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Institut für Wasser- und Umweltsystemmodellierung - IWS



"Effective Microorganisms (EMs) in the activated sludge, their effects in flocculation, sedimentation and microbial community"

One of the most popular methods for removing contaminants in the wastewater is the biological treatment by activated sludge. This process is used for removal of biodegradable contaminants (colloidal or dissolved) in wastewater. In the Activated Sludge System the biodegradable pollutants are attacked by microorganisms (mainly bacteria) that fed upon dead organic matter, decomposing it and converting it into new cells, water, gases and other products.
New technologies are being produced to assist the treatment of wastewater that fulfills strict environmental regulations. One of these new technologies is the one offered by the VTA Group. The product consists of a mixture of a high polymerized aluminum compound with SEMIPOL® and a mixture of microorganisms with bioenergetics regenerative alkali salts used as an aid of precipitation and flocculation.

In the Master Project, the main objective is to identify Biokat VTA´s effects on the microbial community within the Activated Sludge process, to evaluate its efficacy regarding the degradation of carbon compounds and the elimination of Nitrogen and Ammonia and to test physical characteristics of bioflocs for two parallel nearly identical activated sludge treatment plants.
The output of Biokat VTA was evaluated for municipal sewage in a comparative study.
For the comparative study two small scale Activated Sludge Systems were installed at the research facilities of the Institute for Sanitary Engineering, Water Quality and Solid Waste Management (ISWA) at the University of Stuttgart; one using a conventional Activated Sludge Process and a second one treated with Biokat VTA. The setting of each plant consisted of a rectangular stainless steel Aeration Tank (0,89m3) and a funnel-shaped Sedimentation Tank (1.416 m3) both systems having identical inflow stream, size in the aeration and sedimentation tank, returned sludge and aeration input. The systems were operated simultaneously during 4 weeks to ensure their stabilization. After the stabilization period, plant Biokat+ was seeded with Biokat VTA solution at a ratio of 20ppm. The parameters selected to measure the mixed liquor characteristics were Settled Volume, Total Suspended Solids and Sludge Volume Index; parameters that were measured daily and those for testing the quality of the effluent were COD, Nitrate and Ammonia every third day.
The results yielded by this study showed that there is not a significant reduction in the pollutant; however, plant treated with Biokat+ is presumably more stable under disadvantageous conditions (Oxygen supply problems) as well as it showed a notable improvement in the settling behavior and reflected in the sludge volume index specially after the adaptation period was over, around the 10th week of the experiment.
In order to investigate whether the nitrifier communities in flocs differ between the two pilot plants a molecular biological analytical method –fluorescence in situ hybridization- (FISH)- was selected for the analysis.
Besides the effects of the Biokat VTA on the community at the Activated Sludge and their capacity to enhance effluent quality, it was also investigated their ability to promote floc stability and improve settling behavior in the sludge. These parameters were measured by determining the number of floc particles, surface area, shape factor and rough settling velocity were measured with the floc camera and compared both treatments.