Detection of polar organic substances relevant for drinking water

Testfilter systems help in the study of the persistence of organic compounds. Hence, they are remedial measures to control pollution of the environment. The filters used as biological fixed-bed reactors should enable the simulation of the biological degradation of organic compounds before they reach the waterworks. The German chemical industry has used filters based on activated carbon for more than 20 years in order to determine the microbial poorly degradable fraction of the dissolved organic carbon in the sewage effluents. The testfilter systems proved to work well on the basis of group and 'sum' parameters. The new challenge was to investigate whether the testfilter concept holds also for a diversification of drinking water relevant and non-relevant single compounds. Therefore, the first task was to develop analytical methods for classes of drinking water relevant compounds in the very complex matrix of waste water. Thereafter, these methods were applied for the detection of the selected compounds in the testfilter systems and their occurrence in the receiving waters. Methods of analysis were developed for the following classes of chemical compounds: aliphatic amines, aromatic sulfonates, halogenated carboxylic acids and organic phosphates. Furthermore the formation of yet unknown drinking water relevant compounds was studied. As a result it was concluded that the major reasons for the formation of these compounds are: (1) formation of by-products during various steps in the chemical synthesis; (2) chemical reactions in the influents of the treatment plants; and (3) metabolism in the waste water treatment plant. Experiments with compounds like 6-[methyl(phenylsulfonyl)amino]hexanoic acid (HPS) and nitrilotriacetic acid (NTA) which are known from the literature to be well degradable, confirmed that the testfilters can be utilized for simulating the performance of the underground passage. On the other hand, persistent compounds, for which 1,5-naphthalenedisulfonate is a characteristic representative, remained in the filter system without being degraded. As far as the testfilters are concerned it was concluded that the activated carbon retains its adsorption capacity to a certain extent even after a long time of operation. Because it is not possible to distinguish between microbial degradation and adsorption, it was necessary to develop a modified filter set-up for testing single substances. (C) 1999 Elsevier Science Ltd. All rights reserved.