Efficiency of Sligo secondary wastewater treatment plants in the removal of Crytospiridium and other human-virulent enteropathogens

Abstract

Most research on wastewater treatment efficiency compliance focuses on physiochemical and microbial indicators; however, very little emphasis has been placed so far on removal efficiencies of human-virulent enteropathogens and on determining suitable indicator organisms to predict the discharge level of human enteropathogens from municipal wastewater treatment plants to the local environment. This project studies the occurrence of human enteropathogens, including Cryptosporidium parvum, Cryptosporidium hominis, Giardia duodenalis, Enterocytozoon bieneusi, Encephalitozoon intestinalis, Encephalitozoon hellem, genogroup I and II noroviruses, Enterococcus faecalis and Enterococcus faecium in domestic wastewater. To investigate the capability of Sligo secondary wastewater treatment plants, (1) raw wastewater, (2) secondary sewage sludge, (3) final effluent and (4) biosolids/ final sewage sludge from four WWTPs (A-D) were investigated in the removal of human enteropathogens, over one year, using a combination of IFA, FISH and RNA-polymerase based PCR methodologies. This project also looks into the relationship between faecal indicator bacteria (E. coli, enterococci and C. perfringens spores) and human enteropathogens and the potential use for pathogen prediction, especially Cryptosporidium. The results provide evidence that human-virulent enteropathogens are present throughout the wastewater processes and in end products, and can enter the aquatic environment with consequently negative implications for public health. This study also provides important scientific evidence that municipal wastewater treatment plants not only achieve pathogen removal but can also be the environmental pathogen contamination source. This research also shows that seasonal variation in concentration of human-virulent enteropathogens is highest in Spring and Summer during the calving and lambing seasons, and when tourism peaks. A suite of faecal indicator bacteria (E. coli, enterococci and C. perfringens spores) can be used as indicators for the presence of Cryptosporidium oocysts and Giardia cysts. Routine monitoring of faecal indicators in final effluents and biosolids is recommended.