Research On The Water Quality Maintenance Based On Biological Film In The Ecological Rainwater Tank

Based on biological film,the working condition of the rainwater tank which assembled from polypropylene units were studied in this paper.This paper is about the water quality maintenance of storage rainwater.A few suggestions of storage rainwater were based on using software FLUENT to simulate the working condition of the tank were taken,which were in order to improve water quality maintenance.Under the low-intensity rainfall,it’s better to storage the runoff of later period originated from roof and road and whole period from the lawn.Under the moderate and high-intensity rainfall condition,it’s better to storage the runoff of later period originated from roof,road and lawn.After change different conditions of disinfectant,pH and temperature in experiment,it was found that the bacteria number per polypropylene unit in the reactor which add disinfectant was 2~4 log(CFU/cm2)lower than the control group.Turbidity in the reactor which add disinfectant was higher than the blank control reactor in the later period of the experiment.Negative effect was found in the reactor which add disinfectant.More biological film was conducive to water quality maintenance.For example,in condition of pH=7 and the bacteria number per polypropylene unit was 6.5~7 log(CFU/cm2),the degradation rate of COD was 70% and the turbidity was around 2 NTU.The more biological film a reactor,the lower turbidity appeared.Performances of the reactor were stable for long-time running.The concentrations of COD,pH,TN,turbidity and organic nitrogen were 20 mg/L,6.6~7.2,2.5 mg/L,2 NTU,1.5~2.3 mg/L individually.In the working condition of dry period,the biological film can keep active in 15 days.In the working condition of continuous water,the storage water can keep standards of miscellaneous domestic water quality.The greater speed on the ecological water tank module,the greater impact it shearing: import speed is 2.8 m/s flow shear stress on the ecological water tank module for 1~40 pa;inlet velocity is 0.3 m/s flow shear stress on the ecological water tank module for 0~22 pa.The inlet well which reduce the water flow rate can effectively reduce the shear stress on the ecological water tank module the greater the impact.In the condition of effluent,when the diameter of the water outlet 0.10m~0.4m and the water flow shear stress on the module set for 0~11 pa.Wells can effectively reduce the shear stress on the impact of the ecological water tank module,set up out of the well diameter is 0.5 m and the shear stress decreased to 6 pa.