With the rapid socio-economic development, China's highway construction scale has been continuously expanding. Most highway service areas are restrained by region and have few workers, which leads to an imperfect management in water network. According to the survey by the Ministry of Communications, the utilization rate of sewage processing devices was only 50.8% in highway service area, and the sewage was discharged excessively in most areas.Compared with the traditional sewage treating methods, Natural circulation sewage treatment technique has great advantages. The technique is a newly-typed and ecological sewage treating method, which is evoved from the adsorption, absorption, utilization and decomposition by natural soil, plants and microbes. The system uses manually configured soil matrix and introduces specific microbes and aquatic plants in order to constitute a wetland ecosystem, then configuring piping for water flow and injecting sewage into the system, and finally collecting or discharging the treated outlet water.The purpose of this research is to develop a simple but efficient proportioning substrates ststem to remove N and P in accordance with the water quality of highway service areas, which is the important basis of founding the natural circulation sewage treatment system.Through experimenting with the seepage properties and sewage treatment performance of every single substrate, it sieves out the ones with bigger seepage coefficient and better treating effect. Next, dividing the substrates into three kinds of different filler layers: the surface layer, the treating layer and the cushion layer; then adopting different combining and proportioning ways and two ways of water distribution (parallel connection and series connection) to test the respective treatming performances; at last, through comparing the performances to work out the best substrate proportioning of the system.The research shows: the treating effect varies greatly with the depth of single substance, which is better in the middle depth of 30 centimetres.; the water quality also has great difference after treated by different substances when in the same depth; the sewage treatment efficient of proportioning substances is better than that of single one; the overall water quality of series connectin is obviously higher than that of proportioning ones. As for the series connection system, the removal rate of TP is nearly 90~95%, and its concentration is lower than 0.6mg/L; and the rate of NH3-N is above 70%, as concentration below 8.5mg/L. |