Efficient biological treatment: achieving exceptional reductions in pollutants and ensuring environmental compliance

The study assessed the effectiveness of treatment processes in removing organic matter, biogenic compounds and suspended solids at the subsequent treatment stages one of the Polish municipal wastewater treatment plant. In a comprehensive mechanical-biological treatment, for all tested pollution indicators, i.e. biochemical oxygen demand (BOD5), chemical oxygen demand (COD), total nitrogen (TN), total phosphorus (TP) and total suspended solids (TSS), outstanding results, surpassing regulatory standards, were obtained. The achieved average percentage reduction was from 87% for TN (standard deviation of 2.7%) to average 99% for BOD5 (standard deviation of 0.3%). The observed average BOD5/COD ratio of 0.45 aligned with typical values reported, and the decrease in the ratio to 0.13 after biological treatment underscored the efficacy of these processes in organic compounds decomposition and managing difficult-to-degrade substances. The BOD5/TN values emphasized the effectiveness of the treatment, maintaining well-balanced proportions between organic carbon and nitrogen compounds. Moreover, raw sewage showed notable susceptibility to nitrogen removal, indicated by the highest average BOD5/TN ratio of 6.72, suggesting a high propensity for biodegradation. This study highlighted that the average BOD5/TP value of 56 in raw sewage indicated a significant susceptibility to phosphorus compound removal. The treated sewage consistently adhered to environmental regulations, demonstrating minimal variability in pollution indicators. That underscored the effectiveness of treatment processes in meeting stringent standards and achieving significant reductions in pollutants. Effective sewage treatment is even more significant, because it is possible to reuse treated sewage e.g. for irrigation in agriculture, what contributes to the sustainable water management.