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The sustainable management of water resources is crucial for maintaining high-quality tourism, as it ensures the availability and reuse of water through effective wastewater treatment processes. This requires the implementation of technologies and circular measures for managing water resources. In this context, the present study focuses on the Ravda Wastewater Treatment Plant (WWTP), which treats the wastewater of the largest coastal resort in Bulgaria, Sunny Beach. Data from seven consecutive years (2018–2024), including the years of COVID-19 measures, have been analyzed. Particular attention has been paid to analysis during the last two years of this study. For the period 2018–2022, hydrochemical parameters (total nitrogen and total phosphorus, volumetric load of activated sludge/volumetric organic load) and technological parameters (treatment efficiency, COD/BOD5) were examined. In 2023 and 2024, additional parameters such as the SVI, comparative microscopic analysis of activated sludge, dynamics and quantities of aerobic and anaerobic heterotrophic bacteria and denitrifying bacteria, the abundance of genera Pseudomonas and Acinetobacter, and the elemental composition of the water at the inlet and outlet of the treatment plant, were studied. Samples were taken from five critical control points in the course of the treatment process during the off-season, in April and November, when the plant operates with a reduced number of facilities. The aim of this study is to determine the efficiency of water treatment during the off-season and the possibility of its enlargement and improvement to meet the needs during the high season. Overall, the results of the comprehensive analyses show that the biotechnological system has significant biodegradation potential but requires improvement due to large fluctuations in the number of residents. The socio-economic and environmental situation in the area is extremely dynamic, necessitating the introduction of innovative wastewater treatment measures to balance the negative impact on the environment and ensure the sustainability of high-quality tourism. [ABSTRACT FROM AUTHOR]

Natural products and especially those from marine organisms are being intensively explored as an alternative to synthetic antibiotics. However, the exact mechanisms of their action are not yet well understood. The molecular masses of components in the hemolymph fraction with MW 50–100 kDa from Rapana venosa were determined using ImageQuant™ TL v8.2.0 software based on electrophoretic analysis. Mainly, three types of compounds with antibacterial potential were identified, namely proteins with MW at 50.230 kDa, 62.100 kDa and 93.088 kDa that were homologous to peroxidase-like protein, aplicyanin A and L-amino acid oxidase and functional units with MW 50 kDa from R. venous hemocyanin. Data for their antibacterial effect on Escherichia coli NBIMCC 8785 were obtained by CTC/DAPI-based fluorescent analysis (analysis based on the use of a functional fluorescence probe). The fluorescent analyses demonstrated that a 50% concentration of the fraction with MW 50–100 kDa was able to eliminate 99% of the live bacteria. The antimicrobial effect was detectable even at a 1% concentration of the active compounds. The bacteria in this case had reduced metabolic activity and a 24% decreased size. The fraction had superior action compared with another mollusc product—snail slime—which killed 60% of the E. coli NBIMCC 8785 cells at a 50% concentration and had no effect at a 1% concentration. The obtained results demonstrate the high potential of the fraction with MW 50–100 kDa from R. venosa to eliminate and suppress the development of Escherichia coli NBIMCC 8785 bacteria and could be applied as an appropriate component of therapeutics with the potential to replace antibiotics to avoid the development of antibiotic resistance. [ABSTRACT FROM AUTHOR]

Mass tourism puts enormous pressure on wastewater treatment plants due to its expansive growth during the summer months. To adapt to the fluctuations, the Ravda wastewater treatment plant (WWTP) uses innovative methods and technologies, allowing for "shrinking" and "expanding" of the facilities according to the season. This has been built in stages over the years, with two separate biological treatment lines adapting to different numbers of tourists and to the quantity of influent wastewater. The aim of this study is to make a comparative assessment of the work of WWTP Ravda in the summer and winter seasons and its effectiveness, as well as to compare them. In addition, it examines the years of the COVID-19 pandemic, when a much higher consumption of water per person was noted. Data were analyzed for the period of 2018–2022 inclusive, comparing influent and effluent BOD5 and COD in the summer and winter. Nitrogen and phosphorus removal efficiencies were also tracked. The study shows that municipal wastewater treatment is effective, but much higher values, close to the maximum permissible discharge values, are observed during the tourist season. With the continued growth of the tourism sector, the Ravda wastewater treatment plant would not be able to cope with the discharge standards set by the Ministry of Environment and Water, so measures need to be taken promptly. [ABSTRACT FROM AUTHOR]

