Effects of nitrate concentration on biological hydrogen production by mixed cultures

Abstract

The effects of nitrate on fermentative hydrogen production and soluble metabolites from mixed cultures were investigated by varying nitrate concentrations from 0 to 10 g N/L at 35°C with an initial pH of 7.0. The results showed that the substrate degradation rate, hydrogen production potential, hydrogen yield, and average hydrogen production rate initially increased with increasing nitrate concentrations from 0 to 0.1 g N/L, while they decreased with increasing nitrate concentrations from 0.1 to 10 g N/L. The maximum hydrogen production potential of 305.0 mL, maximum hydrogen yield of 313.1 mL/g glucose, and maximum average hydrogen production rate of 13.3 mL/h were obtained at a nitrate concentration of 0.1 g N/L. The soluble metabolites produced by the mixed cultures contained only ethanol and acetic acid (HAc) without propionic acid (HPr) and butyric acid (HBu). This study used the Modified Logistic model to describe the progress of cumulative hydrogen production in batch tests. A concise model was proposed to describe the effects of nitrate concentration on average hydrogen production rate.

Fermentative Hydrogen Production from Waste Sludge Solubilized by Low-Pressure Wet Oxidation Treatment

“…Hydrogen production from treated sludge in this study obtained VHPR of 13.4–24.6 mL h –1 L –1 , which was higher than VHPR of 0.18–6.59 mL h –1 L –1 obtained in the study using alkaline-treated sludge as the substrate . Various studies have found the positive effect of nutrients, such as minerals, vitamins, and trace elements, on fermentative hydrogen production, − concluding that the waste-activated sludge was rich in various nutrients, which can be helpful for fermentative hydrogen production …”

Fermentative Hydrogen Production Using Disintegrated Waste-Activated Sludge by Low-Frequency Ultrasound Pretreatment

“…Besides the carbon sources, nitrogen and phosphorus were also released to the liquid phase, which are necessary elements for microbial metabolism. 43 After sonication, nitrogen was increased from 5.0 to 33.8 mg/L and phosphorus was increased from 22.1 to 44.6 mg/L. A little decrease in pH was observed from 7.7 to 7.2 after the treatment, which may be due to the VFA formation accompanied by carbohydrate reduction in the treatment process.…”

“…Besides the carbon sources, nitrogen and phosphorus were also released to the liquid phase, which are necessary elements for microbial metabolism . After sonication, nitrogen was increased from 5.0 to 33.8 mg/L and phosphorus was increased from 22.1 to 44.6 mg/L.…”

Deciphering acidogenic process towards biohydrogen, biohythane, and short chain fatty acids production: multi-output optimization strategy

“…Molybdenum plays a very specific role in the activity of dehydrogenase which contains subunits requiring molybdenum as cofactor to function (Popov and Lamzin, 1994;McDowall et al, 2014). could lead to decreased productivity (Lin and Lay, 2004; ; Wang et al, 2009 ). An appropriate C/N and C/P are fundamental for any biological processes to function metabolically effective.…”