Waterborne parasitic protozoa removal capacities of wastewater treatment plants with varying processes

2022-8-26
Onursal, Aslı
The parasitic protozoa Giardia intestinalis, Entamoeba histolytica, Blastocystis hominis, and Cryptosporidium parvum are causative agents for human giardiasis, amebiasis, blastocytosis (formerly known as hominis infection) and cryptosporidiosis, respectively. These infections are mostly associated with waterborne diseases. Due to the lack of regulations for monitoring these protozoa in the discharge point of wastewater treatment plants (WWTPs), the discharges that reach to surface waters lead to waterborne transmission. This highlights the importance of WWTPs’ removal capacities for improving water safety sanitation and hygiene to minimize the spread of infectious parasitic agents. For this reason, in this study, five different types of WWTPs from Ankara-Turkey including conventional activated sludge (CAS), biological nutrient removal (BNR), sequencing batch reactor (SBR), membrane bioreactor (MBR), and WWTP with coagulation-flocculation and UV disinfection (CoFlUV) units were investigated over a year, seasonally in terms of their parasitic protozoa removal capacities. Seasonal abundances of these protozoa-specific genes in both influents and effluents of each WWTP were determined by quantitative polymerase chain reaction. The reduction of protozoan rDNA copies in the effluent wastewater samples compared to the influent wastewater samples was assessed as removal capacity in log10 reduction values (LRVs). LRVs 1 and 2 were reachable for G. intestinalis in CAS, SBR, CoFlUV and MBR, for B. hominis in CAS, BNR and CoFlUV and for C. parvum and E. histolytica in all types of WWTPs tested. LRVs > 3 were reachable for E. histolytica in CoFlUV and MBR, for B. hominis in CAS, BNR, SBR and MBR and for C. parvum in all types of WWTPs tested. However, for G. intestinalis none of the WWTPs tested were able to reach LRV > 3. Significant seasonal variations were observed in SBR for G. intestinalis, in CAS, SBR, and CoFlUV for E. histolytica, in all types of WWTPs tested for B. hominis, and in CAS for C. parvum (p<0.05). The results elucidated that the removal of protozoa in WWTPs was highly affected by the process used and the discharges of these WWTPs could need further monitoring and surveillance to minimize the potential risk to public health.

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Citation Formats
A. Onursal, “Waterborne parasitic protozoa removal capacities of wastewater treatment plants with varying processes,” M.S. - Master of Science, Middle East Technical University, 2022.