Petroleum Refinery Wastewater Research Articles

Synergistic adsorption and photocatalytic properties of AC/TiO2/CeO2 composite for phenol and ammonia–nitrogen compound degradations from petroleum refinery wastewater

This study focuses on the utilization of AC/TiO2/CeO2 composite on the removals of phenol and ammonia–nitrogen (NH3-N) compounds from petroleum refinery wastewater (PRW) through a combination of adsorption and photocatalytic process. The composite was prepared by hydrothermal method with the composite formulation of 53.43%-wt of AC, 21.96 %-wt of TiO2, and 24.61 %-wt of CeO2. Characterization results revealed that the surface micromorphology, elemental, and oxide contents on synthesized composite significantly changed with the addition of TiO2 and CeO2. Optical UV–vis analysis showed that the estimated bandgap energy of the synthesized composite was 2.60 eV, which is lower than pristine TiO2 or CeO2, indicating that the photocatalysis is easier to perform that reflecting the successful combination of TiO2 and CeO2 as the photocatalyst in the composite. The Langmuir isotherm and pseudo-second order kinetic showed to be the most favorable isotherm and kinetic model for the adsorption process. The photocatalytic activity and kinetic evaluations showed that the photocatalytic process remarkably improved the removal performance and was followed the pseudo-first order kinetic. Moreover, the rate constants of photocatalysis were higher than the adsorption process, indicating that the rate of photocatalysis on the pollutant degradations is faster than the adsorption process. The final pollutant removals by using AC/TiO2/CeO2 composite were 50.91% for phenol removal and 65.83% for NH3-N removal. Three consecutive cycles test showed that the AC/TiO2/CeO2 composite has excellent durability and can nicely maintain the phenol and NH3-N removals from PRW.

Enhanced pollutants removal and high-value cell inclusions accumulation with Fe2+ in heavy oil refinery treatment system using Rhodopseudomonas and Pseudomonas

Metal ions has been widely used as a method of improving pollutant removal efficiency in wastewater biological treatment system. In order to enhance pollutants removal and high-value cell inclusions accumulation in heavy oil refinery wastewater treatment systems using PSB, different reactors were built feeding with different Fe2+ concentrations respectively, and run with enriching Rhodopseudomonas and Pseudomonas in the reactors. Solute chemical oxygen demand (SCOD), ammonia (NH4+-N), nitrate nitrogen (NO3−-N), nitrous nitrogen (NO2−-N), Fe2+, and related cell inclusions were all detected, moreover, microbial community structure and the quantity of Rhodopseudomonas and Pseudomonas were also detected. The results showed that at the optimal dosage of Fe2+ with 20 mg/L, the corresponding removal ratios of solute chemical oxygen demand and ammonia were 73.51% and 92.26%, respectively. The yields of carotenoid, bacteriochlorophyll, and coenzyme Q10 were 11.18, 6.75, and 9.84 mg/g-DCW respectively. Furthermore, with 20 mg/L Fe2+ dosage, the relative abundance and gene number of Rhodopseudomonas were the highest in the system, which were 91.57% and 1.843 × 106 gene copies/μL, while Fe2+ had no obvious effect on the growth of Pseudomonas. The results showed that adding Fe2+ has improved the removal of pollutants and accumulation of high-value cells inclusions, also provided theoretical guidance for the treatment of heavy oil refinery wastewater using PSB.

A shift from chemical oxygen demand to total organic carbon for stringent industrial wastewater regulations: Utilization of organic matter characteristics

From 2022, industrial wastewater discharge regulations in South Korea will replace chemical oxygen demand (CODMn) with total organic carbon (TOC). A shift from CODMn to TOC is a pioneering change in protecting water bodies from organic contaminants. However, several industries are struggling to meet these TOC requirements even though their effluents met the CODMn limits. Effluent CODMn/TOC ratios (1.28 ± 0.64) found in our study were lower than the CODMn/TOC coefficients (1.33–1.80) suggested by the Ministry of Environment in South Korea. Aliphatic and particulate organic matter contents in effluents likely influenced the CODMn/TOC ratio. Regardless of the industrial category, dissolved organic carbon often consists of low molecular weight neutrals, hydrophobic organic carbon, and protein-like substances in raw and treated industrial wastewaters. The present study also revealed that TOC and CODMn represented different organic matter fractions in the paper mill and oil refinery wastewater, whereas the industrial park wastewater showed similar dissolved organic matter characteristics. Specifically, CODMn was effective in the determination of humic content in paper mill wastewater but was underestimated in oil refinery wastewater. Additionally, only paper mill effluents exceeded the TOC requirements (4 of 6 samples) and required an additional post-treatment process owing to higher organic loads.

