| Anaerobic biological treatment is the most widely used technology in treating high concentrated organic wastewater and municipal wastewater because of its energy efficiency, resource recovery(methane), less excess sludge production. UASB reactor has the advantages of high treating efficiency and can withstand high organic load, so it is widely used in the treatment of beer, alcohol, pharmaceuticals, starch, chemicals, citric acid and carbonated beverage industry wastewater, which has a high concentration of organic. Sludge granulation is the key factor for the successful operation of UASB reactor,so it is important to study the formation, structure and the characteristics of microbial population of the granular sludge.In this study, the performance of an upflow anaerobic sludge blanket(UASB) reactor treating beverage wastewater in Coca-cola Beverage Co., Ltd. and Hans brewery in Xi’an were investigated in terms of COD removal efficiency, volatile fatty acids in effluent, NH4+-N and PO3--P concentration, methane composition, specific methanogenic activities of the sludge, and the scanning electron microscope(SEM) and fluorescence in situ hybridization(FISH) techniques were used to determing the sludge granulation, morphology and the microbial community. To analyze its operation, provide a theoretical basis and reference for practical engineering application.The experiment results showed that, the performance of a full-scale up-flow anaerobic sludge blanket(UASB) reactor treating low strength soft drink wastewater at ambient temperature in Coca-Cola Beverage Co., Ltd. in Xi’an was investigated. The anaerobic sludge was totally flocculent and the reactor experienced a frequent sludge washout during the past 10 years. The analysis of the wastewater composition showed that nitrogen content in the wastewater was very low and could not meet the requirement of microbial growth. Remarkably, the sludge in the reactor was rapidly granulated by adding nutrients(nitrogen). COD removal efficiency, gas production, methane composition, NH4+-N concentration, specific methanogenic activities, sludge morphology and microbial community were determined before and after granulation. The results showed that the particle size larger than 0.5mm accounted for 54.66% of the total sludge. The COD removal efficiency increased from 84.55% to 92.5%. Maximum methanogenic activities for acetate, propionate and butyrate of the granular sludge were 0.69, 0.47 and 0.39 g COD/(gVSS·d) respectively, which were similar to those of flocculent sludge. Fluorescence In Situ Hybridization(FISH)tests showed microbial community presents a layered structure. Fermentative bacteria predominate at the surface of the granule, whereas archaea distribute in the center of the granular. Sludge granulation was deeply related to nutrient content(nitrogen) in the feeding.The monitoring results of UASB reactor in Xi’an Hans Brewery showed that, although the influent load was fluctuated, but effluent COD maintained 150 ~ 400 mg /L, the removal efficiency was stabilized at 80%, the proportion of methane in the biogas was 74.66% which indicated that most of the organic matter was converted to CH4. Maximum methanogenic activities for acetate, propionate and butyrate were 1.29 g COD /(gVSS·d), 0.47 g COD /(gVSS·d), 0.13 g COD/(gVSS·d), respectively. Sludge morphology in the UASB reactor was mainly floc, FISH results showed that large quantities of methanogenic bacteria accompanied by a portion of bacteria existed in the sludge, to ensure a high methane production capacity of the system, so that the anaerobic treatment operated stably. It should be concluded that UASB reactor had following advantages, good performance of its wastewater treatment, high sludge activity,strong resistance to shock loading capability. However, the anaerobic sludge was flocculent and the reactor experienced a frequent sludge washout during the past years, and the problem such as the slow growth of sludge and and particles also exist. |
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