Irina Schneider

MICROBIAL STRUCTURE AND FUNCTIONS OF BIOFILM DURING WASTEWATER TREATMENT IN THE DAIRY INDUSTRY

ABSTRACT The microbial structure and activity of biofilm are two important parameters for the successful operation and control of fixed film processes in wastewater treatment. However, the constant interaction between fixed and suspended biomass requires the parallel investigation of these two biological components. The aim of the present article is to study the key microbiological and enzymological parameters of biofilm and suspended biomass from an anaerobic sequencing batch biofilm reactor for dairy wastewater treatment. The effectiveness of organic matter (measured as COD) removal and nitrates removal was determined. The microbial structure of biofilm and suspended biomass was investigated by the quantity of anaerobic heterotrophs, anaerobic spore-forming microorganisms and denitrifying bacteria. The total dehydrogenase activity and the nitrate reductase activity were used as indicators for biomass activity. The obtained data showed that the enzyme activity of the fixed biomass was higher in comparison with that of the suspended biomass. This result is related to the more heterogenic media of the inert carrier and more dynamic conditions in the biofilm inner layers. The total dehydrogenase activity of the fixed biomass was four times higher and the nitrate reductase activity of the fixed biomass was two times higher than that of the suspended biomass during stable biofilm functioning. The investigated biological system mineralized the organic matter with high effectiveness (to 90%) and removed 67% of the nitrates from dairy wastewater as a result of the controlled water treatment process.

Diversity of the Microbial Communities in River Water and Sediments after Dairy Wastewater Discharge

ABSTRACT Functional diversity of the microbial communities in stream water, sediment water and sediments of Leva River in dependence on dairy wastewater discharge was studied. The aerobic heterotrophs and total coliform bacteria indicated a deterioration of water quality in river after wastewater discharge and vastly increase of the biodegradable organic matter. The deep analysis about the functional role of river microbial communities in organic matter degradation and nitrogen biotransformation was accomplished in the critical station. The obtained results confirmed that the microbial diversity, especially in the sediment zone, play an important role for indication and regulation of self-purification processes in water receiver.

Amendment of the Activity of Microbial Preparation Laktazym to Protein Biodegradation for Dairy Wastewater

ABSTRACT There exist various biological products in the markets for augmentation of wastewater treatment process, but their specificity toward definite substrates is low. In the present study the amendment and the enrichment of biodegradation activity of commercial preparation Laktazym toward a target contaminant in dairy wastewater were investigated. Two microbial dominants—AS-05 and LB-16 with high biodegradation activity to the milk proteins were isolated by the applied selection pressure with casein. Both cultures were detailed characterized by biomass accumulation, effectiveness of organics, protein and lactose removal, as well as by key enzyme activities—total dehydrogenase, phosphatase and nitrate reductase. Anaerobic biodegradation process for dairy wastewater in a critical situation of destabilized biofilm has been simulated in lab with different biological systems. The experimental data showed greater positive effect on the biodegradation of the organic matter, particularly of the milk proteins for the two modifications of investigated preparation with the selected cultures, than for the variant Laktazym. Moreover at the 48th and the 72nd hour the effectiveness of protein removal for the combination Laktazym + AS-05 (Peptostreptococcus sp.) was higher with 67%, than for the variant only with Laktazym.

Control of biogas production process by enzymatic and fluorescent image analysis

ABSTRACT 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.

Microbial community development of biofilm in Amaranth decolourization technology analysed by FISH

The aim of this study was to elucidate the role, the space distribution and the relationships of the bacteria from the genus Pseudomonas in a biofilm community during semi-continuous Amaranth decolourization process in model sand biofilters. The examined parameters of the process were as follows: technological parameters; key enzyme activities (azoreductase, succinate dehydrogenase, catechol-1,2-dioxygenase, catechol-2,3-dioxygenase); the number of azo-degrading bacteria and the bacteria from genus Pseudomonas (plate count technique); the amount and the location of Pseudomonas sp. using fluorescent in situ hybridization (FISH). The results showed that the increase of the Amaranth removal rate with 120% was accompanied with increase of the enzyme activities of the biofilm (azoreductase activity – with 25.90% and succinate dehydrogenase – with 10.61%). The enzyme assays showed absence of activity for сatechol-1,2-dioxygenase and catechol-2,3-dioxygenase at the early phase and high activities of the same oxygenases at the late phase (2.76 and 1.74 μmol/min mg protein, respectively). In the beginning of the process (0–191 h), the number of the culturable microorganisms from genus Pseudomonas was increased with 48.76% but at the late phase (191–455 h) they were decreased with 15.25% while the quantity of the non-culturable bacteria from this genus with synergetic relationships was increased with 23.26%. The dominant microbial factors were identified in the structure of the biofilm during the azo-degradation process by using FISH analysis. Furthermore, the inner mechanisms for increase of the rate and the range of the detoxification were revealed during the complex wastewater treatment processes.

