The Impact of Metallic Coagulants on the Removal of Organic Compounds from Oil Sands Process-Affected Water

Department of Civil and Environmental Engineering, University of Alberta , Edmonton, Alberta, Canada, T6G 2W2.
Environmental Science & Technology (Impact Factor: 5.33). 08/2011; 45(19):8452-9. DOI: 10.1021/es201498v
Source: PubMed


Coagulation/flocculation (CF) by use of alum and cationic polymer polyDADMAC, was performed as a pretreatment for remediation of oil sands process-affected water (OSPW). Various factors were investigated and the process was optimized to improve efficiency of removal of organic carbon and turbidity. Destabilization of the particles occurred through charge neutralization by adsorption of hydroxide precipitates. Scanning electron microscope images revealed that the resultant flocs were compact. The CF process significantly reduced concentrations of naphthenic acids (NAs) and oxidized NAs by 37 and 86%, respectively, demonstrating the applicability of CF pretreatment to remove a persistent and toxic organic fraction from OSPW. Concentrations of vanadium and barium were decreased by 67-78% and 42-63%, respectively. Analysis of surface functional groups on flocs also confirmed the removal of the NAs compounds. Flocculation with cationic polymer compared to alum, caused toxicity toward the benthic invertebrate, Chironoums dilutus, thus application of the polymer should be limited.

