Water samples collected from the water-supply system often towns were examined in order to evaluate the ground water quality in the commune of Gogolin. The changes of 17 parameters of water composition and water quality were determined by analytical methods described in Polish Standards. The quality of ground waters was estimated by comparing the results obtained with both limit values for drinking water in Poland and criteria of classification of ordinary ground waters according to Polish State Environmental Monitoring. It was found that ground water from each of the investigated water intake met all the requirements set for drinking water and household purposes (with few exceptions). The concentrations of most of the parameters determined within the research indicated waters of the highest (class la) and high quality (class lb). However, influence of anthropogenic factors was also marked on water purity. The limit value of the following parameters was occasionally exceeded: nitrate nitrogen - max. by 50% in Obrowiec and 20% in Chorula, sulphates - by 19% in Kamień Śląski, iron - by 100% in Górażdże.

Considering the fact that water quality monitoring programs in Poland are mostly based on physicochemical variables and saprobie systems, it is important to evaluate also the possibility of applying biotic index methods for water quality assessment. The investigation was carried out at the Ścinawa Niemodlińska river (Opole Voivodeship). Benthic macroinvertebrates from seven sampling sites were sampled twice in 1999. Belgian Biotic Index values were calculated on the basis of the results of qualitative and quantitative analyses of the macroinvertebrate community, as the example of the biotic index application. BBi values indicated a low, but different in particular sites, pollution level of the studied ecosystem.

Silicon, an important clement for diatoms, is often beyond the main object of freshwater researches. In the last decade, many detergents containing silicon compounds have been released by municipal sewage to surface water ecosystems. In this paper, an influence of silicates and washing agents which contain silicates on algal primary production and biomass growth has been shown. The experimental analysis revealed that detergents with the silicate addition increased the rate of the biomass growth and had a direct impact on algal primary production.