Recent development in the treatment of oily sludge from petroleum industry: A review

Degradation of alkanes is a widespread phenomenon in nature, and numerous microorganisms, both prokaryotic and eukaryotic, capable of utilizing these substrates as a carbon and energy source have been isolated and characterized. In this review, we summarize recent advances in the understanding of bacterial metabolism of long-chain n-alkanes. Bacterial strategies for accessing these highly hydrophobic substrates are presented, along with systems for their enzymatic degradation and conversion into products of potential industrial value. We further summarize the current knowledge on the regulation of bacterial long-chain n-alkane metabolism and survey progress in understanding bacterial pathways for utilization of n-alkanes under anaerobic conditions.

Bacterial metabolism of long-chain n-alkanes.

Our understanding of the phylogenetic diversity, metabolic capabilities, ecological roles, and community dynamics of oil reservoir microbial communities is far from complete. The lack of appreciation of the microbiology of oil reservoirs can lead to detrimental consequences such as souring or plugging. In contrast, knowledge of the microbiology of oil reservoirs can be used to enhance productivity and recovery efficiency. It is clear that (1) nitrate and/or nitrite addition controls H2S production, (2) oxygen injection stimulates hydrocarbon metabolism and helps mobilize crude oil, (3) injection of fermentative bacteria and carbohydrates generates large amounts of acids, gases, and solvents that increases oil recovery particularly in carbonate formations, and (4) nutrient injection stimulates microbial growth preferentially in high permeability zones and improves volumetric sweep efficiency and oil recovery. Biosurfactants significantly lower the interfacial tension between oil and water and large amounts of biosurfactant can be made in situ. However, it is still uncertain whether in situ biosurfactant production can be induced on the scale needed for economic oil recovery. Commercial microbial paraffin control technologies slow the rate of decline in oil production and extend the operational life of marginal oil fields. Microbial technologies are often applied in marginal fields where the risk of implementation is low. However, more quantitative assessments of the efficacy of microbial oil recovery will be needed before microbial oil recovery gains widespread acceptance.

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Microbial processes in oil fields: culprits, problems, and opportunities.

Microbial enhanced oil recovery (MEOR) represents the use of microorganisms to extract the remaining oil from reservoirs. This technique has the potential to be cost-efficient in the extraction of oil remained trapped in capillary pores of the formation rock or in areas not swept by the classical or modern enhanced oil recovery (EOR) methods, such as combustion, steams, miscible displacement, caustic surfactant-polymers flooding, etc. Thus, MEOR was developed as an alternative method for the secondary and tertiary extraction of oil from reservoirs, since after the petroleum crises in 1973, the EOR methods became less profitable. Starting even from the pioneering stage of MEOR (1950s) studies were run on three broad areas, namely, injection, dispersion, and propagation of microorganisms in petroleum reservoirs; selective degradation of oil components to improve flow characteristics; and metabolites production by microorganisms and their effects.

Microbial Enhanced Oil Recovery (MEOR)

Biotechnology in the petroleum industry: An overview

The use of naturally occurring selectively isolated bacteria for inhibiting paraffin deposition

Microbial degradation of waste hydrocarbons in oily sludge from some Romanian oil fields

From 1975 to 1980, the first generation of MEOR field trials were carried out in Romania, based on microbial flooding recovery technology and using the level of technology of that time, with its pioneering deficiencies. The results were promising, but after 1980, it became apparent that many aspects of the MEOR technology we used should be improved, because a miracle is not possible with very simple MEOR technologies. This was the reason why, between 1980–1986, we prepared a “second generation” of MEOR field trials which took place between 1987–1991. Compared with the first generation of field trials, in this second generation we tried to improve the methods in the following ways: 1. enhancing the performance of the bacterial inoculum; 2. testing the inoculum for the production of substances involved in oil release; 3. with mathematical models, simulating the release of residual oil; 4. formulating a protocol for injecting the wells; 5. ensuring that adequate quantities of inoculum were used; and, 6. controlling nutrients and the time of their administration. In this paper we discuss the results obtained from 1987–1991 at the two reservoirs where cyclic microbial recovery and microbial flooding recovery trials were carried out. The possibilities of extending and improving these technologies at other reservoirs also are discussed.

MEOR, Recent Field Trials in Romania: Reservoir Selection, Type of Inoculum, Protocol for Well Treatment and Line Monitoring

In the present paper, the efficiency of adsorbents and biosorbents for the removal of metal ions and the clean up of leachates, generated at two Romanian mine waste disposal sites is examined. Several adsorbents such as activated charcoal, molecular sieve, shell sand, diatomite, bentonite, kaolin, as well as biosorbents such as xanthan biopolymer and waste biomasses are assessed, in terms of metal ion removal efficiency, in laboratory glass columns, comprising layers of coarse sand and 3 layers of each adsorbent/biosorbent. The effect of immobilized bacterial cells (naturally occurring consortia of acidophilic heterotrophic and chemolithotrophic bacteria) was also studied. The experimental results show that shell sand, molecular sieve and waste biomass have a relatively high efficiency in removing most heavy metal ions present in low pH leachates. Regarding shell sand and for the experimental conditions used, the selectivity follows the order Pb>As>Cd>Ni>Cu>Zn>Al>Co>Mn. From the two types of the isolated from leachates inoculum used as immobilized biomass, only heterothrophic acidophilic bacteria had a positive effect on metal uptake in contrary to chemolithotrophic acidophilic bacteria. The sufficient metal removal efficiency attained even without the use of immobilized bacteria, is mainly due to the stimulation of naturally occurring microbiota by addition of culture media; this stimulation may be considered as a feasible alternative to the use of immobilized cells in biosorption applications, regardless of the type of adsorbent/biosorbent used and the metal ion in concern. © 2002 SDU. All rights reserved.

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Biosorption of Heavy Metals from Leachates Generated at Mine Waste Disposal Sites

After 1985 a “second generation” of MEOR field trials was started in Romania with several improvements: the reservoirs, the bacterial inoculum, the quantity of nutrients and inoculum used, the protocol of well injection and monitoring of the field trials. Presently in Romania four reservoirs are under microbial flooding and ten wells are being treated by cyclic microbial recovery (or to clean out of the wellbore area). Results from a reservoir treated with microbes and from two wells cleaned out by microbes are presented. In the case of microbial flooding the decrease of oil production stopped and in the case of cyclic microbial treatment the wellbore was cleaned out.

S. Dobrota

Papers

The use of naturally occurring selectively isolated bacteria for inhibiting paraffin deposition

Microbial degradation of waste hydrocarbons in oily sludge from some Romanian oil fields

MEOR, Recent Field Trials in Romania: Reservoir Selection, Type of Inoculum, Protocol for Well Treatment and Line Monitoring

Biosorption of Heavy Metals from Leachates Generated at Mine Waste Disposal Sites

Ch. F-2 Preliminary Results of Some Recent MEOR Field Trials in Romania