Impact of silver nanoparticles on wastewater treatment in the SBR

The commonly application of nanoparticles (NPs) in commercial and industrial products inevitably increases their release into the natural environment which poses a threat to human health and ecosystems. A recent study of nanoparticles in wastewater treatment showed that most NPs are retained in the equipment used for biological wastewater treatment. The aim of the study was to determine the effects of silver nanoparticles (Ag NPs) on wastewater treatment in the SBR bioreactor. The effluent from the SBRs was analyzed for total organic carbon (TOC), suspended solids (SS), pH and total silver. Microbial observations of activated sludge were made and, on this basis, the Madonia biotic index was specified. After nanoparticles were added, the composition of microorganism communities of the activated sludge changed, and the largest community was the one of creeping ciliates. The efficiency of the effluent treatment measured by the concentration of TOC removal showed that Ag NPs were found to have remarkable effects on TOC removal in the SBR. The obtained results showed that purified wastewater included a low concentration of Ag nanoparticles. The main removal pathway of Ag NPs was via sorption as well as possible aggregation and sedimentation onto the sludge.