Behavior of Metals, Pathogen Parasites, and Indicator Bacteria in Sewage Effluents During Biological Treatment by Activated Sludge

Abstract

The purpose of this study was to evaluate the behavior of metals, pathogen parasites, and indicator bacteria in sewage effluents during biological treatment by activated sludge in a wastewater treatment plant in Ribeirão Preto (WTP-RP), Sao Paulo, Brazil. The evaluation was done during a period of 1 year. Results showed that metal concentrations in treated effluents decreased, reaching concentrations according to those established by national regulations. The activated sludge process at the WTP-RP promoted a partial removal of parasites considered as possible indicators according to the WHO guidelines. Reduction factors varied between 18.2% and 100% for agents such as Endolimax nana, Entamoeba coli, Entamoeba hystolitica, Giardia sp., Ancylostoma sp., Ascaris sp., Fasciola hepatica, and Strongyloides stercoralis. A removal was also observed in total and fecal coliforms quantification. The present study represents an initial evaluation of the chemical and microbiological removal capacity of the WTP-RP. The results should be of interest for the authorities responsible for the environmental health at municipal, regional, national, and international levels.

Occurrence and potential health risk of Cryptosporidium and Giardia in the Three Gorges Reservoir, China

“…Wastewater can be considered as an important habitat in the transmission of parasitic agents, as protozoan cysts or oocysts survive in extreme conditions of water pollution (Tonani et al, 2010). Other researchers provide evidences that (oo)cysts are present throughout the wastewater processes and in endproducts, and only a part of parasites are removed (Robertson et al, 2006;Cheng et al, 2009;Tonani et al, 2010).…”

“…Wastewater can be considered as an important habitat in the transmission of parasitic agents, as protozoan cysts or oocysts survive in extreme conditions of water pollution (Tonani et al, 2010). Other researchers provide evidences that (oo)cysts are present throughout the wastewater processes and in endproducts, and only a part of parasites are removed (Robertson et al, 2006;Cheng et al, 2009;Tonani et al, 2010). In this study, Cryptosporidium and especially Giardia numbers were much higher in backwater areas of cities, and were highest in outlet water of WWTPs with low concentration of fecal indicators, suggesting that sewage of cities and treated effluent of WWTPs may also have been major sources of these parasites in the TGR, and can enter the aquatic environment with consequent negative implications for public health.…”

Entamoeba histolytica

“…A lower rate of E. histolytica/dispar/moshkovskii removal was reported 0.37 log 10 in Tonani et al (2011) one year work at a WWTP in Sao Paulo, in Brazil. In Iran, Yousefi and Hezarjaribi (2013) found that activated sludge, in a hospital WWTP, coupled with extended aeration presented the lowest rate of E. histolytica/dispar/moshkovskii cysts removal.…”

Waterborne Giardia and Cryptosporidium: contamination of human drinking water by sewage and cattle feces

“…About 2 million tons of sanitary sewage and other effluents are released daily into water resources (UN WWAP, 2010). The biological treatment process, widely used in the world as well as in Brazil, removes most microfauna along with the organic material; however, some pathogens persist in the treated effluent (CAIN et al, 2010;TONANI et al, 2011). In addition to sanitary sewage, agricultural activities such as intensive animal breeding may interfere with the water quality of springs (ROCHA et al, 2006).…”