Degradation of morpholine in several biodegradation tests and in wastewater treatment plants

The biodegradation of morpholine was determined by several static biodegradation tests and in a laboratory-scale wastewater treatment plant which was operated with municipal wastewater. Morpholine proved to be readily biodegradable in the OECD screening test and inherently biodegradable in the Zahn-Wellens test exhibiting a final degradation level greater than 90 %. Nevertheless, an adaption period of 7 to 20 days was necessary before degradation occurred. In the wastewater treatment plant which was supplied with 5 mg/l morpholine the adaption period was 10 to 12 days and the final degradation level was also greater than 90 %. Due to the short hydraulic residence time of the treatment plant shock-loading of morpholine (35 mg/l morpholine) caused an increase of morpholine in the effluent. Furthermore, it could be shown by several toxicity tests (respiration acitivity, dehydrogenase activity, nitrification activity) that the biological activity of activated sludge was not inhibited even at high concentrations of morpholine.