No abstract

In suburban Belgrade, there are some 200 local water supply systems which are not connected to either the Belgrade Water Supply System or to supply systems operated by municipal utilities. The small systems in Belgrade suburbs are either operated by local municipality (local government) or even by the group of local citizens who have neither technical capability nor financial resources to do it properly. Roughly 200,000 of Belgrade's inhabitants obtain their drinking water from these water supply systems. The water quality delivered by these local water supply systems is often compromised in terms of microbiological, physical and/or chemical compliance with drinking water standards in addition to the general lack of strategy on water safety plans and risk assessment. WHO Guidelines on water quality standards as well as the recommendations on safety plans and whole risk assessment are strictly respected in the main (central) Water Supply System in Belgrade. Most frequently, elevated concentrations of ammonia, nitrites, nitrates and iron lead to lack of chemical compliance, while elevated counts of aerobic mesophilic bacteria and the presence of bacteria indicative of faecal pollution tend to be behind microbiological lack of compliance with drinking water standards. In most cases, failure to meet drinking water standards can be attributed to groundwater pollution. No sewer system exists in these areas, and wastewater from septic tanks, in practice infiltration wells, is in direct contact with groundwater. Of a total of 72 laboratory-tested drinking water samples, 51.3% failed to meet physical and/or chemical standards, and 73.6% failed to meet microbiological standards. Groundwater pollution can only be prevented if wastewater disposal system is provided for all households and all suburban residential areas which obtain their water supply from local water supply systems. Some possible mitigation measures have been indicated. In the interim period, water must be disinfected continually, and the feasibility of ozonation or UV irradiation, in addition to chlorination, should be assessed.

No abstract

KAKA §, MARINKOV and DRA §KOVI0, Nondestructive Radioactivation Analysis of Al-cans 75 and Cd are usually present as impurities in Li and Mg, so the undesirable activities i. e. 59 Fe, β5 Ζη, 5e Mn and 115 Cd produced in the target material require their removal prior to the extraction of 28 Mg. It is known from the published data [5-6] that Fe is quantitatively extracted with PMCyP in MIBK at 10' Q> C C Ο -C ο V) c < §10 3 10 0 50 100 150 200 250 300 Channel number Fig. 2. Gamma spectrum of 28 Mg2>H 2.8 while Mn, Zn and Cd are removed at pn 5.4, thus making it possible to separate 28 Mg at p-g. 8-9 by the prior extraction of the impurities with a 10% loss of 28 Mg activities. The radiochemical procedure was tested by separating 28 Mg from a synthetic mixture containing 20 μΟϊ 28 Mg, 25 μΟί M Na, 20 μϋϊ 59 Fe, 20 μϋί 65 Zn and 25 μϋϊ 5β Μη. The whole procedure took few minutes in addition to the time required for evaporating the solution and more than 80% added magnesium activities were recovered. The y-spectrum of 28 Mg separated from all the above elements showed no contamination from foreign ions when compared with the standard source. One such y-spectrum is reproduced in Fig. 2. In the actual production procedure 210 μΟί 28 Mg activities were obtained at the end of 4 days irradiation which corresponds with a specific activity of 17.5 mC/g. Strong F 18 activity was produced by the oxygen impurity in the target and was almost completely removed by evaporating the solution with sulphuric acid which also removed tritium and thus the final product showed no contamination of fluorine and tritium. SummaryImpurities in Al-cans (produced from aluminium of 99.8% purity) used for sample irradiations in the RA-reactor at Vinca, Yugoslavia, have been qualitatively and quantitatively determined by the nondestructive radioactivation analysis. The following impurities have been determined: Ga, Co, Fe, Zn, Cr, Sc, and Cu. The presence of Mn and Na has also been proved but their concentration has not been determined because of the specific conditions. A qualitative analysis has also been made of the contaminants of these cans, which result from the contamination during irradiation in the RA-reactor and repacking of cans in a special cell. The presence of the following radioisotopes: M Na, 1,8 / m Au, 18 'W, m ' 1M Sb, "»La, "°Co, "Sc, β6 Ζη, 192 Ir, "Cr and 6 »Fe was also proved in the smears by the method of radioactivation analysis. ZusammenfassungVerunreinigungen in zur Probenbestrahlung im jugoslawischen RA-Reaktor in VinCa verwendeten Al-Hülsen (Aluminium von 99,8% Reinheit) wurden durch zerstörungsfreie Aktivierungsanalyse qualitativ und quantitativ bestimmt. Folgende Verunreinigungen wurden festgestellt: Ga, Co, Fe, Zn, Cr, Sc und Cu. Das Vorhandensein von Mn und Na wurde ebenfalls nachgewiesen, aber die Konzentration dieser beiden Elemente wurde wegen der spezifischen Bedingungen nicht bestimmt. Auch die Verunreinigungsstoffe in diesen Hülsen, die aus der Kontamination während der Bestrahlung im RA-Reaktor und der Umla...

No abstract