基于三角模糊数的贝叶斯水质评价模型

将贝叶斯理论和模糊集理论引入水质评价领域,分别描述了水质评价过程中模型结构和参数的不确定性,建立了基于三角模糊数的贝叶斯模糊综合水质评价模型.对Ⅰ、Ⅱ、Ⅲ、Ⅳ、Ⅴ类水分别赋值,并根据监测点水质对各类别的后验概率计算水质的综合得分进而确定水质类别.同时,选取了TP、NH4+-N、COD、DO、As及粪大肠菌群为水质评价因子,将建立的模型应用于2010年洞庭湖水质评价中.结果表明,小河嘴、横岭湖、万子湖、目平湖、洞庭湖出口水质达到Ⅱ类水标准;南嘴、岳阳楼水质为Ⅲ类水;东洞庭湖和扁山水质介于Ⅱ类水和Ⅲ类水之间,对各等级的隶属度分别为0.4983/Ⅲ+0.5017/Ⅱ、0.7962/Ⅲ+0.2038/Ⅱ.各监测点位中,仅南嘴水质未达到相应的水质标准.较均值模型、三角模糊数模型和传统贝叶斯模型而言,基于三角模糊数的贝叶斯水质评价模型对不确定性的表达更为全面、更符合实际.     

Drinking water production by ultrafiltration of Songhuajiang River with PAC adsorption

In recent years, membrane ultrafiltration （UF） of surface water for drinking water treatment has become a more attractive technology worldwide as a possible alternative treatment to conventional clarification. To evaluate the performance of ultrafiltration membranes for treatment of surface water in North China, a 48-m^2 low pressure hollow fiber membrane ultrafiltration pilot plant was constructed. Ultrafiltration was operated in cross-flow and with powdered activated carbon （PAC） adsorption. Turbidity was almost completely removed to less than 0.2 NTU （below Chinese standard 1 NTU）. It was found that PAC addition enhanced organic matter removal. The combined process of PAC/UF allowed to 41% removal of CODMn, 46% removal of DOC and 57% decrease in UV254 absorbance. The elimination of particles, from average 12000/ml in the raw water to approximately 15/ml in the permeated, was observed. When PAC concentration was below 30 mg/L, backwashing could recovery the membrane flux with backwash interval/backwashing duration of 1/30.     

Comparisons of the film peeling from the composite oxides of quartz sand filters using ozone, hydrogen peroxide and chlorine dioxide

To solve the problem of shortened backwashing intervals in groundwater plants, several disinfectants including ozone (O₃), hydrogen peroxide (H₂O₂) and chlorine dioxide (ClO₂) were examined to peel off the film from the quartz sand surface in four pilot-scale columns. An optimized oxidant dosage and oxidation time were determined by batch tests. Subsequently, the optimized conditions were tested in the four pilot-scale columns. The results demonstrated that the backwashing intervals increased from 35.17 to 54.33 (H₂O₂) and to 53.67 hr (ClO₂) after the oxidation treatments, and the increase of backwashing interval after treatment by O₃ was much less than for the other two treatments. Interestingly, the treatment efficiency of filters was not affected by O₃ or H₂O₂ oxidation; but after oxidation by ClO₂, the treatment efficiency was deteriorated, especially the ammonia removal (from 96.96% to 24.95%). The filter sands before and after the oxidation were characterized by scanning electron microscopy and X-ray photoelectron spectroscopy. Compared with the oxidation by O₃ and H₂O₂, the structures on the surface of filter sands were seriously damaged after oxidation by ClO₂. The chemical states of manganese on the surfaces of those treated sands were only changed by ClO₂. The damage of the structures and the change of the chemical states of manganese might have a negative effect on the ammonia removal. In summary, H₂O₂ is a suitable agent for film peeling.     

湖泊水体富营养化评价的随机模拟与三角模糊数耦合模型

根据湖泊水环境系统的不确定性,建立了基于随机模拟和三角模糊数的湖泊水体富营养化评价耦合模型,采用三角模糊数表征各营养因子监测值,运用随机模拟方法模拟三角模糊数,得到各变量的随机模拟序列,由综合营养状态指数法确定湖泊的营养等级概率水平。以宁夏沙湖为例,运用此耦合模型对水体的富营养化程度进行评价。结果表明:该方法将水体富营养评价中水环境状态的不确定性以确定性方法融入评价模型,直观表征了水体在各营养状态隶属度的复杂性,评价结果更加全面、合理。     

