A two-stage anaerobic fermentation of red wine distillery wastes with high tannin concentrations (2-3 g/l) and high sulphate concentrations (3-8 g/l) was investigated. Tannins did not inhibit acid production and sulphate reduction in the acidogenic phase. Even with a concentration of 800 mg/l, 30% of the tannins were degraded in the acidogenic reactor.
A concentration of 500 mg/l tannins in the methane reactor progressively limited the methanogenic biological activity by 20%. A strong inhibition effect was detected towards sulphate-reducing bacteria in the methanogenic reactor.