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xx市地处" 辽西走廊" ,是环渤海经济圈的重要组成部分,位于东北经济区和华北经济区的交汇点和连接带上,是重要的节点城市。
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学号： 毕业设计（论文）题目 学 院 专 业 班 级学 生 姓 名指 导 教 师 1. 毕业设计（论文）选题论证书 共 1 页2. 毕业设计（论文）任务书 共 4 页3. 毕业设计（论文）开题报告 共 3 页4. 毕业设计（论文）进度检查表 共 1 页5. 毕业设计（论文）指导教师评定意见 共 1 页6. 毕业设计（论文）评阅人评阅意见 共 1 页7. 毕业设计（论文）答辩记录及成绩 共 1 页8. 毕业设计（论文）答辩委员会评审意见 共 1 页毕业设计题目指导教师姓名职称是否新题是否首次指导毕业设计选题依据设计选题是工程设计题目，设计的内容及难度满足本专业毕业设计要求，知识覆盖面广，能够使学生掌握城市排水工程设计的基本内容、方法、步骤与要求，有利于培养学生综合运用专业知识及相关知识的能力和工程实践能力。该选题满足本专业培养目标并具有水厂规划与设计能力的要求，适应培养设计与管理污水厂人才的需要，有利于提高学生计算机计算与设计能力，利于学生掌握和运用专业知识和技能，学生有必要完成。学生通过专业课的学习，具有完成此课题的理论基础；经过课程实习、生产实习、毕业实习和课程设计对管道和污水厂有较强的感性和理性认识，并有一定的设计基础，学生具备完成该选题的能力。选题工作量适中，学生在毕业设计时间能够完成设计任务。设计内容及成果要求1.设计内容：（1）城市污水处理厂工艺设计（2）污水处理工艺选择及各污水处理构筑物单元设计计算。（3）污泥处理方法选择及污泥处理构筑物的工艺设计计算。（4）污水处理厂的平面布置。（5）污水处理厂纵向布置及高程计算。（6）工程投资及处理成本计算。2.成果要求：（1）图纸要求：应完成 1#图纸 13 张。其中手工绘制至少 1 张，渲染图 1 张。 （2）外文翻译要求：能够较好的翻译本专业外文资料，外文翻译 30005000 字。系（教研室）意见学院毕业设计（论文）领导小组意见主任签字：2013 年 1 月 8 日组长签字：2013 年 1 月 9 日 一、所选题目在其领域的发展现状、设计的目的和意义1.发展现状随着人类社会的不断发展，城市规模的不断扩大，城市的用水量和排水量都在不断增加，加剧了用水的紧张和水质的污染，环境问题日益突出，由此造成的水危机已经成为社会经济发展的重要制约因素。 据统计：目前全国年排污量约为 350 亿立方米,但城市污水集中处理率仅为15，全国超过 80的城市污水未经任何有效的收集处理就直接排放到附近的水体，使得原本具有泄洪和美化景观作用的河渠变成了天然污水渠。特别是在全国 2200 座县城与 19200 个建制镇中，污水排放量约占污水排放总量的一半以上，但这些中小城镇的污水处理能力都明显低于全国平均水平。 目前我国新建及在建的城市污水处理厂所采用的工艺中，各种类型的活性污泥法仍为主流，占 90%以上，其余则为一级处理、强化一级处理、生物膜法及与其他处理工艺相结合的自然生态净化法等污水处理工艺技术。传统上废水的处理方法分为物理法、化学法和生物法。物理法的去除对象是水中不溶解的悬浮物质。化学法是指向废水中投加化学物质，通过化学反应达到净化废水的目的。生物法指采取一定的人工措施，创造微生物生长、繁殖的环境，使微生物大量繁殖，从而提高微生物氧化、分解有机污染物的一种技术。生物法主要用于去除废水中呈溶解态和胶态的有机物，与物理和化学法相比，生物处理在去除废水中有机碳、硫、氮、磷等污染物质方面，存在许多优越之处。传统的活性污泥法与氧化沟，SBR 等工艺相比最大的优点能耗较低，运营费用较低，规模越大，这种有点越明显。 它适用于大中型城市，去除有机物的效率高。当然，我国在污水处理新技术、污水再生利用新技术、污泥处理新技术等方面都取得了可喜的科研成果，某些研究成果达到国际先进水平。国外许多新技术、新工艺、新设备被引进到我国，AB 法、氧化沟法、AO 工艺、A2O 工艺、SBR 法在我国城市污水处理厂中均得到应用。污水处理工艺技术在过去只注重去除有机物发展为具有除磷脱氮功能。国外一些先进、高效的污水处理专用设备也进入了我国污水处理行业市场。题目名称学生姓名学 号专业班级2.设计的目的本设计的选题是工程实际设计题目，通过本次设计，培养我们综合运用给水排水工程基本理论和专业知识的能力，进行城市污水处理工艺系统的选择和单元构筑物设计计算的工程实践技能，独立分析问题和解决工程实际问题的初步能力。并且通过此次设计，训练我们阅读中英文文献的能力、技术和方案的比较能力、理论分析和设计计算能力、工程制图以及编写设计说明说的能力等。设计要求综合运用所学的有关知识，在设计中掌握解决实际工程问题的能力，并进一步巩固和提高理论知识。3.设计的意义（1）了解城市污水处理的发展现状以及发展前景。（2）提高综合运用给水排水工程专业基本理论知识的能力。（3）掌握城市污水处理工艺的选择以及可行性方案的确定。（4）基本掌握排水管网的定线原则和技巧。（5）掌握污水处理工艺单元构筑物的设计计算流程。（6）提高技术经济分析能力。（7）提高设计说明书编写能力。（8）提高相关专业资料查阅能力。（9）提高阅读中英文文献的能力。二、设计主要内容1.城市污水处理厂工艺设计（1）污水处理工艺选择及各单元构筑物的工艺设计计算。（2）污泥处理方法选择及污泥处理构筑物的工艺设计计算。（3）污水处理厂的平面布置。（4）污水处理厂竖向布置及高程计算。2、.工程投资及处理成本计算。 基本掌握影响设计成本的主要因素。三、设计方案及思路本次设计的任务是排水系统的规划及污水处理厂的工艺设计。排水系统的体制一般分为合流制、分流制和混流制。排水体制的选择，应根据城镇的总体规划，满足环境保护的需要，结合当地的地形特点、水文条件、水体状况、气候特征、原有排水设施、污水处理程度和处理后出水利用等综合考虑确定。根据葫芦岛市的实际情况，该市排水系统选用分流制，污水通过管道送至污水处理厂进行处理，达标后排入水体。雨水就近排入水体。污水管道布置充分考虑地形坡度，减小埋深，降低造价。污水处理采用生物二级处理工艺加三级处理，即格栅沉砂池-吸附池中沉池再生池倒置 A20 工艺（即缺氧-厌氧-好氧工艺）二沉池处理工艺-出水在经过絮凝池最终沉淀池消毒处理后排放；污泥采用浓缩厌氧消化机械脱水工艺进行处理，脱水后的污泥外运。本次设计的重点是污水处理工艺的选择以及处理构筑物的选型和参数的确定。指导教师意见系（教研室）意见 签字： 2013 年 3 月 12 日 主任(签字)：2013 年 3 月 14 日时间阶段学生完成的内容指导教师检查意见指导教师签名检查日期第一周收集资料，查阅文献第二周外文翻译第三周毕业实习第四周毕业实习第五周污水处理厂工艺设计及选择第六周污水处理厂构筑物设计选择第七周污水处理厂平面布置第八周污水处理厂构筑物设计计算第九周污水处理厂平面布置图及污水厂平面工艺图（各 1 张）第十周中期检查，曝气池平剖图（2 张）第十一周高程计算，高程图（1 张）第十二周构筑物工艺图（2 张）第十三周泵站工艺设计及工艺图（1 张）第十四周污水处理厂渲染图（1 张）第十五周整理、撰写设计说明书第十六周检查图纸、准备答辩第十七周毕业答辩毕业设计（论文）指导教师评定意见书毕业设计（论文）指导教师评定意见书评定成绩：指导教师签字：指导教师职称： 指导教师单位：毕业设计（论文）评阅人评阅意见书毕业设计（论文）评阅人评阅意见书评阅成绩：评阅教师签字：评阅教师职称： 评阅教师单位： 毕业设计（论文）答辩记录及成绩毕业设计（论文）答辩记录及成绩专业 班级 学生 指导教师 毕业设计题目 答辩时间： 年 月 日 时 分 至 时 分 出出 席席 人人主任委员（组长） 委 员（组员） 、 、 答辩委员会（答辩小组）提出的问题及答辩情况：记录人： 答辩成绩： 主任委员（组长）签字： 毕业设计（论文）答辩委员会评审意见毕业设计（论文）答辩委员会评审意见学生姓名：院（系）：专业班级： 题目名称： 评审意见：毕业设计（论文）成绩评定量化表（按百分制分配）：毕业设计（论文）成绩评定量化表（按百分制分配）：项目评定成绩评阅成绩答辩成绩其他成绩（可选）总分比例分数经评定，该生毕业设计（论文）成绩为： 沈阳建筑大学 学院答辩委员会主 任（签字）： 毕业设计说明书毕 业 设 计 题 目 学 院 专 业 班 级 学 生 姓 名 性别 指 导 教 师 职称 毕业设计任务书毕业设计任务书题题 目目 学 号： 学生姓名 专业班级 学院 指导教师（签字） 职 称 指导教师单位 设计地点 起止日期 1.设计原始条件、主要技术指标与技术参数（或其它数据资料）（1） 、葫芦岛市污水处理厂规划位置图；（2） 、葫芦岛市污水处理厂污水排放量 10 万 m3/d 和水质资料,见下表。 污水水质参数 单位 mg/l水质指标PH 值SSBODCODNH3-NTP进水浓度7.3140200310262.5出水浓度202060100.5（3） 、主导风向：西北风；（4） 、地下其他建筑物不用考虑；（5） 、水文地质资料：、污水处理厂地下水位埋深 2m，冻深 1.3m。（6） 、污水处理厂地面标高 4.0m；（7） 、污水排放水体连山河，连山河最高水位 2.5m、最低水位 2.0m 常水位2.20m。2.设计内容（任务）根据实际情况，在经济上合理和技术上可能并可行的前提下，拟定整个城市的排水系统管网规划方案及污水处理厂设计方案；作出基本的技术决定、工程概算、提出技术经济指标。具体地说，需要进行下列各项工作：（1） 、依据原始资料确定污水泵站工艺设计；（2） 、污水处理厂污水处理工艺设计；1）污水处理工艺选择及各工艺单元的设计；2）污泥处理方法选择及污泥处理构筑物的工艺设计计算；3）污水处理厂的平面布置；4）污水处理厂竖向布置及高程计算；（3） 、污泥处理工艺设计及污水处理厂的工程概算；（4） 、利用 AutoCAD 绘制各种相关图件 12 张（其中含效果图 1 张） 。3.设计工作及成果基本要求设计工作：（1）污水泵站工艺设计要确定水泵机组的台数、水泵型号、泵站的结构形式等。 （2）根据资料与城市规划情况、考虑环境效益与社会效益，合理选择污水处理厂位置。污水处理厂平面布置要紧凑合理，节省占地面积，同时应保证运行管理方便。（3）在确定污水处理工艺流程时，同时选择适宜的各处理单体构筑物的类型。对所有构筑物都进行设计计算，包括确定各有关设计参数、负荷、尺寸与所需的材料与规格等。（4）对污水与污泥处理系统要做出较准确的水力计算与高程计算。（5）对需要绘制工艺施工图的构筑物还要进行更详细的施工图所必须的设计与计算，包括各部位构件的形式、构成与具体尺寸等。（6）污水处理厂要进行经济概算与成本分析基本要求:(1)、绘制 1 张手工图，其余图用 CAD 绘制并出图，(2)、所有图都要求存盘并做成电子文件存档。(3)、外文翻译要求：能够较好的翻译本专业外文资料，外文翻译 30005000 字。4.时间进度安排：时间计 划 完 成 内 容第一周收集资料，开题第二周外文翻译，资料准备第三周污水处理厂工艺选择及设计计算第四周污水处理厂工艺选择及设计计算第五周污水处理厂平面布置及高程计算第六周设计平面、管线布置图第七周设计高程、提升泵房第八周设计平流沉砂池、集配水井第九周设计倒置 A/O 平剖图第十周中期检查、设计接触消毒池第十一周毕业实习参观第十二周毕业实习参观第十三周设计絮凝池、最终沉淀池第十四周设计吸附池、再生池第十五周设计渲染图、整理说明书第十六周检查图纸、准备答辩第十七周毕业答辩5.主要参考文献与资料1.