Elimination of 14C-labelled polyelectrolytes in biological laboratory reactors

The biodegradability of many polymer compounds is poor, or they are non-degradable. In view of the wide range of applications of polyacrylamides and polycarboxylates, for which no selective analysis is available in natural matrix, elimination studies were carried out on laboratory in size sewage treatment systems and in anaerobic batch experiments with 14C-labelled polymers. An anionic and a cationic polyacrylamide and a anionic polycarboxylate were investigated. Mineralisation into CO2 by biological methods was possible only up to 10% in the case of the polycarboxilate, in the case of the cationic polyacrylamide, only 1,2% of 14C were detected in the case of the anionic polyacrylamide, only 1.0% of 14CO2 were detected; in the case of the anionic polyacrylamide, only less than 0,1%. Pretreatment with UV radiation at 254 nm resulted in 14CO2 formation rates of more than 67%; however, the main component of about 60% was due to direct chemical oxidation of the polycarboxylate in the UV irradiation device and not to biological oxidation. The elimination values in the anaerotric batch investigations were similar. In view of the high persistency of the examined electrolytes, it is recommended to have them substituted by substances with better biodegradability. As it is, they can be eliminated only if the sewage sludge B combusted. (orig.) With 71 figs., 15 tabs