 While VFA data are available for influent wastewater, no information was found for effluents. Since VFAs are easily biodegradable BOD, they are oxidized in aerated sections and are poorly concentrated in the effluent. Most of the data collected for non-digested sludge were for thickened primary sludges, that can contain very high VFA concentrations, on the contrary to VFA production from WAS seems to be limited and little data is available. Therefore, the range deducted from literature review (150/500/3500) was lowered to 50/250/2500 to be more representative of both primary sludge and WAS.