Sarah D. A. Daflon a, Igor L. Guerra a, Márcia V. Reynier b, Ana C. Cerqueira c, Clarice R. Botta d, and Juacyara C. Campos a
a School of Chemistry, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil;
b LABTOX-Environmental Analysis Laboratory, Rio de Janeiro, Brazil;
c Research Center of PETROBRAS, Rio de Janeiro, Brazil;
d University of S~ao Carlos, S~ao Paulo, Brazil
ARTICLE HISTORY
Received 6 December 2016
Accepted 27 February 2017
KEYWORDS: Aquatic toxicology; contaminants; industrial wastewater; metals
Introduction
Petroleum refineries are process plants where crude oil is transformed into refined products, such as gasoline, diesel and kerosene.[1] Heavy oil refinery wastewater (HORW) produced in heavy crude oil mining and processing can cause serious water pollution and endanger physical health.[2] Oil refineries use significant amounts of water and thus discharge large volumes of wastewater to surface waters and although most of the contaminants are broken down or recovered at the refinery, a significant amount of toxic substances and compounds can remain.[3]
Along with many other toxicants, the raw wastewater is composed of oil and grease, toxic organic compounds, phenols, ammonia and hydrogen sulfide (H2S).[4] The stream of the desalting unit is the major source of toxic substances, containing benzene, toluene, ethyl benzene and xylenes (BTEX), phenol, and dissolved inorganic compounds.[4,5]
Other toxic compounds found in petroleum refinery wastewaters are polycyclic aromatic hydrocarbons (PAHs), such as chrysene, pyrene, anthracene and fluorine;[6] the authors evaluated the acute toxicity of a refinery wastewater using the test organism Daphnia similis.
The aims of toxicity identification and evaluation (TIE) studies are to identify the agents responsible for wastewater toxicity, isolate the sources of this toxicity, evaluate and implement control actions and verify the effectiveness of measures
taken to reduce the toxic effects.[7]
Tischler [8] applied the TIE approach to some refineries wastewaters in several locations in the USA and noted that the main toxicants present were total dissolved solids (TDS), fluoride, nitrite, ammonia and organic compounds. Metals such as copper, lead, zinc and nickel are not common, although Nwanyanwu et al.[9] have reported the presence of metals as toxic components of this wastewater.
In reality, the composition of refinery wastewaters cannot be generalized because they vary in composition depending on the crude oil characteristics, refining process configuration and procedures applied.[10] Therefore, it is difficult to predict what effects the wastewater could have on the environment, especially on local species.
Resolution 430 of the Brazilian National Environmental Council (CONAMA) [11] establishes the conditions and standards for wastewater discharge. This resolution requires industries to perform toxicity tests on their wastewater. In addition, the environmental agency of each state sets the permitted levels for these toxicity tests.
The objective of this study was to identify the source of the toxicity of a biotreated wastewater generated at a Brazilian petroleum refinery by performing a chronic toxicity identification and evaluation (TIE) using C. dubia as the test species.
Materials and methods
Wastewater samples
Five grab samples were collected from the final stage of a wastewater treatment plant (WTP), originating from the oil/water separation in an API separator, dispersed air flotation, aerated […]