Determination of Cryptosporidium and Giardia Occurance, Infectivity, and Genotyping in Wastewater Effluents
Year Released: 2012
Type: Scientific Investigation
Funding Partner: Bureau of Reclamation
Total Investment: $686,552 (Cash: $393,000, In-Kind: $293,552)
Principal Investigators: Zia Bukhari, PhD and Mark LeChevallier, PhD, American Water; Giovanni Widmer, PhD. Tufts University School of Veterinary Medicine; Udi Zuckerman, PhD. Mekerot Water
Treatment of drinking water was once considered adequate for reducing the risk of infection from pathogenic organisms. However, the increased need for wastewater reuse has focused attention on the potential of wastewater treatment processes for reducing the numbers of pathogenic organisms to acceptable levels.
Goals and Objectives
The project accrued information to better understand the occurrence of Cryptosporidium in reuse effluents from plants employing various upstream treatment processes (secondary clarification, cloth filtration, sand filtration, and MBRs). This information would be pertinent to development of future risk assessment models for human cryptosporidiosis that could arise from exposure to reuse effluents.
To ensure that these data would facilitate development of robust risk assessment models, key parameters for inclusion in the model needed to be organism concentration, infectivity, and species.
Findings and Conclusions
Using standardized methods and molecular tools, this study indicates that species of Cryptosporidium and Giardia of significance to human health can readily pass through wastewater treatment processes. A clear association between the level of treatment and the occurrence of these protozoa in the effluents was noted. Although secondary clarification processes yielded frequent positives at higher concentrations, even advanced treatment processes allowed pass-through of these protozoa. There is no doubt that physical barriers such as MBR, with their submicrometer pore size, have the potential to prevent these relatively large (5–20 µm) parasites from passing through into the effluent; however, this can only be successful if the membrane integrity is guaranteed.
As the need for reuse water continues to increase, risk mitigation strategies will need to be geared to adopting a multibarrier approach incorporating regular operational maintenance, continuous monitoring, adoption of best management practices to protect water quality during storage, and distribution and employment of UV disinfection with or without chemical disinfection.