contaminants. Of particular concern is the removal of naphthenic acids (NAs) due to the high toxicity and persistence. Persulfate (PS) based oxidation processes have shown promising in treating refractory wastewater, while the high costs of prepared catalysts limited their widespread implementation. This study aims to develop a cost-effective natural pyrite activated PS system for PWW treatment. The removal of NAs by pyrite/PS system was initially investigated. More than 90% of cyclohexanoic acid (CHA), a model NA, was removed in pyrite/PS system (2.0 g/L pyrite, 4.0 mM PS) at initial pH of 3–11. Scavenging experiments revealed that Fe(II) on pyrite surface was the reactive site for PS activation to generate reactive species, including sulfate radical (SO4·−), Fe(IV) and hydroxyl radical (·OH) for CHA degradation. Reactions of Fe(III) with S helped restore Fe(II) and enhance PS activation, resulting in the sustained catalytic activity of pyrites over five cycles. Cl−, SO42− and NO3− below 10 mM had minimal impact on CHA degradation in pyrite/PS system. However, over 1 mM of HCO3− inhibited 80% of CHA removal due to the buffer effect to maintain the high solution pH. Removing HCO3− from real PWW restored the removal of CHA and of total organic carbon (TOC) to over 90% and 71.3% in pyrite/PS system, respectively. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) results indicated that O2‒6 species including NAs were primarily eliminated through mineralization and oxygen addition. Besides, O3–5S, NO3–5S and N3O2‒4 species were the most susceptible to oxidation in PWW, resulting in the increase of the oxidation level (i.e., O/Cwa) from 0.41 to 0.56 after treatment. This study provides valuable insights into the treatment of NAs in real PWW, and potential application of natural minerals in the treatment of industrial wastewater.

Application of photocatalytic proxone process for petrochemical wastewater treatment

Industrial wastewaters are different from sanitary wastewaters, and treatment complications due to their unique characteristics, so biological processes are typically disrupted. High chemical oxygen demand, dye, heavy metals, toxic organic and non-biodegradable compounds present in petroleum industry wastewater. This study intends to optimize the photocatalytic proxone process, utilizing a synthesized ZnO–Fe3O4 nanocatalyst, for petroleum wastewater treatment. The synthesis of ZnO–Fe3O4 was done by air oxidation and layer-by-layer self-assembly method and XRD, SEM, EDAX, FT-IR, BET, DRS, and VSM techniques were used to characterize the catalyst. Central composite design (CCD) method applied to investigated the effect of pH (4–8), reaction time (30–60 min), ozone gas concentration (1–2 mg/L-min), hydrogen peroxide concentration (2–3 mL/L) and the amount of catalyst (1–0.5 g/L) on the process. In the optimal conditions, biological oxygen demand (BOD5) and total petroleum hydrocarbon (TPH) removal, reaction kinetic, and synergistic effect mechanisms on the process were studied. Based on the ANOVA, a quadratic model with R2 = 0.99, P-Value = 0.0001, and F-Value = 906.87 was proposed to model the process. Based on the model pH = 5.7, ozone concentration = 1.8 mg/L-min, hydrogen peroxide concentration = 2.5 mL/L, reaction time = 56 min, and the catalyst dose = 0.7 g/L were proposed as the optimum condition. According to the model prediction, an efficiency of 85.3% was predicted for the removal of COD. To evaluate the accuracy of the prediction, an experiment was carried out in optimal conditions, and experimentally, a 52% removal efficiency was obtained. Also, at the optimum condition, BOD5 and TPH removal were 91.1% and 89.7% respectively. The reaction kinetic follows the pseudo-first-order kinetic model (R2 = 0.98). Also, the results showed that there is a synergistic effect in this process. As an advanced hybrid oxidation process, the photocatalytic proxone process has the capacity to treat petroleum wastewater to an acceptable standard.

Efficient and eco-friendly mixed bacterial consortium for petroleum wastewater treatment: Effect of the bio-augmentation and biosurfactant addition on hydrocarbon biodegradation

In the present investigation, we aimed to study biological petroleum wastewater treatment. A bioprocess based on the use of a mixed bacterial consortium along with the addition of Biosurfactant (BioS) and bioaugmentation with BioS producing strains were evaluated. The consortium was the combination of two bacterial strains with the capacity to metabolize hydrocarbons, Baci and B201. Two other strains BH1 and BSS2 selected for their ability to degrade hydrocarbons as well as to produce BioS were also exploited. The effect of ex-situ and in-situ produced BioS on hydrocarbon biodegradation were compared. Obtained results demonstrated a moderate capacity to remove crude oil from contaminated water of about 47% for the consortium. The best improvement of hydrocarbon biodegradation of about 84% was obtained when adding BH1 derived BioS solely. However, ex-situ produced BioS exhibited better results. Regarding the wastewater characteristics, we note a decrease of the COD/BOD5 Ratio to reach 2.64. Thus, the wastewater became easily biodegradable. The described bioprocess is of great interest for the bioremediation of petroleum effluents. BioS addition as well as bioaugmentation enhanced crude oil removal.

