污水的内含能及污水处理过程的耗能与节能
评价方法的优异性，提出了未来水处理可能的节能新途径。在加深污水内含能认识的基础上，结合相关产业与工艺技术，分离回收有价值成分，如营养物（氮、磷）、重金属等，并获得水资源的再利用，以间接补偿处理过程的能耗，从而实现节能目标。
关键词：污水;内含能;能耗;节能;物质流;能量流
中图分类号：X703.1;X131.2 文献标志码：A 文章编号：2096-6717（2019）05-0151-13
Abstract：Wastewater treatment is a complex process with high energy consumption and low efficiency. Different from the traditional concept of wastewater treatment， the pollutants contained of wastewater can be regarded as energy materials or as the raw materials of other products to be havested to reduce the energy consumption. The forms of the pollutants embodied energy in wastewater were examined by employing two calculation methods and taking sewage and coking wastewater as examples. Moreover， two possible path ways for the utilization and maximization of the recovery of embodied energy during the wastewater treatment were discussed. The different forms of energy consumption and their causes in wastewater treatment process were analyzed based on thermodynamic laws and quality characteristics of the wastewater， with reasonable assumptions. The laws of energy transfer and distribution of two specific cases are expressed by the energy flow diagram. Some possible energy-saving approaches and wastewater treatment methods in the future are predicted by comparing different energy saving technologies. Based on in-depth understanding of the embodied energy in wastewaters， valuable elements such as nutrients （nitrogen， phosphorus） and heavy metals can be separated and recovered， and water resources can be reused by combining with related industries and technologies. Therefore， the goal of energy saving can be achieved by the indirect compensation of energy consumption in the wastewater treatment process.
Keywords：wastewater; embodied energy; energy consumption; energy saving; mass flow; energy flow
中国城镇化和工业化的发展以及人民生活水平的提高，增加了污水和工业废水的排放量，加剧了水环境污染的负荷程度。为了解决旧有污水处理厂现状与标准不断提高的工程技術需求的结构性矛盾，污/废水（文中用污水表达污/废水）处理厂的大规模建设不仅消耗一次资源，持续运行的高能耗也成了新的挑战。美国早在1978年就建成15 000多座污水处理厂，目前已经超过20 000座，二级和二级以上生物处理系统占建厂总数的97%[1]。2008年，美国建成了迄今世界上最先进的污水处理厂，造价4.9亿美元，占地8万m2，能将约31.8万m3/d污水转化为饮用水[2]。最近几年，美国加速了污水处理厂的升级改造，包括污泥、废气、能耗、风险等的综合管理升级，在碳减排、深度处理及营养物质循环利用等方面进行集成系统创新[3-4]。中国城市污水处理在20世纪80年代中后期才正式起步，1984年，采用改良传统活性污泥法处理量达26万m3/d的天津纪庄子污水处理厂的投产，标志着中国的污水处理进入一个新的阶段[5]。“十二五”期间，全国城镇污水处理投资4 300亿元，新增污水处理规模4 569万m3/d，升级改造污水处理规模2 611万m3/d，年COD削减量280万t[6]。迄今，中国已经建成污水处理厂5 800多个，形成了全国的基本覆盖面，可以认为，中国的污水处理由污染防治阶段进入了追求生态和谐的技术创新时代。由于污径比的约束，中国大部分地区的地表水已经没有纳污的环境容量，目前的解决途径之一是推进地表Ⅳ类水的污水排放标准，但这将带来水处理能耗的剧增。因此，评估污水的内含能及其开发途径已经成为非常紧迫的任务。