Depuration System Research Articles

Listeria innocua and Salmonella panama in Mussels: A Comparative Study

Bivalve molluscs are exposed to a wide range of contamination by pathogenic bacteria and viruses. Therefore, the behavior of bacterial pathogens in bivalves after harvesting is important in terms of food safety. Mussels were artificially contaminated with Listeria innocua and Salmonella panama, held under different conditions, and then examined for Listeria and Salmonella viable counts. In a simplified depuration system, L. innocua levels were lower than those observed for S. panama in mussels during the same period and under the same conditions. This result may be related to the rapid die-off reported for Listeria in seawater. In mussels stored in air, the two pathogens presented similar behaviors: levels of both pathogens remained constant in mussels during the storage period in air. However, in shucked mussels Listeria innocua counts increased with the duration of storage, whereas Salmonella panama showed a slight decrease.

Reuse of wastewater treated by infiltration percolation

The aim of this work was to determine the depuration efficiencies of an infiltration percolation plant to remove organic matter and nutrients (N and P) and to test the effect of treatment by such system on the fertilizer value of wastewater compared to untreated influent and a control (groundwater). Results of investigations carried out over a month of each season showed the high capacity of this depuration system to remove both particulate and dissolved organic matter (TSS 91%, COD 93% and dCOD 89 to 95%) at all season. Nitrogen and phosphorus were more eliminated at winter and summer. At spring they presented a low percent removal efficiency due probably to overloaded influent. Tests consisting in the reuse a raw wastewater (RW), settled wastewater (SW) or completely treated wastewater (FW) for irrigation of (Lolium perenne) plots showed that biomass yield, nutrients (N,P) exported by plants and protein amount in the plants tissue decreased from plots irrigated by (RW) to completely treated wastewater. But all of them were more important than in the control plants (irrigated by groundwater) and exceeded the mean values reported in literature for meadows plants. The amount of nitrogen and P2O5) applied during the irrigation by wastewater, was equivalent or superior to recommanded dose of fertilizer for meadows. The expected meat or milk production showed a promising potentiality to promove the nutritional quality of farm animals food by using treated wastewater.

Reuse of wastewater treated by infiltration percolation

The aim of this work was to determine the depuration efficiencies of an infiltration percolation plant to remove organic matter and nutrients (N and P) and to test the effect of treatment by such system on the fertilizer value of wastewater compared to untreated influent and a control (groundwater). Results of investigations carried out over a month of each season showed the high capacity of this depuration system to remove both particulate and dissolved organic matter (TSS 91 %, COD 93 % and dCOD 89 to 95 %) at all season. Nitrogen and phosphorus were more eliminated at winter and summer. At spring they presented a low percent removal efficiency due probably to overloaded influent. Tests consisting in the reuse a raw wastewater (RW), settled wastewater (SW) or completely treated wastewater (FW) for irrigation of (Lolium perenne) plots showed that biomass yield, nutrients (N,P) exported by plants and protein amount in the plants tissue decreased from plots irrigated by (RW) to completely treated wastewater. But all of them were more important than in the control plants (irrigated by groundwater) and exceeded the mean values reported in literature for meadows plants.The amount of nitrogen and P205) applied during the irrigation by wastewater, was equivalent or superior to recommanded dose of fertilizer for meadows. The expected meat or milk production showed a promising potentiality to promove the nutritional quality of farm animals food by using treated wastewater.

Ozone depuration of Vibrio vulnificus from the southern quahog clam, Mercenaria campechiensis

Southern quahog clams, Mercenaria campechiensis, were dosed with Vibrio vulnificus and placed in a pilot-scale depuration system using ozonated recirculated artificial seawater. Twentyfour hours of treatment with ozone-treated recirculating artificial seawater reduced the numbers of V. vulnificus in the shellfish meats by an average of 2 log units when compared to natural die-off in control clams. The oxidant levels (up to 3 mg/liter) did not adversely affect shellfish pumping during the depuration process.

Depuration of Mytilus galloprovincialis experimentally contaminated with hepatitis A virus

Mussels ( Mytilus galloprovincialis) were contaminated with known amounts of laboratory strains of hepatitis A virus and Poliovirus 1 and the effectiveness of a self-cleansing mechanism was studied using a pilot depuration system. Both viruses were rapidly bioaccumulated by mussels and the maximal concentration of about 10 4 TCID50/ml was reached within 1.5 hours. Depuration was carried out up to 24 h; infectivity titer decreased to 10 2 TCID50/ml and 10 3.2 TCID50/ml within 6 h in hepatitis A virus and Poliovirus 1 contaminated mussels, respectively, but only a very slight further decrease was obtained after 24 h. E. coli was used as a control; within 24 h the concentration decreased from 40 to 2 bacteria/ml of mussel (MPN). The elimination of bacteria is not a reliable parameter to control the effectiveness of viral depuration.

