Article

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: 5.48). 08/2011; 45(19):8452-9. DOI: 10.1021/es201498v
Source: PubMed

ABSTRACT 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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    • "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 · 3.19 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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    • "Coagulation, flocculation and sedimentation (CFS) [2], adsorption [7], advanced oxidation [6] [8], bioreactors [3] [9], and membrane filtration [10] have been introduced to treat OSPW. To reduce the total dissolved solids (TDS) level in OSPW, membrane filtration can be applied because membrane is one of the best technologies to remove dissolved solids and ionic species from the water phase [11] [12]. "
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    ABSTRACT: This study evaluates membrane systems for the removal of the extractable organic fraction (EOF) from oil sands process-affected water (OSPW). Experiments were performed using in-situ integrated membrane units that consisted of low pressure-driven membrane (LPM) and high pressure-driven membrane (HPM) modules. LPM was prepared with a polysulfone (PSU) phase inversion casting process and HPM was fabricated by polyamide (PA) thin-film composite (TFC) interfacial polymerization. To change membrane physicochemical properties, each membrane was developed with and without multiwalled carbon nanotubes (MWNTs). The MWNTs were modified with strong acid to enhance dispersion in an organic solvent. Dispersion of the MWNTs and physicochemical properties of the membranes were characterized by microscopic and spectroscopic methods. The results showed that acid-modified MWNTs developed surface functional groups that increased their hydrophilicity, increasing the rejection of hydrophobic pollutants, increasing OSPW permeate flux, and significantly reducing membrane fouling. The LPM and HPM combinations with MWNTs were tested for the optimal organic pollutants removal from OSPW.
    Journal of Membrane Science 02/2013; 429:418-427. DOI:10.1016/j.memsci.2012.11.077 · 4.91 Impact Factor
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