Study on two operating conditions of a full-scale oxidation ditch for optimization of energy consumption and effluent quality by using CFD model

The operating condition of an oxidation ditch (OD) has significant impact on energy consumption and effluent quality of wastewater treatment plants (WWTPs). An experimentally validated numerical tool, based on computational fluid dynamics (CFD) model, was proposed to optimize the operating condition by considering two important factors: flow field and dissolved oxygen (DO) concentration profiles. The model is capable of predicting flow pattern and oxygen mass transfer characteristics in ODs equipped with surface aerators and submerged impellers. Performance demonstration and comparison of two operating conditions (existing and improved) were carried out in two full-scale Carrousel ODs at the Ping Dingshan WWTP in Henan, China. A moving wall model and a fan model were designed to simulate surface aerators and submerged impellers, respectively. Oxygen mass transfer in the ditch was predicted by using a unit analysis method. In aeration zones, the mass inlets representing the surface aerators were set as one source of DO. In the whole straight channel, the oxygen consumption was modeled by using modified BOD-DO model. The following results were obtained: (1) the CFD model characterized flow pattern and DO concentration profiles in the full-scale OD. The predicted flow field values were within 1.98 ± 4.28% difference from the actual measured values while the predicted DO concentration values were within −4.71 ± 4.15% of the measured ones, (2) a surface aerator should be relocated to around 15 m from the curve bend entrance to reduce energy loss caused by fierce collisions at the wall of the curve bend, and (3) DO concentration gradients in the OD under the improved operating condition were more favorable for occurrence of simultaneous nitrification and denitrification (SND).     

解读宜城民工潮

宜城市是湖北省首批小康市,位于江汉平原与南(阳)襄(樊)盆地的过渡地带,市域面积2115平方公里,耕地面积60万亩,市域人口54万,其中农村人口36万。近几年来,随着人增地减、农业生产率的提高,有限的土地和农村劳动力富余的矛盾越来越突出,加之乡镇企业二次创业、“五小”关闭,乡镇企业吸纳农民就业的能力锐减,全市农村富余劳力由1998年的     

某制粉车间框架结构混凝土性能检测及分析

通过对面粉厂六层框架结构混凝土性能进行了全面检测，并从施工、原材料、环境、荷载几方面分析了混凝土裂缝产生的原因，提出了框架梁开裂的修补和加固方案。     

Excel在造价工程中的应用

通过简单的实例,介绍了Excel在建筑工程造价中的多种应用,简化了大量繁琐的重复的计算。     

某民航售票楼墙体裂缝事故的分析与处理

论述了一个具体的地基处理及基础加固实例。指出在处理此问题时，首先要搞清引起结构破坏的主要原因，然后据此采取设计及施工措施，才能使加固成功。     

休闲农业区域乡村景观规划设计探索

一、休闲农业的兴起随着人民生活水平的提高及农业的发展,以种养业为主的自然经济型农业正在向集约化、规模化、深加工的产业经济型农业迅速发展。同时,随着世界人口城市化速度的加快,     

某住宅楼桩基工程事故分析与处理

本文介绍某住宅楼桩基工程质量事故原因分析，并根据桩土共同受力的原理，采用加宽承台并在承台下设砂垫层的方法，进行加固处理，效果较好。     

轴颈温度对弹性可倾瓦推力轴承润滑性能的影响

求出了无限长可倾瓦推力轴承的热弹性流体动力润滑数值解，并详细考查了轴颈温度对轴承性能的影响．结果指出．降低轴颈温度可显著增加轴承的承载量，但不会明显改变摩擦系数．     

连拱隧道施工技术初探

随着国家环保措施的逐步加强和完善,隧道工程在公路、铁路建设中所占比例越来越高。大跨度隧道施工难度较大,连拱隧道施工相对安全、结构美观以及相对同等地质条件下的分离式隧道而言具有占地少、投资小等优点。受传统施工方法的制约,连拱隧道多以短隧为主。结合某连拱隧道施工经验,浅谈对连拱隧道施工方法的见解和对连拱隧道质量通病的控制及预防。     

75系列塑钢推拉窗的性能特点及安装施工

阐述了７５系列塑钢推拉窗的特点和性能介绍了该窗的安装施工。