污水处理过程水温变化模型构建与验证

Establishing and verifying a temperature model for the process of wastewater treatment

污水处理是一个复杂的生物、物理及化学反应过程.污水水温直接影响到污染物生物处理效果,并对污水处理运行能耗产生重要影响.另一方面,污水中也蕴含着相当热能,是潜在可以回收的低品位能源,加以利用则有望实现污水处理碳中和运行.然而,现有研究很少涉及污水处理厂污水进、出水水温变化及其影响因素;工程中也只强调冬季保温,并无法从微观角度认识处理过程水温变化规律.为此,研究尝试构建污水处理过程水温变化热量衡算模型,涵盖污水生化反应、机械传热、环境热传递和水蒸发热损失等4个主要涉热过程.与此同时,收集北京某污水处理厂实际水温、气温数据,借助热量平衡图来模拟污水处理过程中水温变化,并对理论模型参数进行校验和修正.通过参数敏感性分析,可以评价不同参数对水温热量的影响程度.基于这些工作,一个污水温度变化模型被构建成功,可用于指导实际污水处理厂水温控制或余温热能回收过程,可助力污水处理厂节能降耗、甚至实现碳中和目标.

Wastewater treatment is a complicated process, including biological, physical and chemical reactions. Water temperature can directly affect the removal efficiency of wastewater temperature, which is associated with energy consumption. On the other hand, there is also a large amount of thermal energy contained in wastewater that can be recovered as a potential low-grade energy, which would contribute to the carbon-neutral operation of wastewater treatment plants(WWTPs). However, there is a very limited number of studies about temperature change between influent and effluent, and influencing factors associated with the temperature change are not paid attention to, and moreover heat preservation is only emphasized in winter but no microscopic mechanisms are revealed. For this reason, this study attempted to establish a temperature model for the process of wastewater treatment, including four main heat-involved processes: biochemical reactions, mechanical heat transfer, environmental heat transfer and heat loss from water evaporation. Then, a set of practical data collected from a WWTP in Beijing were applied to simulate temperature change during wastewater treatment, by which the model was verified and calibrated by the data. Based on a sensitivity analysis, the degrees of temperature change caused by different parameters could be evaluated. Finally, a temperature model was successfully established, which can be applied to guide the practical management of WWTPs on temperature and also on thermal recovery from effluent. In this way, the model can help WWTPs save energy consumption and even utilize thermal energy to achieve the goal of carbon neutrality.