A multivariate biological and chemical characterization of industrial effluents connected to municipal sewage treatment plants

Effluents from middle‐sized industries, connected to municipal treatment plants in two cities in Sweden were sampled daily during 1 week and were characterized chemically and biologically. The results were evaluated mainly with multivariate statistics to find relations between chemistry and toxicity. The principal component analysis (PCA) overview of the chemical variables displayed three main clusters: nitrogen fractions, metals, and organic parameters. An overview of the biological responses showed that inhibition of nitrification was not correlated to the other biological tests. Bivariate statistics found significant correlations existing between different endpoints of Microtox®. In the partial least squares in latent structures (PLS) models created for the biological toxicity tests (Microtox, inhibition of nitrification, and algal growth test with Selenastrum capricornutum), two significant groups causing toxicity were detected, namely inorganic metals and organic pollutants detected by adsorbable organic halogens, chemical oxygen demand, and total organic carbon. When characterizing these industrial effluents, the chemical determinations and the various biological toxicity tests complement each other and none can be excluded.