The biochemical acidogenic potential (BAP) test is an anaerobic characterization method for wastewater. Fermentable organic fractions are obtained through modeling BAP test results. This method was compared to more common fractionation methods such as settling, coagulation, and respirometry, but no direct relationship was found. Biochemical acidogenic potential testing was thus considered to bring new and complementary information. The settleable matter accounted for approximately 50% of the fermentable matter, with a rate comparable to that of aerobic hydrolysis, suggesting a potential assimilable carbon source that could be liberated in sewers or in anaerobic processes. It was also observed that respirometry could underestimate the amount of fermentable substrates while overestimating that of hydrolyzable matter and of heterotrophic biomass involved in anaerobic processes. The BAP fractions are related to the wastewater capacity to produce volatile fatty acids, which are the main substrates of the microorganisms responsible for enhanced biological phosphorus removal (EBPR). The potential contribution of the BAP fractionation to assist the design, operation, and modeling of the activated‐sludge EBPR processes was discussed.