Phosphate enhancing fermentative hydrogen production from substrate with municipal solid waste composting leachate as a nutrient

•Phosphate was supplemented into co-substrate of glucose and MSW fresh leachate.•Orthophosphate show better H2 producing performance than pyrophosphate.•The optimal COD/P ratio for H2 production being 27.64 mg/mg for orthophosphate.•Orthophosphate has duel effects: supplying nutrient and relieving Ca2+ inhibition.

To overcome phosphorus deficiency in municipal solid waste composting leachate, orthophosphate (OP) and pyrophosphate (PP) were separately added into leachate to evaluate the possibility of fermentative H2 production with leachate and phosphorus-rich streams as a full nutrient source. Results indicate H2 production is significantly promoted by OP addition but slightly facilitated by PP in some cases, depending on initial pH and P dosage. The highest hydrogen yield (1.95 ± 0.07 mol H2/mol glucose) was achieved at a COD/P ratio of 27.64 (mg/mg) with OP as phosphorus source at initial pH 5. For PP, a maximum yield of 1.58 ± 0.09 mol H2/mol glucose can be attained at the optimal COD/P ratio of 221.12 (mg/mg) and initial pH 5. OP promotes H2 production via dual approaches: supplying nutrient and relieving inhibition from excessive Ca2+ on granule sludge. However, both the roles in nutrient supply and Ca2+ removal by PP addition are limited.