Wie vollständig ist der biologische Abbau: Ermittlung und Analytik refraktärer Verbindungen am Beispiel von linearem Alkylbenzolsulfonat (LAS)
Linear alkylbenzenesulfonate (LAS) is the worldwide most used synthetic surfactant. Its elimination in activated sludge goes nearly to completion. But in laboratory test systems a well primary but no total biodegradation, measured by removal of dissolved organic carbon (DOC), has been found till now. On a new test system to detect refractory organic carbon (ROC) a commercial LAS yields > 5% of ROC. With HPLC and GC/MS analysis the refractory organic compounds are determined as different isomers of sulfophenylcarboxylates and carboxylated dialkyltetralinesulfonates. Dialkyltetralinesulfonates are beside branched alkylbenzenesulfonates known impurities in commercial LAS. These impurities undergo a complete primary biodegradation in the used test system. It is estimated, that the detected refractory sulfophenylcarboxylates derived from branched alkylbenzenesulfonates and not from LAS. The test to detect ROC effects on the base of a trickling filter, where the test substance is dissolved in a mineral salt solution and trickles over activated sludge, which is fixed on a support. Eluate derived from the trickling filter is readded with new test substrate and fed again to the filter. Readdition is repeated till the content of nondegraded parts in the eluate is high enough. Then the eluate is fed to the filter without substrate readdition as long as the remaining organic carbon in the eluate is constant. The residual DOC is called refractory.
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