A Comparison Of Road Rainwater Stagnation And Purification Of The Different Bio-retention System Composed By Four Kinds Of Plants

With the development of Ecological Garden City and the Eco-sponge city,rainwater harvesting and utilization technology have been being paid more and more attention and application,especially low impact development technology(LID)has developed rapidly.And bio-retention facilities can be a large-scale promotion of the future ecological initiativesas a most representative measure.In this paper,by simulating the natural rainfall intensity and the road rainwater pollutants,control variables were tested under the same condition as the substrate of the bio-retention.To compare road rainwater stagnation and purification of different bio-retention systems composed by four kinds of plants.Firstly,the effects of four kinds of plants(Ophiopogon bodinieri,Polygonum capitatum,Pennisetum alopecuroides,Ficus tikouae)and the whole bio-retention system were compared under the same condition of the designed bio-retention system.Secondly,flooding and drought resistance of the four plants were also compared.Thirdly,the effect of the biological retention system with the overlay(zeolite and volcanic rock)on the removal of the runoff rainwater pollutants was discussed.The main results were as follows:(1)The rainwater retention time of plant layer was 4.8 to 14.0 h,while the whole system was 7.0 to 17.9 h;with the increase of inflow,they demonstrated a significant difference(P<0.05).Under the same condition of substrate,the same plant showed an extremely significant difference(P<0.01)in different amount of inflow,while different plants showed a significant difference(P<0.05)in the same amount of inflow.(2)Evaporation and plant transpiration were lower than 7% in different plant systems under three rainfall intensities.The impoundage of substrate in bio-retention system was stable at 13.68 liters per cubic meter.(3)The four plants could all be employed as road ground covers in terms of their adaptive capacity under different water treatments.The suggested order was Pennisetum alopecuroides,Polygonum capitatum,Ficus tikouae,Ophiopogon bodinieri.(4)(1)The effect of plant layer on rainwater runoff,medium and weak acid roadrunoff was stronger than that of plant layer,and the pH was increased by 0.59 on the basis of plant filtration after substrate permeation and filtration.(2)For the removal of COD,TN and TP from rainwater pollutants in the runoff,the TN value of the runoff of the plant and the system was significantly different(P <0.01),and the system effect was significantly better than that of the plant.(3)Rate from large to small,was followed by the Polygonum capitatum,Pennisetum alopecuroides,Ophiopogon bodinieri,Ficus tikouae.(4)Removal of TN,plant layer and the system measured the removal rate was not a positive correlation,the plant layer to remove TN instability,the removal rate from large to small arrangement of Pennisetum alopecuroides > Euphorbia grass.The overall system TN removal rate from large to small was Polygonum capitatum>Pennisetum alopecuroides> Ficus tikouae> Ophiopogon bodinieri.(5)The removal of TN was more unstable,and the removal rate of plant layer was positively correlated with the system layer.According to the size of the removal of TP rate was,Pennisetum alopecuroides,Ficus tikouae,Polygonum capitatum,Ophiopogon bodinieri.(5)The removal rate of COD was 8.32%,the average removal rate of TN was increased by 12.61%,and the removal rate of TP was increased by 9.23% on average.The removal of the COD,the overall effect of the zeolite and the biological retention system were better than that of the volcanic and biological retention systems;the removal of TN and TP,the overall effect of the volcanic rock and the biological retention systems were better than the whole of zeolite and biological retention systems.