Adsorptions of phenol molecules by graphene-based nanostructures, modified with nitrogen and bromine, from petroleum wastewater using molecular dynamics simulation

Today, industrial wastewater treatment has attracted the attention of many governments and environmental experts. Basically, the pollution of these wastewaters is due to the presence of organic pollutants such as dyes, halogenated hydrocarbons, phenolic compounds, etc. Meanwhile, phenol is widely used in oil, petrochemical, coal production, and pharmaceutical industries. Several methods such as surface adsorption are used to remove phenol from water. In this work, the adsorption of phenol molecules by carbon nanostructures and carbon nanostructures modified with nitrogen and bromine has been investigated using Molecular Dynamics simulation. According to the obtained results, BCN-graphene has been introduced as the best nanostructure for the removal of phenol molecules from the aqueous environment, having the highest adsorption energy and greater adsorption stability. This work paves the way for the development of the use of bromine nitride structures in the treatment of petroleum wastewater.

Continuous cultivation of Debaryomyces hansenii (LAF‐3 10 U) on dodecane in synthetic desalter effluent at varying dilution rates on dodecane

AbstractDesalter effluent (DE) is typically discharged into a petroleum wastewater treatment plant, but its high salt concentration deteriorates the biological treatment. This study used various dilution rates to investigate the treatment of a synthetic DE containing dodecane under saline conditions using a halotolerant yeast, Debaryomyces hansenii, to determine the optimum substrate concentration for use in continuous stirred‐tank reactors (CSTRs). A literature review indicated that this study was the first to examine the biological treatment of DE using D. hansenii in a CSTR system. At a low dodecane substrate concentration, DE did not inhibit D. hansenii growth, and the experimental data approached the Monod model, with μmax and Ks selected as 0.08 h−1 and 1575 mg L−1, respectively. The optimum removal of chemical oxygen demand (95.7% and 85%) was obtained at dilution rates of 0.007 and 0.026 d−1. Using D. hansenii in a CSTR system appeared to be a sustainable approach for the biological treatment of DE. Scale‐up of these laboratory findings to the industrial scale is required to confirm that petroleum DE can be treated using equalization and filtration tanks as a continuous bioreactor. Adjusting the dilution rate can provide sufficient time for biodegradation and hydrocarbon removal from high salt DE by halotolerant yeasts like D. hansenii.

Study of phenol removal from wastewater petroleum industry using molecular dynamics method for two-dimensional adsorbents from the aqueous environment

Phenol is classified as one of the environmental pollutants and is found in the wastewaters of various industries such as petroleum industry, paint and chemical industries, oil refining and textile industries. High concentrations of this substance are harmful to human health and can cause adverse cardiac and neurological effects. Therefore, it seems necessary to eliminate this material from industrial wastewater, although their elimination requires the use of new methods. In this regard, in this work, two-dimensional adsorbents have been used to remove phenol from the aqueous environment. To do this, the ability to simulate molecular dynamics in investigating the interactions of phenol molecules and 4 transition metal dichalcogenides (TMDs)v Used. CdS2 had the largest level of interaction with phenol molecules and had the greatest effect in removing phenol from the aqueous environment. The results obtained from this work have provided new materials to remove phenol from the wastewater petroleum industry and can facilitate the widespread use of these materials in industrial petroleum wastewater treatment.

A review on novel and hybrid/integrated reactor configurations for the removal of recalcitrant organics from petroleum refinery wastewater

AbstractOwing to the high demand of petroleum and petrochemical products, refineries, among the many industries that are set up worldwide, are of special importance. Wastewater generated from such industrial activities, however, contains toxic compounds that are of environmental concern. Due to the presence of highly recalcitrant organics present in refinery wastewater, treatment prior to its discharge into the environment and water bodies in order to meet certain acceptable discharge limits is imperative. Petroleum refineries unavoidably discharge a large volume of wastewater mainly with high chemical oxygen demand (COD). Low‐cost biological wastewater treatment methods are reported to show excellent COD removal efficiency from wastewater but have their own drawbacks. Hence, advanced integrated approaches are of new interest in this field. This review focuses on emerging technologies, in particular bioreactor configurations for petroleum wastewater treatment. It further discusses some future perspective in hybrid/integrated systems for treating PRWW.

