Rapid Treatment Technology For Treatment Of First Flush Rainwater Form Urban Road

Urban road runoff pollution was characterized by monitoring parameters. Rapid filtration experiment on analog first flush of road runoff was carried on. On basis of the experiment, a demonstration project of initial road runoff treatment was designed and constructed in Changzhou, Jiangsu. In addition, the treatment effect and environmental improvement were evaluated.Analysis of urban road runoff shows that there is heavy pollution in road initial runoff which has bad biodegradability, especially for SS and COD, which exceed the second grade criteria of integrated wasterwater discharge standard (GB8978-1996). Particle COD accounts for 60% of total COD and 67~86% of PAHs are high cyclic ones, and the particles whose diameter are larger than 45μm account for 80% of SS. There are various degree of first flush phenomenon for pollutants, which are related to the rainfall intensity and the interval days between two rains. NH3-N and SS shows obvious first flush effect.Rapid filtration experiment on analog first flush of road runoff illustrates: compared with zeolite, quartz sand-activated carbon has better effect. Pollutants can be effectively removed under the hydraulic load of 2m3/m2h. As the filtrate volume increases, the removal rate of SS increases to 97%, while for COD, TN, NH3-N, TP, the removal rates decrease. At the early stage of filtration, removal rates of COD,TN,NH3-N,TP are respectively 64.6%, 58.3%, 48% and 55.9%. Since the filtration volume increases to 16.5 times of column volume, removal rates of COD, TN, NH3-N, TP decrease to 44.2%, 17.8%, 5.4% and 6.3%. Removal rates of PAHs vary with kinds of PAHs. Removal rates of Nap, Ace, Flut and Py are respectively 45%, 23%, 38% and 19%, while there is little effect on Phe. Acy, Flu, An, B[a]A, Chr and the ones have 5 or 6 cyclics can be absolutely removed. The best parameters of backwashing are intensity of 10L/(m2s), impulse type and 2 minutes. The outlet of backwashing waste locates close to the filter material. Taken together, the rapid filtration system of quartz sand-activated carbon gets good effect on urban road initial runoff.On basis of the experiments, a demonstration project was designed and constructed. The treatment effect and environmental improvement were evaluated. Removal rates of SS, COD, TN, NH3-N and TP are respectively 18.3%, 15.2%, 24.9%, 20.6% and 23.3%. The demonstration project can decrease the pollution of first flush and can improve the quality of water body to some extent.