Due to negative environmental effects of nitrogen discharge to recipients and increasingly stringent effluent standards, effective nitrogen removal is necessity. Biological methods are the simplest and cheapest way to treat wastewater; however, it may become an extremely expensive option when high influent nitrogen concentrations are measured and there is a lack of biodegradable organic carbon. Therefore, there is a great need to find new solutions and improve existing technologies. The deammonification is an excellent example of such a new process that requires considerably low amounts of organic carbon and oxygen in comparison to conventional nitrification/denitrification. The main objective of presented research was to investigate an Anammox process accompanied with autotrophic nitrification and heterotrophic denitrification in one rotating biological contactor (RBC). During the research period, it was possible to carry out the Anammox process in low temperature below 20 °C. Additionally, it was found that the process is insensitive to high nitrite concentration in the reactor, up to 100 g NO₂-N m⁻³, resulting only in a temporary decrease in removal rates. Furthermore, analysis of data indicated that the Stover-Kincannon model can be used for the description of ammonium and nitrite removal processes.

Iodinated contrast media (ICM), which are used for radiological visualization of human tissue and cardiovascular system, are poorly biodegradable; hence, new methods of their removal are sought. In this study, the effectiveness of selected X-ray ICM removal by means of UV and UV/TiO₂ pretreatment processes from synthetic hospital wastewater was demonstrated. The following compounds were investigated: iodipamide, iohexol, and diatrizoate. The experiments were as follows: (i) estimated susceptibility of the ICM to decay by UV radiation in different aquatic matrices, (ii) determined an optimal retention time of hospital wastewater in the UV reactor, (iii) determined optimum TiO₂ concentration to improve the effectiveness of the UV pretreatment, and (iv) investigated removal of ICM by combination of the photochemical and biological treatment methods. The quantum yields of selected ICM decay in deionized water (pH = 7.0) were established as 0.006, 0.004, and 0.029 for iohexol, diatrizoate, and iodipamide, respectively. Furthermore, the experiments revealed that diatrizoate and iohexol removal in the UV/TiO₂ process is more efficient than in UV process alone. For diatrizoate, the removal efficiency equaled to 40 and 30 %, respectively, and for iohexol, the efficiency was 38 and 27 %, respectively. No significant increase in iodipamide removal in UV and UV/TiO₂ processes was observed (29 and 28 %, respectively). However, highest removal efficiency was demonstrated in synthetic hospital wastewater with the combined photochemical and biological treatment method. The removal of diatrizoate and iohexol increased to at least 90 %, and for iodipamide, to at least 50 %.

Coke wastewater is known to be relatively difficult for biological treatment. Nonetheless biofilm based systems seems to be promising tool for such treatment. That is why a rotating biological contactor (RBC) system focused on Anammox process was used in this study. The experiment was divided into two parts with synthetic and then, real wastewater. It was proven that it is possible to treat coke wastewater with RBC but such procedure requires a very long start-up period for the nitritation (190 days) as well as for the Anammox process, where stable nitrogen removal over 70% was achieved after 400 days of experiment. Interestingly, it was possible at a relatively low (20.8 ± 2.3°C) temperature. The PCR-DGGE based monitoring of the bacterial community showed that its biodiversity decreased when the real wastewater was treated and it was composed mainly of CG-rich genotypes, probably because of the modelling influence of this wastewater and the genotypes specialization.

Filamentous bacteria in addition to wastewater treatment are responsible for the shape of flocs and sedimentation properties of activated sludge. Their dynamics in activated sludge influences the performance of the whole sewage treatment plant. Therefore the composition of activated sludge biocenosis and its dynamics in the nitrification process was investigated. Four lab-scale activated sludge membrane bioreactors fed with wastewater highly concentrated with ammonium (synthetic wastewater imitating landfill leachate) were operated to obtain a high rate of nitrification. The sludge age was 8, 12, 24 and 32 days. An additional fifth reactor was conventionally ammonium loaded at 12 - day sludge age and served as the reference. A shift in filamentous bacteria population was observed in all operated reactors. There was no influence between sludge age and composition or abundance of filamentous biocenosis. In high ammonium loaded activated sludge Nostocoida limicola, Haliscomenobacter hydrossis and also Type 021N were the most abundant filamentous bacteria. In the reference reactor Type 021N and Sphaerotilus natans dominated the activated sludge.