Treatment of Petroleum Refinery Wastewater by Graphite–Graphite Electro Fenton System Using Batch Recirculation Electrochemical Reactor

Treatment of Petroleum Refinery Wastewater by Graphite–Graphite Electro Fenton System Using Batch Recirculation Electrochemical Reactor

Biochar immobilized petroleum degrading consortium for enhanced granulation and treatment of synthetic oil refinery wastewater

This study investigated the effect of biochar immobilized consortium for enhanced biotreatment of oil refinery wastewater in sequencing batch reactors. The control reactor (R0), and reactors with free bacterial consortium (R1), biochar (R2) and biochar immobilized consortium (R3) were operated in parallel. Results illustrated that granulation was faster in R2 and R3, the proportion of granules >0.45 mm was almost 30% higher than the R0 and R1 during the first 45 days. R3 exhibited optimum operational performance as highest removal efficiencies of COD (97.9%), oil (97.4%), NH4+-N (97.2%) and TN (90.2%) at the end of the experiment. Biochar enriched microbial richness and diversity whereas inoculated consortium positively modulated the community structures. Higher abundance of inoculated Rhodococcus (4.81%) bacteria in R3 suggested successful formation of functional strains in the granular sludge. It concludes that the application of biochar immobilized consortium is a better choice for the treatment of refinery wastewater.

Mineralization of refractory organics in oil refinery wastewater by the catalytic ozonation with magnetic praseodymium-catalysts: Catalytic performances and mechanisms

• PFCN exhibited superior mineralization effect on organics in real oil wastewater. • Combined effect of radicals and non-radicals enhanced organics mineralization. • Low-carbon-number alkanes, benzenes, and alcohols were easily decomposed. • Valence state conversion of Fe and Pr enhanced electron transfer and O 3 decomposition. An efficient mineralization of refractory organics in oil refinery wastewater (ORW) was achieved from a novel magnetic Fe 2 O 3 /Pr 6 O 11 /g-C 3 N 4 (PFCN) based catalytic ozonation (O 3 /PFCN) method. O 3 /PFCN caused 80.4% of refractory organics mineralization within 120 min, which promoted the oxidization of soluble microbial metabolites and aromatic proteins. The kinetic constant of refractory organics mineralization was 0.01385 min −1 , almost twice that of single ozonation. Fe and Pr existed as the polyvalent oxidation states in PFCN, which not only increased the Lewis acid sites on the surface of catalyst, but also enhanced the electron transfer ability. Additionally, the formation of Fe-O-C between CN and ferric oxide could promote the electrons transfer between the aromatic ring of CN and iron ion. Electrons cycling between Fe(II)/Fe(III) and Pr(III)/Pr(IV) caused the decomposition of ozone to produce radicals ( OH, O 2 − ) and non-radicals ( 1 O 2 ), which attacked the organics to oxidize into small molecular intermediates and then further mineralized into CO 2 and H 2 O. 58–88.7% of low-carbon-number alkanes (nC11-nC21) and 76.7–94% of benzenes and alcohols in ORW can be removed easily in O 3 /PFCN, and the toxicity of organics degradation products was lower than that of the parent compound. PFCN with capacities of separation and catalytic oxidation provided a promising alternative for ozonation of recalcitrant tailwater.