李亚峰、尹士君主编给水排水工程专业毕业设计指南 化学工业出版社2 中小城市污水处理投资决策与工艺技术化学工业出版社3姜乃昌、陈锦章， 水泵及水泵站中国建筑工业出版社 19884顾夏生、黄铭荣、王占生， 水处理工程清华大学出版社 1988.125 给水排水设计手册第一、五、十、十一册，中国建筑工业出版社 19866 给水排水工程快速设计手册第二册，中国建筑工业出版社 19968 工程建设标准规范汇编中国计划出版社 19918 给水排水工程基本建设概预算同济大学出版社 19919 排水工程设计分析 哈尔滨建筑工程学院给水排水教研室编10.哈尔滨建筑工程学院主编， 排水工程下册 中国建筑工业出版社 198811重庆建筑工程学院主编， 排水工程上册 中国建筑工业出版社 1988 12 给水排水专业毕业设计参考图集 沈阳建筑工程学院给排水教研室编 系（教研室）意见学院审批意见经论证，该毕业设计任务书 人才培养方案要求。 主任（签字）：经审核， 下发该任务书。主管院长（主任） （签字）：（任务书下发）日期：2013 年 1 月 9 日备注：系（教研室）意见填写“符合” 或“不符合” ；学院审批意见填写“同意”或“不同意”NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency & Renewable Energy, operated by the Alliance for Sustainable Energy, LLC. Contract No. DE-AC36-08GO28308 Energy Efficiency Strategies for Municipal Wastewater Treatment Facilities J. Daw and K. Hallett National Renewable Energy Laboratory J. DeWolfe and I. Venner Malcolm Pirnie, the Water Division of ARCADIS Technical Report NREL/TP-7A30-53341 January 2012 NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency & Renewable Energy, operated by the Alliance for Sustainable Energy, LLC. National Renewable Energy Laboratory 1617 Cole Boulevard Golden, Colorado 80401 303-275-3000 Contract No. DE-AC36-08GO28308 Energy Efficiency Strategies for Municipal Wastewater Treatment Facilities J. Daw and K. Hallett National Renewable Energy Laboratory J. DeWolfe and I. Venner Malcolm Pirnie, the Water Division of ARCADIS Prepared under Task No. IGST.1104 Technical Report NREL/TP-7A30-53341 January 2012 NOTICE This report was prepared as an account of work sponsored by an agency of the United States government. Neither the United States government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States government or any agency thereof. Available electronically at /bridge Available for a processing fee to U.S. Department of Energy and its contractors, in paper, from: U.S. Department of Energy Office of Scientific and Technical Information P.O. Box 62 Oak Ridge, TN 37831-0062 phone: 865.576.8401 fax: 865.576.5728 email: mailto:reports Available for sale to the public, in paper, from: U.S. Department of Commerce National Technical Information Service 5285 Port Royal Road Springfield, VA 22161 phone: 800.553.6847 fax: 703.605.6900 email: orders online ordering: /help/ordermethods.aspx Cover Photos: (left to right) PIX 16416, PIX 17423, PIX 16560, PIX 17613, PIX 17436, PIX 17721 Printed on paper containing at least 50% wastepaper, including 10% post consumer waste. iii ContactsNational Renewable Energy Laboratory Jennifer Daw, PE, CEM, LEED AP Sustainability Project Manager 1617 Cole Boulevard Golden, CO 80401 Phone: 303-275-4678 E-mail: Jennifer.Daw Kathleen Hallett Energy Information Analyst 1617 Cole Boulevard Golden, CO 80401 Phone: 303-275-3725 E-mail: Kathleen.Hallett Malcolm Pirnie, the Water Division of ARCADIS James DeWolfe, PE, BCEE, CWO Principal Environmental Engineer 1951 Pine Hall Road, Suite 125 State College, PA 16801 Phone: 814-867-1477 Email: James.DeWolfe Ifetayo Venner, PE Senior Environmental Engineer 14025 Riveredge Drive, Suite 600 Tampa, FL 33637 Phone: 813-353-5751 Email: Ifetayo.Venner iv Acknowledgements The National Renewable Energy Laboratory (NREL) would like to acknowledge the contributions of the U.S. Department of Energys Technical Assistance Program, the Office of Resource Efficiency, the town of Crested Butte, and Mt. Crested Butte Water and Sanitation District in the funding of this effort and Malcolm Pirnie, the Water Division of ARCADIS and Gunnison County Electric Association for their expertise in performing the energy audit. v List of Acronyms and Abbreviations ASHRAE American Society for Heating, Refrigerating and Air-Conditioning Engineers ATAD Autothermal Thermophilic Aerobic Digestion BOD Biological Oxygen Demand DO dissolved oxygen EPA U.S. Environmental Protection Agency GCEA Gunnison County Electric Association HP horsepower I&I infiltration and inflow MGD million gallons per day NREL National Renewable Energy Laboratory O&M operations and maintenance OpenEI Open Energy Information Initiative SCADA supervisory control and data acquisition TSS Total Suspended Solids UV ultraviolet VFD Variable Frequency Drive WWTP wastewater treatment plant vi Executive Summary Water and wastewater systems are significant energy consumers with an estimated 3%-4% of total U.S. electricity consumption used for the movement and treatment of water and wastewater 1,2. Water-energy issues are of growing importance in the context of water shortages, higher energy and material costs, and a changing climate. In this economic environment, it is in the best interest for utilities to find efficiencies, both in water and energy use. Performing energy audits at water and wastewater treatment facilities is one way community energy managers can identify opportunities to save money, energy, and water. In this paper the importance of energy use in wastewater facilities is illustrated by a case study of a process energy