Enhanced Biohydrogen Production from Sewage Sludge with Alkaline Pretreatment

Abstract

Batch tests were carried out to analyze influences of the alkaline pretreatment and initial pH value on biohydrogen production from sewage sludge. Experimental results of the impact of different initial pH on biohydrogen production showed that both the maximal hydrogen yield occurred and that no methane was detected in the tests of at the initial pH of 11.0. The final pH decreased at the initial pH of 7.0-12.5 but increased at the initial pH of 3.0-6.0, probably due to the combination of solubilized protein from sludge and the formation of volatile fatty acids (VFAs) and ammonia during biohydrogen fermentation. The performance of biohydrogen production using the raw sludge and the alkaline pretreated sludge was then compared in batch fermentation tests at the initial pH of 11.0. The hydrogen yield was increased from 9.1 mL of H 2 /g of dry solids (DS) of the raw sludge to 16.6 mL of H 2 /g of DS of the alkaline pretreated sludge. No methane and less carbon dioxide (0.8% of control) were present in the biohydrogen production from the alkaline pretreated sludge. These results clearly showed that biohydrogen production could be enhanced and maintained stable by the combination of the high initial pH and alkaline pretreatment. The mechanism of biohydrogen production from sewage sludge at high initial pH was therefore investigated because the results of this study were different from previous studies of biohydrogen production. Results showed that protein was the major substrate for biohydrogen production from sewage sludge and that Eubacterium multiforme and Paenibacillus polymyxa were the dominant bacteria in biohydrogen production from alkaline pretreated sludge at an initial pH of 11.0. The combination of alkaline pretreatment and high initial pH could not only maintain a suitable pH range for the growth of dominant hydrogen-producing anaerobes but also inhibit the growth of hydrogen-consuming anaerobes. In addition, the changes in pH value, oxidationreduction potential, VFAs and soluble COD during hydrogen fermentation were also discussed.

Biohydrogen production by locally isolated facultative bacterial species using the biomass of Eichhornia crassipes: effect of acid and alkali treatment

“…A similar trend was obtained in other studies also; higher H 2 yields were obtained with alkaline pre-treated sludge (Cai et al 2004). Alkaline pre-treatment enhances the enzymatic hydrolysis, thereby facilitating H 2 production (Su et al 2010;Aswathy et al 2009).…”

Evaluation of electricity production from alkaline pretreated sludge using two-chamber microbial fuel cell

“…The result suggests that the insoluble organics (proteins and carbohydrates) were converted continuously into soluble organics in the electricity-producing process in the anode chamber. In the anaerobic digestion or biological hydrogen production of pretreated sludge, similar changes in organic concentrations (proteins and carbohydrates) were observed [4].…”

“…Proteins and carbohydrates are the main organic components of the sewage and alkaline pretreated sludge [4][5][6][7]. In the electricity production process of alkaline pretreated sludge, the two components would be hydrolyzed and their concentrations would decrease (Fig.…”

“…Although the sludge amounts to only a few percent by volume of processed wastewater, its handling accounts for 25-65% of the total plant operation cost [2,3] and its disposal has become problematic for many wastewater treatment plants. However, the sewage sludge contains large amounts of organic matter, mainly protein and carbohydrate [4][5][6]. Wilson and Novak [5] found the total protein in primary and secondary wastewater sludge to be 13,400 ± 1700 mg/L and 31,200 ± 1300 mg/L, respectively, and Wang et al [6] found the quantities of protein and carbohydrate in sludge to be 12,036 mg/L and 2109 mg/L, respectively.…”

“…Wilson and Novak [5] found the total protein in primary and secondary wastewater sludge to be 13,400 ± 1700 mg/L and 31,200 ± 1300 mg/L, respectively, and Wang et al [6] found the quantities of protein and carbohydrate in sludge to be 12,036 mg/L and 2109 mg/L, respectively. The organic matter in sludge could be used to produce useful materials and/or energy (such as hydrogen, methane, and electricity), and much research has been conducted, especially on the release of organics from microbial cells of sludge [4,[7][8][9]. It therefore seems logical to recover value from the treatment and disposal of sludge.…”