Anaerobic co-digestion of high sulfate skim latex serum and macroalgae for hydrogen and methane production: Performance of two-stage CSTR–UASB system

Abstract

The natural rubber latex industry produces wastewater with high organic content, requiring efficient treatment. This study evaluated two-stage anaerobic co-digestion (AcoD) of skim latex serum (SLS) and Rhizoclonium sp. macroalgae at 55 °C in batch and continuous experiments. In the first stage (acidogenesis), hydrogen was produced, while the second stage (methanogenesis) used acidogenic effluent to generate methane. Batch tests identified an optimal 60:40 (%VS) SLS-to- Rhizoclonium sp. ratio, yielding 67.2 ± 4.2 mL H<inf>2</inf>/g-VS<inf>added</inf>, and 326.5 ± 22.6 mL CH<inf>4</inf>/g-VS<inf>added</inf>. Continuous operation in a continuously stirred tank reactor (CSTR) and up-flow anaerobic sludge blanket (UASB) reactor achieved 63.1 ± 1.7 mL H<inf>2</inf>/g-VS<inf>added</inf> at 2-day HRT and 308 ± 16 mL CH<inf>4</inf>/g-VS<inf>added</inf> at 18-day HRT. Methylobacterium sp., Alcaligenes sp., and Clostridium sp. dominated the CSTR, while Methanobacterium sp. and Methanothermobacter wolfeii prevailed in the UASB. These results confirm two-stage AcoD as an effective strategy for simultaneous wastewater treatment and bioenergy recovery.