Organic fouling development in a direct contact membrane distillation system was investigated with synthetic model solutions of humic acid (HA), alginate acid (AA) and bovine serum albumin (BSA). A 40-50% flux decline was observed, with BSA and HA showing dominant fouling tendencies, while minimal fouling was observed with AA due to its hydrophilic nature. Based on the feed characterization analysis using liquid chromatography-organic carbon detector, the HA feed solution showed thermal disaggregation to low molecular weight-HA (LMW-HA) organics with increased feed temperature (50 degrees C and 70 degrees C). The HA fouled membrane autopsy analysis showed the penetration of organics through the membrane pores. In comparison, the BSA feed solution showed more significant deposits on the membrane surface (352% higher carbon mass compared to HA foulant) with less significant pore penetration. The mixed organic (MO) feed solution consisting of BSA, HA and AA altogether showed evidence of foulant to foulant interaction. The MO feed solution leads to a significant flux decline of 65% only at a later stage upon the disaggregation of LMW-HA organics that adhered on the membrane. (C) 2014 Elsevier B.V. All rights reserved.