Evaluating the Performance of Sewage Treatment Plants Containing Up-Flow Anaerobic Sludge Blanket Reactors Followed or Not by Post-Treatments

Sewage treatment is essential to prevent disease transmission and adverse environmental impacts. This study evaluated the performance of four Sewage Treatment Plants (STPs) in two cities in the state of Minas Gerais, Brazil. Two STPs (Santana and São José) that have Up-Flow Anaerobic Sludge Blanket (UASB) reactors as the sole biological treatment stage did not comply with the discharge standards in receiving water bodies, particularly for SetS, TSS and O&G parameters. This shows the need for improvements, such as the implementation of post-treatment. For the other plants that have UASB reactors followed by an activated sludge system (Industrial Complex STP) or an up-flow anaerobic filter (Carbonita STP) as post-treatment, only the O&G parameter was not met. With the exception of one of the STPs that lackes post-treatment (São José STP), the other three met the required minimum removals of 60% for BOD5 and 55% for COD. The Carbonita STP promoted the highest average removals of BOD5 and COD, at 90% and 86%, respectively. Despite the discharge of industrial wastewater into the sewage collection network of one of the cities in this study, the biodegradability of the raw sewage remained high (BOD5/COD ratio > 0.4). The wastewater treated by the STPs that have post-treatment showed greater potential for reuse in agricultural practices.