Photodegradation and kinetics of edible oil refinery wastewater using titanium dioxide

Edible oil refinery wastewater (EORW) is one source of environmental pollution in Nigeria. The treatment of EORW before discharge into the environment remains a significant challenge in the edible oil refinery industries. This research was aimed at photocatalytic treatment of EORW using a batch photocatalytic reactor with titanium dioxide photocatalyst. We investigated the physicochemical parameters: chemical oxygen demand (COD), biological oxygen demand (BOD5), oil and grease, phenol, chloride (Cl-), total suspended solids, sulfate (SO42-), and phosphate (PO43-) using American Public Health Association methods. The results showed that the reduction efficiency of the treated EORW with TiO2 catalyst ranged between 65.8% (PO43-) and 87.0% (COD), and the improvement in efficiency was 54.1% (pH) and 60.8% dissolved oxygen. However, the results showed no significant difference (p<0.05) in the control treatment without catalyst. The biodegradability of EORW increased from 0.196 to 0.32. It was observed that the optimum values were an initial EORW concentration of 100 mL/L, irradiation time of 90min, catalyst dose of 1.25 g/L, and an agitation speed of 900 rpm. The kinetics of the photodegradation process was well described by the pseudo-first-order equation (R2>0.96) and pseudo-second-order equation (R2>0.98). The intra-particle diffusion model fairly represented the diffusion mechanism with an R2 value of 0.806. The treated EORW met the most acceptable water quality standards for discharged effluent according to the maximum permissible limits of the Nigerian National Environmental Standards and Regulations Enforcement Agency.Significance: Photocatalytic treatment of EORW gave negligible results in the absence of a photocatalyst. The photocatalytic degradation of EORW improved its biodegradability. Photocatalytic treatment of EORW significantly reduced the pollutants in the wastewater. The pseudo-first-order equation (R2>0.96)

Effect of crude oil shock load on anoxic-aerobic sequential moving bed reactors during petroleum refinery wastewater treatment

Concentrations of pollutants are suddenly increased (shock loads) in the lab-scale bioreactors to examine their stability against sudden change in feeding conditions. In the present study, sudden elevated loads of crude oil were supplied to an anoxic (A1)-aerobic (A2) sequential reactor system, as studies involving series reactors for shock analysis are scarce. The system was previously engaged in the treatment of petroleum refinery wastewater at influent crude oil of 300 mg/L along with phenol, sulfide, nitrate-N and ammonia-N. Influent crude oil was suddenly increased to 600 mg/L and 900 mg/L during first (shock 1) and second (shock 2) shock loadings, respectively, at two different times of operation. An immediate increase in the effluent organics and a decrease in efficiency was observed after each shock. The shock toxicity caused death of microbes and decrease (1–4%) in biomass concentration. Hence, biomass activity reduced, and the pollutants degradation declined by 40–50%. Nitrogen production in A1 decreased which confirmed lesser nitrate utilization during shock. Both the reactors recovered to their original stature after the withdrawal of shock 1. Shock 2 had a permanent effect on A1 as its efficiency decreased from 33% to 11% even after withdrawal of the shock. The combined A1-A2 system successfully tolerated the shock loads, and more than 99% removals of organics, sulfide, and nitrate was achieved after resumed normalcy.

Chemical cleaning procedures on permeability recovery and lifespan of MBR membranes treating petroleum refinery wastewater: From bench- to pilot-scale applications

Different cleaning strategies for membranes from membrane bioreactors (MBR) were investigated and applied to a pilot MBR treating real refinery wastewater. It was assessed different cleaning agents (sodium percarbonate, dodecyl sulfate, citric acid, oxalic acid, and sodium hypochlorite) at different concentrations (500–5000 ppm), temperatures (22–40 °C), pH (without adjustment and pH 12), with and without air scouring, for membranes' permeability recovery. The best cleaning sequence was defined to be oxalic acid (pH 2.5) followed by NaOCl (5000 ppm), which was responsible for the inorganic fouling removal and allowed the oxidant agent to remove more effectively the organic fouling layer. Improvement in permeability recovery at 40 °C (92.7% of the initial permeability) and higher NaOCl concentration (5000 ppm) was found due to the increase in chemical oxidation kinetics and the diffusion rate of the cleaning agents within the fouled layer and membrane. Oxalic acid followed by sodium hypochlorite (40 °C) had a lower effect on membranes' morphology and thermal resistance, proven by thermogravimetric analysis and Fourier transform infrared spectroscopy. The pilot-scale operation was used to estimate the membrane lifespan which was approximately 1916 days of monitoring – about five years.

