Cyanobacterials (Cyanophyta) belong to phytoplancton. In normal stale concentration of cyanobacterial cells in water rangs between a few hundreds to a few thousands in I drn' of water but while blooming may be increased even to one million in I dm3. At this time water has characteristic color, depending on dominated species. Also characteristic smell is the results of the presence ofcyanobacterial and phytoplankton cells producing odour substances. The cyanobacterial blooms are very important hygienic problem for both human and animal health. While blooming they form foams and head coating on water surface. Also cyanobacterial toxins are huge problem. Cyanobacteria may produce acute toxins such as hepatotoxic peptides (microcystins, nodularins and cylindrospermopsin) and neurotoxic alkaloids (anatoxin-a, anatoxin-a(s), homoanatoxin and aphanotoxins). Cyanobacterial toxins are very dangerous substances which can intoxicate hepatocytes and the nervous system in humans and animals. In this situation it is very important to remove them effectively in water pretreatment processes. In the present paper have been presented for the first time in Poland data on removing cyanobacterial toxins from water in pretreatment process with application of chlorine dioxide and ozone on the example of Sulejów - Łódź water pipe system. In period I 998-200 I the effectiveness rnicrocystin-LR removal ranged between 74--92% while for other izoforms they were between 45-94%.

Human activities in relation to aquatic ecosystems result in significant economic losses in the form of contamination of water sources, deteriorating its quality and therefore its availability in lakes, water bodies and even in soil. Hence the need for systematic revitalisation or reclamation of water ecosystems. Such actions, in order to be rational, require a detailed understanding of the causes, and then the use of appropriate technology. The need for the above-mentioned actions result from the weather changes that have been noticeable in recent years, as well as environmental pollutants increasing water eutrophication in reservoirs and stimulating the development of some species of cyanobacteria. These cyanobacteria can cause serious water poisoning, especially in water supply systems. Therefore, a rational, comprehensive technology for the removal of bottom sediments and their processing into organic and mineral fertiliser has been developed with properties similar to manure. It also creates opportunities to improve the structure of soils thanks to the supply of organic carbon, the loss of which was found, among others, in also in soils of Poland and EU. These new possibilities of revitalisation hitherto unknown make it possible to a large extent, compliance with environmental requirements when revitalising water reservoirs and soil.