A test battery approach for ecotoxicological evaluation of disinfectants prepared on the basis of sodium hypochlorite

The research is related to the assessment of the overall sensitivity and applicability of many bioassays representing different trophic levels for the preliminary ecotoxicological testing of commercial disinfectants marked as SA (SAVO, Bochemie a.s., Czech Republic) and DoAm (Dom Amor, BOOS – Biologické substancie, Slovak Republic). Disinfectants were prepared based on sodium hypochlorite (NaOCl). SA contains only NaOCl while earthworm enzymes enrich DoAm. In both commercial products, the NaOCl content did not exceed 5%; pure NaOCl was used as a 10% solution as well. For bioassay, water organisms (Vibrio fischeri, Desmodesmus subspicatus, Daphnia magna and Tubifex tubifex) situated in various trophic levels were used. All the tests were confirmed as suitable for the determination of chlorine’s adverse effects. Because the organisms’ reactions to the tested disinfectants varied, they can be arranged in the following rank order of sensitivity: V. fischeri ≥ D. subspicatus >> D. magna >> T. tubifex. The toxicity of the tested substances (NaOCl, SA, DoAm) depends on the length of exposure, the species of the organism and FAC (free available chlorine) content. The effective concentrations of the tested products ranged from 0.13 to 8.18 μL L^–1, i.e., 0.014 to 0.26 mg L^–1 of FAC. However, in the tests with T. tubifex and V. fischeri the toxic effect of NaOCl was the weakest; the tests with other two organisms confirmed this compound as the most toxic. Only for T. tubifex (96 hrs) did SA have a more adverse effect than DoAm.