Domestic and Industrial Wastewater Treatment with Ozonated Activated Sludge

Poor sludge settleability is a problem encountered in many activated sludge wastewater treatment plants. This study was aimed at combatting the unwanted biological growths at the root of this phenomenon with ozone. Ozone dosed directly into the aeration basins of small activated sludge pilot plants treating both domestic and synthetic fuel wastewaters led to a substantial reduction of the bulking problem even at dosages as low as 6 to 10 mg/L. Ozone did not interfere in the delicate nutrient removal processes and significantly enhanced effluent quality.     

Neutralizing capacity of bottom ash from municipal solid waste incineration of different particle size

This study measures the neutralizing capacity of bottom ash from municipal solid waste incineration of different particle sizes. We examine the effect of particle size on the weathering process, a method popularly used for stabilization of heavy metals in incineration of bottom ash. The distribution of particle sizes in municipal solid waste incineration bottom ash is rather broad, ranging from fine powder to as large as 40 mm in diameter. Although considered a by-product highly suitable as a road construction material, the high level of heavy metal leaching is an obstacle to its reuse. Weathering, a method used to reduce heavy metal leaching, is a lengthy process taking over thee months to complete. The chief reaction involved in weathering is carbonation occurring between Ca(OH)2 in bottom ash and CO₂(g) in the atmosphere. During this process, CaCO₃ is produced, causing the pH level to drop from over 12 to about 8.2 and reducing heavy metal leaching. In this paper, we attempt to determine the particle size best suited for reducing the period required for weathering bottom ash by identifying characteristics of different particle sizes that affect heavy metal leaching and neutralization.     

Extraction of Lipids from Municipal Wastewater Plant Microorganisms for Production of Biodiesel

Municipal wastewater treatment plants in the USA produce over 6.2 × 10⁶ t of dried sewage sludge every year. This microorganism-rich sludge is often landfilled or used as fertilizer. Recent restrictions on the use of sewage sludge, however, have resulted in increased disposal problems. Extraction of lipids from sludge yields an untapped source of cheap feedstock for biodiesel production. Solvents used for extraction in this study include n-hexane, methanol, acetone, and supercritical CO₂. The gravimetric yield of oil was low for nonpolar solvents, but use of polar solvents gave a considerably increased yield; however, the percentage of saponifiable material was less. Extraction of lipids with a mixture of n-hexane, methanol, and acetone gave the largest conversion to biodiesel compared with other solvent systems, 4.41% based on total dry weight of sludge. In situ transesterification of dried sludge resulted in a yield of 6.23%. If a 10% dry weight yield of fatty acid methyl esters is assumed, the amount of biodiesel available for production in the USA is 1.4 × 10⁶ m³/year. Outfitting 50% of municipal wastewater plants for lipid extraction and transesterification could result in enough biodiesel production to replace 0.5% of the national petroleum diesel demand (0.7 × 10⁶ m³).     

Review of Operating Experience Of Ozone Systems In Municipal Plants In The United States

The treatment chemical ozone has now been successfully used in the United States in municipal water and wastewater plants for many years. To insure continuous, successful operations of these applications, operating obstacles had to be dealt with and overcome.

In this paper, examples of field operating problems and their solutions are described. The experiences at specific municipal water and wastewater installations are reviewed in detail. Discussed for each example are : the background and effects of the problem, the problem-solving process, and the eventual resolution of the problem. The examples include simple unit operations to entire processes.

By observing the ozone installation's operation several years after start-up, the design of future ozone systems can be improved and operating problems minimized.     

面向产业链协同商务平台的权限控制模型研究*

分析了产业链企业间协作关系和支持产业链企业间业务协同商务平台的特点,建立了面向动态联盟的四级授权控制模型,对联盟授权管理、企业按联盟协作类别的权限继承管理、企业部门授权管理和部门内具体操作人员的授权管理进行了研究,提出了产业链协同商务平台权限控制算法,并在汽车产业链协同商务平台权限管理中进行了应用验证。     

Characteristics of coal sludge slurry prepared by a wet-grinding process

Coal sludge slurry(CSS) is an alternative fuel and a potential competitive method for sludge reduction.Based on the researches of coal water slurry, we studied CSSs by using a wet-grinding process with different types of regional municipal sludge(sludge) in an orthogonal experiment. The sludge type,sludge mixing proportion, dosage of dispersant, and grinding time were tested in this study. The results show that water content and its occurrence characteristics in the sludge have primary hindering influences on slurry ability. The range of fixed-viscosity concentrations with raw wet sludge is from 50.78%to 44.40%(by weight), while the range is from 53.35% to 51.51%(by weight) with dry sludge. All of the CSSs exhibit shear-thinning behaviors with different variation trends, especially the CSSs with more than 15%(by weight) raw wet sludge in it. Adding the same proportion of raw wet sludge increases the thixotropic properties of CSSs and the highest area of thixotropy loop is 3065 Pa/s, while the highest value of dry sludge is 1798 Pa/s. Hydrophilic group plays an important role in adsorbing water and building three-dimension networks with other particles, which is the main reason for CSS properties.Therefore, the mechanism can be used to find the way for making high quality CSS.     

基于RBAC模型的权限管理改进研究与实现

针对传统RBAC模型无法满足业务审批系统要求的权限可分级、能动态管理的新需求,提出一种改进后的基于角色的控制访问模型。该模型能够动态地创造权限、分配权限、撤销权限,达到资源分离、多级权限管理的目的。结合一个实际项目,采用脚本语言JS （JavaScript）和主流的SSH框架,给出该模型的实现过程,增强各类角色对权限的分级、动态管理,该模型的可行性由此得到验证。     

城市污水处理厂节能水平评估标准探讨

以我国现行典型城市污水处理厂实际运行情况为依托,结合国内外经验成果,在筛选影响城市污水处理厂节能水平重要因子的前提下,初步提出采用打分形式对城市污水处理厂节能水平进行评估的设想,从而建立城市污水处理厂节能水平等级划分标准。     

CA安全认证系统的研究与实现

为提高网络系统的安全性,本文提出了从证书中心、目录服务、注册中心和密钥管理中心等方面入手,构建一个行业级的CA安全认证系统。该方案在烟草某省实施后,经过实际运行证明该方案切实可行。     

基于Struts2拦截实现角色管理与应用系统的解耦

基于Struts2拦截技术,实现角色的权限管理子系统与应用子系统部分的解耦,可以大大减少需求变更所带来的开发成本和代价．并且可以使权限管理子系统重复利用。该方法已经在实际项目中得到了应用。