<p>Experimental setup of the DKS-permeameter.</p>

The outflow was analysed chemically and microbiologically. Following permeameter testing, the hydraulic conductivity, rheological behaviour and microbial community composition of the soil material were determined, and initial and post-test microbial communities were compared. Based on the analysis a conceptual degradation model was developed and discussed.

Polymer degradation was found to depend on the presence and persistence of specific polymer-degrading microorganisms, with Pseudomonas species identified as key contributors. Although PAA⁺ modified MX80 exhibited higher microbial degradation activity, the long-term performance of polymer-modified bentonite was governed primarily by the charge-dependent polymer-clay binding mechanism rather than by the extent of polymer loss.

Surface-bound PAA⁺ showed greater robustness than bridging-dominated PAA^- systems, as confirmed by hydraulic and rheological analyses.</p></div>