A practical and user‐friendly toxicity classification system with microbiotests for natural waters and wastewaters

Abstract

Various types of toxicity classification systems have been elaborated by scientists in different countries, with the aim of attributing a hazard score to polluted environments or toxic wastewaters or of ranking them in accordance with increasing levels of toxicity. All these systems are based on batteries of standard acute toxicity tests (several of them including chronic assays as well) and are therefore dependent on the culturing and maintenance of live stocks of test organisms. Most systems require performance of the bioassays on dilution series of the original samples, for subsequent calculation of L(E)C50 or threshold toxicity values. Given the complexity and costs of these toxicity measurements, they can only be applied in well-equipped and highly specialized laboratories, and none of the classification methods so far has found general acceptance at the international level. The development of microbiotests that are independent of continuous culturing of live organisms has stimulated international collaboration. Coordinated at Ghent University, Belgium, collaboration by research groups from 10 countries in central and eastern Europe resulted in an alternative toxicity classification system that was easier to apply and substantially more cost effective than any of the earlier methods. This new system was developed and applied in the framework of a cooperation agreement between the Flemish community in Belgium and central and eastern Europe. The toxicity classification system is based on a battery of (culture-independent) microbiotests and is particularly suited for routine monitoring. It indeed only requires testing on undiluted samples of natural waters or wastewaters discharged into the aquatic environment, except for wastewaters that demonstrate more than 50% effect. The scoring system ranks the waters or wastewaters in 5 classes of increasing hazard/toxicity, with calculation of a weight factor for the concerned hazard/toxicity class. The new classification system was applied during 2000 by the participating laboratories on samples of river water, groundwaters, drinking waters, mine waters, sediment pore waters, industrial effluents, soil leachates, and waste dump leachates and was found to be easy to apply and reliable.

An assessment of the physicochemical properties and toxicity potential of carwash effluents from professional carwash outlets in Gauteng Province, South Africa

“…After the determination of the percentage effect (EP) obtained with each of the battery of toxicity screening tests performed, the samples were ranked into one of the following five classes following the descriptions of Persoone et al (2003) as follows:…”

Toxicity Assessment of Treated Meat Industry Wastewater in the Anaerobic Process

“…In order to classify the wastewater into the appropriate toxicity classes according to Persoone et al [30], the values of EC 50 converted into toxicity units (TU) were calculated. TU value for the ErC 50 (0÷96 h) and E b C 50 was respectively 5.51 (acute toxicity) and 11.62 (high acute toxicity).…”

The Effect of Low-Temperature Conversion of Plant Materials on the Chemical Composition and Ecotoxicity of Biochars

“…The EC50 values were converted to Toxic Units (TU) according to the formula TU = 1/EC50 9 100. The system of risk assessment developed by Persoone et al [24] was used to estimate toxicity. Finally, the results were classified: class I TU B 0.4 no significantly toxic effect; no acute hazard, class II: 0.4 \ TU B 1 slight acute toxic effect; low acute hazard, class III: 1 \ TU B 10 significantly toxic effect; acute hazard, class IV: 10 \ TU B 100 high acute hazard, class V: TU [ 100 very high acute hazard.…”

“…A percent effect toxicity (PE 15 min) for the studied biochars was 34-95 %. The research results of Persoone et al [24] proved that toxicity percent effect PE \ 20 % indicates no significant toxic effect; however, toxicity percent effect in the range of 20 % \ PE \ 50 % means that the sample is slightly toxic. On the other hand, samples with toxicity percent effect in the range of 50 % \ PE \ 100 % are considered to be toxic.…”