Biohydrogen and polyhydroxyalkanoate production from original hydrolyzed polyacrylamide-containing wastewater

Abstract This work aimed to study biohydrogen (H 2 ) and polyhydroxyalkanoate (PHA) production from original hydrolyzed polyacrylamide (HPAM)-containing wastewater. NH 4 + -N from HPAM hydrolysis was removed efficiently through short-cut nitrification and anoxic ammonia oxidation (anammox). Carbon/Nitrogen (C/N) ratios of effluent reached 51–97, and TOC decreased only 2%–4%, providing potential for subsequent H 2 and PHA production. The maximum yields of H 2 (0.833 mL·mg −1 substrate ) and Volatile Fatty Acid (VFA) (465 mg·L −1 ) occurred at influent C/N ratio of 51. Substrate removal increased linearly with the activities of dehydrogenase and hydrogenase (R 2  ≥ 0.990), and H 2 yield rose exponentially with enzyme activities (R 2  ≥ 0.989). The maximum PHA yield (54.2% VSS) occurred at the 42nd hour and influent C/N ratio of 97. PHA yield was positively correlated with substrate uptake. The change of H 2 -producing, PHA-accumulating and HPAM-degradating bacteria indicated that those functional microorganisms had synergistic effects on H 2 production and substrate uptake, as well as PHA accumulation and substrate uptake.