Strategies to minimize the release of endotoxins in effluents from sewage treatment plants



The occurrence of endotoxins in the effluents generated in a full-scale conventional activated sludge (CAS) wastewater treatment plant was studied, with values up to 843 EU mL−1, which might suppose an important threat to the environment and, if water reuse is considered, event to potential consumers. The use of advanced wastewater treatment technologies such as membrane biological reactors (MBRs), which combines biological process and membrane filtration, is a suitable alternative to minimize these biological micropollutants, thus allowing significant reductions in final effluents (lower than 100 EU mL−1 in this work). Different post-treatment alternatives were applied to the secondary effluent of the full-scale CAS plant such as tertiary membrane filtration (TMF), coagulation-flocculation (CF), adsorption with activated carbon and ozonation. Results indicate that CF and TMF are the best options to minimize the presence of endotoxins in the final effluent (>90% and up to 72%, respectively). The use of powdered activated carbon was not so effective (8–30%) even after a prolonged contact time of 24 h. Finally, ozonation appears not to be adequate due to the low removal efficiencies achieved (40% maximum) as well as the potential generation of more endotoxic material, especially at contact times below 30 min. © 2014 American Institute of Chemical Engineers Environ Prog, 34: 432–436, 2015