ASSESSMENT OF THE COMPOSITION OF POLLUTION OF SOIL CONTAMINATED WITH TPH AND PAHS FOR THE DEVELOPMENT OF THE BIOREMEDIATION TECHNOLOGY

摘要

The executed work was started by performing a review of literature regarding the achievements in the field of remediation of lands contaminated with petroleum derivative substances and by-products of pyrolysis as sources of contamination of the soil with TPH and PAH hydrocarbons. On the basis of literature data regarding technologies for remediation of lands contaminated with petroleum derivative substances, one selected process stages aimed at reducing the content of TPH and PAH in the contaminated soils. As a part of the execution of the work, one performed physico-chemical analyses of soil collected from areas contaminated with petroleum derivative substances, namely from the area of: 1. a decommissioned conventional gas plant, located in the North of Poland. Test samples were collected near old (partially eliminated) gas pitch pits, from a depth of 0-0.5 m below terrain level (GK-1 soil), 2. a mining spoil pit, wherein drill waste contaminated with petroleum derivative substances were kept - soil classified for waste, with an ex code of 17 05 03. The test samples were collected from a depth of 0-0.5 m below terrain level (DU-1 soil). A physico-chemical analysis indicated that the soil from the area of the conventional gas plant was characterized by a high content of PAH and a relatively small content of TPH. Whereas the soil from the area of the mining spoil pit contained large amounts of TPH and relatively small amounts of PAH. Since the fundamental goal for the executed work was to study the processes of TPH and PAH degradation in soil, it was recommended to obtain soil with significant amounts of both TPH and PAH. Excessively high amounts of both PAH and TPH in the soil may hamper its remediation process. That is why the following distribution of soils was used as test material for examining the process of biodegradation of hydrocarbons, performed in ex-situ conditions: GK-1:DU-1 in a ratio of 2:1. Due to the orientation of the studies towards determining the content of TPH and PAH hydrocarbons in the soil, as a part of the execution of the work, one adapted the method of chromatographic determination of petroleum derivative contaminations with a particular focus on polycyclic aromatic hydrocarbons (PAH). In the subsequent stage, one created a station for testing the biodegradation of contaminations, conducted on a semi-technical scale in ex-situ conditions using the compost heap method. One discussed the results of works pertaining to optimization tests for the conduct of the process, including: modification of the structure of the soil in order to increase the bioavailability of petroleum derivative hydrocarbons to microorganisms and nutrients, basic bioremediation stimulated by bioventilation and saturating the waste surroundings with biogenic ingredients supporting the development of indigenous microflora, and bioaugmentation, involving the inoculation of the initially remediated soil with biopreparations developed in Zakład Mikrobiologii INiG - PIB (Microbiology Department of the Oil and Gas Institute - National Research Institute). The selection of biogenic substances for the remediated soil was made on the basis of the results of respirometric tests, measuring the progress of spontaneous and assisted aerobic biodegradation of the petroleum substances contained in the tested soil with varying content of biogenic substances. These tests were performed using the OxiTop®Control kit. The staged process of soil remediation through basic bioremediation, stimulated by biogenic substances and bioaugmentation in ex situ conditions, was carried out for a period of 300 days. The course of the process was controlled using a comprehensive monitoring system, covering soil tests, both physico-chemical and toxicological, performed using ToxKit (Phytotoxkit, Ostracodtoxkit, Spirodela Duckweed ToxKit) and Microtox type tests, the MARA environmental risk assessment test and the Ames genotoxicity test. An equally relevant element, allowing for a broader approach to the course of the process of biodegradation of petroleum derivative contaminations, and determination of the effectiveness of subsequent stages of remediation, was the chromatographic analysis, allowing for a quantitative and qualitative determination of individual hydrocarbons contained in petroleum derivative contaminations. It allowed to observe changes in the content of individual n-alkanes and PAHs during the remediation stages. Furthermore, the introduced n-alkane biodegradation degree indexes in the form of n-C_(17)/Pr and n-C_(18)/F content ratios very visibly illustrate the effectiveness of subsequently executed stages of the developed technology for removal of petroleum derivatives from waste. In order to develop a mathematical model for the biodegradation of petroleum derivative contaminations in drill waste, one utilized normalization of the concentration of analytes using the introduced biomarker - C_(30)-17β(H), 21 β(H)-hopan, which allowed for a complete assessment of the degree of biodegradation of petroleum derivative hydrocarbons. The calculated constants for first-order biodegradation (k) allowed to monitor and compare the kinetics of the course of the biodegradation of individual groups of petroleum derivative contaminations (TPH, Σ n-C_8-n-C_(22), Σ n-C_(23)-n-C_(36)) and PAH (3-, 4-, 5- and 6-cyclic PAHs) in subsequent stages of waste treatment. Furthermore, on the basis of the presented biodegradation constants, one can compare the effectiveness of operation of the biopreparations used. The presented technology is one of the methods of treatment of petroleum derivative contaminants in areas contaminated with petroleum derivative substances, that are tried and environmentally safe, and economically justifiable for use under industrial conditions.