High surface area Eucalyptus wood biochar for the removal of phenol from petroleum refinery wastewater

The presence of phenolic compounds in petroleum refinery wastewater is a matter of significant environmental concern. Its removal is achieved through various methods, among which adsorption is an efficient and economically viable option. This study reports the development of activated biochar (EABC) from Eucalyptus wood pyrolytic biochar (EPBC) to remove phenols from petroleum refinery wastewater. The best activation strategy involved ball-milling of KOH and EPBC in the ratio 3:1, followed by annealing at 800 °C under an N2 atmosphere. The activated biochar (EABC-3–800) exhibited high phenol adsorption capacity (308.9 mg/g), attributed to the presence of heterogeneous pores, corroborated by large BET surface area (2048 m2 /g). As determined through HPLC, the EABC-3–800 could remove nearly 95% phenol (C0=114 ppm) from the wastewater of the delayed coking unit of a petroleum refinery. The best-fitting of the adsorption results in the Freundlich isotherm model substantiates the hypothesis of pore-based adsorption of phenol compared to the surface-adsorption-based Langmuir isotherm. The phenol adsorption kinetics followed the pseudo-second-order model, indicating weak chemical interactions between phenol and activated biochar. The regeneration and reuse of EABC-3–800 for a minimum of five operational cycles demonstrate its potential for industrial wastewater remediation.

Removal of COD from petroleum refinery wastewater using electrocoagulation method

This research assessed the removability of chemical oxygen demand (COD) from petroleum effluent using aluminum-based electrocoagulation reactor. A series of batch flow studies have been conducted to evaluate the impact of current density, electrodes separation, and duration of treatment on the removal of COD from the refinery effluent. The COD levels were determined employing the remaining concentrations using spectrophotometer namely Hach-Lang and standard cuvette test (LCC 514, LCK 314, or APC 400). The findings of the current investigation indicate the capacity of the electrocoagulation technique in a relatively short processing time to reduce the COD levels. The greatest efficiency in removing COD has been determined to be 80.0%. After 100 minutes of electrolysis, a current density of 8 mA/cm2 and electrodes separation of 20 mm achieved the highest percentage removal.

Solar driven homogeneous sodium hypochlorite/iron process in treatment of petroleum refinery wastewater for reusing

This study reports the performance of a new homogenous solar/sodium hypochlorite/iron process in treatment of petroleum refinery wastewater for the aim of water reusing. A pilot-scale solar photo-reactor with capability of automatic rotating against the sun’s surface was employed. Experiments were conducted by following the chemical oxygen demand (COD) and the total organic carbon (TOC) criteria at different times. The optimal operating conditions of 548 mg/L of sodium hypochlorite, 48 mg/L of ferrous salt and pH 3 were found under which COD and TOC removal of, respectively, 78.6% and 69.3% were corresponding after 180 min treatment. The COD removal could easily reach to 88.5% by multiple feeding of the reagents. A significant improvement in the biodegradability was also achieved by raising the BOD5/COD ratio from 0.36 to 0.69. The GC/MS headspace analysis indicated a high degradation level of the most hydrocarbons. Meanwhile, the COD removal was appeared with a pseudo first order kinetic in term of accumulated UV energy. Comparing the performance with the alternative processes including solar Fenton as well as the cost estimates revealed the high preference of the employed process.

The operation characteristics of air cathode Microbial Desalination Cell to treat oil refinery wastewater

This system [microbial desalination cell (MDC)] is considered an excellent sustainable process to treat wastewater by biological anaerobic oxidation of the organic material by electroactive bacteria, desalinate saltwater, and electrical power generation. In the present work, MDC was used for treating oil refinery wastewater in the anode chamber by anaerobic bacteria. Simultaneously, an air pump was used to provide the oxygen to the cathode chamber as an electron acceptor to generate bioelectricity power. The power density generated by this air cathode MDC with 1KΩ external resistance at the 1st experiment was 71.11 μW/m2. It increased to a peak value of 570.86 μW/m2 at the last experiment. The maximum chemical oxygen demand (COD) removal percent of oily wastewater was 96%. The higher salinity removal rate 150.39 ppm/h with a first salt concentration in a desalinating chamber of 35000 ppm.