During adaptation to waters that are rich in xenobiotics, biological systems pass through multiple stages. The first one is related to the restructuring of communities, pronounced destruction of the structure, and multiplication of active biodegradants. The purpose of the present research was to describe the microbiome restructuring that occurs during the adaptation stage in landfill leachate treatment. In a model SBR (sequencing batch reactor), a 21-day purification process of landfill leachate was simulated. Wastewater was fed in increasing concentrations. When undiluted leachate entered, the activated sludge structure disintegrated (Sludge Volume Index—4.6 mL/g). The Chemical Oxygen Demand and ammonium nitrogen concentration remained at high values in the influent (2321.11 mgO2/L and 573.20 mg/L, respectively). A significant amount of free-swimming cells was found, and the number of aerobic heterotrophs and bacteria of the genera Pseudomonas and Acinetobacter increased by up to 125 times. The Azoarcus-Thauera cluster (27%) and Pseudomonas spp. (16%) were registered as the main bacterial groups in the activated sludge. In the changed structure of the microbial community, Gammaproteobacteria, family Rhizobiaceae, class Saccharimonadia were predominantly represented. Among the suspended bacteria, Microbactericeae and Burkholderiaceae, which are known for their ability to degrade xenobiotics, were present in larger quantities. The enzymological analysis demonstrated that the ortho-pathway of cleavage of aromatic structures was active in the community. The described changes in the leachate-purifying microbial community appear to be destructive at the technological level. At the microbiological level, however, trends of initial adaptation were clearly outlined, which, if continued, could provide a highly efficient biodegradation community. [ABSTRACT FROM AUTHOR]

One of the most widespread and risky pollutants in the environment is phenol. It is a by-product of many industrial, agricultural, and other anthropogenic activities. Microbial-assisted transformation, known as bioremediation, is an effective and cheap method for treating groundwater, soil, and sediments contaminated with phenol and its derivates. This study aims to assess the effect of the addition of a selected, pre-adapted bacterial strain Pseudomonas aureofaciens AP-9 on key kinetic, microbiological, and enzymological parameters of simulated bioremediation processes for the removal of phenol (250 mg/kg). The early effect of adding this microbial biodegradant in contaminated sediments is insignificant. The effect of added bacteria is manifested at the 48th hour by a restructuring of the microbial sediment communities and an increase in the number of cultivated microorganisms. This preparation of the sediment communities for a prolonged detoxification process is also confirmed by the repeated induction and very high increase in the activity of the enzymes directly involved in the cleavage of the benzene ring. The effectiveness of phenol removal at the 48th hour is increased by 15%, too. Considering this stimulation of a sustainable long-term bioremediation process, we can conclude that microbiological pre-adapted inoculants are an important mechanism for the management of bioremediation detoxification processes and can increase their effectiveness. [ABSTRACT FROM AUTHOR]

In this paper, an investigation of the interaction of a surface-wave-sustained argon plasma torch with liquids is presented. The plasma is produced by an electromagnetic wave traveling along the plasma–dielectric interface, and at the same time, the plasma is a part of this waveguide structure. Because the interaction of the plasma torch with water (liquid) results in modifications of the properties of both the treated water and the plasma itself, a detailed study of the effects in both media is required. The results of the experimental investigation of a surface-wave-sustained argon plasma torch interaction with liquids show significant changes in the plasma parameters, such as the electron excitation temperature Te and the average rotation temperature Trot. In addition, mechanical waves are produced both in the meniscus surface and in the plasma torch by the interaction between the plasma torch (ionized gas with charged particles and electric field) and the liquid surface, which is different from the effects produced by a neutral gas jet on a liquid surface. As a result of the plasma–water interaction, the water's chemical and physical characteristics, such as the water conductivity, pH, and H2O2 concentration, are modified. As a possible application for water purification, the performed SWD treatment of model wastewater shows a significant variation in nitrate, ammonium, phosphate, and COD (chemical oxygen demand) concentration as a result of the treatment. [ABSTRACT FROM AUTHOR]

