abstract
- Corn processing wastewater (cornWW) from maize lime-cooking is difficult to valorize due to its high organic load, alkalinity, and calcium content. This study evaluated hydrogen production from decalcified cornWW using biochemical hydrogen potential (BHP) assays and a continuous Upflow Anaerobic Sludge Blanket reactor. Decalcification removed up to 99% of calcium and reduced alkalinity to values compatible with anaerobic fermentation while preserving fermentable substrates. Undiluted decalcified cornWW achieved the highest hydrogen yield (31.65 mLH2 gVS¿1) and production rate (1400 mLH2 L¿1 d¿1), with a shorter lag phase than raw cornWW. During continuous operation, sustained hydrogen production and an acetate-dominated fermentation profile were observed at high organic loading rates. In contrast, dilution led to reduced hydrogen production and a metabolic shift toward ethanol. Microbial analysis showed enrichment of Clostridiaceae under hydrogenogenic conditions. Decalcification and substrate control are key to sustaining hydrogen production, with residual COD enabling integration with a downstream methanogenic stage for improved energy recovery.