Study On The Optimization Of Concav-down Green Space Area In Green Building And Community

As the initiating terminal of urban rainwater drainage system, building and community account approximately for 70% of the urban areas. To effectively collect and use urban rainwater, it is essential to run off the water orderly and make efficient use of rainwater in the building and community. Greenbelt is an important part of the building and community and is of great significance in the rainwater’s collection as well as usage in building and community. However, during traditional architecture planning phase, emphasis has been on the landscape effect of green space system while its purification and storage effects on runoff rainwater in community are ignored.According to the basic principle of low impact development technology, low elevation greenbelt device was designed and pilot test was carried out in Shenzhen Yuxin School. Device includes four processing units and in each processing unit, the longitudinal structure from above is the aquifers, lawn, planting soil, sand, packing layer and pebble set layer. Low elevation greenbelt’s water quality purification and reduction effect on the rainfall runoff in building and community are studied. First, under the condition of different thickness of substrate and different area, by monitoring pollutants concentration of influent water and outlet water, then the device’s water quality purification effect on the runoff water is analyzed. Second, under the condition of different area and concave depth, by monitoring influent water quantity and outlet water quantity, the device’s control effect on the runoff water is analyzed with runoff-yielding time, delay flood peak time, runoff flood peak reduction rate and total runoff volume reduction rate as the index. Conclusions can be reached from the above studies are:①The monitoring results of influent water quality show that various pollutant concentrations of influent water are highest in the starting stage with the concentrations of SS, COD, TP, TN, NH3-N and NO3-N are 144.03mg/L~352.67mg/L, 171.38mg/L~259.10mg/L, 2.55mg/L~4.40mg/L, 1.82 mg/L~2.89mg/L, 0.80 mg/L~1.29 mg/L, 0.54 mg/L~0.93 mg/L respectively and that in the mid and late term rainfall, pollutant concentrations gradually reduces. At the end of rainfall, the concentrations of SS, COD, TP, TN, NH3-N and NO3-N are 31.22mg/L~73.17mg/L, 57.13mg/L~94.68mg/L, 0.65 mg/L~1.11 mg/L, 0.50 mg/L~0.77 mg/L, 0.20 mg/L~0.40 mg/L, 0.04 mg/L~0.26 mg/L respectively. In different rainfall events, there are obvious difference in the pollutant concentration changes in the mid and late term. In the early peak rainfall, pollutant concentration decline steadily while in the mid and late peak rainfall, pollutant concentrations fluctuate with many peaks appearing. The monitoring results of influent water quality show that COD, TP, TN, NH3-N and NO3-N in the influent water have a better correlation with SS and the correlation coefficient SS are between 0.7346 and 0.9414.②When the area is 3:1 with different substrate thickness, the monitoring results of pollutants concentration of influent water and outlet water show that substrate layer is thicker, the device’s treatment effect on the runoff contaminants is better. When the substrate thickness is 50 cm and the EMC of SS, COD, TP, TN, NH3-N and NO3-N in the outlet water are 26.30 mg/L, 52.76 mg/L, 0.28 mg/L, 0.37 mg/L, 0.30 mg/L, 0.27 mg/L, the removing rate for SS, COD, TP, TN, NH3-N and NO3-N are 80.2%, 57.03%, 38.11%, 68.73%, 53.32%, 34.66%. When the substrate thickness is 20 cm and the EMC of SS, COD, TP, TN, NH3-N and NO3-N in the outlet water are 63.49mg/L, 50.70mg/L, 0.35mg/L, 0.57mg/L, 0.41mg/L, 0.34mg/L respectively, the removing rate for SS, COD, TP, TN, NH3-N and NO3-N are 64.3%, 38.75%, 23.2%, 51.72%, 36.8%, 18.32%. Therefore, device substrate thickness is recommended 50 cm.③When the area is 3:1 with different substrate thickness, the monitoring results of pollutants concentration of influent water and outlet water show that substrate layer is thicker, the device’s treatment effect on the runoff contaminants is better. When the substrate thickness is 50 cm and the EMC of SS, COD, TP, TN, NH3-N and NO3-N in the outlet water are 22.33 mg/L、30.34 mg/L, 0.22 mg/L, 0.38 mg/L, 0.29 mg/L, 0.23 mg/L respectively, the removing rate for SS, COD, TP, TN, NH3-N and NO3-N are 74.91%, 51.74%, 32.82%, 63.44%, 48.03%, 33.37%. When the substrate thickness is 20 cm and the EMC of SS, COD, TP, TN, NH3-N and NO3-N in the outlet water are 30.25 mg/L, 60.98 mg/L, 0.32 mg/L, 0.46 mg/L, 0.32 mg/L, 31.21 mg/L respectively, the removing rate for SS, COD, TP, TN, NH3-N and NO3-N are 70.63%, 43.73%, 27.71%, 57.83%, 45.03%, 30.69%. The green building and green building rate of our country is above 30%. In the service area of 1:2 green rate is 33.3%, the device can achieve good effluent water quality under the precondition of satisfying the building and community greening rate. Therefore, device substrate thickness is recommended 50 cm.④Device for rainfall runoff time eigenvalues with effect of delaying good and device production flow time between 23 minutes to 39 minutes, the device can delay the peak time in eight minutes to 24 minutes. To reproduce the same period, with the device and area ratio increases, the device of the production flow time and peak runoff delaying function decreased. Rainfall return period is 1 year, service area of device by 1-0 increases to 1:5 and device production flow time by not producing flow for 39 minutes and devices to defer peak time from peak to 24 minutes. Device for rainfall runoff has good peak cut and runoff volume reduction effect, the device for the runoff peak reduction effect in 27.26 ~ 100% between, on the total runoff reduction effect between 49.81% ~ 100. The peak reduction rate and the total reduction rate of the runoff decreased with the increase of the service area of the device under the same repetition period.. Rainfall return period is 1 year, service area of device by 1-0 increases to 1:5, the device of the peak reduction rate reduced from 100% to 71.04% and total runoff cut rate reduced from 100% to 87.15%.Through the study of sunken green technology, we can see concave greenbelt in residential construction and stormwater runoff has good water quality purification and the peak load shifting slow flow and cut size effects of the flow of the, and concave down greenbelt has convenient construction, simple maintenance, suggested in the residential construction and to promote the use.