Recent development of anaerobic digestion processes for energy recovery from wastes

Anaerobic digestion leads to the overall gasification of organic wastewaters and wastes, and produces methane and carbon dioxide; this gasification contributes to reducing organic matter and recovering energy from organic carbons. Here, we propose three new processes and demonstrate the effectiveness of each process. By using complete anaerobic organic matter removal process (CARP), in which diluted wastewaters such as sewage and effluent from a methane fermentation digester were treated under anaerobic condition for post-treatment, the chemical oxygen demand (COD) in wastewater was decreased to less than 20 ppm. The dry ammonia-methane two-stage fermentation process (Am-Met process) is useful for the anaerobic treatment of nitrogen-rich wastes such as waste excess sludge, cow feces, chicken feces, and food waste without the dilution of the ammonia produced by water or carbon-rich wastes. The hydrogen-methane two-stage fermentation (Hy-Met process), in which the hydrogen produced in the first stage is used for a fuel cell system to generate electricity and the methane produced in the second stage is used to generate heat energy to heat the two reactors and satisfy heat requirements, is useful for the treatment of sugar-rich wastewaters, bread wastes, and biodiesel wastewaters.     

Flocculating property of extracellular polymeric substance derived from a marine photosynthetic bacterium, Rhodovulum sp

The effect of the extracellular polymeric substance (EPS) derived from a marine photosynthetic bacterium, Rhodovulum sp., on the flocculation of kaolin is described. The amount of EPS obtained and its flocculating activity were highly dependent on the extraction temperature and duration: high flocculating activity was obtained at a relatively low temperature (30 degrees C) and long extraction time (60 min). The EPS was classified as a weak-anionic high-polymer group based on its pH profile, and its promoting effect on flocculation was dependent on the concentration of cationic ions and their valence. The relative influence of cations on the critical flocculating concentration (Cs,cr) followed the Schulze-Hardy rule for colloidal flocculation. This suggests that the promotion of flocculation by the additions of EPS and cations occurred as a result of the synergistic effect of the release of electrical repulsion by the cations and the formation of bridges between the EPS and the cations.     

Determination of Carbonyl Groups in Starches by Polarographic Techniques Using o-Phenylenediamine. V. Reactions of Periodate Oxidized Starches with o-Phenylenediamine.

The reaction of oxyamylose with o-phenylenediamine (OPD) in alkaline media produces quinoxalines which can be followed by polarographic method and the dialdehyde content can easily be determined polarographically. The lower limit of the determination of dialdehyde content may be 0.01 in the ratio of NaIO₄/AGU. Quinoxalines produced from oxyamylose were studied chromatographically and spectrophotometrically and compared with those from D-glucose. Three quinoxalines were identified with quinoxaline, 2-methylquinoxaline and 2-hydroxyethylquinoxaline. Mechanism of the reaction of oxyamylose with OPD is discussed.