[Survival of Salmonella typhimurium in the solid fraction from a farm waste water treatment plant]. / Prezívanie Salmonella typhimurium v pevnej frakcii z pol'nohospodárskej cistiarne odpadových vôd.

Survival of Salmonella typhimurium pathogens was followed in the slurry solid fraction from a pig farm waste water treatment plant. The tested S. typhimurium pathogens have survived for 117 days. The solid fraction was kept in the laboratory at 20-23 degrees C. Indicatory microorganisms at the beginning of the experiment numbered 10(8)-10(9) CFU in 1 ml sample. This number decreased by 4-5 series throughout the experiment, except for faecal coliform bacteria, which were not detected after 43 days of cultivation. Enterobacteria showed a decreasing tendency until day 83, however, on the final sampling (day 117) their count was almost double. Of physico-chemical parameters, pH showed the most striking variations. Its initial value of 6.9 increased to 8.1 at day 30, then decreased to 7.2 at day 43, and increased to 7.7 at the end of the experiment. Ammoniacal nitrogen in solid fraction was almost twice as high as the initial level. Other physico-chemical parameters were not changed significantly throughout the experiment. On the results of this experiment, decimal reduction times T90 were determined for indicatory microorganisms during the storage of solid fraction under constant conditions: psychrophilic bacteria 31.25; mesophilic bacteria 38.12; coliform bacteria 27.49; faecal streptococci 24.57 and enterobacteria 30.46 days. These data suggest a relatively long time of survival for indicatory microorganisms in the solid fraction from agricultural waste water treatment plants.

[Use of hydrated lime for disinfection of sewage sludge containing Salmonella typhimurium and Ascaris suum as model pathogens]. / Vyuzitie vápenného hydrátu na dezinfekciu modelových patogénov Salmonella typhimurium a Ascaris suum v cistiarenských kaloch.

Hydrated lime was lethal to the strain of Salmonella typhimurium (Sk 14/39) after 60 min of exposure. In the control without addition of hydrated lime this strain was still viable after 168 hours, counting 6.1 x 10(5) pathogens/l ml sludge. 168-hr disinfection of primary sludges with 10 g/l hydrated lime showed no significant reduction in the viability of Ascaris suum eggs. In three experiments, the number of viable eggs was reduced only by 3.6%. Indicator microorganisms, except psychrophilic ones that survive for only 24 hr, were destroyed after 60 min of exposure. The temperature of stabilized sludges did not vary considerably during experiments, ranging between 21 and 25 degrees C. With the addition of Ca(OH)2, sludge pH increased to the values for COD, organic matters and total nitrogen were reduced throughout the experiments. The values for sludge dry residues remained unchanged.

Survival of model bacterial strains and helminth eggs in the course of mesophilic anaerobic digestion of pig slurry.

The effect of methanogenesis on the survival of model bacterial strains (Escherichia coli EC 5, Staphylococcus aureus SA 11, Enterococcus faecium CCM 4231) and non-embryonated helminth eggs (Ascaris suum) was investigated in pig slurry. Two pilot-plant experiments were carried out in two anaerobic digesters (800 and 1,000 litre) in a mesophilic thermal range (35-37 degrees C). The mean hydraulic retention time of the digesters was 20 days. The methanogenesis process was monitored by determining the following chemical parameters: pH, N-NH3, total dry matter (kg/day), organic matter (kg/day) production of methane by supplied and degraded organic matter (m3/kg). The results obtained allow us to state that the anaerobic stabilization of pig slurry in the mesophilic temperature range resulted in total devitalization of model bacterial strains E. coli EC 5 and Ent. faecium CCM 4231. St. aureus SA 11 cells, exposed to the above mentioned conditions, were also reduced in their number from 10.04 to 3.27 and from 8.69 to 2.77 log cfu/ml. It is assumed that the longer retention time of excrements in the digester could also result in total devitalization of St. aureus SA 11 cells. From the microbiological point of view, the above mentioned facts indicate a sufficient hygienization effect of the anaerobic fermentation on the contaminated pig excrements. The survival of A. suum eggs was little affected by the 20-day anaerobic mesophilic digestion of pig slurry. Only 17 or 18% (F1, F2) of the non-embryonated A. suum eggs were damaged after the 20-day exposure.

Use of a polyurethane carrier for assessing the survival of helminth eggs in liquid biological sludges.

Soft expanded polyurethane (plastic foam) was used as an egg carrier. A carrier of helminth eggs and a method for their isolation were tested. They proved applicable to evaluation of the survival of helminth eggs in liquid biological substrates (sludges, liquid excrements). The inside of the carrier was inoculated with 1,000 +/- 50 Ascaris suum eggs. After 21 days of incubation in an aerated medium at room temperature, 660.7 (66.1%) eggs were isolated on the average (n = 10, Tab. I). The carriers incubated in the medium at 4 degrees C yielded 716.2 eggs (71.6%) on the average (Tab. II). The intactness of the carriers in helminth eggs was proved during 21 days of incubation in aerated medium when the detected mean percentage of embryonated eggs was 80.5% (Fab. I). From the carriers kept at 4 degrees C for 21 days and subsequently incubated 76.6% of embryonated eggs were recovered on the average (Tab. II). Control showed 80.95% of embryonated eggs on the average, which is a statistically insignificant difference (P < 0.05). With the use of the carrier more than a 13-fold increase in the viable eggs was recorded, compared with a 5% yield obtained at a direct inoculation into liquid substrates. This method is rewarding for its optimization of experimental results and for reducing the number of eggs used in the experiments.

