R. Dimkov

MICROBIAL TOXICITY OF ETHANOLAMINES

ABSTRACT Metal working fluids (MWFs) are used in metal working industries in processes like grinding, turning, drilling and cutting. In the presence of water the complex mixture of materials in metal working fluids will be susceptible to microbial deterioration. The control of contamination of MWFs usually is performed by the addition of different antimicrobial agents (biocides). Alkanolamines are used in metal working fluids as corrosion inhibitors but they have also antimicrobial effect. Studies of few different alkanolamines showed their antimicrobial effect to be enhanced at high pH. From the other hand, development of resistant populations occurs. The aim of this study was to evaluate the degree of toxicity of mono-, di- and triethanolamine for bacterial strains isolated from metal working fluids at different pH values and different concentration.

Bacterial Microflora of Contaminated Metalworking Fluids

ABSTRACT Metal working fluids (MWF) are commonly used in manufacturing and machining industries. There are four major classes of MWF: (i) which contain lubricant base oils without water (straight oils), (ii) composed of an aqueous oil emulsion with oil in high concentration (soluble oils) or (iii) lower concentration (semi-synthetic MWF) and (iv)formulated with no petroleum oils (synthetic fluid). Historically, microbial contamination of metal working fluids has been a problem in the metalworking industries, primarily because of potential adverse health effects and microbial growth effects on fluid quality and performance. Metalworking fluids are chemically complex mixtures. Such mixtures render MWFs potentially toxic to the environment. One solution to the disposal problem is on-site biological treatment of waste MWFs, using bioreactor systems. Bioaugmentation with selected strains may improve the opportunity to create more reproducible system. In this study the bacterial microflora of soluble oil and synthetic metalworking fluid in-use was quantified, isolated and tentatively identified. An indicator plates for dehydrogenase activity were used in attempt to demonstrate the potential of bacteria isolated from contaminated metalworking fluids to utilize hydrocarbons—a component of MWFs.

Adaptive response of trivial activated sludge towards toxic effect of oNP, PCP and combination oNP/PCP

Abstract The reaction of the real aerobic activated sludge taken from the Sofia Waste Water Treatment Plant (SWWTP) and treated with the xenobiotics pentachlorphenol (PCP) (0.16 mMol), ortho-nitrophenol (oNP) (0.58 mMol) and with a combination of PCP (0.08 mMol), oNP (0.29 mMol) has been investigated in a model detoxification process. The adaptive changes are studied in the microbial structure level and at the level of changes in the qualitative and quantitative parameters of the macro-organisms in the activated sludge (consuments of I and II level). The presence of several different taxonomic groups has been shown by other researchers to be essential in the detoxification process. The quantitative changes in these taxonomic and physiological groups of micro-organisms are studied. The number of micro-organisms from Pseudomonas, Acinetobacter and the bacteria from the xenobiotic-catabolizing complex considerably increased with the individual and the combined effect of the xenobiotics oNP, PCP and oNP/PCP. At the same time the toxic shock leads to a remarkable reduction of NH 3 releasing, nitrifying bacteria and those from family Enterobacteriaceae . It is ascertained that the number of Ciliata, Flagellata apochromata, Oligochaeta and Rotatoria is strongly decreased in the series of samples treated with xenobiotics. The leading role of micro-organisms in the real detoxification of hazardous pollutants was experimentally confirmed by research.

Ortho—Nitrophenol Removal in two Types Activated Sludge: The Role of Microbiological and Enzymological Adaptation

ABSTRACTThe relation between the structural and functional changes in two types anaerobic activated sludge—ASt (activated sludge trivial) and ASg (activated sludge granular) from waste water treatment process with high organic load and working under presence of hazardous pollutants (oNP—ortho-nitrophenol) has been investigated. The adaptive response on the different levels—microbiological structure, effectiveness of oNP-removal, oxygenase and succinate dehydrogenase activities towards the increasing oNP-concentration has been assessed. The obtained results demonstrate that for the complete oNP-biodegradation to harmless products—the aerobic finishing treating process is applicable and needed. In these conditions the amount of microorganisms from genus Pseudomonas and oNP-degrading bacteria, an efficiency oNP-biodegradation and oxygenase activities were increased considerably.

Two Steps for Speeding up of Phenol Detoxification

ABSTRACTTwo steps of enhancement of phenol detoxification by Bacillus laterosporus BT-271 by means of increasing of the rate of aeration and adding in an apropriate moment a carrier (penopolystyrol pellets, covered with active carbon) were studied. The effectiveness of phenol biodegradation was enhanced with 42 %. Comparative study of the oxygenase activities of the freely suspended cells at the two steps of speeding up of the phenol elimination to elucidate the mechanisms of the processes was carried out.

THE SYSTEM OF TRAINING ON BIOTECHNOLOGY IN BULGARIA - FEATURES AND PROBLEMS

ABSTRACT The commencement of Biotechnological education in Bulgaria emerged in the early 1980s when traditional industries—food, beverage and pharmaceutical—were strongly influenced by the ideas of the “new Biotechnology”. Recently, as a consequence of the mass reorganization in the frameworks of the Low for University Autonomy there are six Bulgarian Universities which educate students and award diplomas (Bachelor of Science and Master of Science) in the specialty of Biotechnology. Practically the biotechnological training carries the distinctive features of the different Universities in Bulgaria. According to Bulgarian State Regulations the Universities have adopted the three level structure of training—Bachelor, Master and Doctor (PhD). The specificity of biotechnological education reveal mainly in the set of optional courses. A sustainable trend towards elaborating of PhD Thesis works in the field of biotechnology during the last decade. The diversity of topics at this highest educational degree is logically highly expressed. Some essential problems and disputable topics in the area of biotechnological education in our country are formulated in the present paper. The traditional and developing inter-academic collaboration in the country brings an important impact on overcoming and resolution of the part of listed as well some other real problems in the teaching on Biotechnology. The international collaboration problem takes extraordinary important place in the present situation in Bulgaria, in particular for its science and education. It contributes the biotechnological education quality development and optimization and has a positive effect on the advance of university research activities.

