Improvements in Treatment of Waste From Petroleum Industry in Croatia

Abstract

Exploration and production (E&P) waste generated by the petroleum industry in Croatia from two central oilfield pits (COPs) was investigated in order to (1) examine materials for waste treatment that can preferentially sorb organic contaminants and, in that way, improve the process of stabilization/solidification (S/S), and (2) find field-acceptable methods to reduce the amount of waste to be treated with S/S or some other method. Composite samples from COP Vinkovci were treated in the laboratory with different materials or with combinations of several materials: (a) Cement, (b) organophilic clay, (c) calcined moler clay, (d) lime+organophilicclay+bentonite, (e) cement+organophilicclay+bentonite, (f) lime+calcined moler clay, and (g) cement+calcined moler clay. A sample of E&P waste treated with lime was used for comparison of results. The most successful treatment for the majority of inorganic and organic pollutants was treatment with organophilic clay. Samples treated with organophilic clay release 63 times less total oils, 67 times less mineral oils, 798 times less naphthalene, and 136 times less lead to distilled water than the sample treated with lime. The next most successful material is calcined moler clay. The results clearly show that reduction in hydrocarbon content using some of the field-acceptable methods and detailed chemical analysis of remaining organic and inorganic pollutants must be implemented before selecting the most appropriate method for treatment of technological waste in petroleum industry. A composite sample from COP Žutica was treated in the laboratory using a four-step procedure involving boiling water, condensate, and organophilic clay. Organophilic clay was used because of its ability to sorb hydrophobic pollutants. In the leachate of an E&P waste sample, the lowest values for the majority of inorganic and organic pollutants were observed following the fourth step (treatment with organophilic clay). This is also manifested in the lowest indicator of total discharge (ITD%) values for the fourth treatment step. Considering the concentrations of analyzed parameters in leachates and their ITD% values, the biggest effect for the majority of inorganic and organic pollutants was achieved between the first and the second treatment step. This suggests that treatment with boiling water is the most effective treatment for the majority of inorganic and organic pollutants. Concentrations of benzene, ethylbenzene, toluene, and xylene (BETX) in distilled-water leachate generally increase after each succeeding treatment step. This shows that BETX is added to the E&P waste through condensate addition in the third treatment step.