The present study investigated the removal of ammonia from anaerobic digester effluent using membrane contactors. For mass transfer, hollow fiber membrane contactors offer a multitude of advantages compared to stripping technologies. In conventional applications of membrane contactors, the ammonia rich solution circulates through the fibers. For this kind of application, the very high content of suspended solids in digester effluents requires an additional removal step in order to guarantee undisturbed operation conditions. In a new approach, the membrane fibers were simply submerged into the anaerobic digestate and the performance was investigated at moderate temperatures ranging from 20 to 40 degrees C and pH values lying in the range of 8.6 to 10.0. It was demonstrated that the new approach can be applied efficiently for the treatment of particle rich solutions with high ammonia concentrations of 3.000-3.500 mg/L, obtaining removal rates from 80 up to 98.5%. The mass transfer coefficients lay in the range of 12.4-7.0 x 10(-3) m/h and were absolutely comparable to values reported by other authors.