Naphthenic acids degradation and toxicity mitigation in tailings wastewater systems and aquatic environments: A review

Abstract

Naphthenic acids, NAs (classical formula C(n)H(2n+z)O(2), where n is the carbon numbers, z represents zero or negative even integers), found in oil sands process waters (OSPWs), are toxic to aquatic environments depending upon several factors such as pH, salinity, molecular size and chemical structure of NAs. Among various available methods, biodegradation seems to be generally the most cost-effective method for decreasing concentrations of NAs (n ≤ 21) and reducing their associated toxicity in OSPW, however the mechanism by which the biodegradation of NAs occurs are poorly understood. Ozonation is superior over biodegradation in decreasing higher molecular weight alkyl branched NAs (preferentially, n ≥ 22, -6 ≥ z ≥ -12) as well as enabling accelerated biodegradation and reducing toxicity. Photolysis (UV at 254 nm) is effective in cleaving higher molecular weight NAs into smaller fragments that will be easier for microorganisms to degrade, whereas photocatalysis can metabolize selective NAs (0 ≥ z ≥ -6) efficiently and minimize their associated toxicity. Phytoremediation is applicable for metabolizing specific NAs (O(2), O(3), O(4), and O(5) species) and minimizing their associated toxicities. Petroleum coke (PC) adsorption is effective in reducing the more structurally complex NAs (preferentially 12 ≥ n ≥ 18 and z = -10, -12) and their toxicity in OSPWs, depending upon the PC content, pH and temperature. Several factors have influence on the degradation of NAs in OSPWs and aquatic environments, which include molecular mass and chemical structure of NAs, sediment structure, temperature, pH, dissolved oxygen, nutrients, and bacteria types.

Ozonation of Naphthenic Acids in Water: Kinetic Study

“…A common method for the production of crude oil from oil sands is the hot water extraction process (Clark process) (Kannel and Gan 2012). This process consumes a large volume of fresh water, on average, approximately 3 m 3 m −3 of oil produced (Kannel and Gan 2012;Hwang et al 2013).…”

“…This process consumes a large volume of fresh water, on average, approximately 3 m 3 m −3 of oil produced (Kannel and Gan 2012;Hwang et al 2013). The wastewater generated is known as oil sands process-affected water (OSPW).…”

Treatment of Bio-Oil Refinery Storm Water by a Simulated Constructed Wetland: A Sustainable Management Alternative

“…Carbolic acids are the most common type of organic acids and are a broad classification of acids found in abundance with both salts and esters (Kannel and Gan 2012). Many are produced on an industrial scale and also occur frequently in nature.…”

“…They can be soluble in water, have a higher boiling point than water and are considered a relatively weak acid (Kannel and Gan 2012). Carboxylic acids most simple biodegradation pathway occurs through the conversion into alcohol either through hydrogenation or by ß-oxidation (Toor, Han et al 2013).…”

Biodegradation of naphthenic acid surrogates by axenic cultures

“…Hence, there is a need to remove and/or detoxify NAs in OSPW. Biodegradation is generally considered to be a cost effective treatment for wastewaters, however some NAs are recalcitrant (as reviewed by Brown and Ulrich 2015; Kannel and Gan 2012).…”