Wastewater Treatment Using Constructed Wetland: Current Trends and Future Potential

Constructed wetlands (CW) is an environmentally friendly technique for removing pollutants from wastewater and has been applied to municipal wastewater, petroleum refinery wastewater, agriculture drainage, acid mine drainage, etc. The past decade has seen a remarkable number of innovations in the exponentially growing field of microbiology. This manuscript covers a critical review of key aspects of CW, such as various types of CW, the contaminants and their removal mechanisms, degradation pathways, challenges and opportunities, materials, applications, and theory with a focus on recent advances in the last three decades. In addition, an attempt has been taken to project future advances in the field of CW and facilitate these advances by framing key unsolved problems in CW. Guidelines are prepared for the fast-growing CW field through the standardization of key design aspects. This review covers the evaluation of the current state-of-the-art of CW technology and provides definitions and performance metric nomenclature in an effort to unify the fast-growing CW community. It also contains an outlook on the emerging trends in CW and proposes future research and development directions.

Optimization of AC/TiO2/CeO2 composite formulation for petroleum refinery wastewater treatment via simultaneous adsorption-photocatalytic process using D-optimal mixture experimental design

This study aims to optimize the formulation of activated carbon/titanium oxide/cerium oxide (AC/TiO2/CeO2) composite for petroleum refinery wastewater (PRW) treatment via simultaneous adsorption and photocatalytic process. D-optimal mixture experimental design was applied to predict the optimal formulation of the composite. The experimental data were assessed to generate empirical models for analyzing the effects of components fraction on individual responses. The fitted models were statistically examined (through the standard error of design), considerably validated (via analysis of variance (ANOVA) and model adequacy indicators), and experimentally verified (by estimating errors, root-mean square error (RMSE), and standard error of prediction (SEP) between the predicted and actual values). Finally, the optimized formulation was accepted to have 36.85% total dissolved solid (TDS) removal, 49.23% chemical oxygen demand (COD) removal, treated PRW with pH = 7.22 and electrical conductivity (EC) = 2937.11 µS/cm, 53.76% phenol removal, and 52.86% NH3-N removal, by applying 53.43%-wt of AC, 21.96%-wt of TiO2, and 24.61%-wt of CeO2 with reasonably high desirability score of 0.8874. Based on the characterization results, it can be concluded that the optimized AC/TiO2/CeO2 composite was successfully synthesized. From the diffuse reflectance spectrometry (DRS), the estimated bandgap energy of the synthesized AC/TiO2/CeO2 composite was successfully reduced through the use of CeO2. Our findings show the efficiency, reliability, and feasibility of the D-optimal mixture experimental design from modeling, predicting, and optimizing the formulation of AC/TiO2/CeO2 composite. Overall, our findings prove that the optimized AC/TiO2/CeO2 composite is a prominent and effective material for PRW treatment.

The Impact of Bioaugmentation on the Performance and Microbial Community Dynamics of an Industrial-Scale Activated Sludge Sequencing Batch Reactor under Various Loading Shocks of Heavy Oil Refinery Wastewater

The stable and efficient operation of the activated sludge sequencing batch reactor (ASSBR) in heavy oil refineries has become an urgent necessity in wastewater biotreatment. Hence, we constructed a green and efficient solid bioaugmentation agent (SBA) to enhance the resistance of the reactor to loading shock. The impact of bioaugmentation on the performance and microbial community dynamics under three patterns of heavy oil refinery wastewater (HORW) loading shock (higher COD, higher toxicity, and higher flow rate) was investigated on an industrial-scale ASSBR. Results showed that the optimal SBA formulation was a ratio and addition of mixed bacteria Bacillus subtillis and Brucella sp., of 3:1 and 3.0%, respectively, and a glucose concentration of 5.0 mg/L. The shock resistance of ASSBR was gradually enhanced and normal performance was restored within 6–7 days by the addition of 0.2% SBA. Additionally, the removal efficiency of chemical oxygen demand and total nitrogen reached 86% and 55%, respectively. Furthermore, we found that Burkholderiaceae (12.9%) was replaced by Pseudomonadaceae (17.1%) in wastewater, and Lachnospiraceae (25.4%) in activated sludge was replaced by Prevotellaceae (35.3%), indicating that the impact of different shocks effectively accelerated the evolution of microbial communities and formed their own unique dominant bacterial families.