Treatment of petroleum wastewater by electrocoagulation using scrap perforated (Fe-anode) and plate (Al and Fe-cathode) metals: Optimization of operating parameters by RSM

This study focused on removing chemical oxygen demand and phenol from petroleum wastewater by employing the electrocoagulation (EC) process using scrap electrodes. In the study, in a unique way different from those reported in the literature, scrap cylindrical perforated iron (PS) and plate metals discarded by different industries were used as electrodes by recovery for EC. PS was used the anode, and plate electrodes made of two different materials (Al and Fe) were used as the cathodes. The electrodes were placed at the center of the EC reactor and PS. The effects of the main parameters, namely, initial pH (4−10), initial exposure time (5–45 min), and current density (2–28 mA/cm2), on the EC process were assessed and optimized by employing response surface methodology (RSM). A reasonable correlation between the experimental and predicted data was found through analysis of variance (ANOVA). The ANOVA results revealed that the coefficients of determination (R2) for COD removal and phenol removal were 91.18% and 91.46%, respectively. The maximum predicted removal efficiency rates were 96.18% and 94.02% for respectively COD and phenol under the optimum conditions of pH= 6.30, current density= 22 mA/cm2, exposure time= 39 min, and the Fe cathode. Furthermore, the results showed that the initial current density and exposure time were significantly effective on COD and phenol removal from petroleum wastewater. The total cost was calculated as $3.1/m3. There was no electrode cost in the study due to the usage of scrap metals. The results indicated that the EC process is an effective treatment method for COD and phenol removal from petroleum wastewater using scrap metals as electrodes.

Nitrogen removal intensification of aerobic granular sludge through bioaugmentation with “heterotrophic nitrification-aerobic denitrification” consortium during petroleum wastewater treatment

The bioaugmentation potential of aerobic granular sludge (AGS) was investigated using heterotrophic nitrification-aerobic denitrification (HN-AD) bacterial consortium to improve nitrogen removal during petroleum wastewater treatment. An efficient HN-AD consortium was constructed by mixing Pseudomonas mendocina K0, Brucella sp. K1, Pseudomonas putida T4 and Paracoccus sp. T9. AGS bioaugmented by immobilized HN-AD consortium enhanced nitrogen removal, which showed NH4+-N and TN removal efficiency of 92.4% and 79.8%, respectively. The immobilized consortium addition facilitated larger AGS formation, while granules > 2.0 mm accounted for 16.7% higher than that of control (6.7%). Further, the abundance of napA gene was 4-times higher in the bioaugmented AGS as compared to the control, which demonstrated the long-term stability of HN-AD consortium in the bioreactor. The bioaugmented AGS also showed a higher abundance of xenobiotics biodegradation and nitrogen metabolism. These results highlight that bioaugmentation of AGS technology could be effectively used for enhanced denitrification of petroleum wastewater.

Nitrogen Removal Intensification of Aerobic Granular Sludge Through Bioaugmentation with “Heterotrophic Nitrification-Aerobic Denitrification” Consortium During Petroleum Wastewater Treatment

Nitrogen Removal Intensification of Aerobic Granular Sludge Through Bioaugmentation with “Heterotrophic Nitrification-Aerobic Denitrification” Consortium During Petroleum Wastewater Treatment

Hybrid Photo-Fenton oxidation and biosorption for petroleum wastewater treatment and optimization using Box–Behnken Design

