Biodegradability of substituted aliphatic amines
Prof. Ing. Pavel Pitter, DrSc.
The dissertation thesis deals with ethylenediamine (ED) derivatives biodegradability using mixed culture of activated sludge.
ED and namely its carboxymethyl- derivatives tend to form extremely stable coordination compounds with most metal ions, so called „chelates“. Ethylenediaminetetraacetic acid (EDTA) is the most important derivative of ED from the economical point of view. In natural ecosystems and conventional treatment plants EDTA is biologically non-degradable.
This work was aimed to find the relation between chemical structure of the substance and biochemical stability of complexing agents on ED basis, including EDTA.
Biodegradability of ED and selected ethyl-, hydroxyethyl- and carboxymethyl- derivatives was studied with use of mixed microorganisms culture of activated sludge. Derivatives were gradually approaching to EDTA in terms of the substitution range and characteristics of substituents. The influence of adaptation period and mixed culture retention time (sludge age) on the biodegradation kinetics and rate of individual ED derivatives was also studied.
Biodegradability of ED derivatives generally decreases with increasing substitution range in the molecule. In case of fully substituted ED derivatives biodegradability decreases in order of substituents: ethyl-, hydroxyethyl, carboxymethyl.
ED and all its derivatives are biologically degradable. ED, EED, and N,N-DEED are readily biodegradable by non-adapted activated sludge. N,N‘-DEED and TEED are potentially biodegradable by adapted activated sludge with sludge age of 10 days or higher. Biodegradation decrease with increasing substitution range of ED corresponds to the relation of ED substitution range to chemical oxidation.
Substitution range of hydroxymethyl- derivatives is also the cause of THEED stability and worse biodegradation characteristics of BHEED. HEED is readily biodegradable.
EDTA and HEDTA stability demonstrate the influence of substitution range in case of carboxymethyl- derivatives. EDDA is degradable after adaptation of sludge with sludge age of 5 days, which is important from the view of its strong chelating capacity and thus possible replacement of EDTA.