Landfill leachate is generated from waste degradation in landfill sites, and its treatment includes biological or combined treatment with physico-chemical methods. A frequently applied technology in the biological stage of landfill leachate treatment plants is based on denitrification and nitrification. Nevertheless, with the availability of a huge number of scientific reports, the management of denitrification and nitrification (D/N) processes in the frame of real wastewater treatment plants (WWTPs) is rather difficult and always remains a critical technological problem. This study aims to perform a comparative assessment between denitrification and nitrification processes during landfill leachate treatment in three different situations in the WWTP of the Municipal Enterprise for Waste Treatment in Sofia City, Bulgaria. The comparative assessment is based on the biotransformation effectiveness of ammonium ions in the course of nitrification and of nitrates in the course of denitrification. Mixed samples (wastewater and activated sludge) were taken from the sequencing batch reactors operating in the mode of denitrification and nitrification. All physico-chemical (pH, dissolved oxygen, organics concentration, BOD5:COD, nitrogen and phosphorous) and biological (sludge volume index, sludge biotic index, quantity of aerobic heterotrophs, denitrifiers and nitrifiers, total dehydrogenase activity) indicators were investigated in the samples from the biobasins in the mode of denitrification and nitrification. The conditions for the implementation of the two processes were compared, along with the state of the activated sludge in the different reactors. The obtained results showed that denitrification was the critical process in the technology on the base of D/N. A major factor that managed the denitrification was the lower concentration of biodegradable organic matter which led to a deformation of the activated sludge structure, a decrease in the count of heterotrophic microorganisms, a decrease in the total activity of the activated sludge and an inhibition of the nitrate reductase activity. The nitrification processes were accomplished with high intensity. The results confirmed that D/N could be optimized and controlled using specific wastewater treatment technology parameters and purposely applied indicators. [ABSTRACT FROM AUTHOR]

Anaerobic digestion (AD) has been studied for centuries, but its operation still mainly relies on physicochemical indicators. Recent advanced molecular biological tools can unveil the nature of the AD process since microbial activity is directly related to digester performance. The paper summarized up-to-date microbiological and molecular biological analysis techniques applied in AD, including PCR-based techniques, electrophoresis, next-generation sequencing, MS-based techniques, and visualization-based techniques. In addition, the paper also reviewed the techniques that link microbial identity and activity to ecological function. Molecular biological techniques can identify microbial activity and AD process disturbance, but research on on-site analysis of microbial communities for a full-scale system is lacking. One of the most suitable methods for studying microbial communities in anaerobic digesters is fluorescence in situ hybridization, which does not require preparative isolation and cultivation. Another very important method is the use of physiological fluorescent probes to reveal the functional characteristics of methanogenic communities by CTC (5-cyano-2,3-ditolyl tetrazolium chloride)/DAPI (4'-6 diamino-2 phenylindole), which is a very rapid, sensitive and informative assay. These methods, together with the application of confocal laser microscopy, and the study of polyphosphate granules and Co-factor 420 of the microbial communities allow us a very effective and targeted functional-molecular control of the processes in anaerobic digesters. [ABSTRACT FROM AUTHOR]

Detoxication technologies require the combination of theoretical and practical knowledge of xenobiotic biodegradation, wastewater treatment technologies, and management rules. The purpose of this complicated combination is to propose specialized strategies for detoxication, based on lab- and pilot-scale modeling. These strategies include preliminary created algorithms for preventing the risk of water pollution and sediments. The technologies and algorithms are essentially important outcome, applied in the textile, pharmaceutical, cosmetic, woodtreating, and oiltreating industries. In this paper four rehabilitation technologies for pretreatment of water contaminated by pentachlorophenol (PCP) have been developed in the frame of the European and Bulgarian National projects. Emphasize is put on the biological systems and their potential of detoxication management. The light and transmission electron microscopy of the reconstructed activated sludges the microbial, kinetic and enzymological indicators are presented and approved as critical points in the biocontrol.

Wastewater surveillance for monitoring the spread of SARS-CoV-2 remains important even in the current endemic stage of the COVID-19 outbreak. This approach has already demonstrated its value by providing early warnings of coronavirus spread in different communities. The aim of the present publication is to share relevant experience from the Center of Competence "Clean&Circle", obtained in the development of an effective strategy for SARS-CoV-2 detection in the wastewater of Sofia, Bulgaria. Using four different RNA concentration/extraction methods, we revealed that the key hindering factor for successful viral detection was the presence of PCR inhibitors in the wastewater. The most efficient way to overcome their presence turned out to be the application of a specialized polymerase in the RT-PCR detection setup. Our data showed that using such an enzyme increases the detection efficiency from 1.9% to 70.5% in samples with a spiked control virus. We also evaluated the recovery rates of viral particles by using silica columns (71%), PEG precipitation (23%), ultrafiltration (15%), and MCE filtration (10%). These results support the international effort to unify and standardize the various techniques used for SARS-CoV-2 monitoring in wastewater. [ABSTRACT FROM AUTHOR]

