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 trübe 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.
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