Water quality issues have motivated comprehensive investigations to study character, properties and reactivity of organic constituents in water. Sophisticated characterization tools require the organic carbon in a concentrated and desalted form. The objective of this study was to optimize and apply a novel approach using reverse osmosis (RO) and electrodialysis (ED) to concentrate and desalt organic carbon from water samples. Therefore, DOC-isolates of natural organic matter (NOM) and effluent organic matter (EfOM) samples were generated and analyzed. Results were presented in DOC-mass balances. ED-membrane tests were performed to find the best-suited combination for laboratory-scale operation. Furthermore, biodegradation studies of NOM and EfOM isolates, using batch reactors, revealed the influencing factors on biodegradation of highly concentrated DOC. RO concentration showed DOC-losses of 18% for the NOM sample and 12% for the EfOM sample. DOC rejection in the subsequent ED-step was found to be 97% and 96%, respectively. The overall DOC-recovery of the system was approximately 87% in both experiments. Biodegradation studies suggested that substrat concentration may be the limiting factor controlling degradation of DOC.