In this study, the development of models for the design of an anaerobic upflow filters separated into two and three phases are presented, DI-FAFS and TRI-FAFS. Both reactors have been evaluated in the COD removal performance on a total of 54 tests. The experimentalfactors are the volumetric organic load, the temperature and the depth relationship between two consective phases. The conceptual modelis based on equations derived from a mass balance under stationary conditions dS/dt = 0 and advectives dS/dZ ≠ 0; eight equationsapplicable to the DI-FAFS and TRI-FAFS reactors; four equations for each reactor.The equations to obtain the parameters of degradationof organic matter were compared with bibliographic references. Two models were selected and proposed, after adjusted to observationswith R2 adjusted greater than 0.7 and with standard errors of estimation and the absolute average error in the minimum values.