Cyto-genotoxic potential of petroleum refinery wastewater mixed with domestic sewage used for irrigation of food crops in the vicinity of an oil refinery

Petroleum refinery wastewater combined with domestic sewage were collected from the open channel in the vicinity of Mathura oil refinery, UP (India) and analysed by inductively coupled plasma optical emission spectrometry (ICP-OES) and gas chromatography-mass spectrometry (GC-MS) for elemental analysis and organic pollutants, respectively. Several potentially toxic and non-toxic elements were found to be present in the wastewater samples. GC-MS analysis revealed the presence of several organic contaminants including pesticides. Wastewater samples were extracted using amberlite XAD4/8 resins and liquid-liquid extraction procedures using different organic solvents. The extracts were tested for their cyto-genotoxic potential using bacterial (Salmonella mutagenicity test, E. coli K-12 DNA repair defective mutants, Bacteriophage λ assay) and plant (Vigna mungo phytotoxicity test, Allium cepa chromosomal aberration assay) systems. A significant increase was observed in the number of revertants of TA97a, TA98 and TA100 strains with the test samples and XAD concentrated samples were found to be more mutagenic than liquid-liquid extracts. Colony forming units (CFUs) of DNA repair defective mutants of E. coli K-12 recA, lexA and polA declined significantly as compared to their isogenic wild-type counterparts with the test samples. Significant reduction in plaque forming units (PFUs) of bacteriophage λ was also found on treatment with the solvent extracts. Presence of several toxic pollutants in the wastewater apply prohibitive action on the seed germination process. Germination rate of Vigna mungo seeds as well as radicle and plumule lengths were found to be affected when treated with different concentration of wastewater as compared to control. Present study also indicated concentration dependent reduction in mitotic index of A. cepa i.e., 16.38% at 5% and 9.74% at 100% wastewater and percentage of aberrant cells were highest at 100% effluent. Present findings indicated that mutagenicity/genotoxicity of wastewater is due to the mixture of genotoxins; poses serious hazards to the receiving waterbodies which require continuous monitoring and remedial measures for their improvement.

Bimetallic M-Cu (M = Ag, Au, Ni) Nanoparticles Supported on γAl2O3-CeO2 Synthesized by a Redox Method Applied in Wet Oxidation of Phenol in Aqueous Solution and Petroleum Refinery Wastewater.

Three bimetallic catalysts of the type M–Cu with M = Ag, Au and Ni supports were successfully prepared by a two-step synthesized method using Cu/Al2O3-CeO2 as the base monometallic catalyst. The nanocatalysts were characterized using X-ray diffraction (XRD), temperature-programmed reduction of H2 (H2-TPR), N2 adsorption-desorption, scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM) and ultraviolet–visible spectroscopy with diffuse reflectance (DR-UV-Vis) techniques. This synthesized methodology allowed a close interaction between two metals on the support surface; therefore, it could have synthesized an efficient transition–noble mixture bimetallic nanostructure. Alloy formation through bimetallic nanoparticles (BNPs) of AgCuAlCe and AuCuAlCe was demonstrated by DR–UV–Vis, EDS, TEM and H2-TPR. Furthermore, in the case of AgCuAlCe and AuCuAlCe, improvements were observed in their reducibility, in contrast to NiCuAlCe. The addition of a noble metal over the monometallic copper-based catalyst drastically improved the phenol mineralization. The higher activity and selectivity to CO2 of the bimetallic gold–copper- and silver–copper-supported catalysts can be attributed to the alloy compound formation and the synergetic effect of the M–Cu interaction. Petroleum Refinery Wastewater (PRW) had a complex composition that affected the applied single CWAO treatment, rendering it inefficient.

