潮汐河网地区雨天黑臭治理数学模型研究

Mathematical model for wet-weather black-odorous water bodies treatment in tidal river network

雨天溢流截流是控制城市水体雨天黑臭的重要手段。针对潮汐河网地区水闸调控及降雨径流污染排放与河道水质的动态响应问题,基于开源式水动力水质模型系统HEC-RAS并耦合降雨径流模块,建立了实现雨天河道水质控制目标的雨水截流方案论证数学模型。以我国福州市某潮汐河流区域为例,利用自然潮汐与内河水位差,通过动态控制闸门开度,建立三种引排水方案(南引北排、北引南排和南引南排-北引北排放)的水动力和水质模型,模拟雨天不同降雨截流量水平下的河道水质情况,进行最优方案比选分析。结果表明:①在双向引排水模式下,中部区域水动力条件不佳,污染物回荡累积导致水质日趋恶化;②在相同降雨截流量水平下,南引北排调度时的河道断面水质达标率均高于北引南排调度时的达标率;③以场次降雨低于15 mm为基准,按照雨后72 h80%以上的河道断面水质达标为考核条件(氨氮浓度低于4.0 mg/L),在南引北排调度方案下,临界雨水截流量为6 mm。

Intercepting wet-weather overflow is an important method to treat black-odorous water bodies in urban area.Taking into account the dynamic water quality response to sluice gates control and runoff pollutants discharge in tidal river network area, a mathematical model for optimizing runoff interception to meet the designated river water quality goal was developed, based on open source model system HEC-RAS coupled with runoff pollutant model. With one tidal rive catchment in Fuzhou City as a demonstration area, the hydrodynamic and water quality model that incorporates dynamic sluice gates control was developed and calibrated. Based on water level gap between outside tidal waters and inland rivers, river water quality was simulated for three water transfer schemes, that is, south-north transfer, north-south transfer, local south-south transfer and north-north transfer. Correspondingly, anticipated river water quality after intercepting rainfall was simulated to find the optimal scheme. Simulation results showed that:(1) the local water transfer scheme(i.e., local south-south and north-north transfer) is unfavorable for the pollutants degradation and spread especially in central regions, where accumulated pollutants led to the deterioration of water quality;(2) for the same level of rainfall interception, the river reaches attainable to designated water quality goal under south-north transfer is more than those under north-south transfer;(3) setting more than 80% river reaches were able to meet the rehabilitation goal of ammonia concentration below 4.0 mg/L after 72 hours of rainfall, the critical rainfall interception is 6 mm under south-north transfer, for the precipitation event less than 15 mm.