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The extension of biological processes from carbonaceous impurities removal to nitrogen and phosphorus removal had an impact on the biological system configuration. The system must be well designed, optimized, and operated at its optimum in order to meet the ever more stringent effluent standards. An intermittently aerated completely mixed lab-scale activated sludge bioreactor (IACMB) has been used for modelling biological processes of nutrients removal. Concerning the nitrogen removal, the operating cycles 15-30 (15 minutes of aeration, 30 minutes of only mixing without aeration) and 30-30 were tested. For the experiments with luxury uptake processes, the operating cycles 15-45, 15-90, 30-60 and 15-75 were used. The cycle 15-75 was the most satisfactory with convenient lengths of aerobic, anoxic, and anaerobic period, high efficiency of the nitrification and denitrification processes, and significant decrease in phosphorus concentration. The results have shown that the intermittently aerated bioreactors are suitable for nitrogen removal as well as luxury uptake of phosphorus. The main advantage is high flexibility in maintenance and control of biochemical environments in the bioreactor. [ABSTRACT FROM AUTHOR]

The paper presents the results of a study aimed at the use of simple mathematical models of a sewer network, wastewater treatment plant (WWTP) and receiving water to control the discharge of diluted wastewater from combined sewer overflow system in order to protect water resources. The greatest burden on the receiving water usually occurs at the time of combined sewer system overflow, when diluted municipal wastewater is also discharged into the receiving water. Literature usually presents impact assessment results of either wastewater treatment plants or sewer system on the receiving water. In our work, we assess the impact of the integrated municipal wastewater system on the receiving water. The models for the sewer system, wastewater treatment plant, and receiving water under consideration were developed. Mathematical modelling of the subsystems of urban wastewater system was carried out using simulator SIMBA 6. Simulations were performed using real experimental data. Information about the sewer system overflow during the year (total amount of overflow, pollutant load of COD during overflow) was obtained by using dynamic simulations. The simulation results aimed at the impact assessment of the sewer system overflow and WWTP on the receiving water quality showed that the values of the monitored parameters in the river could exceed several times the environmental quality standards for receiving water. [ABSTRACT FROM AUTHOR]

Seven small wastewater treatment plants were chosen for evaluation. These WWTPs work on the principle of anaerobic pre-treatment and aerobic post-treatment and were made with the cooperation of Slovak Technical University with ASIO-SK s.r.o. Bytca and ASIO s.r.o. Brno. Wastewater treatment plants are made for 5-600 PE. When operated at suitable conditions, the results match the directive water discharge from small wastewater treatment plants in the Slovak Republic. [ABSTRACT FROM AUTHOR]