Direct toxicity assessment with a mini portable respirometer

For assessing the impact of pollutants on the ecosystem, direct toxicity assessment (DTA) of the wastewater has been recommended. Microbial toxicity bioassays could present clear advantages over some other bioassays for DTA. The Baroxymeter is described that has been developed as a portable wastewater direct toxicity device based on manometric bacterial respirometry. In this work we look at detecting toxicity from biocides, metals and a commercially available insecticide preparation in a minimal sample volume of 1 ml. Measurements recorded within 10 min are compared with periods up to 2 h that could be used to reveal hormesis and give a ‘toxicity profile’. The compromise between amount of data/information and assay time is discussed. Hormesis can be revealed in measurement times >20 min, whereas a target ‘rapid’ simple toxicity indication measurement might be 5–10 min. The Baroxymeter showed good reproducibility and comparable responses with methods using microorganisms and assays reported in the literature.