Viability of nematode eggs in high rate algal ponds: the effect of physico-chemical conditions

Abstract

The viability of Parascaris equorum eggs was studied in two experimental pilot-scale high-rate algal ponds (HRAPs) working in parallel with 4 and 10 days hydraulic retention time respectively. Semi-permeable bags of cellulose (15000 daltons pore size) were used to study the effect of physico-chemical conditions on the survival of these helminth eggs. Three thousand eggs were used in each bag. Replicates of these bags were submerged for 4 and 10 days in the HRAPs and egg viability was compared with that in control bags submerged in sterile water. After 4 days exposure, 60% reduction in viability was achieved, reaching 90% after 10 days, much higher than the 16% and 25% found in the control bags for 4 and 10 days respectively. Ionic conditions of the HRAP may have been responsible for up to 50–60% of the egg mortality, suggesting that mortality due to the ionic environment could be more important than physical retention and other potential removal factors.

Effect of Hydraulic Retention Time (HRT) on Surveillance of Coliforms in Waste Stabilization Pond (WSP) System in Central India

“…The WSP system removes the coliforms (total and fecal) with an efficiency of >90% (Table 3 and 4) which are par with the range previously reported for WSPs for treatment of domestic wastewater [24][25]. The low surveillance of coliforms in facultative and maturation cells seems to be due adsorption onto settleable solids, further sedimentation [26] and solar irradiation [27][28] are thought to be the main bacterial removal mechanisms in this cells, with lower depth, although other factors as predation by antagonistic organisms [29], physicochemical conditions [30][31] and toxins excreted by certain algae [32] could also affect the removal of microorganisms. Variability in concentration of coliforms were observed in the WSP system, may be due to seasonal and climatic conditions as seen in data observed for different seasons, as well as differences in the prevalence of infection and fecal excretion levels.…”

Waste Stabilization Ponds

“…to 2 f,g~0 to 1 f,g 2.2 (1.9 to 2.4) a Sources: (Al-Salem and Lumbers, 1987;Anceno et al, 2007;Araki et al, 2001Araki et al, , 2000Ayres et al, 1993;Bausum et al, 1983;Bouhoum et al, 2000;Da Silva et al, 2011;De Oliveira et al, 2011;Dixo et al, 1995;García et al, 2008;Grimason et al, 1996aGrimason et al, , 1996bHachich et al, 2013;Hassani et al, 1992;Hewitt et al, 2011;Joshi et al, 1973;Konaté et al, 2013aKonaté et al, , 2013bMara and Silva, 1986;Nupen, 1970;Oakley, 2004;Oragui et al, 1995Oragui et al, , 1987Ouazzani et al, 1995;Rao et al, 1981;Pescod, 1992, 1991;Schwartzbrod et al, 1989Schwartzbrod et al, , 1987Stott et al, 2003;von Sperling and Mascarenhas, 2005;von Sperling et al, , 2003von Sperling et al, , 2002Young et al, 2016). Typical log 10 removals are arithmetic mean values of the log 10 removals reported in the literature; typical ranges are +/-one standard deviation of the mean.…”

Effect of High-Rate Algal Ponds on Viability of Cryptosporidium parvum Oocysts

“…Algae supply the oxygen demand for bacterial degradation of organic matter, and bacteria excrete mineral compounds that provide the algae with nutrition. HRAPs have proved effective in removing organic matter (13) and in reducing bacterial contamination (8) and the number of nematode eggs (1), but no data are available on their role in removing Cryptosporidium oocysts, a subject of special interest when dealing with rural wastewater. We will focus this study on the effect of the HRAP physicochemical conditions on the viability of Cryptosporidium oocysts as measured with a neonatal mouse infectivity model.…”