基于区间型贝叶斯的湖泊水质评价模型

在贝叶斯水质评价模型中引入区间数表示污染物浓度,采用区间排序法对水质评价结果进行比较,建立了区间型贝叶斯湖泊水质评价模型。同时将该模型应用于某湖泊的5个采样点进行水质监测及评价,结果显示,5个采样点水质逐渐变差,均为劣V类。基于区间型贝叶斯的湖泊水质评价模型更加直观地表示了同类水质采样点的水质差别,避免了传统方法中主观因素的影响,为属于同类别水质的采样点排序提供了评价依据。     

路基沉降的非等间隔时变离散灰色预测模型

本文分析了灰色GM(1,1)模型的缺陷,并以离散GM(1,1)模型为基础建立了路基沉降的非等间隔时变离散灰色预测模型,该模型参数以最小二乘法估计,且以遗传算法优化初始值,通过工程实例与不同预测模型进行对比分析,结果表明非等间隔时变灰色预测模型的精度明显高于其他模型,且最能反映原始路基沉降数据的发展规律.     

熵权多目标决策-理想区间法在地下水环境质量综合评价中的应用

通过将多目标决策-理想区间法与熵值法相结合,建立了基于运用熵权来确定权重的多目标决策-理想区间法,应用一种新思路进行地下水环境质量综合评价。结果表明,该方法可以有效地解决地下水环境质量的优劣评价问题,且使评价过程大大简化,评价结果合理。     

The short-term effects of air pollution on adolescent lung function in Taiwan

A mass screening of lung function associated with air pollutants for children is limited. This study assessed the association between air pollutants exposure and the lung function of junior high school students in a mass screening program in Taipei city, Taiwan. Among 10,396 students with completed asthma screening questionnaires and anthropometric measures, 2919 students aged 12-16 received the spirometry test. Forced vital capacity (FVC) and forced expiratory flow in 1 s (FEV₁) in association with daily ambient concentrations of particulate matter with diameter of 10 μm or less (PM₁₀), sulfur dioxide (SO₂), carbon monoxide (CO), nitrogen dioxide (NO₂), and ozone (O₃) were assessed by regression models controlling for the age, gender, height, weight, student living districts, rainfall and temperature. FVC, had a significant negative association with short-term exposure to O₃ and PM₁₀ measured on the day of spirometry testing. FVC values also were reversely associated with means of SO₂, O₃, NO₂, PM₁₀ and CO exposed 1 d earlier. An increase of 1-ppm CO was associated with the reduction in FVC for 69.8 mL (95% CI: −115, −24.4 mL) or in FEV₁ for 73.7 mL (95% CI: −118, −29.7 mL). An increase in SO₂ for 1 ppb was associated with the reductions in FVC and FEV₁ for 12.9 mL (95% CI: −20.7, −5.09 mL) and 11.7 mL (95% CI: −19.3, −4.16 mL), respectively. In conclusion, the short-term exposure to O₃ and PM₁₀ was associated with reducing FVC and FEV₁. CO and SO₂ exposure had a strong 1-d lag effect on FVC and FEV₁.     

改进的遗传算法在城市污水处理厂区间数优化设计模型中的应用

对于高度非线性的城市污水处理厂区间数优化设计模型(IPODM),若采用传统的方法求解,不仅计算繁琐,且难以有效地寻找全局最优解.本文通过引入遗传算法(GA),与传统的步长搜索法相结合,大大提高了问题的求解效率.本文给出了这种改进算法在某一城市污水处理厂优化设计中的应用实例.结果表明,不仅解的搜索效率有明显的提高,而且目标函数值在原有的基础上改进了20%,有着显著的经济效益;但是由于遗传算法自身的局限性,所求得的解只是一定条件下的最优区间解.     

Effects of chitosan on growth of an aquatic plant (Hydrilla verticillata) in polluted waters with different chemical oxygen demands

Effects of chitosan on a submersed plant, Hydrilla verticillata, were investigated. Results indicated that H. venicillata could prevent ultrastructure phytotoxicities and oxidativereaction from polluted water with high chemical oxygen demand (COD). Superoxide dismutase (SOD) activity and malondialdehyde (MDA) contents in H. verticillata treated with 0.1% chitosan in wastewater increased with high COD (980 mg/L) and decreased with low COD (63 mg/L), respectively. Ultrastructural analysis showed that the stroma and grana of chloroplast basically remained normal. However, plant cells from the control experiment (untreated with chitosan) were vacuolated and the cell interval increased. The relict of protoplast moved to the center, with cells tending to disjoint. Our findings indicate that wastewater with high COD concentration can cause a substantial damage to submersed plant, nevertheless, chitosan probably could alleviate the membrane lipid peroxidization and ultrastructure phytotoxicities, and protect plant cells from stress of high COD concentration polluted water.