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The quality of heavy oil electric desalting wastewaters (HO-EDWs) affects the effectiveness of refinery wastewater treatment plants. In this study, an integrated coagulation-ozonation (ICO) process was used to pretreat HO-EDWs and the influences on the characteristics of dissolved organic pollutants (DOPs) were investigated. Coagulation using aluminum sulfate removed 39% of soluble chemical oxygen demand (SCOD), 21% of dissolved organic carbon (DOC), 57% of petroleum hydrocarbons and 38% of polar oils from Liaohe HO-EDWs and the biodegradability was greatly improved. Ozonation removed 33% of SCOD and 88% of polar oils from the coagulated HO-EDWs. Most species of aromatic compounds, phenols, aliphatic acids, anilines and naphthenic acids with high C numbers and ring numbers were degraded and the unsaturation degrees of DOPs significantly decreased under ozonation. As a result, the biodegradability was further improved and the acute toxicity towards Vibrio fischeri was substantially reduced. Some O x S 1 species and organic nitrogen compounds in HO-EDWs were penetrated through ozonation and caused the residual biotoxicity. The results demonstrate the potential of ICO pretreatment for improving the quality of refractory HO-EDWs., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Owing to the complexity of naphthenic acids (NAs) in oil sands process water (OSPW), previous ozone-treatment studies mainly investigated the removal of classical NAs (aliphatic O 2 -NAs) and the understanding of ozonation reactivity of other NA species has been limited. This work utilized a silver-ion solid phase extraction (SPE) approach to separate individual NA species into 20 fractions before subsequent ozone treatment. The ozonation reactivity of aromatic and oxidized NA species in isolated fractions was studied for the first time. Untreated and ozone-treated SPE fractions were characterized using ultra performance liquid chromatography ion mobility time-of-flight mass spectrometry. The removals of aliphatic O 2 -NAs (Fraction 3), aromatic O 2 -NAs (Fraction 8), O 3 -NAs (Fraction 11), and O 4 -NAs (Fraction 17) with an applied ozone dosage of 16.8 mg L -1 were 97.2%, 94.7%, 59.4% and 44.7%, respectively. The results showed that aromatic and oxidized NAs with larger carbon number were favorably removed during ozonation treatment. Comparison of the ozone utilization efficiency for different NA species indicated that the degradation of oxidized NAs consumed more ozone in molar ratio than the degradation of classical and aromatic NAs. The reactivity of oxidized NAs was lower than that of classical NAs because the former consumed more ozone in molar ratio during reactions. Knowing the reactivity of different NA species is crucial for the design of ozonation systems targeting species with high toxicity. Moreover, the utilization of silver-ion SPE pre-separation approach has been demonstrated for future studies investigating the degradation mechanism of distinct NA species under other treatment conditions., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

This work investigated the oxidative transformation of the organic species in oil sands process-affected water (OSPW) using Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) and ultra-performance liquid chromatography time-of-flight mass spectrometry (UPLC-TOF-MS) in both negative and positive electrospray ionization (ESI) modes. This is the first time to apply FTICR-MS to investigate species transformation in OSPW treatments by ferrate (VI), UV/H 2 O 2 , and molecular ozone, and also this is the first preliminary study to use positive ESI to investigate organic species in addition to naphthenic acids (NAs) in these treatment processes. The oxidation processes with potassium ferrate (VI), UV/H 2 O 2 , and ozone transformed the distribution profiles of O x , O x S y , and O x N y organic fractions (i.e., species containing oxygen, sulfur, and nitrogen, with x, y specifying the oxygen number and sulfur/nitrogen number, respectively), with O x S y distribution profiles showing the most sensitive responses to the oxidation extent and can be used as a signature fraction to evaluate the oxidation effectiveness. Negative mode UPLC-TOF-MS confirmed the transformation pattern of O x species observed with FTICR-MS, but positive mode UPLC-TOF-MS results showed severe discrepancies with FTICR-MS results and should be subjected for future further investigation, regarding the relatively low mass resolution of UPLC-TOF-MS. The investigation of the transformation patterns of different organic species using two ionization modes was a preliminary study to enhance the understanding of the efficiency, selectivity, and mechanism of different oxidation processes in OSPW remediation for both NAs and non-NA species., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

