Fruit peel crude enzymes for enhancement of biohydrogen production from synthetic swine wastewater by improving biohydrogen-formation processes of dark fermentation.

Biohydrogen is a promising clean fuel but with a low yield. This study aims to enhance biohydrogen production from synthetic swine wastewater by employing crude enzymes obtained from different fruit peels (orange, mandarin, and banana) to improve the biohydrogen-formation processes of dark fermentation. Results indicated that dosing with crude enzymes affected volatile fatty acids (VFAs) and biogas composition insignificantly, while increased biohydrogen yield from 1.62 ± 0.00 (blank) to 1.90 ± 0.08 (orange peel), 2.01 ± 0.00 (mandarin peel), and 1.96 ± 0.01 (banana peel) mol H2/mol glucose, respectively. Banana peel crude enzyme was the most effective additive, with 1 g/L protein improving 97.41 ± 3.72 % of biohydrogen yield. The crude enzymes wielded less influence on acetic acid and butyric acid pathways but enhanced other biohydrogen production pathways. These observations demonstrated that fruit peel-based crude enzymes as additives are advantageous to improving biohydrogen yield towards higher biohydrogen production.

Selective production of volatile fatty acids at different pH in an anaerobic membrane bioreactor.

This study investigated the production of major volatile fatty acid (VFA) components in an anaerobic membrane bioreactor (AnMBR) to treat low-strength synthetic wastewater. No selective inhibition was applied for methane production and solvent-extraction method was used for VFA extraction. The results showed acetic and propionic acid were the predominant VFA components at pH 7.0 and 6.0 with concentrations of 1.444 ±â€¯0.051 and 0.516 ±â€¯0.032 mili-mol/l respectively. At pH 12.0 isobutyric acid was the major VFA component with a highest concentration of 0.712 ±â€¯0.008 mili-mol/l. The highest VFA yield was 48.74 ±â€¯1.5 mg VFA/100 mg CODfeed at pH 7.0. At different pH, AnMBR performance was evaluated in terms of COD, nutrient removal and membrane fouling rate. It was observed that the membrane fouled at a faster rate in both acidic and alkaline pH conditions, the slowest rate in membrane fouling was observed at pH 7.0.

Optimization of hydraulic retention time and organic loading rate for volatile fatty acid production from low strength wastewater in an anaerobic membrane bioreactor.

This study aims to investigate the production of volatile fatty acids (VFAs) from low strength wastewater at various hydraulic retention time (HRT) and organic loading rate (OLR) in a continuous anaerobic membrane bioreactor (AnMBR) using glucose as carbon source. This experiment was performed without any selective inhibition of methanogens and the reactor pH was maintained at 7.0 ±â€¯0.1. 48, 24, 18, 12, 8 and 6 h-HRTs were applied and the highest VFA concentration was recorded at 8 h with an overall VFA yield of 48.20 ±â€¯1.21 mg VFA/100 mg CODfeed. Three different ORLs were applied (350, 550 and 715 mg CODfeed) at the optimum 8 h-HRT. The acetic and propanoic acid concentration maximums were (1.1845 ±â€¯0.0165 and 0.5160 ±â€¯0.0141 mili-mole/l respectively) at 550 mg CODfeed. The isobutyric acid concentration was highest (0.3580 ±â€¯0.0407 mili-mole/l) at 715 mg CODfeed indicating butyric-type fermentation at higher organic loading rate.