audit performed for Crested Butte, Colorados wastewater treatment plant1. The energy audit identified opportunities for significant energy savings by looking at power intensive unit processes such as influent pumping, aeration, ultraviolet disinfection, and solids handling. This case study presents best practices that can be readily adopted by facility managers in their pursuit of energy and financial savings in water and wastewater treatment. This paper is intended to improve community energy managers understanding of the role that the water and wastewater sector plays in a communitys total energy consumption. The energy efficiency strategies described provide information on energy savings opportunities, which can be used as a basis for discussing energy management goals with water and wastewater treatment facility managers. 1 Wastewater Division of the Public Works Department: /889an5h vii Table of Contents 1 Introduction 1 Energy Use in the Water and Wastewater Sector 1 EPA Region 8 Partnership 1 2 Case Study: Crested Butte 2 Background 2 Crested Buttes WWTP 3 Energy Audit 3 Collecting Data 4 Existing Process Performance 5 Influent Pumping/Headworks 5 Aeration/Oxidation Ditch 6 Clarification 6 Ultraviolet Disinfection 6 Solids Handling 6 Plant Walkthrough 6 Primary Opportunities for Energy Savings 8 Influent Pumping/Headworks 8 Aeration/Oxidation Ditch 8 Ultraviolet Disinfection 9 Solids Handling 9 Reducing Influent Flow 10 Community Support 10 Next Steps for Crested Butte11 3 Strategies To Consider 11 Process Energy 11 Operational Controls 12 Repair and Replacement 12 Biosolids 12 Infiltration, Inflow and Leaks 13 On-Site Renewable Energy 13 Conservation 13 4 Resources 14 5 Conclusion 14 6 References 15 viii List of Figures Figure 1. Crested Butte, Colorado 2Figure 2. Crested Butte WWTP process flow diagram 3Figure 3. Energy audit levels 4Figure 4. Collecting UV system power draw data 7Figure 5. Measuring DO profile 7Figure 6. Mechanical aerator in oxidation ditch 9Figure 7. Typical WWTP energy consumers 11Figure 8 Quality versus energy 12 List of Tables Table 1. Crested Butte WWTP: Major Energy Consumers 5Table 2. Energy Savings Recommendations 10Table 3. Energy Efficiency Strategies for Municipal WWTPs 13 1 1 Introduction Energy Use in the Water and Wastewater Sector Water and wastewater systems are significant energy consumers. An estimated 3%-4% of U.S. electricity consumption is used for the movement and treatment of water and wastewater 1,2. The exact cost of energy use can vary widely from one utility to the next, with estimates ranging from 2%60% of total operating costs 3,4. Energy represents a substantial cost to wastewater utilities, as it is typically required for all stages in the treatment process, from the collection of raw sewage to the discharge of treated effluent. Given that water and wastewater treatment plants are not primarily designed and operated with energy efficiency as a chief concern, these systems can be overlooked when communities fund energy improvement projects. However, substantial energy and financial savings can be uncovered through operational changes and capital improvements at water and wastewater utilities. Operators and managers of water and wastewater facilities have a wide range of priorities, of which energy consumption is just one 5. Some of their primary duties include: Complying with regulatory requirements to meet customer, public health, and ecological demands Providing reliable service at reasonable and predictable rates Balancing repair and replacement needs with long-term debt, equipment condition, ongoing operations and maintenance costs, and revenue Optimizing operations and maintenance to reduce costs and ensure longevity of assets. Allocating time to conduct an energy audit and make the necessary physical and operational changes can produce substantial benefits. Energy audits help identify the greatest energy-consumers at a facility, reveal opportunities for operational improvements, and detect issues with aging and underperforming equipment. The results of an audit can help to improve energy efficiency, which represents an opportunity for municipalities to reduce operating costs as well as impacts on both the environment and the surrounding community. EPA Region 8 Partnership The U.S. Environmental Protection Agency (EPA) Region 8 office serves the Intermountain West: Colorado, Montana, North Dakota, South Dakota, Utah and Wyoming. In October 2010, EPA Region 8 initiated the EPA Region 8 Utilities Partnership Energy Management Initiative for Public Wastewater and Drinking Water Utilities program with a focus on helping municipal water and wastewater utilities reduce energy consumption, improve reliability and performance, and minimize environmental impacts. In this program, the Region 8 office partnered with 10 15 community water and wastewater facilities to complete the following tasks: Benchmark current and future energy