This study tries to compare the separation performance of three kinds of membrane distillation (VMD, DCMD and SGMD) used in the removal of ammonia front water in terms of mass transfer coefficient (K-a) and selectivity (beta). For all three MD configurations, equations to determine their K-a and beta values from experimentally obtained results were derived. Experiments of three MID configurations were conducted, respectively, to measure the ammonia concentration and transmembrane flux. So, on the ground of derived equations, K-a and beta were evaluated. It was found that, in comparison of three MID configurations with each other under similar operation conditions, VMD shows the highest K-a but the lowest beta, DCMD gives the highest beta and moderate K-a, and SGMD has the moderate beta and lowest K-a. Factors that may affect the separation processes, such as the membrane characteristics, the feed temperature, the feed and permeate velocity, and the initial concentration and PH of the feed were also experimentally examined. (c) 2006 Elsevier B.V. All rights reserved.