Water Quality of the Danube in Hungary and its Major Determining Factors

Abstract

Three District Water Authorities cover the whole Hungarian stretch of the Danube. Since the formation of the monitoring network fifteen years ago, the water quality has been observed at fifteen sampling points. Throughout this time, sampling has been performed under different hydrometeorological conditions. Based on these investigations, it was found that the quality of the river was influenced equally by the local and the hydrometeorological conditions. Major pollution sources are: the sewage from Bratislava, Györ and Budapest; the paper pulp, chemical, and sugar beet factories in the Slovakian catchment; the Hungarian chemical, petro-chemical, and food industries; and non-point source pollution from agriculture. The effects of these sources depend on the degree of wastewater treatment, and on the mixing rate. The waste loads provide a continuous source of nutrients, giving rise to bacterial proliferation. The organic nitrate and phosphorus loads are increasing, which is compensated for by biodegradation. In the winter, when the water temperature falls below 10°C and solar radiation is low, saprobic conditions characterize the water quality. In the summer, when solar radiation and temperature increase, trophic conditions determine the water quality. Thus, in winter the ammonia content increases, but in the spring, nitrification starts to improve and, especially in the lower reaches, algal overproduction can be detected. This situation changes during flood periods, when the concentration of polluting material is decreased by dilution, and at the same time, the high level of suspended solids inhibits the growth of organisms needing solar radiation. The most unfavourable water quality conditions occur in the winter low-flow period, when problems may occur in drinking water supply if the water is chlorinated.

Ecotoxicity of fluvial sediments downstream of the Ajka red mud spill, Hungary

“…In the other measurement points of Marcal, where red mud is not present in appreciable quantities, toxicity remains under 20%, with gypsum dosing having no noticeable effect compared to reference samples. The high toxicity in the R aba (R2) and Mosoni-Duna (MD1) samples is most likely a diffuse pollution signal from decades of industrial activity and municipal sources in the area of Gy} or city, 41 which may include organic contaminants not measured here. There are highly significant positive correlations between Lemna minor inhibition rate and exchangeable Na (rs ¼ 0.69, p ¼ 0.002), Co, Cr, Fe and Ni (rs between 0.70 and 0.75; p < 0.001; Fig.…”

Study of Physico-Chemical Characteristics of Wastewater in an Urban Agglomeration in Romania

“…Thus an important element in preventing and controlling river pollution by an effective management of STP is the existence of reliable and accurate information about the concentrations of pollutants in wastewater. Studies of wastewater in Danube basins can be found, for instance, in central and eastern European countries [ 13 – 15 ], but we are not aware of extensive studies of wastewater quality at regional/national level in Romania.…”

Occurrence of Clostridia in the Sediment of an Extremely Polluted Danube Reach

“…In the sediment the heavy metal concentrations were much higher (100...1 000 times) than in the water [11,12]. Presumably sediment works as a trap for heavy metals, in the form of highly insoluble sulfides.…”