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: 5.33). 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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    • "Raw OSPW contains about 2000e2500 mg/L of inorganic and organic dissolved solids (Allen, 2008a). The primary toxic constituents of OSPW are naphthenic acids (NAs) (Scott et al., 2005), comprising about 50% of the acid extractable organic fraction (AEF) in OSPW (GarciaeGarcia et al., 2011;Pourrezaei et al., 2011). Classical NAs are a complex mixture of alicyclic and noncyclic alkylsubstituted carboxylic acids with the general chemical formula C n H 2nþZ O 2 , where n indicates the carbon number and Z shows the number of hydrogen atoms lost in the formation of rings or double bonds. "
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    ABSTRACT: Two integrated fixed-film activated sludge (IFAS) reactors were operated continuously to treat raw (untreated) and ozonated (30 mg/L) oil sands process-affected water (OSPW). After 11 months, 12.1% of the acid extractable fraction (AEF) and 43.1% of the parent naphthenic acids (NAs) were removed in the raw OSPW IFAS, while 42.0% AEF and 80.2% of parent NAs were removed in the ozonated OSPW IFAS. UPLC/HRMS analysis showed that NA biodegradation significantly decreased as the NA cyclization number increased. Confocal laser scanning microscopy (CLSM) results showed that the biofilm in the ozonated OSPW IFAS was significantly thicker (94 ± 1.6 μm) than the biofilm in the raw OSPW IFAS (72 ± 2.8 μm) after 283 days of cultivation. The quantitative polymerase chain reaction (q-PCR) revealed that the abundance proportions of both nitrifier genes (AomA, NSR and Nitro) and denitrifier genes (narG, nirS, nirK and nosZ) within total bacteria were significantly higher in biofilms than in flocs in the raw OSPW IFAS system, but a different trend was observed in the ozonated OSPW IFAS system. Copyright © 2015 Elsevier Ltd. All rights reserved.
    Full-text · Article · Aug 2015 · Water Research
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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.
    Full-text · Article · Jun 2015 · Journal of Environmental Management
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    • "Much of the toxicity of OSPW is attributed to its organic acids, known as naphthenic acids (NAs) (Seifert and Teeter,1970; Hsu et al., 2000). To date, many different kinds of treatment processes have been investigated for their ability to remove NAs from OSPW, some of which are physical treatments, such as membrane filtration and physical adsorption (Peng et al., 2004; Mohamed et al., 2008), while others are physico-chemical, such as coagulation and flocculation (Kim et al., 2011; Pourrezaei et al., 2011). Many of these physical and physico-chemical approaches have shown some success in OSPW detoxification and the removal of recalcitrant OSPW organic compounds such NAs. "
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    ABSTRACT: The effects of different ozone pretreatment doses on the performance of endogenous microbial populations in degrading naphthenic acids (NAs) for the treatment of oil sands process-affected water (OSPW) were evaluated in this study. Ozone pretreatment enhanced OSPW biodegradability and accelerated the growth of microbial populations in bioreactors. After ozone pretreatment, the maximum chemical oxygen demand (COD) removal through biodegradation occurred at an ozone dose of 50 mg/L. Although OSPW pretreated with a higher ozone concentration removed a higher COD concentration and acid extractable fraction (AEF), organics removal through biodegradation was not further improved. After pretreatment with an ozone dose of 200 mg/L and bioreactor operation for 73 days, the batch bioreactor removed more than 80% of the COD and more than 95% of AEF. High-resolution mass spectrometry analysis showed complete degradation of NAs with specific degrees of cyclization (Z = −2 and −4) after combined treatments of ozonation and biodegradation. At high pretreatment doses of ozone (116 and 200 mg/L), biodegradation completely eliminated the toxicity of OSPW toward Vibrio fischeri (IC20 > 100% v/v).
    Full-text · Article · May 2015 · International Biodeterioration & Biodegradation
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