中文摘要：

小城镇污水处理项目在初期运行时往往由于收集系统不完善、雨污分流不完善等原因，呈现出进水量少、进水浓度低等特点，从而导致污水处理系统启动较为困难。结合陕南某CAST工艺污水厂的启动与调试项目，研究了小城镇污水处理系统初期运行的工艺特征与启动策略。CAST工艺的启动必须保证足够大的交换比λ（λ≥0．17），且水力停留时间不宜过长（不超过35h），其关键控制指标为SRT和曝气时间比，SRT宜控制在20d左右，曝气时间比应根据进水水质水量及水温等条件灵活控制，但不宜小于0．5。另外，内源呼吸比叩。。可作为污水处理厂调试运行措施有效性控制参数，即控制ηen／C（内源呼吸与去除有机物呼吸比例）在5％～10％和ηen／N（内源呼吸与去除氨氮呼吸比例）值在15％～20％，可使污水处理工艺稳定运行且对有机物有较好的去除效果。

英文摘要：

During the initial operation period of a WWTP in small town, the influent is frequently characterized with relatively small inflow and low concentrations of pollutants because of the lack of collection systems and uncompleted rainwater and sewage separation systems. Based on the start-up and commissioning of a WWTP using CAST process located in the south part of Shaanxi Province, the process character and start-up strategy during the initial operation period of WWTP in small town were studied. enough exchange rate （ λ≥0.17 ） should be ensured for the start-up of CAST process, and the HRT should not be longer than 35 h. The key control indexes included SRT （ approximately 20 d） and the ratio of aeration time （ larger than 0. 5 ） that should be adjusted according to the influent quality, quantity and temperature. Additionally, the endogenous respiration ratio could well indicate that status of the operation of WWTP, i. e.,ηen/C （ the ratio of endogenous and organic removal respirations） and ηen/N （the ratio of endogenous and ammonia removal respirations） were controlled in the range of 5% to 10% and 15% to 20% respectively, indicating the good performance of WWTP .