Nanodiamonds (ND) are nano-particles with a size of 4–5 nm which are intensively investigated for a number of properties that make them suitable for bio-applications. They could be chemically modified, they have a high adsorption capacity, high mechanical and chemical stability. Because ND have all these properties, they are also suitable for application in specific wastewater treatment and especially when the treated water is polluted with toxic compounds. The effect of ND applied in laboratory sand biofilter was investigated in this research. Synthetic wastewater with a model toxicant, the azo-dye amaranth, was used. The results showed that, in the presence of ND, the efficiency of amaranth removal remained high (more than 90%) in concentrations close to the critical one. The level of carbon-containing pollutants (assessed as chemical oxygen demand (COD) and total organic carbon (TOC)) decreased. The number of bacteria from the key detoxification groups increased 98 times for Pseudomonas sp. and 105 times for azo-degrading bacteria, while aerobic heterotrophs increased only 6 times after ND were applied. The abundance of Pseudomonas spp. after ND addition was confirmed with fluorescence in-situ hybridization.The activities of the key enzymes increased with 26–57%. Also, the activities of cathechol-1,2-dioxygenase and catechol-2,3-dioxygenase were found after ND addition but not before that. The obtained data showed that after ND were introduced in the wastewater treatment system, the number of biodegrading bacteria increased. They synthesized large amounts of azoreductases and oxygenases that led to the improved parameters of azo-detoxification process. [ABSTRACT FROM AUTHOR]

The pollution of aquatic ecosystems is a big problem that has its impact on river sediments. In recent decades, an effective solution to this problem has been the application of bioremediation technologies. Nanoremediation is an innovative part of these technologies. We still know little about the efficiency of nanoparticles, especially nanodiamonds, in modelled conditions. The aim of the present study is to investigate the effect of nanodiamonds on the key parameters of modelled bioremediation of river sediments that are polluted with phenol, as well their effect on the structures and functions of microbial communities. An important indicative mechanism that was used is the application of fluorescent in situ hybridization for sediment microbial communities. The results of this study revealed the positive role of nanodiamonds that is associated with their intoxication with high concentrations of phenol. Readaptation was also found, in which the xenobiotic biodegradation potential evolved by increasing the relative proportions of non-culturable bacteria, namely Acinetobacter (at the 144th hour) and Pseudomonas (at the 214th hour). The results can help to find an effective solution to the question of how information from such precise molecular methods and the application of nanodiamonds can be translated into the accessible language of management and bioremediation technologies. [ABSTRACT FROM AUTHOR]

The transformation of our linear "take-make-waste" system to a cyclic flow of materials and energy is a priority task for society, but the circular use of waste streams from one industry/sector as a material input for another must be completely safe. The need for new advanced technologies and methods ensuring both microbiological safety and the removal of potential chemical residues in used materials and products is urgent. Non-thermal atmospheric plasma (cold atmospheric plasma—CAP) has recently attracted great research interest as an alternative for operative solutions of problems related to safety and quality control. CAP is a powerful tool for the inactivation of different hazardous microorganisms and viruses, and the effective decontamination of surfaces and liquids has been demonstrated. Additionally, the plasma's active components are strong oxidizers and their synergetic effect can lead to the degradation of toxic chemical compounds such as phenols and azo-dyes. [ABSTRACT FROM AUTHOR]

Biological treatment is a key technology in landfill leachate treatment However, often its efficiency is not high enough due to the pollutants in concentrations above the critical ones. The present study aimed to investigate the adaptive responses that occur in activated sludge (AS) during landfill leachate purification. A model process with AS from a municipal wastewater treatment plant and landfill leachate in increasing concentrations was constructed. The data showed that when dilutions 25 and 50 times had been applied the structure of the AS was preserved, but the COD cannot be reduced below 209 mg O2/L. The feed of undiluted leachate destroyed the AS structure as SVI was reduced to 1 mL/g, biotic index to 1, floc size was greatly reduced and COD remained high (2526 mg O2/L). The dominant group of protozoa was changed from attached to free-swimming ciliates. An increase of the bacterial groups responsible for the xenobiotics elimination (aerobic heterotrophs, genera Pseudomonas, Acinetobacter, Azoarcus, Thauera, Alcaligenes) was registered. This was accompanied by a significant increase in free bacteria. The obtained data showed that for optimal treatment of this type of water it is necessary to include a combination of biological treatment with another non-biological method (membrane filtration, reverse osmosis, etc.). [ABSTRACT FROM AUTHOR]