use in the EPA Portfolio Manager tool 6 Perform process energy audits 2 Develop an Energy Management Plan using EPAs Ensuring a Sustainable Future: An Energy Management Guidebook for Wastewater and Water Utilities2 Commit to implementing energy efficiency improvements and sharing results with the EPA Region 8. To increase the breadth of this program and provide value to municipalities that did not participate, EPA Region 8 plans to create a set of case studies to share with other water and wastewater utilities across the Intermountain West that profile some of the participating utilities and illustrate the process, benefits and challenges of optimizing energy performance. Figure 1. Crested Butte, Colorado Source: NREL/PIX 19943 2 Case Study: Crested Butte Background In support of their participation in the program, the town of Crested Butte was required to perform a process energy audit of its wastewater treatment plant (WWTP). The energy audit focused on readily implementable opportunities for energy reduction through process modification and operational improvements. The audit considered optimization of existing processes to realize improved control, monitoring, and WWTP effluent quality. The audit also helped the town begin tracking and benchmarking its WWTP energy use. The Department of Energys National Renewable Energy Laboratory (NREL) partnered with the town of Crested Butte, Malcolm Pirnie, the Water Division of ARCADIS, the Office of Resource Efficiency, and Gunnison County Electric Association (GCEA) (who served as the assessment team) in performing the energy audit. This partnership created an opportunity for these organizations to support local capacity development, working to educate communities and water/wastewater utilities on how to analyze and achieve energy efficiency savings. The intent of this paper is to share energy efficiency strategies learned from the Crested Butte process energy audit with other communities in order to help them achieve their energy reduction and environmental goals. 2 /owm/waterinfrastructure/pdfs/guidebook_si_energymanagement.pdf 3 Crested Buttes WWTP Crested Butte is a small town located on the Western Slope of Colorado and is a major tourist destination for outdoor sports. The WWTP, constructed in 1997, serves the town, which has a permanent population of 1,500 people. The WWTP treats wastewater from residential and commercial customers, with no major industrial discharges to the plant. The plant also accepts solids from the Mt. Crested Butte Water and Sanitation District. The town has an oxidation ditch WWTP, with a permitted capacity of 0.6 million gallons per day (MGD) for a 30-day average daily flow. The plant consists of grit removal, influent pumping, aeration, clarification, ultraviolet (UV) disinfection, and solids handling processes. Treated effluent from the plant discharges to the Slate River. Sludge is thickened and dewatered on-site and hauled to a local landfill for disposal. A simplified process flow diagram for the plant is shown in Figure 2. Figure 2. Crested Butte WWTP process flow diagram Source: NREL Energy Audit As part of the towns participation in the EPA program, an energy audit of the treatment process was required. While not included in this study, building energy audits, which evaluate lighting, heating, cooling, and ventilation systems, can also yield substantial financial and energy savings in treatment facilities. There are three levels of energy audits outlined by the American Society for Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). These audit levels differ with respect to level of complexity, depth of analyses, and the degree of detail the audit can provide. Audits range from Level 1 (a walkthrough) to Level 3 (computer modeling). 4 Figure 3. Energy audit levels Source: NREL For Crested Butte, a Level 1 audit was performed, which included a plant walkthrough focused on treatment process energy use. The Level 1 audit: Evaluates energy consumption and efficiency through an on-site survey to identify maintenance and/or operational needs and deficient equipment Uses energy consumption information to understand usage patterns and to develop an energy baseline Estimates energy and cost savings with an emphasis on low or no-cost measures. Collecting Data The process energy audit was initiated by compiling data from drawings, operational records, utility bills, and equipment inventories to develop an understanding of plant energy usage patterns. The assessment team consulted drawings to look for any operational or energy issues that could be associated with the physical layout of the plant. For example, the drawings showed that the existing dissolved oxygen (DO) meter was located in the anoxic zone of the oxidation ditch. This configuration does not establish an ideal feedback for oxygen control or oxidation ditch performance. It is typically more effective to locate this measurement device where DO