TABLE OF CONTENTS The pathogens of concern in land treatment systems are parasites, bacteria, and virus. The pathways, or vectors, of concern are to groundwater, contamination of crops, translocation or ingestion by grazing animals, and off-site transmission via aerosols or runoff. The removal of pathogens in land treatment systems is accomplished by adsorption, desiccation, radiation, filtration, predation, and exposure to other adverse conditions. The SR process is the most effective, removing about five logs (10 5) of fecal coliforms within a depth of a few feet. The RI process typically can remove two to three logs of fecal coliforms within several feet of travel, and the OF process can remove about 90 percent of the applied fecal coliforms.36
Parasites may be present in all municipal wastewaters. Ascaris, Entamoeba histolytica, helminths, and other parasitic types have been recovered from wastewaters and biosolids. Under optimum conditions the eggs of these parasites, particularly Ascaris, can survive for many years in the soil. Because of their weight, parasite cysts and eggs will settle out in preliminary treatment or in storage ponds, so most will be found in sludges and biosolids.
There is no evidence available indicating transmission of parasitic disease from application of wastewater in properly operated land treatment systems. Transmission of parasites via sprinkler aerosols should not be a problem owing to the weight of the cysts and eggs. Schistosomiasis, which is a very serious parasitic problem in many parts of the world due to direct contact by humans with...
