废水产氢产酸/同型产乙酸耦合产酸条件优化

为了更好地发挥产氢产酸/同型产乙酸耦合系统在废水厌氧发酵生产乙酸方面的优势,有必要寻找一种简单有效的方法以获得该系统产酸的优化条件.利用经过加热处理并活化的厌氧污泥作种泥,以模拟废水中的葡萄糖为底物,针对发酵时间、底物浓度、种泥浓度、初始pH进行4因素10水平均匀设计实验,得到了乙酸生产指标与产酸条件之间关系的回归方程;也得到了以高乙酸产量为主要目标导向同时兼顾高乙酸产率和高乙酸生产强度目标的优化条件;优化条件实验乙酸浓度比均匀设计中最高乙酸浓度提高20%左右.研究表明,将均匀设计应用于废水产氢产酸/同型产乙酸耦合产酸条件优化,可以避免盲目性,迅速获得满意结果.     

Enhancement of solubilization and acidification of waste activated sludge by pretreatment

The effects of various pretreatment methods, including thermo-acid, thermo-alkaline, ultrasonic-alkaline and ultrasonic-acid, on solubilization and subsequent acidification efficiency of waste activated sludge (WAS) were investigated. The results showed that both thermo-alkaline and ultrasonic-alkaline significantly improved the solubilization of WAS at a high concentration (7.4% of total solids). Solubilization of volatile solids (VS) and crude protein was 60.2-61.6% and 66.8-67.5%, respectively. Thermo-alkaline or ultrasonic-alkaline pretreatment also enhanced the efficiency of subsequent WAS acidification. Experimental results showed that they had similar effects on the acidification of WAS. The conversion ratio from VS to total volatile fatty acids (TVFAs) was 0.230 in the case of the ultrasonic-alkaline pretreatment. Through this pretreatment, the level of TVFAs was 68% more than the untreated WAS after 252 h of fermentation. The mechanism of TVFAs production under different pretreatment methods was further investigated and the results indicated that soluble protein was the main substrate for TVFAs production from the WAS after the thermo-alkaline or ultrasonic-alkaline pretreatment.     

三峡库区大宁河流域非点源污染研究

以大宁河流域巫溪水文站控制流域为研究对象,应用分布式非点源污染模型SWAT,利用实测流量、泥沙负荷及氮、磷负荷数据对模型进行了率定和验证,并模拟了大宁河流域的径流量和营养物质氮、磷的排放.结果表明,月平均流量在率定期和验证期的效率系数分别达到了0.93和0.62;泥沙负荷的效率系数分别为0.70和0.34;氨氮和总磷的效率系数分别达到了0.31和0.37.大宁河流域污染物质的排放存在着较大的空间差异,有机氮和有机磷的5年平均排放量区间分别为2.01～38.15和0.35～5.89 ks/(hm2·a),其中,流域西南部子流域的有机氮和有机磷平均排放量最大,分别为38.15和5.89 ks/(hm2·a),是大宁河流域污染物排放的最敏感区域.     

人工湿地处理城市污水效能的影响因素分析

为解决人工湿地占地面积大、处理效率低、容易堵塞,往往需要间歇运行等问题,通过对传统的人工湿地进行改造,设计一套新型人工湿地床系统——折流式湿地床 侧流式湿地床,并通过试验对其处理城市污水的运行效能的影响因素进行了研究.研究结果表明,降雨、蒸腾和蒸发、温度、植物收割及堵塞作用对人工湿地运行有不同程度的影响,人工湿地受降雨因素的影响,其出水COD值比降雨前低,同时较人工湿地由于降雨作用所导致的COD稀释浓度高2.4～5.7 mg/L,而降雨使出水SS比降雨前高5.0～7.2 mg/L;堵塞缩短了折流湿地床的运行周期及降低了COD的去除,水力负荷为102.87 cm/d时,运行周期为20 d,水头损失由5.2 cm增至14.8 cm,COD去除率由84.35%降至21.19%;水力负荷为137.16 cm/d时,运行周期为16 d,水头损失由5.0 cm增至15.0 cm,COD去除率由81.26%降至7.35%.     

超声波预处理提高污泥好氧消化性能研究

为评价超声波预处理对提高污泥生物消化的作用,采用超声波预处理与好氧消化衔接,测试了污泥消化的溶解性有机物(SCOD)、TSS及蛋白酶变化过程.结果表明,污泥超声波预处理效果较好的能量密度与时间分别为12 kW/L和10 min,此时有机物释放与能量输入之比较优;在此条件下,经预处理后的污泥好氧消化性能明显比未处理的高.消化时间为10.5 d时,经超声波预处理的污泥TSS减量42.7%,而未处理的污泥仅减量20.9%.经超声波预处理后,污泥中的蛋白酶活性明显提高;同时,超声波预处理释放出较多的可溶性物质.因此,增加的可溶性物质与蛋白酶活性使得污泥迅速降解,提高了污泥好氧消化效率,缩短了污泥好氧消化时间.     

