Analysis of carbon monoxide budget in North China

A global chemical transport model (MOZART-2; model of ozone and related tracers, version 2) was used to assess physical and chemical processes that control the budget of tropospheric carbon monoxide (CO) in North China. Satellite observations of CO from the measurements of pollution in the troposphere (MOPITT) instrument are combined with model results for the analysis. The comparison between the model simulations and the satellite observations of total column CO (TCO) shows that the model can reproduce the spatial and temporal distributions. However, the model results underestimate TCO by 23% in North China. This underestimation of TCO may be caused by the uncertainties of emissions. The tropospheric CO budget analysis suggests that in North China, surface emission is the largest source of tropospheric CO. The main sinks of tropospheric CO in this region are chemical reaction and stratosphere_and_troposphere exchange. The analysis also shows that most of inflow CO to Pacific regions comes from the upwind regions of North China. This transport of CO is significant during Winter and Spring time.     

污水湿地处理工程水力停留时间的测定

利用ＵＡＰ对一个湿地处理工程的实际水力停留时间进行了测定,进而对相关问题进行了探讨。     

垃圾填埋场中硝酸还原酶测定条件优化

作为垃圾填埋场中氮素转化的关键酶之一,硝酸还原酶在填埋场氮素转移的过程中起着重要的作用。以生物反应器填埋场中的垃圾样品为研究对象,以土壤酶学测定方法为基础,对填埋场中硝酸还原酶的测定条件进行了优化研究。结果表明,填埋场中硝酸还原酶的最佳测定条件为：垃圾样品的风干温度为30℃,分别加入1%的KNO₃溶液2.0 mL和1%的葡萄糖溶液0.5 mL,抽气7 min后,置于20℃的培养箱中培养36 h。在该条件下对填埋场中硝酸还原酶活性进行测定,RSD小于1.66％,说明该分析方法结果可靠,精密度高。     

Characterization of the airborne bacteria community at different distances from the rotating brushes in a wastewater treatment plant by 16S rRNA gene clone libraries

Biological risks of bioaerosols emitted from wastewater treatment processes have attracted wide attention in the recent years. However, the culture-based analysis method has been mostly adopted for detecting the bacterial community in bioaerosols, which may result in the underestimation of total microorganism concentration as not all microorganisms are cultivable. In this study, oligonucleotide fingerprinting of 16S rRNA genes was applied to reveal the composition and structure of the bacterial community in bioaerosols from an Orbal oxidation ditch in a Beijing wastewater treatment plant (WWTP). Bioaerosols were collected at different distances from the aerosol source, rotating brushes, and the sampling height was 1.5 m which is the common respiratory height of a human being. The bacterial communities of bioaerosols were diverse, and the lowest bacterial diversity was found at the sampling site just after the rotating brush rotating brush. A large proportion of bacteria in bioaerosols were affiliated with Proteobacteria and Bacteroidetes. Numerous bacteria present in the bioaerosols also emerged in water, indicating that the bacterial community in the bioaerosols was related to that of the aerosols’ sources. The forced aeration of rotating brushes brought about observably distinct bacterial communities between sampling sites situated before and after the rotating brush. Isolation sources of closest relatives in bioaerosols clone libraries were associated with the aqueous environment in the WWTP. Common potential pathogens in bioaerosols as well as those not reported in previous research were also analyzed in this study. Measures should be adopted to reduce the emission of bioaerosols and prevent their exposure to workers.     

Assessing genetic structure, diversity of bacterial aerosol from aeration system in an oxidation ditch wastewater treatment plant by culture methods and bio-molecular tools

Airborne bacteria emissions from oxidation ditch with rotating aeration brushes were investigated in a municipal wastewater treatment plant in Beijing, China. Microbial samples were collected at different distances from the rotating brushes, different heights above the water surface, and different operation state over a 3-month period (April, May, and June) in order to estimate the seasonal variation and site-related distribution characteristics of the microorganisms present. The concentration of bacterial aerosol was analyzed by culture methods, while their dominant species, genetic structure and diversity were assayed using bio-molecular tools. Results showed that total microbial concentrations were highest in June and lowest in April. The mechanical rotation caused remarkable variation in concentration and diversity of culturable airborne bacteria before and after the rotating brushes. The highest concentration was observed near the rotating brushes (931?±?129–3,952?±?730 CFU/m³), with concentration decreasing as distance and height increased. Bacterial community polymerase chain reaction and denaturing gradient gel electrophoresis indicated that diversity decreased gradually with increasing height above the water surface but remained relatively constant at the same height. All dominant bacteria identified by DNA sequence analysis belonged to Firmicutes. Pathogenic species such as Moraxella nonliquefaciens and Flavobacterium odoratum were isolated from the bioaerosols. Due to the serious health risks involved, exposure of sewage workers to airborne microorganisms caused by brush aerators should be monitored and controlled.     

