Spraying for Safety

Reclaimed water is becoming a popular solution to urban water scarcity. It's used for things like landscape fountains, urban greening, agricultural irrigation, and road cleaning. But when water is sprayed into the air, it can create aerosols that carry pathogens. These pathogens can pose health risks to people nearby.

Researchers developed a new framework to assess the risks of infection from these aerosols. They focused on scenarios with multiple nozzles spraying water. The team used a discrete phase model to simulate how aerosols travel and spread in the air. They chose Pseudomonas aeruginosa and Coxsackievirus as examples of bacteria and viruses that could be present in the aerosols.

By combining computer simulations with quantitative microbial risk assessment, the researchers were able to measure the risks of infection from inhaling these aerosols. They looked at how different wind speeds affected the spread of aerosols and the risks of infection.

The study found that the concentration of aerosols and the risks of infection dropped sharply within 10 meters of the spray source. But higher wind speeds carried the aerosols further downwind, increasing the exposure range. The researchers also identified the concentration of pathogens in the reclaimed water as the most important factor in determining infection risks.

Exposure frequency and duration were also important factors. Based on US Environmental Protection Agency guidelines, the researchers recommended safe distances of more than 8 meters upwind and more than 10 meters downwind of the spray source. This study provides a scientific basis for designing and managing reclaimed water spray systems that minimize health risks.