levels are greater than zero, such as near the effluent of the ditch. Operational records and parameters such as Biological Oxygen Demand (BOD) and Total Suspended Solids (TSS) were used to distinguish patterns in raw water quality and WWTP performance. Plant operational data were used to establish three “operating seasons” with distinct raw water conditions. These seasons reflect changes in temporary population and infiltration experienced in the collection system throughout the year. The conditions associated with the three seasons are summarized below: Season 1 (October March): Low flow, low load (BOD, TSS on a pound per day basis), and low wastewater temperature Season 2 (April June): High flow, average load, and low wastewater temperature Season 3 (July September): Average flow, high load, and higher wastewater temperature. Energy Audit Levels 7 Level 1: Walkthrough assessment Level 2: Energy survey & analysis Level 3: Detailed analysis/ modeling 5 The assessment team reviewed equipment inventories to determine the age and horsepower of plant equipment and to identify major energy consumers within the facility. An abbreviated list of major energy consumers in the towns WWTP, along with their typical operations and controls, are summarized in Table 1. This information was used to focus audit efforts on major energy consuming processes within the plant to maximize energy savings opportunities. Table 1. Crested Butte WWTP: Major Energy Consumers Existing Process Performance Each process was discussed in detail with plant operations staff to understand performance trends and concerns. General observations on the WWTPs process performance and operational strategies are described in the following paragraphs. Influent Pumping/Headworks The influent system consists of three pumps: one 4.7 horsepower (HP) pump (Pump No. 1) two 17.5 HP pumps (Pumps No. 2 and No. 3). Pump No. 2 runs continuously based on level detection in the wet well. All pumps have Variable Frequency Drives (VFDs). Equipment Quantity Horsepower Operations Controls Mechanical Aerator 1 75 Continuous Variable Frequency Drive (VFD), manual adjustment Centrifuge 1 40 10-20 hrs/week VFD, fixed speed Influent Pump (No. 1) 1 4.7 Continuous VFD, speed based on flow Influent Pumps (No. 2 & 3) 2 17.5 Pump No. 2 continuous Pump No. 3 back-up VFD, speed based on flow VFD, speed based on flow Blowers 3 15 Intermittent Fixed speed Mixers 3 4 Continuous Fixed speed UV System 2 banks 7.3 (kW) Continuous Fixed, 2 banks 6 Aeration/Oxidation Ditch The towns WWTP has one oxidation ditch that provides aerobic removal of BOD and ammonia. There is an anoxic portion of the ditch that provides denitrification, recovers alkalinity, and reduces oxygen demand. The ditch has one 75 HP aerator running on a VFD that is operated based on manual adjustment from a daily DO concentration reading. Typically, energy savings from VFDs come from adjustments that are made automatically to adapt to system conditions, not manual adjustments. The ditch also has two continuously operated mixers in the anoxic zone. The existing DO meter located in the anoxic zone is not operational. Clarification The WWTP has two clarifiers, one that operates continuously and a supplemental clarifier for high flow events. Ultraviolet Disinfection The UV system was designed for a plant flow rate of 1.3 MGD (double the permitted capacity of the facility). The system currently operates with both banks on-line. Plant staff change UV system lamps once a year for preventative maintenance. Since 2008, the average effluent fecal coliform concentration has been 8.3 counts/100 milliliters (mL) with a 7-day average of 214.3 counts/100 mL. The permitted effluent Escherichia Coli (a part of the group fecal coliform) concentration is 1372 counts/100 mL (30-day average) and 2,744 counts/100 mL (7-day average). The current operational approach results in effluent fecal coliform levels that are significantly below permit requirements. Solids Handling The WWTP has an Autothermal Thermophilic Aerobic Digestion (ATAD) system, which is not operational due to odor problems. Therefore, sludge is currently thickened in the raw sludge storage tank and transferred to the thickened sludge storage tank for holding. Due to existing plant piping configurations, sludge must be pumped from the thickened sludge storage tank to the ATAD holding tank to reach the centrifuge for dewatering. Although this allows for additional storage, and therefore potentially less frequent trips to the landfill, it also requires that the 15 HP blower associated with the ATAD storage tank remain operational. The 40 HP centrifuge is controlled by VFD, but typically runs at a constant speed. The centrifuge fills a 20 cubic yard dumpster once a week. Centrate from the centrifuge is piped to the oxidation ditch, which may affect performance of the oxidation process. Plant Walkthrough Using this operational insight, the assessment