Research On Rainwater Recycling Technology In Large Public Buildings

Rainwater collection and utilization is one of the main contents of sponge city construction engineering technology research.If rainwater can be fully collected and utilized,urban water shortage,threat of urban waterlogging and flood control pressure can be alleviated,and water ecological environment can be improved.The feasibility and importance of rainwater recycling in Wanzhou High-speed Railway Station were analyzed in the research.The main task is to carry out research on rainwater collection and utilization technologies such as rainwater abandonment,rainwater treatment technology and rainwater recoverable amount in the medium and large public building environment of mountainous cities.It also provided reference and data support for the construction of sponge cities.The main conclusions of this study are as follows:?1?The rainfall runoff quality of the different underlying surfaces had regularity along with the rainfall duration,under the different rainfall intensities.The pollutants concentration reached peak value at the early stage of the rainfall duration.Combined with the analysis of the rainfall runoff quality,it was proposed to use the rainfall runoff of the high-speed railway station roof and the station square.The phenomenon of first flush in the initial rainfall runoff of the different underlying surfaces was analyzed by the cumulative curve.The results showed that the first flush effects were different under different underlying surfaces.Namely,the percentage of cumulative pollutants in rainwater runoff was higher than the percentage of transport of cumulative runoff.The roof of the high-speed railway station and station square tended to form first flush easily,and the first flush effects was more significant in the former.The abandoning flow of the initial rainwater could simplify the rainwater treatment process and effectively reduce the treatment cost.Consequently,the volumetric abandonment device for 3 mm initial rainfall was recommended.?2?The treatment process of the rainwater recycling for the large public buildings was as fllows:rainwater?initial rainfall abandonment?grit sink?filtration?disinfection?rainwater recylcling.The results demonstrated that the filtration technology and filter material were the main factors affecting the performance of filter.The pollutants concentration was relatively low in the rainfall runoff,after abandoning the initial rainwater.And considering the convenience and economy of the filter materials,the quartz sand single-stage filter material or quartz sand and anthracite graded filter material was recommended for the conventional rapid filter.?3?The designed filtration rate and filter layer in filter of pilot-scale device were 7.5m/h and quartz sand single-stage filter,respectively.The operation mode was constant speed and varying-head with the hydraulic retention time of 0.2h and the backwash flow rate?q?of 15L/?s·m²?.The results showed that the average removal rates of TN,NO₃^--N,NH₃-N,TP,COD and SS in the filter were 43%,47%,50%,29%,53%,63%,respectively.After backwashing for 6h,the filter recovered the ability for removing or adsorbing various pollutants.By analysising Box diagram,it showed that the effluent quality of the filter was relatively stable at each time.The single factor index and the Nemero index analysis showed that the effluent of the filter achieved at the requirements of miscellaneous water.In the practical engineering,it was recommended to use the stratified filter material of quartz sand and anthracite for the conventional rapid filter.?4?The InfoWorks ICM software was applied to forecast recyclable amount of rainwater and carry out benefit evaluation in this study.The modified Morris screening method was used to analyze the local sensitivity of the model parameters.The results showed that the main influencing factors of rainfall runoff were fixed runoff coefficient,Manning coefficient and initial loss value are.Different rainfall intensities and durations have impacts on the sensitivity coefficient S of fixed runoff coefficients,Manning coefficient,and initial loss to different degrees.The sensitivity discriminant factor S of the initial loss was the most susceptible variable.The recoverable rainfall volume was29410 m³ in the study area,accounting for 61.8%of the total annual rainfall.The total demand of miscellaneous water in Wanzhou High-speed Railway North Station was43389 m³,and the recoverable rainfall accounted for 67.8%of the total water demand.The quality of rainfall runoff pollutants such as TN,NO₃^--N,NH₃-N,TP,COD and SS could be removed by filter,effectively.The resource utilization of rainwater in the study area of the high-speed railway station could alleviate the natural water restoration of the Tianzi Lake,reducing the rainwater discharge,alleviating the contradiction between supply and demand of urban water resources.Meanwhile,the rainwater recycling also had good economic,environmental and social benefits.