Biodegradation in laboratory activated sludge plants and aquatic toxicity of herbicides

The biodegradation and the aquatic toxicity of four herbicides (isoproturon , terbuthylazine, mecoprop, metamitron) were investigated. Laboratory activ ated sludge plants were used for biodegradation experiments. The biodegrada tion of mecoprop reached nearly 100 %, the other herbicides were not elimin ated by biodegradation. The acute Daphnia magna 24-h assay, the algal 72-h inhibition test, and the recently developed lemna growth inhibition 7-d tes t were applied to evaluate the biological effects of herbicides as original substances. EC 50 and EC 10 Values were determined. Algal and lemna test s how that isoproturon and terbuthylazine are both much more toxic than mecop rop and metamitron. Daphnids are generally less sensitive against herbicide s than plants. Biodegradation and toxicity test were coupled for mecoprop to assess biolog ical long-term effects of possible biodegradation products of this herbicid e. The effluents of the laboratory activated sludge units were used in toxi city tests (Daphnia magna 21-d reproduction test, lemna growth inhibition 7 -d test). No inhibiting effect on the tested organisms was observed. (C) 19 99 Elsevier Science Ltd. All rights reserved.