A “toolbox” for biological and chemical monitoring requirements for the European Union's Water Framework Directive

The presence of contaminants considerably restricts the application of sewage sludge for the fertilisation and reclamation of soils. Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in the environment and vary widely in sewage sludge depending on the input of industrial effluents. The objective of the study was the investigation whether the pyrolysis affect (reduces or adds) the total quantity of PAHs in sewage sludge-derived biochars and whether the pyrolysis changes the PAHs spectrum in terms of relative contributions of more hazardous components. Additionally, the trace metal content was determined before and after pyrolysis as well as the ecotoxicological parameters test towards plant (Lepidium sativum), bacteria (Vibrio fischeri) and crustacean (Daphnia magna). Sewage sludges conversion to biochar significantly reduced the content of PAHs (from 8- to 25-fold depending on pyrolysis temperature and kind of sludge). The exception was the content of naphthalene. Naphthalene was predominant in sewage sludge-derived biochars. However the concentration of the most hazardous 5- and 6-rings PAHs in sewage sludge-derived biochars was much lower compared to sewage sludge. The pyrolysis of sewage sludges caused also a significant reduction of their toxicity towards the test organisms. Only in the case of crustacean it was observed that the extracts from some biochars, obtained at higher temperatures (600 °C and 700 °C) were more toxic to D. magna than extracts from sewage sludge. In turn, after pyrolysis an increase was noted for trace metals content (Pb, Cd, Zn, Cu, Ni and Cr).

The conversion of sewage sludge into biochar reduces polycyclic aromatic hydrocarbon content and ecotoxicity but increases trace metal content

Estimation of the environmental risk posed by landfills using chemical, microbiological and ecotoxicological testing of leachates.

Bioassays for toxicological risk assessment of landfill leachate: A review

Evaluation of toxicity, genotoxicity and environmental risk of simulated textile and tannery wastewaters with a battery of biotests.

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.

Boris Kolar

Papers

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