Multifunctional Approach to Evaluate the Efficiency of Urban Wastewater (UWW) Treatment from San Justo city (Santa Fe, Argentina)

REGALDO, L; RENO, U; SCHMUCK, J; KERGARAVAT S.V; ROMERO, N; POLLA, W; GIMENEZ, L; BORCA, J; BASSO, E; MÁRQUEZ, V; GAGNETEN, A.M

Montevideo

Congreso; SETAC Latin America 15th Biennial Meeting; 2023

Society of Environmental Toxicology and Chemistry

Urban wastewater treatments (UWTs) transform biodegradable material into nontoxic products, to remove nutrients, and contaminants from different sources. The aim of the study was to know: (1) the physicochemical characteristics, including the presence of hormones, of UW during periods of high and low temperature and rainfalls; (2) the ecotoxicity of UW using Chlorella sorokiniana, and (3) the detection of SARS-CoV-2 in raw and treated UW. The UWT consists of (i) two anaerobic ponds; (ii) two primary facultative ponds; (iii) two secondary facultative ponds (SFPs); and (iv) a chlorination chamber. Raw UW and treated UW in SFPs were collected for three winter months (WIN - 2021 and 2022), and three summer months (SUM - 2021, 2022, and 2023), for physicochemical and hormonal analysis. Estrogenic/antiestrogenic and androgenic/anti androgenic activities were evaluated in UW samples at both seasons. For the ecotoxicological tests, different dilutions of UW from the SFPs were used in algal growth inhibition assays. The % removal of chemical oxygen demand (COD) (WIN 64% - SUM 52%), biological oxygen demand (BOD5) (WIN 81% - SUM 79%), total suspended solids (TSS) (WIN 28% - SUM 25%), ammonium (WIN 36% - SUM 27%), and phosphorus (WIN 52% - SUM 12%) were higher in WIN. Higher % removal was only obtained in SUM for sulfide (SUM 97% - WIN 79%). Only COD and ammonium exceeded slightly the values proposed in the current provincial regulations. The decrease of ammonium is related to the biological processes of nitrification and its conversion to nitrate and nitrite by oxidation reactions. The biodegradability index registered in the raw UW was very similar between seasons (0.45-0.46), but decreased in the treated UW, being slightly higher in WIN (0.24 and 0.19). Estrogenic activity was detected only in SUM samples. A dilution of 90% UWW inhibited the algal growth (50%) of C. sorokiniana. According to the risk classification system for wastewater discharged into the aquatic environment, the UW presented an Acute Toxicity Class III. Of the total positive samples, 77% correspond to untreated UW, 23% to prechlorination, and no SARS-CoV-2 RNA was registered at the post-chlorination sampling site. This work could contribute to building a network for wastewater-based epidemiology. The results can be used to put management policies into practice, with the purpose of contributing to the river ecosystem´s integrity.