Human health risks of untreated groundwater third pipe supplies for non-potable domestic applications

Abstract

A quantitative microbial risk assessment (QMRA) was undertaken to determine the potential human health risks associated with use of untreated groundwater from a superficial aquifer in a new residential urban development. In situ pathogen survival experiments determined the attenuation rates of selected pathogens. Cryptosporidium oocysts, Giardia cysts, E. coli, Campylobacter jejuni, and MS2 bacteriophage had 1 log10 (90%) reduction times (T90) ranging from 2 to 42 days. Adenovirus displayed distinctly non-linear broken stick decay rates with an initial T90 of 5 days to day 14, after which the T90 declined to ∼100 days. The QMRA suggested that aquifer attachment was the dominant form of pathogen removal followed by natural attenuation. The QMRA results showed that under the exposure scenarios tested the mean human health risks were all acceptable with calculated Disability Adjusted Life Years (DALYs < 1 × 10− 6/person/year).