Tratamento de ácidos naftênicos em água derivada do processamento de areias betuminosas

Abstract

Oil sands industries produce a large amount of oil sands processed water (OSPW) in the refining processes of bitumen. The constituents of OSPW include polycyclic aromatic hydrocarbons (PAHs), salts (Na+, K+, Cl-2, SO4-2, and HCO3), metals (Al, B, Sb, Ba, Co, Ni, Mg, Mn, Fe, and Si), and a complex mixture of naturally occurring aliphatic and alicyclic carboxylic acids known as naphthenic acids (NAs). NAs are toxic compounds that affect human health and the environment. Using suitable treatment technologies for the removal of these compounds is a challenging task, due to their high molecular composition and the high operational cost of the treatment process. Conventional biological treatment processes are not effective for the degradation of oil sands industrial wastewater due to the sensitivity of microorganisms, water salinity, and toxicity of the samples. Chemical oxidation is very effective for the degradation of complex molecules where biological treatments are not amenable. For efficient chemical treatment on an industrial scale, the oxidation process may require reaction boosters such as the addition of metal salts, treatment with UV and ultrasound, huge electrical power, and various other chemical combinations that are very expensive and not feasible for industrial applications. The objective of this project is to investigate the effect of a hybrid treatment system based on the chemical and biological methods for the oxidation of naphthenic acids present in OSPW. The optimum operating conditions are established for the pretreatment of OSPW using UV, H2O2 and the combination of UV/H2O2, followed by the removal of oxidation products by microbial treatments. The effect of dosage of oxidizing agents and reaction time on the pretreatment of OSPW was studied. The UV/H2O2 combined pretreatment process was the most effective, compared to the other treatment processes, showing the removal of 46% Naphthenic acid fractional compounds (NAFCs) and 56% Chemical Oxygen Demand (COD). The microbial treatment of the UV/H2O2 pretreated samples was carried out and the process was optimized for maximum removal of naphthenic acid fractional compounds.