This study investigates the treatment of petroleum wastewater (PWTP) effluent using hybrid techniques (photo-Fenton oxidation and adsorption) to remove organic pollutants such as chemical oxygen demand (COD) and phenol. All the experiments were carried out in batch mode. The effects of pH, ferrous salt (Fe 2＋ ), and H 2 O 2 oxidation factors on the photo-Fenton process were studied. The response surface methodology (RSM) approach for experiment design and optimization yielded maximum COD and phenol removal at Fe 2＋ , H 2 O 2 , pH of 20 mM, 400 mM, and 3.8, respectively. In this optimal scenario, phenol reduction from the initial value of COD 12654.6 mg/L, phenol 213.0 mg/L was accomplished by 69.97% and 95.66%, respectively. Response surface methodology (RSM) photofenton based modeling and optimization was done using a Box–Behnken. The high coefficient of regression R 2 = 0 . 97 and 0.98 for COD and phenol oxidation is suggested by variance analysis (ANOVA). The PWTP effluent treated by Fenton oxidation with COD 4139.1 mg/L and phenol 70.1 mg/L was treated with Phragmites australis. Phragmites australis was chosen as an adsorbent. Phragmites australis was analyzed and characterized using several techniques, including Fourier transform infrared spectroscopy, Scanning Electron Microscopy, Zeta potential, and particle size distribution. The adsorption process step followed the photo-Fenton treatment process. The adsorption process achieved 69.04 % and 95.80% for COD and phenol removal. Kinetic studies showed that the statistics match very well in the nonlinear pseudo-first and second-order models based on the correlation coefficients (R 2 = 0 .999) and (R 2 = 0 .996), respectively, for COD and phenol removal in the adsorption phase. The severe adsorption potential for COD and phenol removal is 14421.97 mg/g and 374.90 mg/g, respectively. Finally, as a natural material, P. australis is a promising adsorbent material. • Box–Behnken Experimental Design (BBD) was used to determine the optimal removal efficiency for both COD and phenol for the photo-Fenton process. • Statistical analysis of the data indicated that H 2 O 2 significantly affected COD, phenol degradation for petroleum wastewater. • The optimum conditions for pH, Fe +2 , H 2 O 2 are 3.8, 20 mM, 400 mM for 69.97% COD, and 95.66% Phenol. • Phragmites australis was used as an adsorbent in the adsorption step. P. australis showed remarkable surface characteristics and adsorption ability. • The maximum adsorption capacity to remove COD and phenol of 14421.97, 374.90 mg/g, removal ratio 69.04%, and 95.80%, and the data fits very well in the nonlinear pseudo-first and second-order models.

Performance Evaluation of Ultra-Violet Light and Iron Oxide Nanoparticles for the Treatment of Synthetic Petroleum Wastewater: Kinetics of COD Removal.

In this study, the use of ultra-violet (UV) light with or without iron oxide nanoparticles (IONPs) for the degradation of synthetic petroleum wastewater was investigated. The IONPs was synthesised by sodium borohydride reduction of ferric chloride solution and was characterised by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectrometry (FTIR), x-ray fluorescence spectrophotometry (XRF), and energy dispersive spectroscopy (EDS). The amount of degradation was evaluated by chemical oxygen demand (COD) determination. Experimental results show that the COD removal from synthetic petroleum wastewater by IONPs/UV system was more effective than they were independently. The combination of UV light at a wavelength of 254 nm, pH of 8, and 1.0 g of IONPs resulted in COD removal from 10.5% up to 95.5%. The photocatalytic degradation of synthetic petroleum wastewater is about 1.3–2.0 times faster in comparison to UV light only. The removal of COD from synthetic petroleum wastewater by UV light and IONPs follows the pseudo-first-order kinetic model with rate constant k ranging from 0.0133 min−1 to 0.0269 min−1. Consequently, this study has shown that the use of UV light in the presence of IONPs is favourable and effective for the removal of organic pollutants from petroleum refinery wastewater.

Optimization of the petroleum wastewater treatment process using TiO2/Zn photocatalyst

The present study was conducted to investigate the optimum conditions in a laboratory work for the real petroleum wastewater treatment plant using both new methods (TiO2/ZnO/Fenton/Solar and TiO2/ZnO/Air/Solar) to remove Chemical Oxygen Demand (COD) and Total Organic Carbon (TOC) from the real petroleum wastewater from the Sohar oil refinery (SOR). Maximum treatment efficiency was obtained by the TiO2/ZnO/air/Solar process. The ZnO dosage of 54 g/L and TiO2 dosage 50 g/L were required for removing 74% of COD and 99% of TOC under optimal conditions. The solar photocatalyst of TiO2/ZnO/Fenton method was the most efficient in the neutral pH, therefore no need to adjust pH during this treatment. In acidic conditions, the solar photo-Fenton process was more efficient than the TiO2/ZnO/air process while it was less efficient than the TiO2/ZnO/air process in (pH>7). The Fe+2 and H2O2 concentration were the main factors to improve the efficiency of the TiO2/ZnO/Fenton/Solar process while pH and the TiO2 dosage were the main factors for the TiO2/ZnO/air/Solar process. The estimated cost of treatment for the TiO2/ZnO/air process was 9 $/m3 while it was 8 $/m3 by the TiO2/ZnO/Fenton process. The final expected effluent concentrations met the acceptable levels of COD and TOC set by the Wastewater Discharge Standard of Oman.

