Batch and continuous fermentative production of hydrogen with anaerobic sludge entrapped in a composite polymeric matrix

Abstract

Cell immobilization techniques were adopted to biohydrogen production using immobilized anaerobic sludge as the seed culture. Sucrose-based synthetic wastewater was converted to H 2 using batch and continuous cultures. A novel composite polymeric material comprising polymethyl methacrylate (PMMA), collagen, and activated carbon was used to entrap biomass for H 2 production. Using the PMMA immobilized cells, the favorable conditions for batch H 2 fermentation were 35 °C, pH 6.0, and an 20 g COD l −1 of sucrose, giving a H 2 production rate of 238 ml h −1 l −1 and a H 2 yield of 2.25 mol H 2 mol sucrose −1. Under these optimal conditions, continuous H 2 fermentation was conducted at a hydraulic retention time (HRT) of 4–8 h, giving the best H 2-producing rate of 1.8 l h −1 l −1 (over seven-fold of the best batch result) at a HRT of 6 h and a H 2 yield of 2.0 mol H 2 mol sucrose −1. The sucrose conversion was essentially over 90% in all runs. The biogas consisted of only H 2 and CO 2. The major soluble metabolites were butyric acid, acetic acid, and 2,3-butandiol, while a small amount of ethanol also detected. The PMMA-immobilized-cell system developed in this work seems to be a promising H 2-producing process due to the high stability in continuous operations and the capability of achieving a competitively high H 2 production rate under a relatively low organic loading rate.