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Bioremediation of soils polluted with petroleum compounds is a widely accepted environmental technology. We compared the effects of biostimulation and bioaugmentation of soil historically contaminated with aliphatic and polycyclic aromatic hydrocarbons. The studied bioaugmentation treatments comprised of the introduction of differently developed microbial inoculants, namely: an isolated hydrocarbon-degrading community C1 (undefined—consisting of randomly chosen degraders) and a mixed culture C2 (consisting of seven strains with well-characterized enhanced hydrocarbon-degrading capabilities). Sixty days of remedial treatments resulted in a substantial decrease in total aliphatic hydrocarbon content; however, the action of both inoculants gave a significantly better effect than nutrient amendments (a 69.7% decrease for C1 and 86.8% for C2 vs. 34.9% for biostimulation). The bioaugmentation resulted also in PAH removal, and, again, C2 degraded contaminants more efficiently than C1 (reductions of 85.2% and 64.5%, respectively), while biostimulation itself gave no significant results. Various bioassays applying different organisms (the bacterium Vibrio fischeri, the plants Sorghum saccharatum, Lepidium sativum, and Sinapis alba, and the ostracod Heterocypris incongruens) and Ames test were used to assess, respectively, potential toxicity and mutagenicity risk after bioremediation. Each treatment improved soil quality, however only bioaugmentation with the C2 treatment decreased both toxicity and mutagenicity most efficiently. Illumina high-throughput sequencing revealed the lack of (C1) or limited (C2) ability of the introduced degraders to sustain competition from indigenous microbiota after a 60-day bioremediation process. Thus, bioaugmentation with the bacterial mixed culture C2, made up of identified, hydrocarbon-degrading strains, is clearly a better option for bioremediation purposes when compared to other treatments.

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The paper reports microbiological study of Sulfate Reducing Bacteria activity in underground gas storage and preventive action against H2S formation. Complex research was performed on natural gas reservoir in Swarzow, where one of a few gas storages in Poland had been arranged. The presence of hydrogen sulfide in the 10-th cycle of UGS exploitation gave impact to search a new effective methods which might limit the microbial processes of sulfate reduction in the reservoir. Having the long-term experience, in 1995–96 operation of biocide treatment in SWARZOW UGS was completed with success. Selective biocides (quaternary ammonium compounds) were applied into the reservoir for the first time in Poland, in accordance with patented technology worked out in Oil and Gas Institute, Department of Microbiology. In 1997–98 the biocide injections to exploitation wells were repeated. These operations conduced to the total elimination of Sulfate Reducing Bacteria from the formation waters and caused partial reduction of H2S content in natural gas recovered from the reservoir. In 2003 the new technology based on synergetic action of biocide, represented by triazine derivatives, and H2S Scavenger (Sulfa Clear) was implemented for the first time in underground environment. Practical application of this technology on 2 objects of UGS was finished with a great success. Content of hydrogen sulfide in the recovered gas and formation waters now accords with European Standards. The paper also discusses microbiological studies of processes observed in the natural gas reservoir in Wierzchowice, which is the largest store in Poland. Its final capacity will be ca. 4,3 billion cubic meters of natural gas. The research was conducted between the 1st and the 8th cycle of UGS exploitation. Present investigations were performed in the monitoring system and included microbiological and chemical analysis of formation waters and drilling fluids. Active strains of H2S producing bacteria (Desulfovibrio sp. and Desulfotomaculum sp.) isolated from the reservoir, have been used for testing biocides selected to protect exploitation wells of WIERZCHOWICE UGS. Introduction Microbiological research and technologies based on selected microorganisms are widely applied in the world oil industry and environment protection. Balanced industrial development and ecosystem safety are taken into account in all exploration and exploitation operations realized on oil and gas reservoirs and the underground gas storage. It also concerns applied technologies, performance on storage's wells and application of chemicals during drilling processes. Toxic substances are excluded now and replaced by new environmental friendly, biodegradable compounds (for example biocides). The research concerning processes of hydrogen sulfide formation were initiated on the object of natural gas reservoir SWARZOW UGS. The first Underground Gas Storage was created in the south of Poland in a depleted deposit of natural gas with appropriate geological conditions and exploitation parameters. The bedrock of UGS is Cenomanien sandstone (thickness is 6,0 - 12,5 m) and Kimmeridgian limestone directly underneath it. In the gas-bearing part of the limestone-dolomite the thickness is 10,0 - 13,5 m. This part of the limestone is separated from the series of limestone and dolomite (total thickness about 250 m) by a 7 m rider of marls slate. The sandstone and the gas-bearing part of the limestone form one dynamic system. They are screened above by Cretaceous marls and Miocene slates. From the other side they are separated by 7-m interval of slate rider, which probably function as a complete seal. The UGS in Swarzów is a small reservoir, but from 1970 was used to cater for the most urgent needs of gas transport in the south-eastern Poland at that time. At the present time this object is one of a few gas storages, but it is still necessary in polish gas industry1,2. Due to the lack of field experience, the storage was an experimental unit at the beginning. The research was conducted prior to its construction on the process of extrusion of the formation water that entered the deposit during and after the operation. In 1979, locally - produced and methane - rich imported gas began to pumped into the UGS. Neither of them contained H2S. In the 10th cycle of the UGS operation (February 1989), high percentage of hydrogen sulfide was recorded in the gas recovered from the reservoir. Since then microbiological research has been conducted and action taken to prevent formation of H2S.

The article presents the results of studies on substances with a biocidal effect in terms of their possible use as additives to drilling muds and fracturing fluids. The aim of the work was to identify the most effective biocides by examining their action on aerobic and anaerobic bacteria, fungi, sulfate-reducing bacteria (SRB), and a consortium of microorganisms. Various chemicals have been considered, due to a constant and overriding goal to find the one with the highest activity, and above all, the ones that have not yet been tested. Particular attention was paid to substances that, apart from known biocidal properties, have also the ability to neutralize hydrogen sulfide, and to reduced sulfur compounds (H2S scavengers), and the so-called “green biocides”, i.e. those that are considered safe for the environment. Most of the tested biocidal agents were effective against aerobic and anaerobic bacteria, while 10 out of 12 showed good or very good activity against SRB (low MIC and MBC values), including 3 out of 4 H2S scavengers. On the other hand, only some biocidal agents proved to be effective against fungi and microbial consortium; among them were agents containing quaternary ammonium compounds (Bardac LF and Barquat CB-80), triazine derivatives (Biostat and Petrosweet HSW 82165) and DBNPA (Biopol C-103L). Bardac LF and Barquat CB-80, together with the mixture of Grotan OX and Preventol GDA 50, upon introduction to the drilling mud and fracturing fluid, were superior over other biocidal agents (Biostat, Petrosweet HSW 82165 and Biopol C-103L), showing the full activity at 800 ppm. Environmentally friendly biocide Aquacar THPS 75 appeared to be the least effective.