The presence of naphthenic acids (NAs) and other organic constituents in oil sands process-affected water (OSPW) stored in tailings ponds, poses a serious environmental threat due to their potential toxicity to aquatic organisms and wild life. In this work, four fractions of OSPW, extracted by dichloromethane at different pHs, were ozonated to determine the ozone impact on NAs degradation. Extracts distributions showed that high carbon number NAs (14-22) were associated with higher pH fractions (pH>7) and smaller carbon number NAs (7-13) with lower pH fractions (pH≤7). Extracts showed similar hydrogen deficiency (Z-number) patterns centered on Z=6. Analysis of the speciation of NAs and oxidized NAs in the four fractions showed that ozonation degraded most NAs (55% to 98%). Despite the high degradation levels, there was still significant toxicity of the fractions toward goldfish macrophages and measurable toxicity toward Vibrio fischeri. The toxicity of such a complex matrix as OSPW may be attributed to other organic compounds and degradation by-products not currently detected. Thus, there is a need to elucidate which compounds are responsible for the remaining OSPW toxicity and to determine if combined processes, such as ozonation followed by biological treatment, are able to completely detoxify OSPW. This work is taking the first steps into this direction, narrowing down the range of compounds which might be responsible for the toxicity., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Oil sands process-affected water (OSPW) is a toxic and poorly biodegradable mixture of sand, silt, heavy metals, and organics. In this study, qualitative and quantitative comparisons of naphthenic acids (NAs) were done using ultraperformance liquid chromatography time-of-flight mass spectrometry (UPLC TOF-MS), Fourier transform ion cyclotron resonance (FT-ICR) MS, and ion mobility spectrometry (IMS). The unique combination of these analyses allowed for the determination and correlation of NAs, oxidized NAs, and heteroatom (sulfur or nitrogen) NAs. Despite its lower resolution, UPLC-TOF MS was shown to offer a comparable level of reliability and precision as the high resolution FT-ICR MS. Additionally, the impacts of ozonation (35 mg/L utilized ozone dose) and subsequent NAs degradation on OSPW toxicity were assessed via a collection of organisms and toxicity end points using Vibrio fischeri (nonspecific), specific fish macrophage antimicrobial responses, and fish olfactory responses. Fish macrophages exposed to ozonated OSPW for 1 week showed higher production of reactive oxygen and nitrogen intermediates; however, after 12 weeks the responses were reduced significantly. Fish olfactory tests suggested that OSPW interfered with their perception of odorants. Current results indicate that the quantification of NAs species, using novel analytical methods, can be combined with various toxicity methods to assess the efficiency of OSPW treatment processes.

Oil sands process-affected water (OSPW) is the water contained in tailings impoundment structures in oil sands operations. There are concerns about the environmental impacts of the release of OSPW because of its toxicity. In this study, ozonation followed by biodegradation was used to remediate OSPW. The impacts of the ozone process evolution on the naphthenic acids (NAs) speciation and acute toxicity were evaluated. Ion-mobility spectrometry (IMS) was used to preliminarily separate isomeric and homologous species. The results showed limited effects of the ozone reactor size on the treatment performance in terms of contaminant removal. In terms of NAs speciation, high reactivity of NAs with higher number of carbons and rings was only observed in a region of high reactivity (i.e., utilized ozone dose lower than 50 mg/L). It was also found that nearly 0.5 mg/L total NAs was oxidized per mg/L of utilized ozone dose, at utilized ozone doses lower than 50 mg/L. IMS showed that ozonation was able to degrade NAs, oxidized NAs, and sulfur/nitrogenated NAs. Complete removal of toxicity toward Vibrio fischeri was achieved after ozonation followed by 28-day biodegradation period. In vitro and in vivo assays indicated that ozonation reduced the OSPW toxicity to mice.