Petroleum refinery wastewater treatment using a polysulfone-nano TiO2 hybrid membrane coupled with an ozonation process as a pre-treatment

Fouling has been the main problem that seriously hinders membrane applications for petroleum wastewater treatment. This study aimed to explore advanced membrane process integrated with ozonation as a preliminary treatment. Ozone utilization was set at a constant dose of 3000 mg/h for different ozonation times and temperatures. A longer ozonation time significantly improved the removal of pollutants. Ozonation at 30°C for 120 min removed up to 38.25% total dissolved solids (TDS), 73.33% organic compounds expressed as chemical oxygen demand (COD), 11.6% ammonia, and 62.15% total phenol. Although an increase in the ozonation temperature increased the ammonia removal by up to a remarkable 82%, it did not significantly affect the TDS, COD, and phenol removal efficiencies. Scanning electron microscope (SEM) and Fourier-transform infrared (FTIR) evaluations of the used membrane revealed that membrane fouling was caused by organic compounds consisting of hydrocarbon oil, benzene, toluene, xylene, phenol, and salt. Ozonation enhanced the permeate flux of the membrane by up to 96% and improved pollutant removal by up to 77%. The ozonation process was also responsible for the reduction of fouling resistance on the membrane surface by up to 21%.

A Review on the Treatment of Petroleum Refinery Wastewater Using Advanced Oxidation Processes

The petroleum industry is one of the most rapidly developing industries and is projected to grow faster in the coming years. The recent environmental activities and global requirements for cleaner methods are pushing the petroleum refining industries for the use of green techniques and industrial wastewater treatment. Petroleum industry wastewater contains a broad diversity of contaminants such as petroleum hydrocarbons, oil and grease, phenol, ammonia, sulfides, and other organic composites, etc. All of these compounds within discharged water from the petroleum industry exist in an extremely complicated form, which is unsafe for the environment. Conventional treatment systems treating refinery wastewater have shown major drawbacks including low efficiency, high capital and operating cost, and sensitivity to low biodegradability and toxicity. The advanced oxidation process (AOP) method is one of the methods applied for petroleum refinery wastewater treatment. The objective of this work is to review the current application of AOP technologies in the treatment of petroleum industry wastewater. The petroleum wastewater treatment using AOP methods includes Fenton and photo-Fenton, H2O2/UV, photocatalysis, ozonation, and biological processes. This review reports that the treatment efficiencies strongly depend on the chosen AOP type, the physical and chemical properties of target contaminants, and the operating conditions. It is reported that other mechanisms, as well as hydroxyl radical oxidation, might occur throughout the AOP treatment and donate to the decrease in target contaminants. Mainly, the recent advances in the AOP treatment of petroleum wastewater are discussed. Moreover, the review identifies scientific literature on knowledge gaps, and future research ways are provided to assess the effects of these technologies in the treatment of petroleum wastewater.

Treatment of petroleum wastewater contaminated with hydrocarbons and inorganics by anoxic-aerobic sequential moving bed reactors

The present study deals with the biotransformation of virulent petroleum refinery concoction with phenol (750 mg/L), emulsified crude oil (300 mg/L), S2− (750 mg/L), NH4+-N (350 mg/L) and NO3−-N (1000 mg/L) in anoxic (A1) - aerobic (A2) moving bed reactors operated in series. The efficacy of the system was analysed through measurement of pollutant concentrations, GC-MS and FTIR peaks of the influent and effluent, and biomass activity studies. The system was able to eliminate the organics and inorganics with more than 99% efficiency at 80 h HRT and 64 h cycle time. GC-MS results revealed breakage of high molecular weight organics to smaller compounds after anoxic treatment. Further treatment of anoxic effluent by aerobic biomass reduced the number of peaks in the final effluent significantly. FTIR results were in accord with the GC-MS results. Heterotrophic activity (HA) of the aerobic biomass was higher than anoxic biomass due to its higher free energy change. Anoxic biomass showed chemolithotrophic activity (CA), suggesting survival in the absence of organics. Gas generated from anoxic reactor consisted of 91% nitrogen, 1% CO2, 1% H2S and rest was unaccounted.

Treatment of Petroleum Wastewater Using a Sequential Hybrid System of Electro-Fenton and NZVI Slurry Reactors, Future Prospects for an Emerging Wastewater Treatment Technology

In this study, treatment of a 750 mL petroleum wastewater sample was evaluated using a hybrid system consisting of electro-Fenton and nano zero-valent iron (NZVI) slurry reactors in sequence. In bo...