Fabrication, characterisation and application of Poly Allyl Amine Hydrochloride / Poly Styrene Sulphonate/Zinc Oxide (PAH/(PSS/ZnO)n bilayers in the removal of pollutants from oil refinery waste water

ABSTRACT The application of nanomaterials in the oil and gas industry has been widely studied in the past few years, and polymeric nano thin films have become an area of interest among researchers. In this work, multilayer nano thin films were fabricated using poly(ally lamine hydrochloride) (PAH), zinc oxide (ZnO) and poly(styrene sulphonate sodium salt) (PSS) on glass template by Layer-by-Layer (L-b-L) technique and its potential application for the photo degradation of oil refinery wastewater have been reported. The L-b-L fabrication of the thin film was carried out at an assembly pH of 8.0. The morphological characterisation and elemental composition of the fabricated thin films were studied using Scanning Electron Microscope (SEM) and Energy Dispersive X-Ray Analysis (SEM – EDX). Chemical bond and surface functional groups were identified using Fourier Transform Infrared Spectroscopy (FTIR). SEM characterisation depicted the uniform deposition of ZnO particles in the polyelectrolyte matrix. The outcome of the FTIR analysis is justified by the presence of strong C=C bonds favouring the strength of bilayer deposition. A comparative study on the degradation efficiency was carried out using oil refinery effluents for the photo degradation of ZnO/PSS/PAH thin films and suspension form of ZnO by varying the process parameters such as number of bilayers and contact time. The ZnO/Polyelectrolyte multilayer thin films performed extremely well in reducing the chemical oxygen demand (COD) and Total Organic carbon (TOC) to the standards. A maximum COD removal efficiency of 80.1% was obtained at conditions where PAH/(PSS, ZnO)5 bilayers were used at pH 7.2 with a contact time of 120 minutes. The total organic carbon removal was around 55% under optimum conditions of pH 7.2 and PAH/(PSS, ZnO)5 at 120 minutes. This study illustrates that immobilised zinc oxide nanoparticles can effectively remove pollutants from oily wastewater and the process seems to be attractive in the environmental applications.

Removal of pollutants and accumulation of high-value cell inclusions in heavy oil refinery wastewater treatment system using Rhodopseudomonas and Pseudomonas:Effects of light intensity

Photosynthetic bacteria (PSB) wastewater treatment is a special technology which can simultaneously remove pollutants from wastewater and produce high-value cell inclusions, but the characteristics of PSB in the heavy oil refinery wastewater treatment system are not clear. This study evaluated pollutants removal with different light intensities, and the accumulation of biomass, carotenoid, bacteriochlorophyll, and coenzyme Q10 while treating heavy oil refinery wastewater in PSB system. Furthermore, high sequencing technology and q-PCR were used to analyses microbial community structure and the quantity of Rhodopseudomonas and Pseudomonas in the systems. Results showed that 500 lx was the optimal intensity for SCOD and NH4+-N removal, the corresponding removal ratios were 62.66% and 91.54%, respectively, and the yield of coenzyme Q10 reached the highest on the 8 th day, which was 9.90 mg/g-DCW, with the highest dehydrogenase concentration reaching 71.83 mg/L. While 4000 lx was the optimal light intensity for the yield of carotenoid, bacteriochlorophyll and biomass production, the corresponding accumulations were 10.64 mg/g-DCW, 5.88 mg/g-DCW, and 550 mg/L, respectively. Furthermore, the relative abundance of Pseudomonas was the highest at 500 lx, which was 37.13%, and the gene number was 4.56 × 105 gene copies/μL, 2.34 times of that before the reaction. At 4000 lx, the relative abundance of Rhodopseudomonas was the highest, which was 58.91%, and the gene number was 9.51 × 105 gene copies/μL, 7.15 times of that before the reaction. The results proved that it was feasible for culturing Rhodopseudomonas and Pseudomonas in PSB system to treat heavy oil refinery wastewater and realized cell inclusions accumulation simultaneously. The results could provide theoretical guidance for industrial treatment of refinery wastewater.