Hydrogen production from alcohol wastewater by an anaerobic sequencing batch reactor under thermophilic operation: Nitrogen and phosphorous uptakes and transformation

The objective of this study was to investigate hydrogen production from alcohol wastewater using an anaerobic sequencing batch reactor (ASBR) under thermophilic operation and at a constant pH of 5.5. Under the optimum COD loading rate of 68 kg/m3d, the produced gas contained 43% H2 without methane and the system provided a hydrogen yield and specific hydrogen production rate of 130 ml H2/g COD removed and 2100 ml H2/l d, respectively, which were much higher than those obtained under the mesophilic operation. Under thermophilic operation, both nitrogen and phosphate uptakes were minimal at the optimum COD loading rate for hydrogen production and most nitrogen uptake was derived from organic nitrogen. Under the thermophilic operation for hydrogen production, the nutrient requirement in terms of COD:N:P was found to be 100:6:0.5, which was much higher than that for the methenogenic step for methane production under both thermophilic and mesophilic operations and for the acidogenic step for hydrogen production under mesophilic operation.

► Thermophilic ASBR gave higher hydrogen production performance than mesophilic UASB. ► Thermophilic operation can provide higher hydrogen content than mesophilic operation. ► Thermophilic ASBR requires a very high nutrient ratio of COD:N:P = 100:6:0.5. ► Hydrogen-producing bacteria preferentially utilize organic nitrogen.