Reclaimed Wastewater: An Idea That Could Soak In

"Managing reclaimed water by pretreating before using it toirrigate, monitoring for viruses, choosing correct crops andperiodically leaching the soils should be successful and safe," saidDr. George Di Giovanni, Texas Agricultural Experiment Stationenvironmental microbiologist.

Di Giovanni and his colleaguesstudied the movement of viruses carried in water through sandy and claysoils on which spinach was planted. They were interested in how longviruses in the water remain in the soil, how they move through the soiland whether they could harm humans or livestock. Their findings havebeen accepted for an article in Agriculture Ecosystems and Environmentjournal.

"No bacteriophage (virus) was found on the spinach leaves, regardless of the type of soil they grew in," Di Giovanni said.

Thetests were done in a greenhouse in soil collected from the region. Twotypes of water were tested – a blend of reclaimed water and filteredwastewater laced with bacteriophage, which is a type of virus thatinfects only bacteria. A bacteriophage is often used in studies as asubstitute for human viruses, Di Giovanni said. The water was drippedunder the soil surface in plastic columns built for the test.

Theresearch found that bacteriophage could be found on the crusty surfacesof both soil types and remained in the clay soil for about a monthafter irrigation ended.

"That suggests that human viruses couldalso linger in the soil," Di Giovanni said. "Reclaimed water must beeffectively treated to remove or kill pathogens before use, regardlessof irrigation method."

Finding such uses for reclaimed water is vital, said Experiment Station wastewater researcher Dr. Naomi Assadian.

"Wastewaterreuse for agriculture and managed landscapes will be necessary to meetgrowing water demands and conserve current drinking supplies in aridregions such as the upper Rio Grande River area," Assadian said. "Butalternative supplies, such as treated municipal wastewater, oftencontain microbial and chemical elements that may affect public healthand/or the environment."

Assadian and Di Giovanni collaborated onthe project with Dr. Jaime Iglesias, Texas Cooperative Extension agentin El Paso County; Dr. Juan Enciso, Experiment Station agricultureengineer in Weslaco; and Dr. William Lindemann, New Mexico StateUniversity agronomist.

The researchers said a "closed system," asin their method of using underground pipes to apply water to the crop,limited exposure to the soil surface and edible parts of the crop, apositive finding as scientists continue to explore how to reuse water.

Whiletheir study showed a feasible use of wastewater, the researchers saidsimilar trials would need to be conducted at each site where such asystem is considered. That's because variations in soil might yielddifferent results, they said.

The study was funded by the Texas Department of Agriculture, U.S. Department of Agriculture and the Experiment Station.