污泥回流对平流式沉淀池去除率的影响分析

针对目前的沉淀理论没有考虑回流污泥量将影响颗粒去除效率这一问题,在深向混合沉淀理论的基础上,得出了考虑回流比的非理想沉淀模型.根据所得模型分析了在平流沉淀池中吸泥机带走的污泥回流量对颗粒沉降的影响.并以某污水悬浮物的剩余量与沉速关系曲线为例进行分析.结果表明,在不考虑污泥回流的情况下,颗粒的去除率为72.8%;考虑污泥回流时,当回流比由0.5变化到3.0时,颗粒的去除率则由71.1%递减到50.9%,均小于不考虑污泥回流时的去除率,且回流比为3.0时,颗粒的去除率为50.9%,相对于未考虑回流污泥时的去除率降低了30%.由此可见,污泥回流量使悬浮颗粒的去除率小于无回流量时的去除率,且随着回流比的增大颗粒沉降效率将显著减小.     

污水厂二维沉淀池水流和悬浮物运动数值模拟

 以典型城市污水处理厂平流矩形沉淀池速度和浓度分布计算为例,利用涡量-流函数法建立控制方程,并以有限差分法中的控制容积法对方程进行了离散,求出速度分布场后,利用二维浓度迁移方程对沉淀池浓度分布进行了计算.通过与实验数据的对比,验证了方法的有效性与可行性.另外还对沉淀池数值模拟的应用进行了初步探索.     

Numerical modeling method on the movement of water flow and suspended solids in two-dimensional sedimentation tanks in the wastewater treatment plant

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Numerical modeling method on the movement of water flow and suspended solids in two-dimensional sedimentation tanks in the wastewater treatment plant

Taking the distributing calculation of velocity and concentration as an example,the paper established a series of governing equations by the vorticity-stream function method, and dispersed the equations by the finite differencing method.After figuring out the distribution field of velocity, the paper also calculated the concentration distribution in sedimentation tank by using using the two-dimensional concentration transport equation.The validity and feasibility of the numerical method was verified through comparing with experimental data.Furthermore,the paper carried out a tentative exploration into the application of numerical simulation of sedimentation tanks.     

数值模拟方法在二维沉淀池优化设计中的应用

简要介绍了数值方法在沉淀池悬浮物浓度计算中的应用方法 ,并尝试通过数值模拟过程建立起沉淀池沉降效率与几何尺寸间的关系 ,将其作为约束条件之一建立了一个简单的沉淀池优化设计模型。最后通过实例阐明了这种基于数值计算的优化设计模型的可行性和优势     

大洋山围垦工程对邻近海域环境的影响

利用FVCOM三维海洋数值模型,模拟嵊泗大洋山围垦工程建设填海前后的流场及泥沙运动,对该工程附近海域潮流及各层泥沙分布变化进行了探讨。结果显示,围垦实施后,工程位置西侧及东南侧海域涨、落急潮流减弱、泥沙浓度减小,影响范围主要位于离岸0.26 km以内海域,以外海域潮流和泥沙场格局基本不变;工程东南侧缓流区可能会出现轻微淤积,西侧前沿可能存在冲刷。     

太湖水质时空分布特征及内源释放规律研究

将太湖 2 0 0 1～ 2 0 0 2年的水质监测数据与空间数据相结合 ,采用基于因子分析的主成分分析方法将太湖的水质参数概括为 5个主成分 ,提取并反证了湖泊水质各个主成分的科学内涵 ,分别为 :水体营养指数 (F1)、富营养化指数 (F2 )、水体溶解氧指数 (F3 )、水体色度指数 (F4)和水体酸碱指数 (F5 ) ;研究了各主成分的空间分布特征和随时间的变化规律 .在室内环形水槽内模拟了水动力条件下太湖底泥的起动规律 ,得到了太湖底泥在 3种不同起动标准 (个别动、少量动、普遍动 )下的起动流速 ,并利用泥沙起动的理论模型给予了验证 ,最后得出太湖底泥在 3种不同起动标准下的起动流速分别为 :3 7.9cm·s- 1 ,46 7cm·s- 1 ,5 9 8cm·s- 1 .通过考察上覆水中TN、TP浓度的变化 ,建立了底泥中TN、TP释放率与水体流速的定量化关系 .并将太湖水量水质的同步监测资料应用在数学模型中 ,解决了以往模型中底泥释放率取为常数的不足 ,取得了较好的效果     