Multivariate Analysis of Interactions Between Phytoplankton Biomass and Environmental Variables in Taihu Lake, China

Phytoplankton variation in large shallow eutrophic lakes is characterized by high spatial and temporal heterogenity. Understanding the pattern of phytoplankton variation and the relationships between it and environmental variables can contribute to eutrophic lakes management. In this study Taihu Lake, one of the largest eutrophic fresh water lake in China, was taken as study area. The water body of Taihu Lake was divided into five regions viz. Wuli bay (WB), Meilian Bay (MB), West Taihu Lake (WTL), Main Body of Taihu Lake (MBTL) and East Taihu Lake (ETL). Concentrations of chlorophyll-a and the related environmental variables were determined in each region in the period 2000–2003. Factor analysis and multivariate analysis were applied to evaluate the interactions between phytoplankton variation and environmental variables. Results showed that the highest average concentrations of TN, TP and Chl-a were observed in WB, followed in a descending order by MB and WTL, and the lowest concentrations of TN, TP and Chl-a were observed in MBTL and ETL. Chl-a and TP concentrations in most regions (except ETL) declined during the study period. It suggested that to some extent the lake was recovering from eutrophication. However, persistent ascending of TN and NH₄–N in all five regions indicated the deteriorating of water quality in the study period. Results of multivariate showed that the relationships between phytoplankton biomass and environmental variables varied among regions. TP illustrated itself a controlling role on phytoplankton in WB, MB, WTL and MBTL according to the significant positive relations to phytoplankton biomass in these regions. Nitrogen could be identified as a limiting factor to phytoplankton biomass in ETL in view of the positive correlations between TN and phytoplankton and between NH₄–N and phytoplankton. Spatial variation of interactions between phytoplankton and environmental parameters suggested proper eutrophication control measures were needed to restore ecological system in each region of Taihu Lake.     

Characteristics of real-world vehicular emissions in Chinese cities

On-board emission measurements were performed on 49 light-duty gasoline vehicles in seven cities of China. Vehicle-specific power mode distribution and emission characteristics were analyzed based on the data collected. The results of our study show that there were significant differences in different types of roads. The emission factors and fuel consumption rates on arterial roads and residential roads were approximately 1.4-2 times those on freeways. The carbon monoxide, hydrocarbon, and nitrogen oxides emission factors of Euro II vehicles were on average 86.2, 88.2, and 64.5% lower than those of carburetor vehicles, respectively. The new vehicle emission standards implemented in China had played an important role in reducing individual vehicle emissions. More comprehensive measures need to be considered to reduce the total amount of emissions from vehicles.     

Short-term effects of gaseous pollutants on cause-specific mortality in Wuhan, China

In Asia, limited studies have been published on the association between daily mortality and gaseous pollutants of nitrogen dioxide (NO2), ozone (O3), and sulfur dioxide (SO2). Our previous studies in Wuhan, China, demonstrated long-term air pollution effects. However, no study has been conducted to determine mortality effects of air pollution in this region. This study was to determine the acute mortality effects of the gaseous pollutants in Wuhan, a city with 7.5 million permanent residents during the period from 2000 to 2004. There are approximately 4.5 million residents in Wuhan who live in the city's core area of 201 km2, where air pollution levels are highest, and pollution ranges are wider than the majority of the cities in the published literature. We used the generalized additive model to analyze pollution, mortality, and covariate data. We found consistent NO2 effects on mortality with the strongest effects on the same day. Every 10-microg/m3 increase in NO2 daily concentration on the same day was associated with an increase in nonaccidental (1.43%; 95% confidence interval [CI]: 0.87-1.99%), cardiovascular (1.65%; 95% CI: 0.87-2.45%), stroke (1.49%; 95% CI: 0.56-2.43%), cardiac (1.77%; 95% CI: 0.44-3.12%), respiratory (2.23%; 95% CI: 0.52-3.96%), and cardiopulmonary mortality (1.60%; 95% CI: 0.85-2.35%). These effects were stronger among the elderly than among the young. Formal examination of exposure-response curves suggests no-threshold linear relationships between daily mortality and NO2, where the NO2 concentrations ranged from 19.2 to 127.4 microg/m3. SO2 and O3 were not associated with daily mortality. The exposure-response relationships demonstrated heterogeneity, with some curves showing nonlinear relationships for SO2 and O3. We conclude that there is consistent evidence of acute effects of NO2 on mortality and suggest that a no-threshold linear relationship exists between NO2 and mortality.     

Monitoring and Assessment of Persistent Organochlorine Residues in Sediments from the Daliaohe River Watershed, Northeast of China

Surface sediment samples from 12 sites of the three selected rivers in Daliaohe River watershed (Hunhe River, Taizihe River and Daliaohe River) were analyzed with the objective of establishing sources and hazard of the organochlorinae pesticides (OCPs) and polychlorinated biphenyl (PCBs) in surface sediments. The total concentrations of OCPs varied from 3.06 to 23.24 ng g⁻¹. ∑HCH (α-HCH, β-HCH, δ-HCH, γ-HCH), ∑DDT (p, p′-DDE, p, p′-DDD, o, p′-DDT, p, p′-DDT) and ∑Cyclodiene (Heptachlor, Aldrin, Heptachlor epoxide, Dieldrin, Endrin) ranged from 1.86 to 21.48, 0.5 to 2.81 and 0.56 to 1.53 ng g⁻¹, respectively. Results of OCPs also illustrate that the most dominant pollutants among the OCPs was ∑HCH, and γ-HCH was the most dominant isomer in HCH, which was evidence of recent input of lindane. It possibly came from the runoff of polluted soils and long-scale transportation. Total PCB concentrations ranged between 1.88 and 16.88 ng g⁻¹. The peak concentrations of PCBs were found in sediments from station T5 and D3, which are in the vicinity of industrial areas and ferry, respectively. These data show a moderate level of OCPs and PCBs contaminations compared to that in other countries.