Effect of volatile fatty acids in anaerobic conditions on viability of helminth ova (Ascaris suum) in sanitization of municipal sludge

Abstract

The present work aimed at evaluating the effect of four different mixtures of diverse volatile fatty acids (VFAs) on the viability of helminth ova (Ascaris suum), under mesophilic (35°C) anaerobic conditions and at different incubation times, in order to reproduce the process of two-phase anaerobic digestion. The mixtures of VFAs contained acetic, propionic, butyric, valeric, and isovaleric acids, used at concentrations normally found in acidogenic anaerobic digesters. The four treatments all showed a reduction in Ascaris suum ova viability, among which Treatment III (4.2 g-acetic acid L + 2.2 g-propionic acid L + 0.6 g-valeric acid L + 0.6 g-isovaleric acid L) resulted the most efficient. We found that the full effect of VFAs on the viability loss of Ascaris suum ova in mesophilic conditions requires a minimum incubation time of 3 days. The highest efficiency in the loss of viability was observed with Treatment III and 4-day incubation. Interestingly, the proportion of acetic acid was three times as much in this treatment than in the other ones and resulted in an effect in a minimum time of 3 days. The mesophilic condition, however, was not sufficient to induce a complete loss of viability.

Inactivation of Ascaris Eggs in Human Fecal Material Through In Situ Production of Carboxylic Acids

“…Previous studies have shown that carboxylic acids inhibit growth of many bacteria, − and recent work has also investigated their toxicity to Ascaris eggs. − In HFM, Ascaris lumbricoides eggs are considered the most-resistant pathogens to waste treatment processes due to the hydrophobicity of the innermost lipid layer of the egg. − At a pH below the p K a (∼4.8), carboxylic acids exist primarily in the uncharged acid form, which is more hydrophobic than the corresponding conjugate base and able to cross the lipid layer. Butkus et al exposed Ascaris eggs to solutions of carboxylic acids for 20 h at 37 °C at different pH values and concluded that carboxylic acids were more effective when the pH was below the p K a of the acid and that carboxylic acids with longer carbon chains are more effective, likely due to the increased hydrophobicity of the chain .…”

Changes in the viability of the eggs of Ascaris suum under the influence of flavourings and source materials approved for use in and on foods

“…The work of Rojas-Oropeza et al (2016) covers the study of the influence of volatile fatty acids (VFA) of four different compounds on the viability of eggs of A. suum. The compounds included acetic, propionic, butyric, valeric, and isovaleric acids.…”

Pathogen and Indicator Organism Inactivation and Quantification for Low-Cost Low-Tech Biosolids Treatment

“…VFAs are naturally present in biosolids and may play an important role in pathogen inactivation. In particular, VFAs appear to be significant in the inactivation of Ascaris ova [38][39][40] and enteric bacteria [41][42][43]. However, it is also well documented that bacteria that infects the human gut are relatively tolerant against high concentrations of VFAs [44][45][46][47][48][49].…”