Peptides isolated from the mucus of Cornu aspersum could be prototypes for antibiotics against pathogenic bacteria. Information regarding the mechanisms, effective concentration, and methods of application is an important tool for therapeutic, financial, and ecological regulation and a holistic approach to medical treatment. A peptide fraction with MW < 10 kDa was analyzed by MALDI-TOF-TOF using Autoflex™ III. The strain Escherichia coli NBIMCC 8785 (18 h and 48 h culture) was used. The changes in bacterial structure and metabolic activity were investigated by SEM, fluorescent, and digital image analysis. This peptide fraction had high inhibitory effects in surface and deep inoculations of E. coli of 1990.00 and 136.13 mm2/mgPr/µMol, respectively, in the samples. Thus, it would be effective in the treatment of infections involving bacterial biofilms and homogenous cells. Various deformations of the bacteria and inhibition of its metabolism were discovered and illustrated. The data on the mechanisms of impact of the peptides permitted the formulation of an algorithm for the treatment of infections depending on the phase of their development. The decrease in the therapeutic concentrations will be more sparing to the environment and will lead to a decrease in the cost of the treatment. [ABSTRACT FROM AUTHOR]

To stimulate plant development in phytoremediation or in the cultivation of non-food crops in potentially contaminated soils, a biotechnologically created product could be applied. The aim of this study was to explore the possibility of creation of biofertiliser, based on activated sludge combined with bacterial strain with detoxifying and plant growth promoting properties. The presented study is focused on the effect of phenol in the following concentrations: 5 mg/l, 100 mg/l, 250 mg/l, 500 mg/l and 1000 mg/l on the metabolic activity of Brevibacillus laterosporus BT271. The gradual increased concentration of phenol was used to study the metabolic activity of mineralised activated sludge and B. laterosporus BT271. The CTC/DAPI staining showed high activity of the bacteria even at the highest concentration. The greatest amount of biomass was accumulated at 5 mg/l phenol (4.44 × 107 cells/ml). At this toxicant concentration, a total dehydrogenase activity of 5.72 × 10-4 µg H+/ml*min was found. Studies of the metabolic activity of microorganisms in experiments involving a combination of mineralised activated sludge, B. laterosporus BT271 and phenol at three concentrations (5 mg/l, 250 mg/l and 1000 mg/l) showed the highest value for dehydrogenase activity in the variant with average phenolic concentration (up to 6.39 × 10-6 µg H+/ml*min. The results proved the detoxification potential of B. laterosporus BT271 when different concentrations of phenol were present. The combination of a mineralised activated sludge and selected highly active biodegrading B. laterosporus BT271 showed valuable properties of detoxification and metabolic activity and keep these potentials up to 1000mg/l phenol. [ABSTRACT FROM AUTHOR]

The upper Iskar sub-catchment is one of Bulgaria's most important economic and socially significant water sources because of its role in supplying Sofia with drinking water. Among the critical factors that carry potential high-risk levels for water quality in this hydrosystem are the discharge from the Samokov Wastewater Treatment Plant (WWTP), diffuse pollution from agriculture, and the percolation of untreated sewage from the small villages. In this study, we assessed the effect of treated wastewater effluent on water quality, and on the ecological state and microbial communities in the river sector of Samokov's WWTP discharge area. The assessment was based on the complex use of chemical and microbiological indicators and biological quality elements. The concentrations of organics, nutrients and microcomponents were determined with results confirming the expected increase for parameters associated with the discharge of urban wastewater. The ecological state, according to macrozoobenthos indicators, was "good" throughout the river sector but local deterioration was registered in a proximal location downstream of the WWTP outfall. The analysis of stream water and bed sediment microbial communities by a fluorescent technique showed the high metabolic activity and intensive transformation processes in addition to high abundance registered with standard cultivation methods. The importance of the studied sub-catchment for the functioning of the urban water cycle, and for the quality of Sofia's drinking water, underlines the need to extend an existing monitoring program with a more detailed assessment of the environmental impact of wastewater discharge. [ABSTRACT FROM AUTHOR]

Wastewaters from the industrial sector and, in particular, those from the textile industry have a diverse composition of organic dyes. These dyes are xenobiotics for living organisms and, falling into natural water, can lead to severe consequences for aquatic flora and fauna. This is the case with the azo-dyes, such as, for example, the amaranth. The adaptive responses of the micro- and metafauna communities in activated sludge towards shock loading of high concentrations of the azo-dyes in wastewater treatment plants (WWTPs) have been poorly studied. The aim of this research was to study the adaptation mechanisms of the communities of micro- and metafauna in activated sludge towards the shock loading of amaranth (200 mg/L)with and without the addition of Pseudomonas aureofaciens AP-9 as a bioaugmentation agent (3.03 × 107 cells/mL). To achieve this, the change in the quantities of key groups of micro- and metafauna was monitored in the course of a model biodegradation process involving real activated sludge from a WWTP and toxic pollutant amaranth at a concentration of 200 mg/L. The results showed that in the case of such shock loading with amaranth, the microfauna communities changed very quickly. In addition, a positive bioaugmentation effect of the added strain of Pseudomonas aureofaciens AP-9 was observed for the micro- and metafauna. The bacteria in a homogenous form provide easily accessible food for the macro-organisms and contribute to their adaptation in the conditions of a toxic shock. This is particularly pronounced in the representatives of free-swimming ciliates and small flagellates. [ABSTRACT FROM AUTHOR]