team visited the WWTP to perform a Level 1 plant walkthrough. This effort consisted of visual inspections to identify operational or maintenance issues and the collection of energy data from major plant equipment. These data will be used by the town to develop estimated cost savings associated with operations and maintenance (O&M) and to prioritize capital improvements to the facility. GCEA assisted the assessment team during the audit by measuring actual power draw for major equipment, including sludge transfer pumps and blowers, which were rotated into operation for 15-minute increments to record actual power use. Using a consistent time interval to measure 7 power draw allows sufficient time for power consumption associated with equipment start-up to level out. These data will be considered by the town to help make prioritizations for improvement. Figure 4. Collecting UV system power draw data Source: NREL/PIX 19941 During the audit, DO concentrations were measured in the oxidation ditch to determine aeration effectiveness. These concentrations created a DO profile that was used to better understand plant operations. Figure 5. Measuring DO profile Source: NREL/PIX 19942 8 A BioWin model3 was developed for the plant using influent characteristics, temperature, historical DO concentrations, typical aerator speeds, and the measured DO profile. Using this process model, the assessment team determined that the existing aerator, which is approximately 15 years old, had poor transfer efficiency relative to newer aerators meaning more energy is used to drive the aerator than would be expected for the resulting DO levels. Primary Opportunities for Energy Savings Based on plant operational information and data collected during the audit, the assessment team developed energy savings recommendations for the WWTP. Influent Pumping/Headworks Flow data provided for the WWTP indicates that infiltration and inflow (I&I) is problematic during Season 2 (April June). To mitigate these issues, it is helpful to identify critical I&I areas in the collection system caused by leaks and breaks. This information will help to prioritize efforts to repair or replace system piping. Another best practice for Crested Buttes WWTP is to tailor the operational strategy for the headworks to meet the three distinct seasons mentioned above. Using smaller horsepower equipment, such as Pump No. 1, to the extent possible, can reduce ongoing energy consumption. Based on typical daily flow patterns, Pump No. 1 could address nightly and mid-day low flow periods in Season 1 (October March) and nightly low flow periods in Season 3 (July September). As Pump No. 1 ages, the town may consider replacing it with a slightly higher capacity pump controlled by VFD to address wet well fluctuations. This increased capacity and improved controls would extend the pumps operations during lower flow periods and minimize usage of the higher horsepower pumps. Aeration/Oxidation Ditch The DO levels measured in the oxidation ditch, in concert with other operational data, indicated that the aerator was not performing efficiently. Given that this is the largest horsepower motor at the WWTP, and that the aerator is nearing the end of its useful life, the assessment team recommends replacing it with a more energy-efficient model. The WWTP may also consider installing a new DO meter and/or ammonia sensor near the ditch outfall to provide more useful feedback on ditch performance. Connecting this meter to the plant supervisory control and data acquisition (SCADA) system will allow for continuous monitoring and control of DO levels. Additional energy savings can be achieved if these DO readings are used to automatically control the speed of the aerator. As a best practice, the mixers are recommended to only be used when the aerator is not operating, which will further reduce the energy use of this process. 3 BioWin is a Microsoft Windows-based simulator used in the analysis and design of wastewater treatment plants. /products/bw32/bw32intro.php 9 Figure 6. Mechanical aerator in oxidation ditch Source: NREL/PIX 19944 Ultraviolet Disinfection Current operations of the UV system are consistent with the ultimate design flow rate, 1.3 MGD. With a current maximum operating flow rate of 0.6 MGD (less than half of the design flow rate of the UV system), the WWTP is surpassing permit requirements. Accordingly, the assessment team recommends that the WWTP operate only one bank of the UV system instead of both banks. Since the system was designed to treat significantly more wastewater than the WWTP currently receives, the facility could also work with the manufacturer to potentially modify the system to save energy by removing bulbs and retrofitting or de-energizing some of the ballasts. Connecting the UV system to SCADA would also improve control of performance. The WWTP may also consider replacing UV system lamps less frequently the manufacturer recommends