高温厌氧膨胀颗粒污泥床反应器处理聚氯乙烯离心母液废水启动方法

采用高温厌氧膨胀颗粒污泥床(EGSB)反应器处理低浓度、难降解聚氯乙烯(PVC)离心母液废水,以天津市经济技术开发区污水处理厂序批式活性污泥法(SBR)工艺好氧污泥和生物接触氧化法处理PVC离心母液废水污泥的混合污泥为接种污泥,以葡萄糖模拟废水为基质,不断增加PVC离心母液废水所占比例的方法驯化厌氧微生物,实现了系统的成功启动。系统启动期间,进水有机负荷(以COD计)和水力停留时间分别保持在0.2 kg/(m3.d)和50 h左右,出水COD去除率和pH分别稳定在80%和8.0左右。结果表明,添加共代谢基质能利用基质间的协同作用缓解有毒物质对微生物的毒性作用,显著提高了废水的可生化性。通过采用改变水质、保持稳定负荷实现EGSB反应器处理PVC离心母液废水的成功启动证明,该启动方法具有良好的稳定性和可靠性。     

电感耦合等离子体质谱检测水中的汞

本文针对汞易挥发、不稳定、记忆效应强、不易洗脱等一系列的问题,研究了电感耦合等离子体质谱(ICP-MS)检测水中汞元素的可行性方法.结果表明,用5%HNO_3+100μg·L~(-1) Au配置汞溶液, 5%HCl作为冲洗溶液,选用~(185)Re作为内标溶液,分析水中汞~(202)Hg,准确度和精密度较好,仪器检出限满足要求,是检测水中汞的一种可行性方法.     

基于改进混合遗传-支持向量机的CMF产水预测研究

将模拟退火思想和加速遗传特性相结合,改进选择策略和遗传算子,建立加速遗传模拟退火算法（AGSA）;基于支持向量机（SVM）的非线性回归和改进混合遗传算法的因子筛选,构造了支持向量机模型参数的自适应优化算法,提出连续微滤系统（CMF）产水预测模型;通过实测中试规模连续微滤系统产水量变化对模型进行验证,结果表明：该模型较好...     

Effect of influent C/N ratio on N2O emissions from anaerobic/anoxic/oxic biological nitrogen removal processes

The problem of producing strong greenhouse gas of nitrous oxide (N₂O) from biological nitrogen removal (BNR) process in wastewater treatment plants (WWTP) has elicited great concern from various sectors. In this study, three laboratory-scale wastewater treatment systems, with influent C/N ratios of 3.4, 5.4, and 7.5, were set up to study the effect of influent C/N ratio on N₂O generation in anaerobic/anoxic/oxic (A²O) process. Results showed, with the increased influent C/N ratio, N₂O generation from both nitrification and denitrification process was decreased, and the N₂O-N conversion ratio of the process was obviously reduced from 2.23 to 0.05%. Nitrification rate in oxic section was reduced, while denitrification rate in anaerobic and anoxic section was elevated and the removal efficiency of COD, NH₄ ⁺-N, TN, and TP was enhanced in different extent. As the C/N ratio increased from 3.4 to 7.5, activities of three key denitrifying enzymes of nitrate reductase, nitrite reductase, and nitrous oxide reductase were increased. Moreover, microorganism analysis indicated that the relative abundance of ammonium-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) were positively correlated with N₂O generation, which was reduced from (8.42 ± 3.65) to (3.61 ± 1.66)% and (10.38 ± 4.12) to (4.67 ± 1.62)%, respectively. NosZ gene copy numbers of the A²O system were increased from (1.19 ± 0.49) × 10⁷ to (2.84 ± 0.54) × 10⁸ copies/g MLSS with the influent C/N ratio elevated from 3.4 to 7.5. Hence, appropriate influent C/N condition of A²O process could optimize the microbial community structure that simultaneously improve treatment efficiency and decrease the N₂O generation.

     

Change of stream network connectivity under polder-type flood control measure

Polder is usually used for flood control in the river delta area. With the rapid development of urbanization, the dikes or pumps cut the original stream network system, and the stream network connectivity (SNC) and the river system pattern have changed. The dikes or pumps generally force up the river's water level, and regional flood formation mechanisms and processes have changed. In order to quantitatively describe the characteristics of polder-type flood control measure (PFCM) and the change law of SNC, firstly, the streams inside polders were generalized as virtual streams, a hydrological-hydrodynamic model was constructed by connecting Hydrologic Engineering Center-Hydrologic Modeling System and MIKE11 model. Secondly, an SNC evaluation model was constructed based on flow resistance and hydrological process. Finally, the SNC under different scenarios was simulated and evaluated to reveal the influence of the PFCM on SNC. And the dominance analysis method obtained the main control factors of SNC changes. The results showed that the pumps as the main drainage facility under the PFCM, SNC after the opening of the pumps were increased by 0.060, 0.103, and 0.311 for 50%, 30%, and 3% frequency flood scales compared with the pumps closed, respectively. However, compared with the natural stream (without the PFCM), the SNC decreased by 0.391, 0.456, and 0.487, respectively, at the same time of the same flood scale. The PFCM negatively impacted the SNC, and the number of pumps was the main control factor of the SNC.