Effects of spring season solar drying process on sanitation indicators in sewage sludge and potential as a method for fertilizer production

The agricultural use of sewage sludge is possible on condition of maintaining microbiological and parasitological standards, and one of the most modern methods improving its sanitary state is solar drying. In the presented study, the effect of this process on the elimination of indicator microorganisms (Escherichia coli, Salmonella Senftenberg W775, Enterococcus spp.) and eggs of Ascaris suum introduced into the biomass of sludge was examined. The experiment was carried out in the spring period with a maximal temperature of 18 °C inside the drying plant. Bacteria and parasite eggs were introduced into special carriers (cylinders filled with sewage sludge) and placed at selected points of the drier. The carriers were removed every 7 days and subject to a research procedure in order to estimate the number of bacteria and percentage of live eggs of Ascaris suum. Sanitization of the material was not obtained, since after 28 days of the process the final product contained a large concentration of Enterococcus spp. and S. Senftenberg W775 (10(5) -10(9) MPNg(-1)). Only the number of E. coli decreased by 6 log. During the process, the fastest decrease in the number of bacteria was observed in E. coli (ca 0.2 log/day), slower in enterococci (0.02-0.081 log/day), and the slowest in bacilli of the genus Salmonella (0.011-0.061 log/day). Sludge after drying also still contained 57-66% of live eggs of A. suum. The study proved that the solar drying of sludge in the spring period results in a product which poses a hazard for public and animal health and environmental sustainability, and should not be used as a fertilizer.

Enumeration of viable and non-viable larvated Ascaris eggs with quantitative PCR

The goal of this study was to further develop an incubation-quantitative polymerase chain reaction (qPCR) method for quantifying viable Ascaris eggs by characterizing the detection limit and number of template copies per egg, determining the specificity of the method, and testing the method with viable and inactivated larvated eggs. The number of template copies per cell was determined by amplifying DNA from known numbers of eggs at different development stages; the value was estimated to be 32 copies. The specificity of the method was tested against a panel of bacteria, fungi, protozoa and helminths, and no amplification was found with non-target DNA. Finally, fully larvated eggs were inactivated by four different treatments: 254 nm ultraviolet light, 2,000 ppm NH(3)-N at pH 9, moderate heat (48 °C) and high heat (70 °C). Concentrations of treated eggs were measured by direct microscopy and incubation-qPCR. The qPCR signal decreased following all four treatments, and was in general agreement with the decrease in viable eggs determined by microscopy. The incubation-qPCR method for enumerating viable Ascaris eggs is a promising approach that can produce results faster than direct microscopy, and may have benefits for applications such as assessing biosolids.

Inactivation of single-celled Ascaris suum eggs by low-pressure UV radiation

Intact and decorticated single-celled Ascaris suum eggs were exposed to UV radiation from low-pressure, germicidal lamps at fluences (doses) ranging from 0 to 8,000 J/m2 for intact eggs and from 0 to 500 J/m2 for decorticated eggs. With a UV fluence of 500 J/m2, 0.44-+/-0.20-log inactivation (mean+/-95% confidence interval) (63.7%) of intact eggs was observed, while a fluence of 4,000 J/m2 resulted in 2.23-+/-0.49-log inactivation (99.4%). (The maximum quantifiable inactivation was 2.5 log units.) Thus, according to the methods used here, Ascaris eggs are the most UV-resistant water-related pathogen identified to date. For the range of fluences recommended for disinfecting drinking water and wastewater (200 to 2,000 J/m2), from 0- to 1.5-log inactivation can be expected, although at typical fluences (less than 1,000 J/m2), the inactivation may be less than 1 log. When the eggs were decorticated (the outer egg shell layers were removed with sodium hypochlorite, leaving only the lipoprotein ascaroside layer) before exposure to UV, 1.80-+/-0.32-log reduction (98.4%) was achieved with a fluence of 500 J/m2, suggesting that the outer eggshell layers protected A. suum eggs from inactivation by UV radiation. This protection may have been due to UV absorption by proteins in the outer layers of the 3- to 4-microm-thick eggshell. Stirring alone (without UV exposure) also inactivated some of the Ascaris eggs (approximately 20% after 75 min), which complicated determination of the inactivation caused by UV radiation alone.

Effect of Electric Power Network Frequency Magnetic Field on Embryonic Development of Ascaris suum (Nematoda)

Fertilised Ascaris suum eggs were subjected to an alternating electromagnetic field of frequency 50 Hz and density 2 mT for 60 days. The developing embryos in both control and experimental cultures were examined daily under a microscope. The experiment resulted in an accelerated rate of embryogenesis in the eggs incubated in the electromagnetic field, higher rates of malformed embryos as well as much higher mortality rate of L2 larvae.