Recent Study Finds Protozoa Survive Wastewater Treatment Process

Following a study conducted by the Water Chemistry and Microbiology group from the Technical University of Valencia, it was discovered that pathogenic protozoa Cryptosporidium and Giardia remained present in the sludge produced by the wastewater treatment process, which poses the potential for negative health effects on the public.

“Treated WWTP sludge is typically used in farming as a fertilizer and a soil quality contributor,” said Inmaculada Amoros, one of the authors of the study. “So it is paramount to understand the wide range of pathogenic microorganisms that are found in sewer sludge as it affects public health.”

In total, the study analyzed 60 samples, 30 of raw sludge and 30 samples which had undergone treatment. The results showed that the protozoa remained in 26 of the 30 raw sludge samples and in 25 of the 30 treated samples. The five treated samples that did not demonstrate any remains of the protozoa were sourced from a compositing plant rather than a traditional wastewater treatment facility, suggesting potential alternative to effectively eradicate sludge of Cryptosporidium and Giardia.

“An evaluation of risks associated with elimination or the use of biosolids and the appropriate regulations are necessary from a public health standpoint,” Amoros said. “More research is needed to establish whether treatment options could turn sewer sludge into pathogen-free biosolids.”

The subject protozoa can cause gastrointestinal illness in both humans and animals. The use of sludge in farming has increased in recent years due to financial concerns, but this has raised the likelihood of contamination in soil and crops.