Assessment of the wastewater toxicity in the karst area using algal growth inhibition test

Toxicity assessment is performed by acute tests that indicate potential toxic effect on aquatic organisms. In our research, toxicity testing was performed in the upstream flow of the Krka River, directly impacted by inappropriately treated industrial and municipal wastewaters, using green algae (Pseudokirchneriella subcapitata (Korshikov) F. Hindák, 1990). Toxicity of water in karst area was tested at five sites, Krka River source (KRS, reference site), near municipal (MWW) and industrial wastewater outlets (IWW) and in tributaries Orašnica (TOR) and Butišnica (TBU). The average algal specific growth and the percentage of inhibition was calculated according to ISO 8692:2012 after 24, 48 and 72 h incubation by measuring the optical density on a spectrophotometer at 670 nm. The final result of the test is presented by the highest concentration at which no inhibition was observed (