In the field of the microbial ecology of biofilms and activated sludges, it is widely accepted that the microstructure of the communities depends on the environmental factors. Nevertheless, due to their complexity, the exact mechanisms are still unknown. In this study, we applied a stepwise increase of an azo-dye concentration as a selective factor for adaptation towards biodegradation. The degrading biofilm was developed in a lab-scale sand biofilter. It functioned in a semi-continuous regime for 623 h. The concentration of the azo-dye amaranth was increased from 10 to 55 mg L−1. The effectiveness was 90% and the rate of amaranth elimination was 1.136 mg h−1. The fluorescence in-situ hybridisation (FISH) revealed zones with high activity of Pseudomonas sp. Also increasing importance of the unculturable Pseudomonas sp. and the relationships in the biofilm were found. At the final stage of the experiment, a decrease of the azoreductase activity and an increase of the catechol-1,2-dioxygenase activity were established in the depth of the biofilter. The obtained results were linked with different Pseudomonas microstructures (shown by FISH). The obtained data showed that the changes in the biofilm structure occurred accordingly to the biodegradation of the toxic compound and it included the development of cooperative microbial relationships in the key genus Pseudomonas. [ABSTRACT FROM AUTHOR]

Plasma-based technologies take an increasing place in the new conceptions of wastewater management as a promising tool for the treatment of persistent organic pollutants with low biodegradability. Plasma major advantage is the synergy of diverse active components with high oxidative action and additional benefits as disinfection of treated water. But the bactericidal effect of plasma can influence the treatment effectiveness when this technology is used in combination with biological methods for the removal of pollutants. The aim of this paper is to study the effect of non-thermal atmospheric plasma torch on key enzymes from phenol biodegradation pathways in Pseudomonas aureofaciens (chlororaphis) AP-9. The strain was isolated from contaminated soils and had a high potential for biodegradation of aromatic compounds. The used plasma source is surface-wave-sustained discharge operating at 2.45 GHz in argon produced by an electromagnetic wave launcher surfatron type. The enzyme activities of phenol 2-monooxygenase (P2MO), catechol 1,2-dioxygenase (C12DO), catechol 2,3-dioxygenase (C23DO), protocatechuate 3,4-dioxygenase (P34DO) and succinate dehydrogenase (SDH) were measured in control and after plasma treatment of 10, 30 and 60 s. At short-time treatment, the activities of intradiol dioxygenases increased with 26% and 59% for C12DO and P34DO, respectively. Other oxygenases and SDH were inhibited with 35% even at 10 s treatment. Longer treatment times had a clear negative effect but SDH kept the higher activity at 60 s treatment compared to the oxygenases. Our data suggest that plasma-based technologies are a useful approach for post-treatment of aryl-containing wastewater in order to increase the effectiveness of biological removal. [ABSTRACT FROM AUTHOR]

The application of complex ecological approaches in biological wastewater treatment, assessment of its effect on the effectiveness of the process and comparison of the obtained data to the restrictions in the environmental legislation are key elements of the study. The processes in an anaerobic sequencing batch biofilm reactor, the first module from diphase anaerobic-aerobic biotechnology for dairy wastewater treatment, are investigated. The creation of highly specialized biological system by means of complex approaches based on adaptation, immobilization and bioaugmentation, as well as purposely designed process control are the eco-innovation in this study. A model wastewater with whey (a waste product from cheese manufacture when technologies for it utilization are missing) was used. The main components of whey are proteins and lactose. The dynamics of organic matter concentration (measured as chemical oxygen demand – COD), concentration of proteins and lactose were investigated during the process. The obtained results showed that the anaerobic process with immobilized biomass was appropriate for initial decrease of organics. The most effective approach for creation of active biofilm was the combination of purposely accomplished adaptation with immobilization because it increased with 67% protein biodegradation and with 5% COD removal. In the same time, that approach accelerated COD removal process from 135 hours to 14 hours and protein hydrolysis from 135 hours to 72 hours. [ABSTRACT FROM AUTHOR]