FISH analysis of microbial communities in a full-scale technology for biogas production

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.

Modelling of risk effect of mercury on nutrient transformation in lake sediments

The influence of mercury on the transformation processes in the waters and the sediments in the reservoir of a small hydroelectric power plant (SHPP) Lakatnik was simulated in laboratory conditions. SHPP Lakatnik is the first (of nine similar) SHPPs put into exploitation in the middle part of the Iskar River (Bulgaria). In previous studies of the sediments in the reservoir of SHPP Lakatnik, our team found high concentrations of mercury, sometimes exceeding maximum concentration limit (MCL). In model bioreactors we studied the effect of mercury on the dynamics of the following hydrochemical and microbiological indicators: NH4+, NO3−, NO2−, PO43−, chemical oxygen demand (COD), total organic carbon (TOC); aerobic and anaerobic heterotrophs (AH and AnH), Pseudomonas spp. (Ps.), Acinetobacter spp. (Ac.), sulphate-reducing bacteria (SR), denitrifying microorganisms (Dn). We looked for linear correlations among the studied indicators in order to find quick, mutual replaceability among them. The extent to which mercury affects the amount of key microbial groups and the rate of transformation of biogenic elements was calculated in percentages. The microorganism dynamics showed that AH, AnH and Ps. adapt more quickly and their number increased more in the presence of mercury, whereas SR, Dn and Ac. were inhibited to a greater extent by the presence of mercury. Mercury had a marked stimulating effect on Ps., which showed a 312% increase in number at the 192nd hour. The obtained results can be used when decisions have to be taken in risky situations related to increased concentrations of mercury in the sediments.

Stabilizing Role of Nanodiamonds on the Amaranth Transformation in Model Biofilters

The present article is focused on studying the first phase of a model dye biodegradation, the reduction of the azo bond, and the following amaranth decolorization. This phase is speed-limiting, i.e. it defines the speed of the whole process. The process is with a periodic regime of feeding and is simulated in reactors of the “biofilter’ type in the presence of trivial organic matter (peptone and yeast extract). In the first part of the studies the dynamics of the amaranth and the organic matter (measured as TOC) is followed as well as the decolorization effectiveness and the effectiveness of decreasing concentration of the organic matter. The spatial and temporal distribution of important groups of microorganisms in depth of the inert carrier has been followed, which take part in the biotransformation of the azo dye. The azoreductase activity of the immobilized community is studied. The second part of the article investigates the modulation effect of nanodiamonds on the residual concentration of amaranth and organic matter, as well as on the effectiveness of their biotransformation. The obtained results showed that the medium layer of the inert carrier in the biofilter has the most favorable conditions for carrying out the reduction of the azobond. The key groups of microorganisms in the biofilm which carry out the process are: the anaerobic heterotrophs; the anaerobic azo degraders, the bacteria from genus Pseudomonas and Acinetobacter. Nanodiamonds have a stimulating effect on the technological parameters of the system. It is expressed in maintaining a stable biofilm with a high activity, maintaining an optimal flow of the system and increasing the effectiveness of amaranth decolorization and organic matter removal.

Analogous Modeling of Nutrient Transformation in Iskar River Sediments at Different Moisture Content: Microbiological and Enzymological Indicators

ABSTRACT This study was focused on the R&D of the elements of the systems for early warning of risk events as well as on the selection of the mechanisms and indicators for their management. The aim was to derive the mathematical dependences, bioalgorithms, and indicative correlations for upgrading of the HSPF hydrological model. For this purpose analogous modeling of transformation of organics in the river sediments of the parafluvial zone as a function of moisture (in%) was performed. This upgrading can be applied for correct and effective prognosis of the rate of self-purification in the Iskar River in the section from Beli Iskar Reservoir to Iskar Reservoir. The results showed that the combination of total dehydrogenase, nitrate reductase and phosphatase activities could be considered an effective instrument for water quality management and for prediction of the rate of transformation processes. The derived linear mathematical dependences can be applied to calculate other microbiological and kinetic indicators important for monitoring, as well as to create special modules for the HSPF model with a well-functioning verification strategy.