nan Ikbal

Influence of Mineral Nutrients on High Performance during Anaerobic Treatment of Wastewater from a Beer Brewery

Abstract The BOD of wastewater from beer breweries is around 2,000–3,000 mg/l, which is considered to be low-strength wastewater; however, high-strength wastewater, known sometimes as trube wastewater (BOD, about 80,000 mg/l), is also produced as a result of the filtration of wort. This high-strength wastewater was found not to respond well to treatment by a mono-phase thermophilic methane fermentation process using an anaerobic fluidized-bed reactor. Considering the composition of the wastewater and the pathway for methane fermentation, NH4+ at 500 mg/l, Ni2+ at 7 mg/l, Co2+ at 2 mg/l and Fe3+ at 30 mg/l were added to the wastewater. After five-fold dilution by volume, the diluted wastewater treated anaerobically in the same manner. As a result, the TOC (total organic carbon) concentration in the effluent was constant at about 400 mg/l, and no further problems were encountered. The volumetric loading rate of TOC was studied by treating variously diluted samples of high-strength wastewater (TOC 15,000, 23,500, 47,000 mg/l). The results obtained with the raw wastewater (TOC 47,000 mg/l) were remarkably good, with a maximum volumetric loading rate of TOC of 14 g/l·d, a gas yield of 1.2 l/g TOC consumed and a methane content of 59%. From tests involving omission of the mineral nutrients, it appears that Ni2+ and Co2+ play important roles in the anaerobic treatment of the wastewater.

Treatment of coffee waste by slurry-state anaerobic digestion

Slurries containing 20% (w/v) coffee waste solids were treated anaerobically in one- and two-phase thermophilic methane fermentation systems (53°C) with or without pH control. In one-phase methane fermentation using a roller bottle reactor, the maximum gas evolution rate of 0.87 l/l·d was achieved during treatment for 91 d. However, this one-phase methane fermentation did not yield reproducible data. In a two-phase methane fermentation system consisting of a completely stirred tank reactor type (CSTR-type) liquefaction reactor without pH control and an anaerobic fluidized bed type gasification reactor, three-repetitions of treatment were conducted. Each treatment was very stable and the average gas evolution rate per volume of the gasification reactor was about 2.4 l/l·d. Two-repetitions of treatment were then done while controlling pH in the liquefaction at more than 6. The average gas evolution rate per volume of gasification reactor was found to have increased to 10.2 l/l·d, a value which corresponded to 0.84 l/l·d per total volume, including the liquefaction reactor. It was observed that treatment in a two-phase methane fermentation could be repeated in a stable fashion even in the closed system without discharging anything but the coffee waste residues.

Anaerobic Digestion of Coffee Waste by Two-Phase Methane Fermentation with Slurry-State Liquefaction

Abstract Anaerobic digestion of components of coffee waste was investigated. When the coffee waste was treated by a liquefaction process only, the degradation efficiency was 42%, taking into account the soluble materials that adhered to the surface of the waste. However, in a two-phase anaerobic digestion system consisting of liquefaction and gasification processes, the degradation efficiency increased to 70%. The components of coffee waste, namely, materials that could be eluted by a mixture of alcohol and benzene (hereafter called alcohol-benzene soluble materials), holocellulose and lignin, were degraded by 91%, 70% and 45%, respectively. The gas yield was 451 ml/g degraded coffee waste and 28.2% of the carbon in the waste was converted to biogas. The methane content in the gas evolved from the gasification reactor was high, being 66% (v/v).

Liquefaction and gasification during anaerobic digestion of coffee waste by two-phase methane fermentation with slurry-state liquefaction

Abstract In order to improve the gas evolution rate during anaerobic digestion of coffee waste by two-phase methane fermentation with slurry-state liquefaction, the liquefaction and gasification processes were separately investigated. In the liquefaction process (including the acidification process), treatment at a pH above 6 had no major effects on the liquefaction and acidification rates. However, the VFA production rates were 880 and 320 mg/l·d during mesophilic (37°C) and thermophilic (53°C) liquefaction, respectively. Mesophilic conditions were superior to thermophilic conditions in the liquefaction. With respect to the gasification process, a high TOC volumetric loading rate of 21 g/l·d was achieved during thermophilic gasification. However, the mesophilic gasification did not yield stable data, even at a low TOC volumetric loading rate of 2 g/l·d. The gas yield was 1.7 l/g TOC consumed during thermophilic gasification. The thermophilic liquefaction and thermophilic gasification reactors were connected in series and a two-phase experiment was conducted with the reactors at various volumetric ratios. The maximum gas evolution rate of 1.43 l/l·d was achieved with a combination of a gasification reactor with a 0.45l working volume and liquefaction reactor with a 2l working volume. This rate was 1.7 times higher than the rate obtained in a previous study.

Anaerobic Treatment of Wastewater with High Salt Content from a Pickled-Plum Manufacturing Process

Abstract Anaerobic treatment of wastewater with a high salt content generated during a pickled-plum manufacturing process (TOC, 14g/l; ash, 150g/l; pH 2.7, hereafter called pickled-plum effluent) was investigated for its effect on the high salt content of the wastewater. The synthetic wastewater, including NaCl up to 30g/l, was treated anaerobically by a draw and fill method (treatment temperature, 37°C; volumetric loading rate of organic matter, 2g/l·d). The TOC removal efficiency and rate of gas evolution then gradually decreased as salt content increased, although stable operation was maintained. At NaCl concentrations above 30g/l, TOC removal efficiency decreased rapidly and stable operation could not be maintained. Five-fold-diluted pickled-plum effluent was treated by the same method at a volumetric TOC loading rate of 2.9g/l·d with a TOC removal efficiency of 71%. Five-fold-diluted pickled-plum effluent was also treated in an anaerobic fluidized-bed reactor (AFBR) at a maximum volumetric TOC loading rate of 3.0g/l·d, which gave almost the same results as the draw and fill method. However, ten-fold-diluted pickled-plum effluent could be treated in the AFBR at a maximum volumetric TOC loading rate of 11.1g/l·d with a TOC removal efficiency of 84.6%. The red pigment in the pickled-plum effluent was completely decolorized by the anaerobic treatment.