Longitudinal Water Quality Profile Measurements and their Evaluation in the Nitra River basin (Slovakia)

The Nitra River is one of most polluted rivers in the Slovak Republic, due to numerous industrial and municipal emissions, and low level of wastewater treatment. Policy-oriented water quality management study on the basin was undertaken jointly by IIASA, the Water Research Institute in Bratislava (VUVH), and the Vah River Basin Authority. One of the components of the research were the water quality profiles experiments incorporating both emission and river water sampling, followed by an analysis with mass balance method. Two experiments were performed in the basin, in August 1992 and June 1993, respectively. The first experiment was focused on the "conventional" water quality parameters affecting dissolved oxygen balance, such as BOD, COD and nitrogen. The second, although limited only to certain regions of the basin, was aimed at understanding more detailed water quality processes in the river such as sedimentation and hydrolysis of organic material. Rough estimates of the process rates were obtained with mass balance method. The results of the work were used for calibration of water quality models essential for the formulation of economically feasible wastewater treatment policy in the basin based on water quality criteria

Optimization of RHDV type 1 and 2 inactivation modes

The purpose of these studies was to optimize RHDV type 1 and 2 (RHDV1 and RHDV2) inactivation modes to use the obtained antigens in inactivated vaccines and diagnosticums. The inactivating effect of aminoethylethylenimine and β-propiolactone was studied in different concentrations in correlation with the exposure time and temperature. The correlation between the inactivating effect of the compound used and the accepted test conditions (concentration, temperature, and exposure time) was studied on a group of rabbits, each of which was injected intramuscularly with 1 cm3 of the inactivated material sample. At the end of the maximum exposure interval, a control sample of the viral material, kept under the same conditions without any inactivant added was similarly tested. Lethality was considered to evaluate the damaging action in the test and control groups: L = m/n, where m is the number of dead animals; n is the total number of rabbits in the group for testing of the inactivated material sample. The postmortem diagnosis was confirmed by testing the rabbit liver tissue homogenate for relative antigens using ELISA. It was found that aminoethylethylenimine and β-propiolactone did not have the same effect on the studied variants of the virus. In order to preserve at maximum the antigenic structures of the virus, the following inactivation modes were considered to be optimal: for RHDV1-aminoethylethylenimine at a concentration of 0.3% at 37 °C, exposure time – 72 hours, or β-propiolactone at a concentration of 0.1–0.3% at 25–37 °С, exposure time – 24–48 hours; for RHDV2 – aminoethylethylenimine at a concentration of 1% at 37 °C, exposure time – 72 hours, or β-propiolactone at a concentration 0.3% at 25 °С, exposure time – 24 hours