Heavy Metal Distribution in Anaerobic Sludges

Abstract On the basis of a depuration system, by anaerobic processes, for wastewaters which contain variable amounts of copper, nickel, and zinc, a study is made of the distribution of these cations betwen the solid sludge and the supernatant liquid of the effluent. In all the experiments, amounts approximating 90% of the metals existing in the substrate were retained in the solid sludges, a very small amount of the metals remaining in the clear liquid of the effluent.

Tissue distribution of a coliphage and Escherichia coli in mussels after contamination and depuration

Experiments were undertaken to determine the tissue distribution of Escherichia coli and a coliphage after contamination of the common mussel (Mytilus edulis). Mussels were contaminated with high levels of feces-associated E. coli and a 22-nm icosahedral coliphage over a 2-day period in a flowing-seawater facility. After contamination, individual tissues were carefully dissected and assayed for E. coli and the coliphage. Contaminated mussels were also analyzed to determine the tissue distribution of the contaminants after 24- and 48-h depuration periods. The majority of each contaminant was located in the digestive tract (94 and 89% of E. coli and coliphage, respectively). Decreasing concentrations were found in the gills and labial palps, foot and muscles, mantle lobes, and hemolymph. Our results indicate that contamination above levels in water occurred only in the digestive tract. Contaminated mussels were depurated in a commercial-scale recirculating UV depuration system over a 48-h period. The percent reductions of E. coli occurred in the following order: digestive tract, hemolymph, foot and muscles, mantle lobes, and gills and labial palps. The percent reductions of the coliphage were different, occurring in the following order: hemolymph, foot and muscles, gills and labial palps, mantle lobes, and digestive tract. Our results clearly demonstrate that E. coli and the coliphage are differentially eliminated from the digestive tract. The two microorganisms are eliminated at similar rates from the remaining tissues. Our results also clearly show that the most significant coliphage retention after depuration for 48 h is in the digestive tract. Thus, conventional depuration practices are inappropriate for efficient virus elimination from mussels.

Differential depuration of poliovirus, Escherichia coli, and a coliphage by the common mussel, Mytilus edulis

The elimination of sewage effluent-associated poliovirus, Escherichia coli, and a 22-nm icosahedral coliphage by the common mussel, Mytilus edulis, was studied. Both laboratory-and commercial-scale recirculating, UV depuration systems were used in this study. In the laboratory system, the logarithms of the poliovirus, E. coli, and coliphage levels were reduced by 1.86, 2.9, and 2.16, respectively, within 52 h of depuration. The relative patterns and rates of elimination of the three organisms suggest that they are eliminated from mussels by different mechanisms during depuration under suitable conditions. Poliovirus was not included in experiments undertaken in the commercial-scale depuration system. The differences in the relative rates and patterns of elimination were maintained for E. coli and coliphage in this system, with the logarithm of the E. coli levels being reduced by 3.18 and the logarithm of the coliphage levels being reduced by 0.87. The results from both depuration systems suggest that E. coli is an inappropriate indicator of the efficiency of virus elimination during depuration. The coliphage used appears to be a more representative indicator. Depuration under stressful conditions appeared to have a negligible affect on poliovirus and coliphage elimination rates from mussels. However, the rate and pattern of E. coli elimination were dramatically affected by these conditions. Therefore, monitoring E. coli counts might prove useful in ensuring that mussels are functioning well during depuration.

Elimination of Bacteria by the Soft Shell Clam, Mya arenaria

Factors significant to the uptake and elimination of coliform bacteria by the soft shell clam, Mya arenaria, were investigated. Uptake kinetics resembling those in the northern quahaug suggest that a steady state exists in functioning animals wherein the number of organisms taken in and eliminated are in balance. In contrast to the quahaug, most of the animals accumulate the organisms very shortly after being placed in the environmental water. The lower limits on the temperature, salinity, and flow rate of the environmental water for acceptable elimination (depuration) were about 10 C, 20‰, and 7 ml/rain per animal respectively. In the feasibility study for a flow-through depuration system using naturally polluted animals, consistently good elimination to very low elevated temperature (ET) coliform levels was observed if the initial level of contamination did not exceed about 2000 ET coliforms per 100 g. Results comparable with those in the flow-through system were obtained in a recirculating depuration system, thereby indicating the feasibility of the recirculating depuration system for the elimination of coliforms in marginally polluted animals.