CFD模拟气调库快速降氧过程O_2和CO_2浓度变化规律

O2和CO2浓度对果蔬的贮藏品质有着极大的影响,获得其在气调库内的变化和分布规律可以为气调库优化设计提供理论依据。该文以西安某苹果气调库为研究对象,采用k-ε紊流模型建立了气调库内气体流动、传热与传质的三维数学求解模型,并通过编写UDF程序获得苹果呼吸强度和冷风机送风口O2、CO2质量分数随库内气体组分浓度变化实时数据。经过对该气调库的快速降氧过程数值模拟获得库内O2和CO2浓度随时间变化的规律,并与试验数据呈现较好的一致性,相对偏差平均值为0.027。结果表明库内气体区O2浓度随时间呈指数衰减。该文的研究对象经过4.1 h,气体区O2浓度下降速度小于货物区,此时提高制氮机制氮体积分数会缩短降氧时间。气体区和货物区CO2浓度变化规律相似,升高速度逐渐变小。库内O2和CO2浓度分布在气体区比较均匀,在货物区则存在一定的梯度,货物区中心位置不利于果蔬的贮藏。该文研究对于获取实际气调库降氧时间及选择合理的制氮机,改进气调工艺具有重要参考价值。

Effects of anaerobic composting on tetracycline degradation in swine manure

Oxytetracycline(OTC) and tetracycline(TC) are the most common TC antibiotics used in human and veterinary medicine.Residual amounts of these antibiotics in manure pose a potential threat to public and ecological health as a result of the potential for them to be released to the environment following land application of manure from animals treated with antibiotics.We investigated the degradation of OTC and TC during anaerobic composting.We tested the effects of temperature and antibiotic concentration on degradation rates in a control and in manure spiked with TCs.We examined changes in p H,biological degradation material(BDM),and moisture corresponding with antibiotic degradation of TCs in the swine manure.Results showed that the OTC and TC concentrations decreased by between 68.54% and 95.50% in all nine treatments following 14 days of anaerobic composting,and the highest removal ef ficiencies were observed at an incubation temperature of 55°C and initial concentrations of 10.36 μg·g^(-1),and 5.96 μg·g^(-1) of OTC and TC,respectively,which were degraded by 95.50%,and 90.06%.During composting at 55 °C and at added concentrations of 5 μg·g^(-1),OTC decreased rapidly,and the time required for50% and 90% degradation was 4.1 and 9.8 days,respectively;for TC,these values were 4.4 and 14.0 days,respectively.Removal ef ficiencies for all TCs correlated well with moisture content of the manure.These results show that composting may be a practical and useful means to reduce concentrations of OTC and TC in swine manure prior to its land application.

Photochemical Degradation of the Ciprofloxacin Antibiotic and Its Microbiological Validation

In this research, it used advanced oxidation processes for the recovery, detoxification and mineralization of wastewater mainly contaminated by antibiotics （ciprofloxacin）. These processes can be used alone or in combination with each other or by complementing traditional methods, even allowing the disinfection of bacterial and viral inactivation. With the use of experimental systems UV/H202/O3, UV/H202, it can achieve total mineralization of the compound. Ciprofloxacin solutions used at 50, 100, 200, 300, 400 and 500 ppm, degraded to 100% of antibiotics and by a microbiological method show that the loss of biological activity is inversely proportional to the time of irradiation.

Oxygen Stable Isotopic Ratio in Precipitations in Niigata Prefecture, Japan

Time-course of oxygen stable isotopic ratios （i.e., δ^18O） as well as seasonal variation of δ^18O has been examined to investigate the characteristics, sources and the passing route of precipitations in Niigata Prefecture. The precipitation samples have been mainly collected with a filtrating bulk sampler at the rooftop of Niigata University. Furthermore, backward trajectories analyses have been also conducted for these samples taken sequentially for a short period. Consequently, the following features have been mainly clarified for the precipitations in Niigata Prefecture： （1） the δ^18O values varied between -14.57%o and -3.86%0 in the precipitations of Niigata University; （2） as for the comparison among sampling points, the mean value of δ^18O at seaside spots （i.e., Niigata City： -6.93%0） is larger than that of inland spots （Sanjyo City： -8.68%0）; （3） δ^18O value was generally small in the rainy or typhoon season, and relatively large in summer; （4） decreasing δ^18O content with time is a predominant feature of sequentially sampled rainfalls as predicted by Rayleigh models of atmospheric vapor condensation.

Removal of Pharmaceutically Active Compounds in Sequencing Batch Reactor

Biological treatment efficiency of six pharmaceutical compounds （acetazolamide, metronidazole, opipramol, piracetam, salicylamide and tinidazole） was evaluated using lab-scale Sequencing Batch Reactor （SBR）. Comparative biological degradation processes of two types of activated sludge from municipal and pharmaceutical industry sewage treatment plants were examined. Three different organic loadings （0.05 g COD/g MLSS.d, 0.1 g COD/g MLSS.d and 0.2 g COD/g MLSS-d） and reaction time on the efficiency of Active Pharmaceutical Ingredient （API） decomposition were examined. Chemical oxygen demand, non-purgeable organic carbon as well as ammonium nitrogen contents were monitored by standard methods. Percentage of API decomposition was analysed by High Performance Liquid Chromatography （HPLC）. The overall API removal efficiency was strictly dependent on the type of activated sludge origin. The main biodegradation products were identified using HPLC-MS,1H NMR and 13C NMR methods as e.g. （{4-[3-（5H-dibenzo[b,f]azepin-5-yl]piperazin-l-yl}methanamine） and （2-amino-1,3,4-thiadiazol-5-sulfonamide） for opipramol and acetazolamide respectively.

Experimental and model comparisons of H_2O_2 assisted UV photodegradation of Microcystin-LR in simulated drinking water

The degradation of Microcystin-LR (MC-LR) in water by hydrogen peroxide assisted ultraviolet (UV/H2O2) process was investigated in this paper. The UV/H2O2 process appeared to be effective in removal of the MC-LR. MC-LR decomposition was primarily ascribed to production of strong and nonselective oxidant-hydroxyl radicals within the system. The intensity of UV radiation, initial concentration of MC-LR, MC-LR purity, dosages of H2O2, the initial solution pH, and anions present in water, to some extent, influenced the degradation rate of MC-LR. A modified pseudo-first-order kinetic model was developed to predict the removal efficiency under different experimental conditions.