Abstract

Standard ready biodegradability tests are conducted at unrealistically high test concentration and therefore cannot properly evaluate toxic substances to microorganisms. The present study evaluated the effects of four adsorbent carriers in modified ready biodegradability tests of four quaternary ammonium salts (QASs) demonstrating microbial toxicity according to the Organization for Economic Co-operation and Development Test Guideline 301F and cautions for using carriers were found. In the tests with silica gel, the concentration of all QASs in the test solutions decreased due to adsorption. The percentages of biodegradation of octadecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, and benzyldimethyloctadecylammonium chloride, which have a linear alkyl chain, were 89.9%, 80.6%, and 70.1% on day 28, respectively; benzethonium chloride, with a branched alkyl chain, did not undergo biodegradation. In the tests with activated carbon, although the concentrations of QASs greatly decreased, no QASs underwent biodegradation. In the tests with sea sand or quartz sand, QASs were not adsorbed on the carriers and were not biodegraded. Using an adsorbent carrier for toxic substances will increase biodegradation, but it has no effect on highly persistent substances with specific chemical structures, e.g., branched carbons, which is very important because ready biodegradability is not overestimated. Carriers having moderate adsorbability should be selected.

摘要

标准的可生物降解性测试是在非常高的测试浓度下进行的，因此无法正确评估对微生物的有毒物质。本研究根据经济合作与发展组织测试准则301F评估了四种吸附剂在四种经证明具有微生物毒性的季铵盐（QAS）的现成生物降解性试验中的效果，并发现了使用载体的注意事项。在硅胶测试中，由于吸附，测试溶液中所有QAS的浓度均降低。在第28天，具有直链烷基链的十八烷基三甲基氯化铵，十六烷基三甲基溴化铵和苄基二甲基十八烷基氯化铵的生物降解百分比分别为89.9％，80.6％和70.1％；带有支链烷基链的苄索氯铵未发生生物降解。在用活性炭进行的测试中，尽管QAS的浓度大大降低，但没有QAS进行生物降解。在用海砂或石英砂进行的测试中，QAS不会吸附在载体上，也不会被生物降解。使用吸附剂载体处理有毒物质会增加生物降解性，但对具有特定化学结构的高度持久性物质（例如支链碳）没有影响，这非常重要，因为现成的生物降解性不会被高估。应该选择具有中等吸附能力的载体。在用海砂或石英砂进行的测试中，QAS不会吸附在载体上，也不会被生物降解。使用吸附剂载体处理有毒物质会增加生物降解性，但对具有特定化学结构的高度持久性物质（例如支链碳）没有影响，这非常重要，因为现成的生物降解性不会被高估。应该选择具有中等吸附能力的载体。在用海砂或石英砂进行的测试中，QAS不会吸附在载体上，也不会被生物降解。使用吸附剂载体处理有毒物质会增加生物降解性，但对具有特定化学结构的高度持久性物质（例如支链碳）没有影响，这非常重要，因为现成的生物降解性不会被高估。应该选择具有中等吸附能力的载体。