[The importance of flies (Diptera-Brachycera) in the dissemination of helminth eggs from sewage treatment plants]. / Význam múch (Diptera-Brachycera) pri sírení vajícok helmintov z cistiarenských kalov.

Screenings were carried out in four mechanico-biological municipal wastewater treatment plants in two climatico-geographic regions of Slovakia (submontane region: Levoca, Poprad and Tatranská Lomnica, lowland region: Michalovce). Ovoscopical studies traced the occurrence of helminth eggs in stabilized sludges in sludge beds. The flies (Diptera-Brachycera) are considered as potential biological vectors of helminth eggs. The stabilized sludges in sludge beds showed the presence of a wide range of helminth eggs Ascaris sp. 0-184 spec. Hymenolepis sp. 0-5 spec. Toxocara sp. 0-17 spec. Taenia sp. 0-2 spec. Trichuris sp. 0-17 spec. a Capillaria sp. 0-4 spec./100 g of sample dry matter. In the areas of four sewage treatment plants 461 fly specimens (358 females, 103 males) were captured, belonging to 31 species. On three specimens of Protophormia terraenovae ectoparasites (mites) were detected. No eggs were found on the body surface of the flies.

Devitalization of bacterial and parasitic germs in sewage sludge during aerobic digestion under laboratory conditions.

The survival of 8 bacterial species (Pseudomonas sp., Salmonella sp., Enterobacteriae, Streptococcus sp., Escherichia coli) was detected in municipal sewage sludge up to 37 hours of mesophilic aerobic digestion under laboratory conditions. The model strain Enterococcus faecium CCM 4231 survived almost twice as long as the above-mentioned isolates. Similar findings, regarding the viability of the microorganisms studied, were also determined during thermophilic aerobic digestion of municipal sewage sludges. The final reduction in the total count of bacteria was not directly dependent on the temperature during aerobic digestion. It may be supposed that E. faecium CCM 4231 strain as a bacteriocin-producing strain with a broad antimicrobial spectrum, inoculated into the sludges, could inhibit the growth of microorganisms in the sludges by the way of its bacteriocin activity. Studying the effect of aerobic digestion on the viability of helminth eggs, the observed negative effect of higher temperatures was more expressive in comparison with bacterial strains. During thermophilic digestion process all helminth eggs (Ascaris suum, Toxocara canis) were devitalized. All eggs of T. canis were killed in experiments under mesophilic temperature. However, 32% of nonembryonated A. suum eggs remained viable.

[Survival of Ascaris suum eggs in sewage treatment plant sludge]. / Prezívanie vajícok modelového helminta Ascaris suum v kalových poliach cistiarní odpadových vôd.

In the period between June 1992 and May 1993 the survival of nonembryonated eggs of A. suum was studied in two sludge drying beds of sewage treatment plants (STP) under different climatic-geografical conditions: STP Michalovce in the East Slovak Lowland (elevation 111 m above sea-level) and STP Poprad in the submontane area of the Poprad valley (elevation 695 m). Sludge drying beds of both sewage treatment plants (STP) showed different survival of eggs (Fig. 1). In STP Michalovce we detected a rapid reduction in viable eggs from October through December (from 80.4% at the initiation of the experiment to 19.8% in December 1992). Later this decrease became less rapid and at the end of the experiment, after 240 days only 5% of eggs were viable. In STP Poprad the viability of eggs was reduced rather gradually, and after 320 days of exposure 36% of viable A. suum eggs were still recorded. Sludge dry matter in STP Poprad increased from 2.2% to 14.2% and in STP Michalovce from 4.1% to 19.2% at the termination of the experiment. Sludge pH showed no marked variation in both STPs, ranging between 7.1 and 7.8. The percentage of sludge organic matter was higher in STP Poprad, ranging from 55 to 75%, than in STP Michalovce, with 34-31%. We studied the correlation coefficients (Tab. I) of exposure time, air temperature, sludge drying bed temperature at 10 cm depth, pH, dry matter (Figs. 2 and 3) to the viability of model A. suum eggs.(ABSTRACT TRUNCATED AT 250 WORDS)

[The effect of experimental aerobic stabilization of swine slurry on survival of Salmonella typhimurium and Ascaris suum]. / Vplyv aeróbnej stabilizácie tekutých exkrementov osípaných v laboratórnych podmienkach na vitalitu zárodkov Salmonella typhimurium a Ascaris suum.

Laboratory aerobic mesophilic stabilisation (fermentation) of pig slurry reduced the survival time of S. typhimurium, compared with their prevalence in anaerobic excrements. The decimation time T90 for S. typhimurium, was 32 hours. The effect of aerobic stabilisation on the survival of nonembryoed eggs of the model helminth A. suum was lower than that observed in Salmonella. After 54 hours of aerobic stabilization of slurry only 32% of eggs were devitalized. Stabilized control group did not develop 13% of eggs into their embryonated stage.