皮口至大长山岛海域现代沉积特征

2003年9月国家海洋环境监测中心对皮口至大长山岛海域进行了海洋资源综合调查与评价.取表层沉积物样90余个,3柱柱状样,通过实验室分析,将表层沉积物类型及其分布特征进行分析,并应用210Pb测年技术,测得调查区海域现代沉积物的堆积速度,探讨其沉积物的沉积速率.结果表明,该区表层沉积物类型以细颗粒沉积为主,具有淤泥质岸带的沉积特征.210Pb测得沉积速率揭示出测区的北岸潮滩区高于水下岸坡也高于大长山岛北侧近岸海域.该区物质来源丰富,沿岸鸭绿江、大洋河、碧流河、和庄河携带的泥沙严格控制了沉积物类型的分布特征.     

Experimental study on sediment-copper distributions in hyper-concentrated turbulent solid-liquid system

This study presents a special problem on vertical distribution for sediment and copper in hyper-concentrated turbulent solid-liquid system that is essentially different from the ordinary low-concentrated turbulent system. A resonance type turbulent simulation equipment is used for the experimental study in which a vertically uniform turbulent field of the mixture of loess and water is produced in a testing cylinder with a grille stirrer that moves up and down harmoniously with varying vibration frequencies, in order to compare the variations of the vertical profiles of sediment and copper in low- and hyper-concentratod solid-liquid system, different scenarios for input sediment content ranging from 5 to 800 kg/m^3 was considered in the experimental studies. It was found that solids copper content increases with input sediment content, So, and reaches its peak as So goes to 10 kg/m^3 and then decreases rapidly with increasing input sediment content. Such a behavior is possibly resulted from the joint effect of the specific adsorption of copper on loess, precipitation of carbonate and hydroxide of copper due to high carbonate content in the loess and the so-called ＂particulate concentration effect＂ due to the present of the sediment variation in water. The vertical sediment concentration distribution resulted from the uniform turbulence is generally uniform, but slight non-uniformity does occur as sediment concentration exceeds certain value. However, the vertical concentration distributions of soluble copper seem not to be affected much by the variation of sediment concentrations.     

Fraction distribution and risk assessment of heavy metals in sediments of Moshui Lake

To examine the status and risk of heavy metal pollution in urban lakes, in China, the distribution of several heavy metals (e.g., Cr, Cu, Ni, Pb, Zn) in the sediment of Moshui Lake, Hangyang District, Wuhan City, was characterized. The process of rapid urbanization and industrialization of the district was also studied to find out its relationship with the metal accumulation profile in the sediment. It was found that the total concentration of heavy metals in the sediment was higher than the severe e ect level (SEL), at all sampling sites, except those in the riparian zone. The Cr and Cu maximum concentrations were 1,780 and 1,250 mg/kg, approximately 16 and 11 times as much as the SEL values, and they appeared as deep as 32 cm in one sample. The carbonate and exchangeable fractions of Zn were more than 50% of the total Zn content, resulting in very high risk according to the Risk Assessment Code (RAC). For Cu and Ni, a medium RAC value was found for carbonate and exchangeable fractions of 11%–20%. As sensitive indicators of contaminants in aquatic systems, heavy metals in the sediment reflect the outcome of regional urbanization, industrialization, and environmental management. With rapid urbanization, sedimentary Pb and Zn concentrations increased. The experimental results showed that high sedimentary heavy metal concentrations had resulted from rapid urbanization and industrialization, which would absolutely lead to substantial aquatic environmental decline in urban lakes.