A new Iodobismuthate Method with a Low Volume Filtration Device as a New Tool for the Determination of Microgram Oxyethylate Amounts

The standard procedure of non-ionic surfactant detection by using the Bismuth Active Substances method offers low sensitivity, precision and a high consumption of the reagents. A new spectrophotometric (λmax = 460 nm of the visible spectrum) iodobismuthate method was developed, which may be successfully used to determine the presence of non-ionic surfactants at microgram levels. The oxyethylates were precipitated with the modified Dragendorff reagent, filtered, dissolved and afterwards the spectrophotometric determination of the equivalent bismuth amount was carried out. Several key factors, which influence the results of the proposed oxyethylate determination method, were optimized. The consumption of chemical reagents was notably decreased and the sensitivity of the method increased significantly in comparison to the standard method of non-ionic surfactant determination.

The value of biodegradation screening test results for predicting the elimination of chemicals' organic carbon in waste water treatment plants

Based on the test results of a large number of chemical substances, the comparability of different biodegradation test methods was assessed in terms of passing or failing threshold values commonly used for the biodegradability characterisation of chemicals. The comparison revealed a high consistency of the ready biodegradability evaluations in OECD 301 tests regardless of the analytical parameter used, i.e., by mineralisation (CO2 evolution or biological oxygen demand/BOD) or by organic carbon removal measurements. Substances meeting the ready biodegradability threshold values in OECD 301 tests exhibited a high (> 80%) carbon removal in model waste water treatment plants (OECD 303A). Results from the Modified Zahn-Wellens test (OECD 302B) representing a screening test with high sludge concentration, were also shown to be useful for the prediction of the organic carbon removal under WWTP conditions provided some prerequisites are met. The analysis of the compared data pairs formed a solid basis for the conclusion that positive results of a chemical in biodegradability screening tests can be used for a reliable prediction of their carbon-based removal in waste water treatment plants.