Application of Toxkit microbiotests for toxicity evaluation of river waters and waste waters in the region of Warsaw in Poland

The toxicity of surface waters (Vistula river in Warsaw) and of raw and treated wastewaters (treatment plants in Grodzisk Mazowiecki and in Piaseczno) has been measured at 2 occasions with 4 Toxkit microbiotests: the Algaltoxkit F (TM), the Daphtoxkit F (TM) pulex, the Thamnotoxkit F (TM) and the Protoxkit F (TM). Although the Vistula river is classified as being highly polluted, only the Thamnotoxkit F (TM) could detect toxicity; undiluted surface water induced 50% in the test organisms after 24h exposure. The raw wastewaters of the 2 plants were toxic to all test organisms, but most of all to the microalgae, with 72h EC50's below the 5% dilution level. Mechanical treatment of the wastewater of the plant in Piaseczno only decreased the toxic impact on the test biota marginally. Biological treatment in turn had a more pronounced effect, but did not succeed either in making the treated wastewater harmless to the test biota, except for the micro-algae in the Grodzisk Mazowiecki plant. This preliminary study indicates that the Toxkit microbiotests seem to be a very convenient tool for toxicity assessment of wastewaters in treatment plants, and in particular for monitoring the impact of biological treatment on the toxic hazard. In turn, at the exception of the Thamnotoxkit Faa assay, the other microbiotests were not enough sensitive to detect the presence of toxicants in the highly polluted Vistula river.