Yet, it is important to know the occurrence and concentration of specific contaminants in order to assess the health risk of water reuse. There exist various waterborne diseases, which can be transferred to people through a fecal to oral route of infection from human to human or animal to human if the water is not properly treated. The microorganisms associated with waterborne diseases are primarily intestinal pathogens such as protozoa, bacteria, and viruses. Unknown or emerging waterborne pathogens pose the greatest risk to humans, because of the difficulty in regulating and treating unknown diseases. Therefore, any city that is considering a potable reuse project needs to estimate the increased risk from microbial and chemical contaminants compared to natural water sources.
Pretreatment procedures can decrease the risk of health effects from the reclaimed water.
For example, effective source control of pollutants via pollution prevention and industrial pretreatment of waste is a beneficial procedure. The most effective method of health risk prevention is through the treatment process of wastewater reclamation. From 1941 to 1980, 41.7 percent of drinking water disease outbreaks were due to inadequate or interrupted water treatment, which illustrates the importance of an effective water treatment process. Multiple barriers are a form of wastewater treatment, which have been beneficial to the decrease in water contaminants. In the multiple barrier method contaminants are first filtered out of wastewater as the water passes through membranes with tiny holes.