Human health trade-offs in the disinfection of wastewater for landscape irrigation: microplasma ozonation vs. chlorination

Abstract

Wastewater reuse is becoming increasingly common, and there is a need for decentralized and small-scale systems to support the safe recovery of water resources. In this study, an integrated life cycle assessment (LCA) and quantitative microbial risk assessment (QMRA) were used to compare microplasma ozonation (an emerging technology) to chlorination (an established technology) for the disinfection of wastewater for landscape irrigational reuse. Three waterborne pathogens, Legionella pneumophila, Giardia, and Cryptosporidium parvum, were selected to include bacteria and protozoans covering the transmission routes of inhalation and ingestion. Inactivation data from the literature were coupled with bench-scale experiments (to establish inactivation parameters for L. pneumophila by ozone in wastewater) for the design and simulation of disinfection processes. Microplasma-based ozonation reduced more life cycle human health impacts as compared to chlorination for five of the six impact categories, because of the high susceptibility of the pathogens to ozone and the lower impacts stemming from electricity (required in ozonation) vs. chemical production (required in chlorination). These results were consistent across the electricity-fuel mixes of all fifty U.S. states. These results indicate that from the point of view of reducing human health impact, the emerging microplasma ozonation technology is superior to chlorination for wastewater reuse disinfection. To reduce the overall human health impact, future design efforts should focus on reducing process consumables (i.e., chemical and electricity consumption) through longer hydraulic residence times (HRTs), while maintaining adequate disinfectant dosing to provide reliable disinfection efficacy despite influent variability in compounds that may quench or interfere with the disinfectant.