Structural/Functional Changes in Activated Sludge in PCP- and ONP-Biodegradation Technologies

ABSTRACT Different detoxication technologies (aerobic, anaerobic, two stage, hybrid) using oNP, PCP, DCP, TCP like model xenobiotics, have been accomplished in the last 8 years. The results about the details of the technologies have been described previously. In this paper the comparison between the efficiency of the different technologies and structural/functional changes of AS (activated sludge) has been made. The paper is illustrated by means of microscopic and transmission microscopic photographs. The results showed well expressed connection between the efficiency of xenobiotic elimination, type of technology, initial concentration of the particular xenobiotic and adaptive structure of AS. At aerobic shorter adaptation genus Pseudomonas played more important role in the detoxication. At time of the longer anaerobic and anoxic processes genus Acinetobacter assumed the govern role in the structure of xenobiotic-degrading bacterial complex. The deep knowledge of the adaptive structure of the different detoxication technologies presents the valuable information for quick and intelligent management of the detoxication bioremediation technologies.

Pentachlorophenol Biodegradation in Anaerobic and Aerobic Continuous Flow Processes

ABSTRACT Pentachlorophenol (PCP) biodegradation was studied comparatively in anaerobic and aerobic conditions. Two laboratory scale systems of completely mixed continuos flow bioreactor and secondary clarifier were used. Simultaneous treatment of municipal and industrial wastewater with high concentration of PCP (25 mg/l) was investigated. The results show that the biodegradation of trivial organic and PCP in aerobic conditions was better than in anaerobic conditions: the removal efficiencies were 83,3%(COD) and 55%(PCP) in the aerobic system against 41,3% (COD) and 47%(PCP) in the anaerobic system. The mean values of the effluent concentrations were 337 mg/l (COD) and 11 mg/l (PCP) for the aerobic experiment against 1263 mg/l (COD) and 12,8 mg/l (PCP) for the anaerobic experiment. Although the removal efficiencies of PCP and COD were relatively good for the investigated extremely high influent PCP concentration, both schemes did not meet the standards for the effluent concentration. Therefore the investigated bioreactors could be used only as a first stage in a system of bioreactors for completely PCP removal.

Depth Distribution of Freshwater Microorganisms and Physicochemical Characteristics in Iskar Reservoir

ABSTRACT The depth distribution of different physiological and taxonomical groups of freshwater bacteria in Iskar reservoir—the main drinking water source for Sofia city, was studied. Samples were taken from several depth layers in the area of intake water tower of the reservoir and studied for presence of aerobic, anaerobic heterotrophs, oligotrophs, ammonifiers, nitrifiers and denitrifiers, genera Aeromonas and Pseudomonas and coliform bacteria with cultivation methods. We found close distribution of observed microbial groups according to the correlation coefficients of their numbers in different water layers. Two zones with similar distributions were presented—upper zone in the upper layers from the surface down to the fifth meter, and another zone under 10 meters depth. Exception was the observed distribution of microbial groups in the water layer at 25 meters, which showed closer correlation with the upper zones than with the contiguous layers. We determined also some physicochemical, chlorophyll a and phaeophytin concentration, chemical oxygen demand (COD), nitrogen forms and phosphate concentration. Correlation was presented also between the bacterial numbers, chlorophyll a and organic matter (COD). The dominating groups are aerobic heterotrophs and oligotrophs through the whole water column representing up to 31.34% respectively 48.58% from all culturable bacteria.

Biodegradation of Phenol by Immobilized in Peo-Cryogel Bacillus Laterosporus BT-271 in Sequencing Batch Biofilter

ABSTRACT A long (20 days) model process of phenol biodegradation was performed in biofilters in sequencing batch regime and with active biological system—polyethylene oxide cryogels (PEO-cryogel) with immobilized bacteria Bacillus laterosporus BT-271. The model waste water, containing mineral medium and phenol as the only source of carbon and energy with 300 mg/l in the effluent, was used. One of the key investigated parameters was the manner of immobilization of the bacteria in polyethylene oxide cryogels. The two variants of the experiment were: 1) direct immobilization of the inoculation material (SBB-D) and 2) inoculation of the biomass after preliminary separation and further concentration (SBB-S). The process was characterized on the basis of the following parameters: concentration of phenol in the influent, efficiency of phenol biodegradation, rate of phenol biodegradation, debit of purified water, loading of biofilters, rate of phenol degradation and efficiency, oxygenase enzyme activity of the cells immobilized in the cryogel and of the free cells in the effluent. The implantation of the gel with the immobilized microorganisms in a sequencing batch biofilter showed good biodegradation, kinetic, enzymological characteristics, as well as self-renovating adequate biofilm structure in laboratory conditions. The two biofilters functioned well and the efficiency of phenol elimination reached 100% in 15 days. The variant SBB-D showed a more stable process, as well as an easier way of preparing the initial PEO-plate biofilm. The SBB-D system is suitable for scaling and future implementation of the water purification processes in practice.