The anaerobic digestion is a biological process that consists of four stages. At the final step of the biodegradation of the organics the most sensitive to the ambient factors group of microorganisms – the methanogens, produces biogas with main component methane. Common problems of these technologies are low biogas yield, production of biogas with low quality or situations in which the plant gets out of exploitation. These problems are related to the lack of biological indicators of the process used in the practice and lack of understanding of the structure and functioning of the methanogenic consortium. Different fluorescent techniques have the potential to fulfill this gap and to contribute to the deep understanding of the structure of the microbial communities. In this study it was applied fluorescence in situ hybridization analysis for identifying and localization of microorganisms by the Archaea domain in digesters of wastewater treatment plant "Kubratovo". High negative correlation between the quantity of Archaea and the biogas and methane production has been registered. This method has the potential to be used as a tool for analyzing the structure of the microbial communities in the digesters and thus to allow the adaptation of the consortium and the optimization of the whole process. [ABSTRACT FROM AUTHOR]

The shock loading of wastewater treatment plants (WWTPs) with toxic pollutants remains a critical problem with crucial significance for the technologies. On 5 November 2014, 30 tons of mazut were emitted in Sofia's WWTP 'Kubratovo', passing through equipment and damaging the functioning of the technological modules. The rehabilitation of activated sludge (AS) after shock loading as well as the development of detoxification activity were investigated. The hydrocarbon index of petroleum products, filamentous index (FI), sludge biotic index, sludge volume index (SVI), chemical oxygen demand (COD), biochemical oxygen demand (BOD5), oxygenases and succinate dehydrogenase activities were analyzed for a period of two weeks. The results show that independently from prolonged rehabilitation period, AS remained with filamentous bulking (SVI over 200 ml/g and FI over 1.107 μm/mg). At the same time, the detoxification potential of the AS was developed. Although the morphological and functional structure was still not fully recovered, the AS developed two adaptive mechanisms. First, activation of shorter, more effective ways for benzene ring cleavage, operated by catechol 2,3-dioxygenase; second, strong increase of succinate dehydrogenase activity, which is consistent with the activation of the degradation of trivial substrates for energy generating to overcome the intoxication and synthesis of oxygenases. [ABSTRACT FROM AUTHOR]

The process of methanogenesis, which is in the essence of the widely distributed technologies for biogas production, is slow, has multiple steps and occurs under anaerobic conditions. These factors make the control and the management of the anaerobic digestion difficult and impose the testing and implementation of new indicators for control which are fast and focused on the activity and functioning of the methanogenic community in addition to the traditionally used technological parameters. In this study, the biogas production process in wastewater treatment plant ‘Kubratovo’ was analysed in two different seasonal situations and a correlation was made between the studied parameters for control. The complex methodological arsenal included the activities of aerobic and anaerobic dehydrogenase, fluorescent image analysis and key chemical and technological indicators. The correlation analysis showed that the fluorescent image analysis parameters (number/mean size of clusters; fluorescence intensity; area) had the strongest relationship with the biogas production. Based on these results, we propose a fluorescent indicative system for control of the biogas production technologies. It is a fast tool for assessment the effectiveness of the process of anaerobic digestion. Its focus on the activity and functioning of the biological system could contribute to the optimization of the whole performance of these technologies and could serve as a prediction tool for potential problems in the future. [ABSTRACT FROM AUTHOR]

The article discusses a study that developed a novel and effective approach for enzyme immobilization based on entrapment into the walls of poly(N-isopropylacrylamide) (PNIPAAm) cryogels. It details the use of ultraviolet (UV) irradiation technique and hydrogen peroxide as an initiator to prepare the supermacroporous PNIPAAm cryogels containing urease. It is suggested that the PNIPAAm cyrogels could be used as a permeable membrane for direct removal of traces of urea from continuously flowing feed solutions.