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Available from: Leonidas Perez-Estrada,
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    • "In fact, the synthetic PACl at the highest applied coagulant dose of 3.0 mM Al caused a decrease in the OSPW toxicity to 43.3 ± 3.0%. Given the results of previous studies (Pourrezaei et al., 2011), it was expected the OSPW toxicity would increase with increasing coagulant addition. However , it was noted that the residual Al concentration in all treated OSPW samples was found to be below the detection limit of 0.02 mg/L, which is much lower than Al concentration in raw OSPW Fig. 3. Representative metal removal (%) by PACl vs pK a of the metal cations at an applied coagulant dose of 1.5 mM Al. (Note: error bars indicate mean ± SD with n ¼ 3). "
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    ABSTRACT: This study investigated the application of polyaluminum chloride (PACl) for the treatment of the oil sands process-affected water (OSPW). These coagulants are commonly used in water treatment with the most effective species reported to be Al13. PACl with 83.6% Al13 was synthesized using the slow base titration method and compared with a commercially available PACl in terms of aluminum species distribution, coagulation/flocculation (CF) performance, floc morphology, and contaminant removal. Both coagulants were effective in removing suspended solids, achieving over 96% turbidity removal at all applied coagulant doses (0.5-3.0 mM Al). The removal efficiencies of metals varied among different metals depending on their pKa values with metal cations having pKa values (Fe, Al, Ga, and Ti) below OSPW pH of 6.9-8.1 (dose dependent) being removed by more than 90%, while cations with higher pKa values (K, Na, Ca, Mg and Ni) had removals of less than 40%. Naphthenic acids were not removed due to their low molecular weights, negative charges, and hydrophilic characteristics at the OSPW pH. At the highest applied coagulant dose of 3.0 mM Al, the synthetic PACl reduced Vibrio fischeri inhibition effect to 43.3 ± 3.0% from 49.5 ± 0.4% in raw OSPW. In contrast, no reduction of toxicity was found for OSPW treated with the commercial PACl. Based on water quality and floc analyses, the dominant CF mechanism for particle removal during OSPW treatment was considered to be enmeshment in the precipitates (i.e., sweep flocculation). Overall, the CF using synthesized PACl can be a valuable pretreatment process for OSPW to create wastewater that is more easily treated by downstream processes. Copyright © 2015 Elsevier Ltd. All rights reserved.
    Journal of Environmental Management 06/2015; 160:254-262. DOI:10.1016/j.jenvman.2015.06.025 · 2.72 Impact Factor
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    • "Physical-Chemical −Chemical precipitation −Metals, hardness Pourrezaei et al. (2011) −Coagulation/flocculation −Suspended solids, colloidal organic matter, NAs −Sedimentation/filtration −Suspended solids −Dissolved air flotation −Suspended matter such as oil and grease and solids Chemical Oxidation −Ozonation −Hydrocarbons, NAs Gamal El-Din et al. (2011) −Advanced oxidation process −Hydrocarbons, NAs Wang et al. (2013) Advanced Physical −Adsorption −Hydrocarbons, NAs Pourrezaei et al. (2014) −Ion exchange −Ionic contaminants, calcium and magnesium ions, heavy metals Zubot et al. (2012) Kim et al. (2011) Alpatova et al. (2014) −Membrane filtration (microfiltration, ultrafiltration, nanofiltration, reverse osmosis) −Suspended solids, colloidal organic matter, hydrocarbons, NAs, dissolved solids, salts, trace metals, hardness, organic acids, ammonia Biological −Biodegradation −Hydrocarbons, NAs Han et al. (2009) −Biofilm based-biological treatment −Hydrocarbons, NAs, ammonia Hwang et al. (2013) Islam et al. (2014) Natural Remediation −Natural and/or constructed wetlands −Suspended solids, hydrocarbons, NAs, ammonia Toor et al. (2013) −Filtration through substrates −Suspended solids, hydrocarbons, other organics, ammonia that more than 76% of the acid-extractable fraction (AEF) in OSPW, which includes NAs species among other organic acids, were removed using a semi-batch ozonation system at a utilized ozone (O 3 ) dose of 3.1 mM. It has also been reported that ozonation preferentially reacts with classical NAs with more rings (or double bond equivalents) and with more carbon numbers (Gamal El-Din et al. 2011; Perez-Estrada et al. 2011; Wang et al. 2013). "
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    ABSTRACT: 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.
    Ozone Science and Engineering 01/2015; 37(1):45-54. DOI:10.1080/01919512.2014.967835 · 0.95 Impact Factor
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    • "Although many different treatments have been investigated for their ability to remove NAs from OSPW, most of the approaches have shown poor efficiency for removal of the most recalcitrant compounds. Additionally, the relatively high costs of many of these treatments may limit their applications in large-scale industrial treatments (Kim et al. 2011; Pourrezaei et al. 2011). Treatment using biodegradation has the potential to be an economical, energy-efficient, and environmentally protective approach for tailings water remediation . "
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    ABSTRACT: Treatment of oil sands process-affected water (OSPW) using biodegradation has the potential to be an environmentally sound approach for tailings water reclamation. This process is both economical and efficient, however, the recalcitrance of some OSPW constituents, such as naphthenic acids (NAs), require the pre-treatment of raw OSPW to improve its biodegradability. This study evaluated the treatment of OSPW using ozonation followed by fluidized bed biofilm reactor (FBBR) using granular activated carbon (GAC). Different organic and hydraulic loading rates were applied to investigate the performance of the bioreactor over 120 days. It was shown that ozonation improved the adsorption capacity of GAC for OSPW and improved biodegradation by reducing NAs cyclicity. Bioreactor treatment efficiencies were dependent on the organic loading rate (OLR), and to a lesser degree, the hydraulic loading rate (HLR). The combined ozonation, GAC adsorption, and biodegradation process removed 62 % of chemical oxygen demand (COD), 88 % of acid-extractable fraction (AEF) and 99.9 % of NAs under optimized operational conditions. Compared with a planktonic bacterial community in raw and ozonated OSPW, more diverse microbial communities were found in biofilms colonized on the surface of GAC after 120 days, with various carbon degraders found in the bioreactor including Burkholderia multivorans, Polaromonas jejuensis and Roseomonas sp.
    Biodegradation 07/2014; 25(6):811-823. DOI:10.1007/s10532-014-9701-6 · 2.34 Impact Factor
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