Study On Initial Split-flow And Purification Of Rainwater Runoff In Mountainous City

The topography of mountainous cities is larger,the flow velocity of surface stormwater runoff is large,and the peak flow rate appears early.It has obvious flushing effect on the pollutants that are enriched on the surface.As a typical mountainous city on the upper reaches of the Yangtze River,Chongqing City integrates large cities,large reservoir areas,and large mountain areas,and is of great value for the study of early rainwater treatment.This paper mainly studies the abandonment and purification of the initial rainwater,in order to provide technical reference and theoretical basis for rainwater pollution construction and management in mountainous cities.The main findings are as follows.（1）The optimal abandonment flow of COD_Cr is 4mm;the optimal abandonment flow of SS,turbidity and color is 2mm;the content of TN and TP in the roof runoff in this area is relatively low,and if the amount of reuse water is insufficient,initial abandonment may not be considered.（2）Quartz sand filter has better removal effect on TN and TP,disc filter has less effect on TN removal.（3）The greater the flow rate,the worse the effect of quartz sand filter on SS removal and the better the removal effect of TN and TP,while the disc filter increases with the increase of flow velocity.The removal effects of SS,TP and COD_Cr increase first and then decrease.The optimum flow rates of disc filters for SS,TP and COD_Crr were 9 L/min,9 L/min and 5-10 L/min,respectively.（4）From the perspective of the growth of plant leaves and the ability to grow,Iris pseudacorus,Iris germanica,Phyllostachys heteroclada Oliver and Ceratophyllum demersum are the dominant species.（5）Iris pseudacorus,Iris germanica,and Canna indica have better removal effects on TN,and the removal rate of TN by yellow iris is 95.3%.Phyllostachys heteroclada Oliver,Canna indica,and Iris germanica have better removing effect on TP,and the removal effect of water bamboo on TP is better.It can reach 90.4%;Canna indica,Thalia dealbata Fraser,Phyllostachys heteroclada Oliver has a good removal effect on COD,and Canna indica removed COD by 80.6%.（6）The combined packing had the highest amount of hanging film in the same culture cycle,and the maximum amount of sludge per unit mass was about 0.68 g/g.The combined packing has better removal effect on COD and total nitrogen,and the removal effect on total phosphorus is not obvious.The COD removal rate can reach64.8%.The total nitrogen removal rate can reach 86.67%.