Performance of an integrated system for the treatment of veterinary hospital wastewaters: assessment of organic load and toxicity levels.

Despite its toxic potential, the treatment of wastewaters generated at veterinary hospitals has been neglected. Thus, this is a pioneering study that addresses the treatment of this effluent through an integrated system composed of an upflow anaerobic sludge blanket (UASB), an anoxic filter (AF), an aerobic reactor (AR), a sludge thickener tank (STT) a horizontal flow subsurface constructed wetland (HFSSCW) and a parshall gutter (PG) and with a hydraulic retention time of 10 days. Approximately 5 m³ of wastewater is produced daily, with antibiotics and analgesics being the most commonly used classes of pharmaceutical compounds. Several of the analyzed parameters did not comply with national and international guidelines. In this context, the integrated treatment system demonstrated good results, achieving mean removals of: 98% for COD and 59% for BOD₅; 87.5% for Total N and 44% for Total P; 83.8% and 69.9% for DOC and TDC; 95% and 65% for Turbidity and EC; and 78% for TDS. The bioassays with Allium cepa indicated a strong genotoxic potential of the raw wastewater, which was completely eliminated after treatment. Thus, it can be concluded that the integrated treatment system showed promising results regarding the treatment of the investigated wastewaters and can be considered a viable alternative to meet effluent disposal limits established in Brazilian and international standards, as well as significantly reduce their toxic potential.