Detergent based aqueous two-phase systems have several specific properties, e.g., extreme smalt density differences between the two liquid phases (0.003-0.005 g/cm(3)), low interfacial tensions (5-10 mu N/m) and complex rheological behavior of the product containing detergent-rich phase, which make processing difficult. We describe the successful separation of these aqueous two-phase systems in the pilot scale (1-20 kg) in the presence and absence of microbial cells, either by settling under gravity or in centrifugal separators. The performance of self-desludging liquid-liquid separators and of a nozzle separator was analyzed in detail to judge large scale application. With a feed rate of 16 L/h, stable operation was possible in the desludging machine. Up to 56 Uh could be processed with very close control of the hydrodynamic balance. In a small nozzle separator, feed rates of 90 Uh could be realized, but the purity of the separated phases and the yield of the top phase was slightly lower than in the liquid-liquid separator. The presence of surface-active components in the feed may alter the separation characteristics of the phase systems significantly.