Non-Point Source Pollution Control And Simulation Of Rainwater Runoff In Suburban Open Channels

With the rapid development of cities,the underlying surfaces of lakes,rivers,woodlands,grasslands,wetlands,etc.,capable of intercepting and infiltrating rainwater have decreased sharply,and the heat island effect has led to a significant increase in local rainfall in large cities.This has led to a significant increase in urban surface runoff,and a large amount of surface pollutants will enter the rainwater pipe network system along with the rainwater runoff and finally enter the receiving water body.Pollutants exceeding the capacity of the water environment enter the receiving water bodies such as urban open channels,which deteriorate the water quality of the receiving water bodies,and even the black and odorous phenomenon of the receiving water bodies repeatedly occurs with heavy rain.This paper selects an open channel in the suburbs of a city as the research object,studies the flow rate and water quality changes of the rainwater pipe network system under different rainfall conditions,also studies the effect of low-impact development measures to reduce pollution,and finally studies the pollution control plan inside the open channel.The main conclusions are as follows:(1)The the initial rainwater pollution of short-duration rainfall is more serious,and the initial rainwater pollution is more serious under the rain condition with a longer return period.Under the most serious pollution situation,the peak flow rate of the drainage outlet of the rainwater pipe network system exceeded 8m~3/s,the peak concentration of TN was close to 11mg/L,and the peak concentration of COD was close to 105 mg/L.(2)Through the simulation of the storm runoff management model(SWMM),the optimal LID measure obtained is a combination of 62.5ha of plant depressions,49ha of green roofs and 6000m~2 of rain buckets.This measure can reduce the peak flow rate by up to 75%and the total outflow flow rate by up to 45%.(3)Through the simulation of the environmental fluid dynamics model(EFDC),the combined pollution control measures in the open channel have the best effect.The combined treatment measures of 5000m~3/d of reclaimed water plus bypass treatment of 5000m~3/d and1600m~2 of fixed aquatic plants.Combined treatment measures can restore the open channel to non-black and odor within two days,and can also ensure that the open channel has a flow velocity greater than 0.1m/s.