Urban wastewater treatment in stabilization ponds: occurrence and removal of pathogens

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

“…In fact, the study of these parasites is interesting not only due to its pathogenesis but also because of their persistence in the majority of processes used in sewage treatment [19]. The removal of helminths occurs in the activated sludge system by means of enmeshment into the biofloc during secondary settling (sedimentation of helminthes) [19][20][21]. During the biological wastewater treatment, pathogenic protozoa can be considered predators in that ecosystem.…”

“…They are removed through attachment to activated sludge flocs and subsequent settling [1]. According to Amahmid et al [20] and Stott et al [22], the most effective treatment for the removal of parasites is the stabilization pond process with a high detention time. As commented above, the hydraulic detention time at BWTP-RP is 6 to 8 h for sewage.…”

Possible scenarios of environmental transport, occurrence and fate of helminth eggs in light weight aggregate wastewater treatment systems

“…Although one of the main disadvantages of anaerobic treatment is the low removal rate of pathogens, it excludes helminth eggs that can be effectively captured in the sludge (Seghezzo et al 1998). This phenomenon may be attributed to the fact that nematode eggs, and in general all helminth eggs, are bigger and heavier than some protozoan cysts and oocysts (Ben Ayed et al 2009;Watson et al 1983) and thus settle out more effectively because of their sedimentation speed: Ascaris eggs were estimated to settle at 65 cm/h compared to 1 cm/h for protozoa such as Giardia cysts (Amahmid et al 2002;references therein). WHO (2006) recent guidelines on the reuse of wastewater, excreta and greywater cite a reduction of 90% for helminth eggs in full scale primary sedimentation units.…”

“…This process is unquestionably the main removal path of helminth eggs (Amahmid et al 2002;Gaspard and Schwartzbrod 2003;Katsenovich et al 2008;Liberti et al 2002;Mandi et al 1996;Maynard et al 1999;Molleda et al 2008). During sedimentation, the eggs are removed from the liquid phase of wastewater to the settled solids that are digested to sludge.…”

Hybrid Nanostructure-based Immunosensing for Electrochemical Assay of Escherichia coli as Indicator Bacteria Relevant to the Recycling of Urban Sludge

“…Furthermore, some of these pathogens are known to survive for several months in the environment. In order to reduce the risk of spreading pathogens and protect the public health, monitoring of pathogens is essential for the routine sludge assessment prior to its recycling [6,7]. Nowadays, the main criterion for evaluating the levels of pathogens in urban sludge is the density of Escherichia coli (E. coli) as indicator bacteria, and the presence of E. coli suggests that pathogenic microorganisms (e.g., pathogenic bacteria, viruses and parasites) might also be present [8].…”