that bulbs be replaced after 13,500 hours of operation or every 1.5 years. Current operational practices are to replace bulbs as part of scheduled annual maintenance, regardless of running hours. Increasing the bulb replacement interval will save material costs and waste associated with operation of the plant. Solids Handling The current solids handling process is operating inefficiently due to the use of existing ATAD system piping to reach the centrifuge for dewatering. When the ATAD system becomes operational again, this inefficiency will improve. However, the WWTP may also consider making piping retrofits to allow sludge to move directly from the thickened sludge tank to the centrifuge, bypassing the ATAD system. This change would eliminate transfer pumping within the solids handling system. One of the principal products of a WWTP is sewage sludge or biosolids 8. Until two or three decades ago, the typical practice for WWTPs in Region 8 was to dispose of biosolids via landfill or incineration. These days, however, more facilities put biosolids to beneficial reuse and 85% of the biosolids generated in Region 8 are now recycled 9. Most commonly, biosolids are used as a soil amendment to fertilize agricultural land or to restore soils on reclaimed land. Crested Buttes WWTP may also want to consider studying the energy requirements that are needed to treat its biosolids in order to divert them from the landfill for beneficial uses such as fertilizer for agriculture. While more energy is required to treat solids to a Class A or B standard4, it could also reduce vehicle miles to haul the material to the landfill, alleviate some of 4 EPA Sewage Sludge (Biosolids): /polwaste/wastewater/treatment/biosolids/genqa.cfm 10 the long-term environmental burden of landfill disposal, and reduce greenhouse gas emissions associated with landfilled sludge. Reducing Influent Flow Pinpointing areas in the collection system with I&I problems can help the WWTP to focus repair and replacement efforts. Infiltration of groundwater can be a major contributor to the WWTP influent flow. Regular cleaning, inspection, and slip lining of collection system piping can greatly mitigate infiltration and reduce the quantity of wastewater being treated. Community Support An active community-wide conservation program is another essential factor in reducing WWTP plant inflow. Working with the community to promote conservation awareness and to take actions such as installing water efficient fixtures, can significantly reduce flows at the WWTP and save energy. Recommendations and estimated energy and annual financial savings are shown in Table 2. These recommendations have been divided into short-term opportunities, which are lower cost and more readily implementable, and long-term opportunities, which would require more planning and capital expenditure. As presented in the table below, the aeration process offers the largest opportunities for energy and financial savings for the town of Crested Butte. Table 2. Energy Savings Recommendations Process Recommendations Savings (kWh - % energy - $/year) Influent Pumping/Headworks Use Pump No.1 during low flow (ST) Conduct I&I study (LT) Replace Pump No.1 (LT) 4,300 - 10% - $150 14,000 - 35% - $550 8,700 - 20% - $350 Aeration/Oxidation Ditch Turn mixers off when aerator operates (ST) Replace DO meter (ST) Connect new DO meter to SCADA/ Replace aerator (LT) 45,900 - 90% - $1,750 19,800 - 10% - $750 123,000 - 40% - $4,700 UV Disinfection Remove one UV bank from service/ Determine if bulbs can be removed (ST) 32,000 - 50% - $1,200 Solids Handling Retrofit piping to feed sludge directly from thickened sludge tank to centrifuge (LT) 23,500 100% - $1,000 ST = short-term, LT- long-term 11 Next Steps for Crested Butte As a next step, the town will further quantify energy savings associated with the recommended improvements and begin work on their Energy Management Plan. The Energy Management Plan will establish the objectives and targets to be used to measure the towns progress in energy reduction and will guide the towns capital improvement efforts as well as plant O&M activities. Further information on how this information will be used can be found in the EPAs Guidebook 10. Crested Buttes WWTP will also use its energy data to benchmark operational performance against other WWTPs, with the EPA Portfolio Manager. Portfolio Manager is a tool that can help the town identify further opportunities for performance improvement and prioritize investments. 