Efficienza e stagionalità di WWTPs civili e industriali: una valutazione ecotossicologica con saggi biologici acuti e cronici ed indici integrati

Ecotoxicology has applications in the environmental analysis and control; it's the best way to predict potential toxic effects on real ecosystems and can detect the effects of chemical mixtures, synergic effects of different compounds, presence of unknown or under analytical competence substances (micropollutants). These factors make it the only valid method for the evaluation of wastewaters (WWs) as a whole (EC Directive 2008/1 IPPC). Wastewater treatment plants (WWTPs) are often addressed as the principal source of pollution by micropollutants. Ecotoxicity testing is made with bioassays (BAs) of opportune biological indicators in contact with the target matrix. The best method for the evaluation of environmental risk is the use of a battery of BAs followed by elaboration with an integrated index (II). The results of single BA can't be considered a reliable indicator of environmental toxicity and ecological predictions. To avoid potential biases is important to use phylogenetically and ecologically different organisms among the ones of ecological relevance. The aim of this thesis is to use a battery of acute BAs elaborated with IIs and chronic BAs to assess the abatement efficiency of civil and industrial WWTPs, and to evaluate toxicity seasonality. Samples were collected from 3 WWTPs in Northern Italy, WWTP1, WWTP2, WWTP3 which lead in the same Collector. 10 acute BAs with 6 organisms and 3 chronic BAs with 3 organisms where used. Most of the BAs were performed in the ARPA Piemonte's Specialized Laboratory in Cuneo (Italy). Seasonality is often relevant, normally higher inhibition percentages (I%) are found in spring and summer. Pattern varies among BAs. The industrial samples were different from civil ones which instead were often quite similar in I% output or pattern within each BA. Civil WWs widely vary in I% across the seasons, whereas industrial ones are almost always constant and highly toxic (I%>50%). In some cases, the effluent showed a greater toxicity than its influent. In the chronic BAs, D. magna was stimulated in the reproduction and had a seasonal pattern with a maximum in spring and minimum in autumn, L. variegatus was heavily inhibited in biomass production and L. sativum growth BA was not highly affected apart from spring which had high biostimulation. All the WWTPs analysed in this work have a good abatement capacity with always negligible (1) or moderate (3) effluents toxicity judgment. IIs and batteries are confirmed as the best tools in ecosystems monitoring and ecological risk evaluation. Future development could further integrate biostimulation as an important part of the toxicity output of WWs and to integrate more use of chronic toxicity in ecotoxicological evaluations.