The oxidation of bromoxynil and trifluralin was investigated using ozone (O(3)) and O(3) combined with hydrogen peroxide (H(2)O(2)) in natural waters using batch reactors. The results indicated that these pesticides could not be completely degraded during ozonation, achieving degradation levels lower than 50%. An enhancement of the level of degradation was observed using O(3)/H(2)O(2) process. A biphasic behaviour of O(3) was also observed. Depending on the experimental conditions, the rate constant for O(3) decomposition was estimated to be between 7.4 × 10(-4) s(-1) to 5.8 × 10(-2) s(-1), and 3.2 × 10(-3) s(-1) to 4.2 × 10(-2) s(-1) for bromoxynil and trifluralin samples, respectively. Acute toxicity analysis performed using Microtox(®) showed a decrease in the toxic effects of the samples on the luminescent bacteria during the first few minutes of treatment, followed by an increase of the toxic effects at the end of the reaction for both pesticides. The quantification of oxidation by-products generated during treatment was also addressed. The total molar balances of the degradation by-products versus the initial pesticide concentrations ranged from 60 to 103% under different experimental conditions., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

This study evaluated the reaction kinetics and degradation mechanism of the pesticides bromoxynil and trifluralin during conventional ozonation. The second-order rate constants for the direct molecular ozone and hydroxyl radical reactions with bromoxynil and trifluralin were determined using a rapid-scan stopped-flow spectrophotometry, competition kinetics, and an organic substrate monitoring method. High reactivity toward ozone and hydroxyl radicals was observed for bromoxynil and trifluralin. The second-order rate constants for the reaction with ozone were about 10(2)M(-1)s(-1). The values of the second-order rate constants for the reaction between hydroxyl radicals and bromoxynil and trifluralin in ultrapure water at 20 degrees C were estimated to be around 8.4x10(9) and 7.5x10(9)M(-1)s(-1), respectively. The identification of oxidation by-products generated during ozonation was also addressed. It was found that hydroxylation and debromination were the primary pathways for the bromoxynil degradation, whereas hydroxylation and dealkylation were found to be the major mechanisms for trifluralin oxidation., (2009 Elsevier Ltd. All rights reserved.)

The toxicological effects from all components in oil sands process-affected water (OSPW) are not known. Alternatively, monitoring the variations and abundance of different classes and compounds after treatments might be a useful approach in OSPW remediation. In this study, the variations in the compositions of classical and heteroatomic naphthenic acids (NAs) after treatment using advanced oxidation processes (AOPs), mainly ozone and peroxone, and two different mass spectrometry methods; ultra-performance liquid chromatography time-of-flight (UPLC-TOFMS) and Fourier transform ion cyclotron resonance (FTICR-MS), were examined. Two markers (O 2 S:O 3 S:O 4 S and O 2 :O 4 ratios) were used to reveal changes and similarities of the treated water characteristics with those in natural waters. Both ratios decreased after all treatments, from 2.7:4.8:2.1 and 3.59 in raw OSPW to 0:1.4:0.5 and 0.7, respectively, in peroxone (1:2), becoming close to the reported ratios in natural waters. Toxicity toward Vibrio fischeri showed residual toxic effects after AOPs, suggesting that part of OSPW toxicity may be caused by specific compounds of NAs (i.e., similar reduction (50%) was achieved in both toxicity and abundance in O 2 species with carbon 15–26) and/or generated by-products (e.g., O 3 S classes at double bond equivalent (DBE) = 4 and C 9 H 12 O 2 at DBE = 4). Although by-products were generated, the best biodegradability enhancement and chemical oxygen demand reduction were achieved in peroxone (1:2) compared to ozone, suggesting the possibility of using combined OSPW remediation approaches (i.e., peroxone coupled with biological process). The recommended indicators can assist in evaluating the treatments' performance and in examining the best removal levels to accomplish significant toxicity reduction. [ABSTRACT FROM AUTHOR]