3 Strategies To Consider The Crested Butte case study is an excellent demonstration of how conducting an energy audit can improve a facility or community energy managers understanding of energy savings opportunities at water and wastewater facilities. The following sections provide a brief overview of several general energy savings strategies. Facility and community energy managers alike may want to consider how these energy savings strategies (summarized in Table 3) could be adopted at their communitys water and wastewater treatment facilities. Operators or managers who are ready to develop and implement a comprehensive energy management plan, and readers who are interested in step-by-step guidance, can get started with EPAs Ensuring a Sustainable Future: An Energy Management Guidebook for Wastewater and Water Utilities 10. Process Energy When conducting an energy audit, focus efforts on the biggest energy consumers at the facility. This can be determined by reviewing drawings, nameplate data, or by measuring power draw of equipment. The aeration process is the largest energy consumer for most WWTPs as demonstrated by the typical WWTP energy usage patterns in Figure 7 11. Figure 7. Typical WWTP energy consumers Source: Malcolm Pirnie, the Water Division of ARCADIS 12 Quality Energy Operational Controls Running a WWTP is not a “one size fits all” operation. Regularly evaluating influent and effluent trends can help utilities to tailor operational strategies accordingly. These parameters may vary by season, time of day, and/or have other unique characteristics. System controls that use SCADA feedback and VFDs can be used to optimize effluent quality and energy consumption. This balancing act is a continuous process that facility managers must consider, knowing that higher effluent quality is often at the expense of increased energy use. Achieving an optimal balance between quality and energy is the ultimate goal. Figure 8. Quality versus energy Source: NREL Repair and Replacement As part of capital planning efforts, a best practice for facilities is to regularly evaluate the condition, performance and remaining useful life of process equipment. Aging equipment is more inefficient, can be costly to repair, and typically requires more energy than newer models. When doing an energy audit, equipment age and operational efficiency are major considerations. Evaluating preventative maintenance practices also helps to ensure that equipment is receiving appropriate maintenance for the level of use 12. Biosolids There are significant environmental and financial tradeoffs between providing higher quality biosolids and the subsequent energy demands. When evaluating biosolids treatment and disposal options, the following factors are important for facilities to consider 13: Transportation distance from the WWTP to the landfill affects cost to haul biosolids for disposal Additional costs tipping fees and additional treatment for land application may incur additional costs for biosolids Revenue WWTPs may receive payment for their biosolids as a soil amendment Carbon emissions landfilling of biosolids can result in greater emissions than land application Sustainability using biosolids reduces demand for landfills and synthetic fertilizers, and can help the reclamation and re-vegetation process for brownfield sites. 13 Infiltration, Inflow and Leaks The wastewater collection system is another area of opportunity for utilities. A considerable amount of energy is wasted treating groundwater that infiltrates systems through pipes that are broken or out of alignment. Similarly, breaks and leaks in the collection system increase the energy required to pump sewage to the treatment plant. Focusing efforts on identifying areas with I&I, breaks, and leaks can enable utilities to direct repair and replacement efforts to areas that will provide greater energy and financial savings. On-Site Renewable Energy A best practice for all communities is to look for opportunities to incorporate on-site renewable energy at their facilities. After energy efficiency, renewable energy is another effective way to save money by reducing energy purchases. All renewable resources available within the community, including wind, solar, water, and wastes generated on-site, may be considered as potential energy sources. These renewable systems are selected and installed to maximize energy production 14. WWTPs with anaerobic digestion provide a unique opportunity to create on-site heat and power, by capturing biogas emissions as fuel for on-site energy generation 15. Conservation Effective outreach within the community can yield substantial reductions in water use and wastewater generation. Programs can be implemented that incentivize community members, businesses, and/or industries to reduce their water usage. By providing low-flow fixtures at a discounted fee, conducting water audits, and/or using inverted block rate structures, utilities can substantially reduce the amount of effluent to be treated and dramatically lower energy use within the community. Creating behavioral change through public education programs is another essential element in promoting conservation. As allowed by local water rights, maximizing the use of “fit for purpose” or reuse water may be considered as another conservation strategy. Table
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