The aim of the conducted research was to assess the effectiveness of the nitrification process, at different concentrations of ammonium nitrogen, in biologically treated wastewater in one of the largest municipal and industrial wastewater treatment plants in Poland. The studies also attempted to acclimate nitrifying bacteria to the limited concentration of ammonium nitrogen and determined the efficiency of nitrification under the influence of acclimated activated sludge in the biological wastewater treatment system. The obtained results indicate that the concentration of ammonium nitrogen above 60.00 mg·dm⁻³ inhibits nitrification, even after increasing the biomass of nitrifiers. The increase in the efficiency of the nitrification process in the tested system can be obtained by using the activated sludge inoculated with nitrifiers. For this purpose, nitrifiers should be preacclimated, at least for a period of time, allowing them to colonize the activated sludge. The acclimated activated sludge allows reducing the amount of ammonium nitrogen in treated sewage by approx. 35.0%. The process of stable nitrification in the biological treatment system was observed nine days after introducing the acclimated activated sludge into the aeration chamber.

Water reuse is now becoming a global necessity. However, one of the drawbacks in releasing wastewater into the environment is some persistent pollutants that are not completely removed in wastewater treatment plant. Residual bacteria and antibiotics in the inflowing wastewater can contribute to the antibiotic resistance spread in the aquatic environment. This study determined the effectiveness of activated sludge process for fecal coliform bacteria elimination, and also the Escherichia coli resistance to antimicrobial agents as erythromycin, azithromycin, clarithromycin, ofloxacin, ciprofloxacin, trimethoprim, and metronidazole in treated wastewater. The research was carried out using the membrane filtration technique, and the susceptibility of isolates to antimicrobial agents was tested by the disc diffusion method. The concentrations of fecal coliform bacteria and Escherichia coli differed significantly depending on the seasonal period in which it was carried out. Despite up to 99% reduction in the number of sanitary indicators in biologically treated wastewater, 89% of E. coli isolates resistant to the tested antibiotics was found, while 100% of the isolates were susceptible to metronidazole. Most of the isolates showed resistance to trimethoprim, and the fewest isolates were resistant to ofloxacin, indicating that some strains may react differently to antibiotics.

A busca por soluções eficazes e de baixo custo para o tratamento de efluentes, visando mitigar seu elevado potencial de degradação ambiental, levou à avaliação da digestão anaeróbia. Embora seja um processo econômico e eficiente na degradação de matéria orgânica, a digestão anaeróbia gera o digestato, um subproduto que, dependendo de sua composição, requer um pós-tratamento rigoroso. Este estudo objetivou verificar a eficácia do processo O₃/UV (Ozônio/Radiação Ultravioleta), um Processo Oxidativo Avançado (POA), na degradação do digestato coletado de um biodigestor em uma indústria frigorífica, com a meta de adequá-lo às normas brasileiras de lançamento. O tratamento foi realizado por duas horas, e a avaliação comparativa entre o digestato bruto e o tratado analisou o pH, Cor Verdadeira, Demanda Química de Oxigênio (DQO) e Nitrogênio Amoniacal (N–NH₃). Os resultados obtidos indicaram um desempenho notável do processo O₃/UV, com uma remoção de Cor Verdadeira de 83,54% e um decaimento da DQO de 45,96%, enquanto o pH variou de 7,5 para 8,4 e o N–NH₃ permaneceu estável. Em conclusão, embora o tratamento O₃/UV não tenha atendido integralmente a todas as exigências das normas vigentes, ele se mostrou uma alternativa tecnicamente viável e promissora devido ao seu elevado potencial na melhoria das características físico-químicas do digestato, reduzindo significativamente seu impacto ambiental.