Assessment of Cryptosporidium and norovirus risk associated with de facto wastewater reuse in Trinity River, Texas

Abstract

De facto reuse refers to the use of surface water that contains a considerable portion of wastewater effluent from upstream communities as a source water for drinking water supplies. In contrast to the highly regulated domestic wastewater reuse practices in the U.S., not much is known regarding the human health risk associated with de facto reuse. Trinity River, Texas, a wastewater dominated river that is used as the main source of drinking water for Houston, is used as an exemplar to quantify the health risk associated with exposure to Cryptosporidium and norovirus through drinking water contaminated with wastewater effluents. The results show that the annual infection risks exceed the U.S. EPA recommended annual safe drinking water health risk of 10-4 per person per year (pppy) for all scenarios considered. However, a comparison of the corresponding disease burdens with the World Health Organization's annual disease burden for safe drinking water of 10-6 DALYs pppy indicates the disease burdens are mostly within the acceptable range of the guideline. This difference in risk interpretations reflects the difference in the fundamental definition of the two risk benchmarks as well as the gaps in data and risk models (including the conversion from infection to illness risk and expected DALY per infection). The results also imply that the current safe drinking water regulatory framework should be reexamined to best achieve the goal of human health protection. The outcomes of this study provide an overall picture of the potential risk associated with de facto reuse, which contributes to a better understanding of the practice and decisions in wastewater reuse in the U.S. and the rest of the world.

Drivers of Microbial Risk for Direct Potable Reuse and de Facto Reuse Treatment Schemes: The Impacts of Source Water Quality and Blending

“…The authors similarly noted annual risks below 10 −4 for varying treatment trains and that the use of DPR can provide public health benefits when blended with conventionally treated waters. Results from a QMRA by Lim et al [ 15 ] of de facto reuse in Trinity River, Texas also indicated that de facto risks exceeded traditional benchmarks, with the caveat that disease burdens may be within allowable limits using World Health Organization Disability Adjusted Life Year (DALY) benchmarks.…”

“…Although currently no national regulations for direct potable reuse exist in the United States, microbial quality targets for IPR in California and DPR in Texas use a goal of 1 infection per 10,000 people per year as a risk benchmark to inform the 12–10–10 pathogen log-reduction values for enteric viruses, Cryptospordium , and Giardia , respectively [ 10 , 11 , 12 , 13 ]. Previous work has modelled the microbiological health risks of various water reuse treatment trains [ 12 , 14 ] as well as de facto reuse [ 15 ]. However, the microbiological impact of blending highly-treated reclaimed water produced from DPR with conventionally treated effluent impacted surface water (de facto reuse) has not been explored.…”

A dynamic transport model for quantification of norovirus internalization in lettuce from irrigation water and associated health risk

“…The initial viral concentration ( C eff ) in the irrigation water was drawn from an empirical distribution reported previously by Lim et al (2016) for NoV in activated sludge treated secondary effluent. As justified by Lim et al (2016) , the sum of the concentrations of two genotypes known to cause illness was used to construct the distribution. The NoV concentrations in lettuce shoot were estimated at typical harvest times: t ht, h = 35 days in the hydroponic system and t ht, s = 70 days in soil.…”

The occurrence and control of waterborne viruses in drinking water treatment: A review

“…As is shown in Table S1 , human adenovirus (HAdV) was reported to exhibit high resistance to different tertiary and advanced treatments at wastewater reclamation plants ( Prado et al, 2019 ). At a de facto reuse situation, in which raw water contains a high fraction of wastewater effluent from upstream communities, infection risk of viruses (e.g., Norovirus (NV)) may violate local drinking water benchmarks ( Lim et al, 2017 ). When the water body serves as both receiving water of the waste water treatment plant and source water of DWTP, free chlorine disinfection in DWTP plays an important role in providing sufficient removal of viruses ( Sokolova et al, 2015 ).…”