Discharges of Wastewater Treatment Plants Needed Further Monitoring to Minimize Potential Risk of Entamoeba and Blastocystis for Public Health

Abstract

The protozoan parasites Entamoeba histolytica and Blastocystis hominis are responsible for causing human amebiasis and hominis infections, respectively. These infections are highly prevalent and are often linked to waterborne diseases. Due to the absence of regulations for monitoring these protozoa at the discharge points of wastewater treatment plants (WWTPs), the effluents reaching surface waters contribute to waterborne transmission. This underscores the significance of the removal capacities of WWTPs in reducing the spread of these infectious parasites. Therefore, this study examined five different types of WWTPs in Ankara, Turkey, over a year to assess their capacities to remove E. histolytica and B. hominis. The seasonal abundances of genes specific to these protozoa in both the influents and effluents of each WWTP were measured using a quantitative polymerase chain reaction. The reduction in the number of protozoan rDNA copies between the influent and effluent samples was evaluated as the removal capacity, expressed in log10 reduction (LRV) values. The results elucidated that the removal of E. histolytica and B. hominis was highly affected by the process used. Membrane bioreactor systems displayed the highest removal capacity with LRV > 3. Therefore, discharges of WWTPs with other processes could need further monitoring to minimize the potential risk for public health.