Surface waters are used for disposal of industrial and municipal effluents. The regulations limit effluent concentrations of contaminants to protect rivers and their biota. Only low concentrations of various contaminants are usually found in treated effluents but they have often been accumulated over time in sediments. Sediment quality investigations are necessary beside water quality determination for assessment of harmful impacts of discharges on the river.
The quality evaluation of Krka river was used as a case study for assessment of the impact of effluents from both industrial and municipal wastewater treatment plants. The evaluation of the impact of treated wastewaters on the river is based on chemical analysis of river water, sediment, sediment elutriates and pore water (COD, BOD, nutrients and metals) as well as toxicity measurements of river water and sediment elutriates. Sediment elutriates were prepared by natural leaching process simulation. By comparative investigations upstream and downstream from the wastewaters' discharges the influence of pollution upon the Krka river was studied.