Effects of lethal and sublethal concentrations of peracetic acid and active chlorine of calcium hypochlorite on Chironomus xanthus

Freshwater ecosystems are vulnerable to residual concentrations of chemical agents from anthropogenic activities, and the real impacts of such compounds can only be evaluated accurately using ecotoxicological tests. The assessment of ecotoxicological effects of peracetic acid (PAA) and the active chlorine of calcium hypochlorite (Ca(ClO)₂) on the insect Chironomus xanthus Meigen (Diptera: Chironomidae) is highly relevant as there are few reports on its effects in fresh water ecosystems. To our best knowledge, this is the first study to assess the chronic toxicity of the compounds to C. xanthus. The toxicity bioassays for C. xanthus included the acute effect (CL₅₀) and the chronic effects based on body length, head width, and cumulative emergence. The results obtained in the acute effect tests indicated that the active chlorine of Ca(ClO)₂ is 14 fold more toxic than PAA to C. xanthus. In sublethal evaluations, the active chlorine of Ca(ClO)₂ presented higher toxicity than PAA in terms of percentage emergence, body development, and head width. In general, the results showed lower PAA toxicity relative to the active chlorine of Ca(ClO)₂, demonstrating that PAA is a promising substitute for chlorinated disinfectants. In addition, the study facilitates the establishment of reference values for the safe release of effluents treated with PAA into water bodies.

Comparative ecotoxicological evaluation of peracetic acid and the active chlorine of calcium hypochlorite: Use of Dugesia tigrina as a bioindicator of environmental pollution

Chlorine plays a primary role in the disinfection of drinking water and wastewater due to its effectiveness as a biocide; however, there is evidence of the formation of toxic byproducts from its application, and this has promoted the search for alternatives. Alternative disinfectants can be effective in the inactivation of pathogenic microorganisms and are less damaging to human health and aquatic ecosystems. However, more information is needed on the effect of residual concentrations on the environment. This work compares the ecotoxicological effects of PAA disinfectants and the active chlorine of calcium hypochlorite in relation to the organism Dugesia tigrina (planaria), in terms of the acute effects: LC₅₀, and chronic effects: feeding, locomotion, regeneration, reproduction and fertility. The results indicated that the active chlorine was more toxic than PAA, with LC₅₀ (96 h) of 2.63 mg.L^-1 and 3.16 mg.L^-1, respectively. Sub-lethal exposure to active chlorine was more toxic when compared to PAA, and there was evidence of significantly reduced feeding and locomotion, causing a greater delay in regeneration and impairment in reproduction and fertility. The results allowed the comparison of the two disinfectants using half-life constants of the compounds and the lowest observed effect level (LOEC) of the oxidants. Chlorine represents a greater risk to the ecosystem for a longer period. The results obtained in this study can help in the establishment of discharge limits for PAA in water bodies.