Design Of Road Runoff Treatment Measure With Constructed Wetland In Water Source Protection Areas

In recent years,the effects to the environment by roads' construction and operation are increasingly concerned by domestic and foreign scholars.As runoff could carry pollutants from the road surface,it could bring a certain influence to the water environment when roads acrossing some water sensitive areas such as water source protection areas.Currently,researches on the runoff collection and treatment in water source protection areas are still less and not very systematic,which still needs people to do some further studies.In this paper,some typical structures and the materials that used for the road runoff treatment are studied.Among these structures,the constructed wetland is considered as a suitable measure for some water source protection areas since it is environmental and has advantages on the treating load and the purification efficiency.Therefore a measure that uses constructed wetland for the road runoff collection and treatment is proposed.And researches on the constructed wetland design and the purification ability of the wetland designed are made based on this measure.By this way,a systematic research on wetland design is taken which includes the structure design,parameters design,layout principles,runoff collection and some other aspects.In the research,some layout principles of the wetland and runoff collecting methods are proposed.During the structure design,four structure plans are proposed based on the characters of the wetland.They are a normal vertical flow wetland,an U-shaped combined wetland which makes a combination of vertical flow wetland and subsurface flow wetland,a connected wetland that is connected by two vertical flow wetlands and a normal surface flow wetland,respectively.Meanwhile,the design methods of some parameters are proposed,including the depth of the water in wetland,the wetland's size and so on.The effect of plants and the wetland structures are considered for the research on the purification ability of the wetland designed.The purifying effect of plants is analyzed based on the existing studies,while the wetland structures' efficiency on the runoff treatment are tested by building three models according to the structure plans of the normal vertical flow wetland,the combined wetland and the connected wetland,and making some comparative experiments on them.From the test results,two points could be figured out.First,all the three plans have a good effect on runoff purification,and the other two plans are far better than the normal vertical flow wetland structure.The combined wetland works the best on the runoff treatment but the time it spends is a little longer relatively.The connected wetland has a better effect counting the treatment and the treating time.Second,adding an activated carbon layer to the wetland's fillers could effectively improve the removal on heavy metals,organics and petroleum,especially a significant increase on the organics' removal.At last,an application of constructed wetland treatment measure in Guangdong is introduced which is under building for an expressway that acrossed some water source protection areas.And some advices on the system's improvements,maintenance and management are proposed according to the problems found during the constructing.