Investigating helminth eggs and Salmonella sp. in stabilization ponds treating septage

Abstract

Sludge management arises as a relevant problem after being accumulated in primary ponds of septage treatment plants. One of the most attractive options for sludge disposal is its use in agriculture and then specific guidelines regarding hygienic quality must be fulfilled. This study aimed at evaluating the storage time needed to inactivate Ascaris eggs and Salmonella in sludge accumulated in a primary pond treating septage. Raw septage exhibited very low concentrations of viable Ascaris eggs, thus experiments with Ascaris suum eggs spiking were conducted. The concentration of Ascaris eggs in the solids accumulated at the bottom of the pond was 20 eggs/g of total solids (g TS) at the time of pond closure. Although it decreased, some eggs remained viable (0.59 mean viable eggs/g TS) up to 20 months of in-pond storage of the biosolids. Salmonella survival was studied after developing an analytical method that inhibited the native flora. Sludge was seeded with Salmonella enteritidis. An equation adequately describing Salmonella die-off in biosolids subjected to 115 days of in-pond storage/dewatering, was found to be represented by the regression: y = log MPN Salmonella/g TS = 6.67 x t(-0.086), with t = storage time elapsed in days. The initial concentration was 7.0 x 10(6) MPN/g TS and the removal efficiency was 99%.

Use of RNAlater® as a preservation method for parasitic coprology studies in wild-living chimpanzees

“…The fact that we were able to observe nematode eggs, ranging from resistant ( Trichuris eggs, Sanguinetti et al, 2005) to more fragile (strongylid eggs, Waruiru et al, 1998), supports the efficacy of RNA later ® as a preservation method. The observation of Troglodytella was also particularly interesting, demonstrating that it is possible to identify a ciliate trophozoite (which is a more fragile cellular element compared to parasite cysts or thick-walled helminth eggs) in samples stored in RNA later ® .…”

The effect of different percentages of bulking agent (sawdust) on microbial quality of faecal sludge

“…They have high resistance to chemical and physical conditions such as lime, ammonia, temperature, and as such they are the most resistant form of parasites. Studies have revealed that Ascaris eggs can survive under high moisture content in biosolids stored in the environment (Whanton 1979;Stromberg 1997;Sanguinetti et al 2005), but when biosolids are dried, it speeds up the desiccation rate of Ascaris eggs, reducing egg survival (Feachem et al 1983;Gaspard & Schwartzbrod 2003;Cappizzi-Banas et al 2004). Studies have revealed that Ascaris eggs can survive under high moisture content in biosolids stored in the environment (Whanton 1979;Stromberg 1997;Sanguinetti et al 2005), but when biosolids are dried, it speeds up the desiccation rate of Ascaris eggs, reducing egg survival (Feachem et al 1983;Gaspard & Schwartzbrod 2003;Cappizzi-Banas et al 2004).…”

Large area radiation source for water and wastewater treatment

“…The eggs are difficult to inactivate [3] and can survive for long periods of time (e.g. 20 months) in pond treatment [4]. An effective treatment using x-ray irradiation would be highly advantageous for the disinfection of municipal biosolids.…”