Occurrence and genotypes of giardia cysts in wastewater in North China

The recycling of treated wastewaters has been recognized as one of the important methods to solve the shortage of fresh water resources at the global level. The importance of microbiological and parasitological criteria for recycled water has been repeatedly emphasized. Among water-borne pathogens, protozoa of the genera Giardia are known to be highly resistant to water treatment procedures and to cause outbreaks through contaminated raw or treated water. An investigation for Giardia spp. cysts in three wastewater treatment plants (WTP) in north China was conducted. The presence of cysts was examined using an immunofluorescence assay with monoclonal antibodies. Giardia cysts were detected in all the influent and effluent samples and at maximum concentrations of 2120.93 cysts pre liter in the influent and at 42.75 in the effluent. The overall removal efficiencies of cysts in the WTP with secondary treatment processes ranged from 1.70-lg to 1.85-lg. The betagiardin and triose phosphate isomerase (TPI) genes were amplified and sequenced. Cysts were typed as assemblage A or B of Giardia lamblia, both of which are human infectious. Many WTP in China discharge effluent into rivers and lakes, thus, risk of contamination of water course by Giardia is considerable.