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.
The introduction of an integration approach for management of the water basins, including assessment and control of stream water quality and sediment quality, as well as regulation of the pollutant influx in the water receiver, is necessary. The changes in the microbial communities, as a response to the chronic discharge of untreated dairy wastewater, were followed in river and in depth, in three river components "stream water-sediment water-sediments". The water quality of Leva River decreased after dairy wastewater discharge as the microbial communities reacted with structural and functional changes, related with enhancement of aerobic heterotrophs and the values of total dehydrogenase activity and phosphatase activity index. The result was a decrease of organic matter and nutrients in the stream water in Station 4. However, an improvement of river water quality was not ascertained according to the Bulgarian State Standard. The applied ecological theory for r/K-strategists showed that in the stream water the microbial community is presented with fast growing populations, while in the sediment water and sediments prevailed slow growing bacteria. In the sediments aerobic heterotrophs were with higher density and showed higher activities of total dehydrogenase, phosphatase and protease. The obtained results confirmed that microbial community in the sediment zone is an important factor for the regulation of the transformation processes of organic matter and nutrients in water and sediments, as well as for the formation of river water quality in water receiver.
The creation of a biofilm as a specialized biosystem, its development, and activity were studied at 3 critical control points of biofilter operation: start-up, transition from batch to sequencing batch regimen, and set-up of stable sequencing batch process. Five variants of biosystems were investigated with an inoculum from specially adapted real activated sludge, enriched with various combinations of 3 microbial preparations. A stable and working biofilm was developed in the phase of stabilized sequencing batch process. The differences among biodegradation effectiveness of the 5 variants were insignificant during that phase and the effect of the preparations was low. The effectiveness of organic removal for the 5 bioaugmentation approaches reached 60% for protein, 70% for chemical oxygen demand, and 97% for lactose. Commercial inocula did not improve final reactor performance over an inoculum from a municipal wastewater treatment plant alone.
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.
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