Project Title: Efficiency of Sligo Secondary Sewage Treatment Systems in the Removal of   Cryptosporidium and other Human Enteric Pathogens 

Student Name: Ms. Hui-Wen (Angel) Cheng

Supervisors: Dr. Frances Lucy and Dr. Michael Broaders 

Funding Body: 2005-2006: National Science Association, Taiwan, 2007-2011: STRIVE Programme, Irish Environmental Protection Agency, 2009-2010: Research and Education Foundation, Sligo General Hospital

Abstract:

The aims of the study are (1) to routinely investigate the fate of human-virulent pathogens, i.e., Cryptosporidium parvum, C. hominis, Giardia duodenalis, Encephalitozoon hellem, E. intestinalis and Enterocytozoon bieneusi and some microbial indicators (i.e., E. coli, Enterococci, and Cl. perfringens), (2) to establish an assay for Norovirus detection in concentrated wastewater and resulting sludge, and (3) identification and differentiation of immunofluorescent stained Cryptosporidium oocysts, Giardia cysts and microsporidian spores. Wastewater samples (raw sewage, secondary activated sludge, and final effluents) and resulting biosolids were collected monthly.

A significant correlation between the removal of oocysts and cysts was found at Plants A, B, and D in processed samples. For microsporidia, E. bieneusi was the predominant species at all four plants, with the highest concentration at Plant A, followed by Plant C. Among the four plants, Plant A had the highest concentration of all microsporidian spores (up to 1,014 spores/L), including 240 and 277 spores/L for E. hellem and E. intestinalis, respectively. Dewatered biosolids contained high concentration of (oo)cysts and spores at all plants and Plant D, which is resulted in primary sludge,  had the highest abundance. Plant C contained the lowest pathogen loadings. For microbial indicators, over 98% removal efficacy was achieved at all plants but for Cl. perfringens, the rate varied between 24% and 100%.

The occurrence of Cryptosporidium oocysts and other human-virulent pathogens in the wastewaters indicated that cryptosporidiosis and giardiasis are present in the investigated population. The effluent and biosolids contain viable pathogens, with subsequently risks of cryptosporidiosis and giardiasis for public health. Norovirus Genotype I and II were observed in the raw sewage samples collected in March, April, July (2008), and Jan (2009). For GI, detectable viral nucleic acid was still found in the treated effluent, except in July. For GII, no detectable viral nucleic acid was observed in the effluents (except in March and Jan 2009). This EPA-funded project will be conducted until the end of year of 2011.

Publications/Conferences attended:

1.      Peer-reviewed publications

2.      Conference attended

EPA doctoral and fellowship seminar

 (a): Oral presentations at Conferences/Workshops to date

 (b): Poster presentations at Conferences/Workshops to date