Prevalence and fate of giardia cysts in wastewater treatment plants

Abstract

Summary The present study was conducted to review factors affecting the prevalence and concentration of Giardia in raw wastewater. The removal and inactivation efficiency of Giardia by wastewater treatment technologies was also reviewed. Data published for the prevalence of Giardia in wastewater and the removal by wastewater treatment plants was reviewed. Giardia cysts are highly prevalent in wastewater in various parts of the world, which may reflect the infection rate in the population. In 23 of 30 (76·6%) studies, all of the tested raw wastewater samples were positive for Giardia cysts at concentrations ranging from 0·23 to 100 000 cysts l−1. The concentration of Giardia in raw wastewater was not affected by the geographical region or the socio‐economic status of the community. Discharge of raw wastewater or the application of raw wastewater for irrigation may result in Giardia transmission. Activated sludge treatment resulted in a one to two orders of magnitude reduction in Giardia, whereas a stabilization pond with a high retention time removed up to 100% of the cysts from wastewater. High‐rate sand filtration, ultrafiltration and UV disinfection were reported as the most efficient wastewater treatment methods for removal and disinfection of Giardia cysts. Wastewater treatment may not totally prevent the environmental transmission of Giardia cysts. The reviewed data show that a combination of wastewater treatment methods may results in efficient removal of Giardia cysts and prevent their environmental transmission.

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“…Estão entre as principais causas de doenças diarreicas em seres humanos em todo o mundo e são considerados para a Saúde Pública, os mais importantes protozoários patogênicos veiculados pela água, devido à elevada resistência à maioria dos processos convencionais para o tratamento de água potável, resistência ao cloro e a alta infectividade (Putignani e Menichella, 2010;WHO, 2011;Fregonesi et al, 2012). Esses protozoários potencialmente patogênicos também são resistentes à maioria dos processos empregados para o tratamento de esgoto doméstico (Nasser et al, 2012;Nasser, 2016). As formas infectantes destes patógenos estão presentes nas fezes dos hospedeiros infectados, que compõem o esgoto bruto que chega às ETE (Estação de Tratamento de Esgoto), tornando o esgoto doméstico, uma das principais fontes de contaminação dos mananciais (Nasser et al, 2012;Nasser, 2016).…”

“…Esses protozoários potencialmente patogênicos também são resistentes à maioria dos processos empregados para o tratamento de esgoto doméstico (Nasser et al, 2012;Nasser, 2016). As formas infectantes destes patógenos estão presentes nas fezes dos hospedeiros infectados, que compõem o esgoto bruto que chega às ETE (Estação de Tratamento de Esgoto), tornando o esgoto doméstico, uma das principais fontes de contaminação dos mananciais (Nasser et al, 2012;Nasser, 2016).…”

Risk assessment of Giardia from a full scale MBR sewage treatment plant caused by membrane integrity failure

“…Nasser et al (2012) reported that in 23 out of 30 studies, all tested raw wastewater samples were positive for Giardia, at concentrations ranging from 2.3 to 1,000,000 cysts/10 L, showing that Giardia pollution is quite universal and requires effective control to secure the biological safety of reclaimed water. Giardia concentrations in raw wastewater and primary, secondary and tertiary treatment effluents were 1300-36,000, 5330-20,330, 0-320 and 0-21 cysts/10 L, respectively, in three municipal wastewater treatment plants in Beijing, China (Fu et al, 2010).…”

“…Giardia sp. has been detected in sewage (Gassman and Schwartzbrod, 1991;Nasser et al, 2012) as well as in tertiary treatment effluents after chlorination and chloramination (Nasser et al, 2012;Quintero-Betancourt et al, 2003;Ryu et al, 2007).…”

“…Both UV and ozonation are efficient in parasite disinfection (Nasser et al, 2012;Linden et al, 2002;Widmer et al, 2009). On the other hand, physical disinfection using membrane filtration has recently been a focus because theoretically it could intercept almost all of the particles larger than its pore size, including pathogenic microbes (Lonigro et al, 2006).…”