The main transformation processes effected by the natural microbial consortium of upper Iskar River with predominant participation of sediment biofilm were simulated in the laboratory by the use of portable devices (chambers). The dynamics of real heterotrophic respiration, organic matter oxidation, denitrification and ammonification were analysed by oxygen depletion, reduction of chemical oxygen demand, nitrate uptake and ammonium accumulation, under the conditions prevailing during high and low flow periods. The experimental results showed fast oxygen consumption and high process rates - indicators for intensive respiration by a heterotrophic microbial consortium and good functioning of the ecosystem component studied. The nitrogen transformations occurred at slower rates but in mutual dynamic balance and their simultaneous realisation was due to precise, adaptive division in time and space. [ABSTRACT FROM AUTHOR]

A loamy sand soil sampled from a species-rich permanent grassland at a long-term experimental site (Wildekamp, Bennekom, The Netherlands) was used to construct soil microcosms in which the microbial community compositions had been modified by fumigation at different intensities (depths). As expected, increasing depth of fumigation was shown to result in progressively increasing effects on the microbiological soil parameters, as determined by cultivation-based as well as cultivation-independent (PCR-DGGE, PLFA) methods. Both at 7 and at 60 days after fumigation, shifts in the bacterial, fungal and protozoan communities were noted, indicating that altered community compositions had emerged following a transition phase. At the level of bacteria culturable on plates, an increase of the prevalence of bacterial r-strategists was noted at 7 days followed by a decline at 60 days, which also hinted at the effectiveness of the fumigation treatments. The survival of a non-toxigenic Escherichia coli O157:H7 derivative, strain T, was then assessed over 60 days in these microcosms, using detection via colony forming units counts as well as via PCR-DGGE. Both data sets were consistent with each other. Thus, a clear effect of fumigation depth on the survival of the invading strain T was noted, as a progressive increase of depth coincided with a progressively enhanced inoculant survival rate. As fumigation depth was presumably inversely related to community complexity, this was consistent with the hypothesis that soil systems with reduced biological complexity offer enhanced opportunities for invading microbial species to establish and persist. The significance of this finding is discussed in the light of the ongoing discussion about the complexity–invasiveness relationship within microbial communities, in particular regarding the opportunities of pathogens to persist.The ISME Journal (2007) 1, 204–214; doi:10.1038/ismej.2007.21; published online 31 May 2007 [ABSTRACT FROM AUTHOR]

Natural products have long played a major role in medicine and science. The garden snail Cornu aspersum is a rich source of biologically active natural substances that might be an important source for new drugs to treat human disease. Based on our previous studies, nine fractions containing compounds with Mw <3 kDa; <10 kDa; <20 kDa; >20 kDa; >30 kDa>50 kDa and between 3 and 5 kDa; 5 and 10 kDa; and 10 and 30 kDa were purified from the mucus of C. aspersum and analyzed by tandem mass spectrometry (MALDI-TOF/TOF). Seventeen novel peptides with potential antibacterial activity were identified by de novo MS/MS sequencing using tandem mass spectrometry. The different fractions were tested for antibacterial activity against Gram─ (Pseudomonas aureofaciens and Escherichia coli) and Gram+ (Brevibacillus laterosporus) bacterial strains as well the anaerobic bacterium Clostridium perfringens. These results revealed that the peptide fractions exhibit a predominant antibacterial activity against B. laterosporus; the fraction with Mw 10–30 kDa against E. coli; another peptide fraction <20 kDa against P. aureofaciens; and the protein fraction >20 kDa against the bacterial strain C. perfringens. The discovery of new antimicrobial peptides (AMPs) from natural sources is of great importance for public health due to the AMPs' effective antimicrobial activities and low resistance rates. [ABSTRACT FROM AUTHOR]

Non-thermal (cold) plasma is subject of intensive scientific interest as an alternative sterilization technique for advanced control of microbial quality and safety in food biotechnology. The cold plasma is a flow of weakly ionized gas at atmospheric pressure that includes radicals, H2O2, O3, ultraviolet radiation, charged particles, exited metastable atoms, electric fields. One of the major benefits of plasma-based technologies is the synergy between the strong effects of these highly active components that provides a high bactericidal efficiency at low costs, time-saving and non-toxicity. The aim of this study is to assess the bactericidal effect of cold argon plasma in liquids and surfaces, contaminated with Gram-negative and Gram-positive spore-forming bacteria. The used plasma source is surface-wave-sustained discharge (SWD) operating at 2.45 GHz in argon (plasma torch) produced by an electromagnetic wave launcher surfatron type. The bactericidal effect was studied by direct contact treatment of contaminated liquids and agar plates with Pseudomonas aureofaciens AP-9 and Brevibacillus laterosporus BT-271. The results show that the cold argon plasma is able to inactivate bacteria at short exposure time (under 1 min). The clear sterilization zones on treated surfaces with diameter depending on exposure time and initial bacterial density were obtained. In bacteria-contaminated liquids the partial disinfection was observed at least. The potential of plasma based technologies as innovative sterilization approach is high and can be used for various purposes related to microbial control and food safety. [ABSTRACT FROM AUTHOR]