In this study, succinic acid fermentation using acid whey and oat pomace was investigated at 30 L technical scale. Acid whey and oat pomace were mixed in a ratio of 3:1 (v/w) and around 20 g L−1 succinic acid was obtained after 72 hours of fermentation using Actinobacillus succinogenes. The productivities after 24, 48 and 72 hours were 0.46, 0.35, and 0.27 g L−1 h−1 and the overall yield was 0.77 g succinic acid per g total sugars consumed. Acid whey introduced lactic acid and several cat- and anions, which were removed from fermentation broth using a simplified downstreaming processing including filtration and repeated evaporation and crystallization. After three cycles of evaporation and crystallization all organic acids (lactic, acetic, and formic acids) as well as most of the salt ions were removed. From the initial 749 g succinic acid 53 % with a purity of >99 % was recovered.