Microbial Hydrogen Production with Immobilized Sewage Sludge

Abstract

Municipal sewage sludge was immobilized to produce hydrogen gas under anaerobic conditions. Cell immobilization was essentially achieved by gel entrapment approaches, which were physically or chemically modified by addition of activated carbon (AC), polyurethane (PU), and acrylic latex plus silicone (ALSC). The performance of hydrogen fermentation with a variety of immobilized-cell systems was assessed to identify the optimal type of immobilized cells for practical uses. With sucrose as the limiting carbon source, hydrogen production was more efficient with the immobilized-cell system than with the suspended-cell system, and in both cases the predominant soluble metabolites were butyric acid and acetic acid. Addition of activated carbon into alginate gel (denoted as CA/AC cells) enhanced the hydrogen production rate (v(H2)) and substrate-based yield (Y((H2)/sucrose)) by 70% and 52%, respectively, over the conventional alginate-immobilized cells. Further supplementation of polyurethane or acrylic latex/silicone increased the mechanical strength and operation stability of the immobilized cells but caused a decrease in the hydrogen production rate. Kinetic studies show that the dependence of specific hydrogen production rates on the concentration of limiting substrate (sucrose) can be described by Michaelis-Menten model with good agreement. The kinetic analysis suggests that CA/AC cells may contain higher concentration of active biocatalysts for hydrogen production, while PU and ALSC cells had better affinity to the substrate. Acclimation of the immobilized cells led to a remarkable enhancement in v(H2) with a 25-fold increase for CA/AC and ca. 10- to 15-fold increases for PU and ALSC cells. However, the ALSC cells were found to have better durability than PU and CA/AC cells as they allowed stable hydrogen production for over 24 repeated runs.

Performance analysis of immobilized and co-immobilized enriched-mixed culture for hydrogen production

“…It showed that activated carbon acted as a support for alginate matrix. The average of immobilized and co-immobilized beads this study is less 100 times than Wu et al(2002) [22] (Table 4). It is assumed that the microorganisms used in this study were 16.7%, the alginate material was technical, and the concentration of CaCl2 was 50%.…”

“…Figure 4 shows that the hydrogen yields (mol H 2 /mol glucose) on the co-immobilized bead is larger than the immobilized bead. It is assumed that alginate stability reduced due to chelate complex compound (for example, phosphates), cells growth in the beads, as well as the evolution of gas causing pressure inside the beads will rise so that the integrity of the gel was reduced [22][28]. Although microbes growth in both beads, but the presence of activated carbon in the co-immobilized beads was stronger than the immobilization beads [22][27].…”

“…Hydrogen production using immobilized mixed culture are four times more than suspended cells [20] [21]. Hydrogen concentration using cell immobilized with a mixture matrix consisted of sodium alginate and activated carbon or sodium alginate and polyurethane were 50% of total biogas [22].…”

“…The optimum sodium alginate concentration was 2% which used immobilized mixed culture [26] and municipal sewage sludge [22][21] for biohydrogen production. Co-immobilization used two matrices where the activated carbon was an inert support matrix could strengthen the structure of the alginate beads [22][27].…”

Impact of Culture pH Regulation on Biohydrogen Production using Suspended and Immobilized Microbial Cells

“…These include better handling and the repeated use of cells as well as improved solid to liquid separation efficiency [16]. Immobilized cell culture systems for the continuous production of hydrogen using pure and mixed cultures have been reported [16][17][18].…”