Microbiological toxicity tests using standardized ISO/OECD methods-current state and outlook.

Microbial toxicity tests play an important role in various scientific and technical fields including the risk assessment of chemical compounds in the environment. There is a large battery of normalized tests available that have been standardized by ISO (International Organization for Standardization) and OECD (Organization for Economic Co-operation and Development) and which are worldwide accepted and applied. The focus of this review is to provide information on microbial toxicity tests, which are used to elucidate effects in other laboratory tests such as biodegradation tests, and for the prediction of effects in natural and technical aqueous compartments in the environment.

Toward the future of OECD/ISO biodegradability testing-new approaches and developments.

In the past decades, industrial and scientific communities have developed a complex standardized system (e.g., OECD, ISO, CEN) to evaluate the biodegradability of chemical substances.

Inhibition of nitrification in laboratory tests and model wastewater treatment plants.

The microbial elimination of nitrogen by combined nitrification and denitrification is a well-known technology in wastewater treatment processes. Nitrification in wastewater treatment plants is a sensitive microbiological process, which can be disturbed by toxic substances. Two laboratory methods for nitrification inhibition (ISO standard 9509 and a modification of the respiration inhibition test ISO 8192) were investigated with selected substances and compared with results from sewage model plants.

Development and evaluation of an online CO(2) evolution test and a multicomponent biodegradation test system.

Well-established biodegradation tests use biogenously evolved carbon dioxide (CO(2)) as an analytical parameter to determine the ultimate biodegradability of substances. A newly developed analytical technique based on the continuous online measurement of conductivity showed its suitability over other techniques. It could be demonstrated that the method met all criteria of established biodegradation tests, gave continuous biodegradation curves, and was more reliable than other tests.

Evaluation and further development of the activated sludge respiration inhibition test.

The activated sludge respiration inhibition test is an important bacterial test system for the determination of bacterial toxicity of chemical compounds. The exposure period recommended by OECD 209 and ISO 8192 protocols is 30 and 180 min. A modified version of the test was developed which allowed a prolonged incubation period of 27 h to enhance the possibilities of the test system.

A critical comparison of respirometric biodegradation tests based on OECD 301 and related test methods.

Biodegradation studies of organic compounds in the aquatic environment gain important information for the final fate of chemicals in the environment. A decisive role play tests for ready biodegradability (OECD 301) and in this context, the respirometric test (OECD 301F). Two different respirometric systems (Oxitop and Sapromat) were compared and in two of ten cases (diethylene glycol and 2-ethylhexylacrylate) differences were observed indicating that the test systems are not always equivalent.