Due to their recalcitrance, naphthenic acids (NAs) are one of the constituents of interest in oil sands process water (OSPW). In this study, peroxymonosulfate (PMS) activated by ozone was employed to degrade NA model compounds in buffer solutions. At an ozone/PMS ratio of 2:1, a removal of 85 % was observed for a model diamondoid NA compound (1-adamantanecarboxylic acid; ACA) after 45 s of reaction. Compared with ozone alone, the degradation of ACA was accelerated in the presence of ozone/PMS, with an overall pseudo-first order rate constant (k obs) increasing from 8.02 × 10−4 s−1 during ozone treatment to 6.74 × 10−2 s−1 in the ozone/PMS system. Although ozone/hydrogen peroxide (H 2 O 2) showed high degradation for ACA, the ozone/PMS system showed a higher k obs of 5.44 × 10−2 s−1at a PMS dose of 0.042 mM, while at the same dose of H 2 O 2 , k obs was equal to 3.62 × 10−2 s−1 for ozone/H 2 O 2. This result showed the synergetic effect of ozone and PMS on the degradation of ACA. Relative kinetics studies using mixtures of model NA compounds showed better performance for ozone/PMS to degrade aromatic NAs compared to ozone/H 2 O 2. Hydroxyl radicals and sulfate radicals were found to be responsible for the removal of ACA, with limited effect of molecular ozone. The proposed degradation pathways for ACA included hydroxylation, carboxylation, and polymerization under ozone/PMS, while hydroxylation and carboxylation were the main degradation pathways under ozone/H 2 O 2. The results of this study emphasize the potential of ozone/PMS process to treat OSPW by accelerating the degradation of recalcitrant organic compounds. [Display omitted] • PMS was successfully activated by ozone to degrade naphthenic acids model compounds. • The degradation of ACA was accelerated in the presence of ozone/PMS. • Hydroxyl radicals and sulfate radicals were responsible for the removal of ACA. • Limited effect of molecular ozone was observed for the oxidation of model NAs. • Ozone/PMS produced intermediates via hydroxylation, carboxylation and polymerization. [ABSTRACT FROM AUTHOR]

Naphthenic acids (NAs) are persistent compounds that contribute to the toxicity of oil sands process-affected water (OSPW). In this study, the effects of ozone and ozone/hydrogen peroxide on the NAs degradation in buffered water and OSPW were examined. Cyclohexanoic acid (CHA) was used as a model NAs compound in buffered water experiments at two different pHs, using radical scavengers. At pH 9, the addition of carbonate did not have any effect on CHA degradation. Additions of tert-butyl alcohol and tetranitromethane decreased the CHA degradation levels. For the OSPW experiments, degradation of acid-extractable fraction (AEF) and NAs was examined. Approximately 90% of AEF was oxidized in a semi-batch system. In a batch system, 99% of OSPW NAs were degraded. This study demonstrated that ozone and ozone/hydrogen peroxide could be suitable treatment processes for OSPW remediation. [ABSTRACT FROM AUTHOR]

This treatability study evaluated the overall effectiveness of advanced oxidation processes (AOPs) to treat membrane concentrates containing the pesticides bromoxynil and trifluralin. The results of study indicate that high levels of pesticide degradation were achieved using ozone (O3) plus hydrogen peroxide (H2O2) for all concentrate matrices. However, the toxicity of the samples during the O3/H2O2 process was higher than that obtained during ultraviolet (UV) light combined with H2O2. Low levels of pesticide oxidation were observed in experiments using a mixture of pesticides during all treatment options. [ABSTRACT FROM AUTHOR]