| Subsurface wastewater infiltration system has many advantages: high removal capacity, low investment costs, low maintenance and operation costs, simple operation and maintenance, water resource can reuse. They are applied widely in Europe, America and Japan. However, the current subsurface wastewater infiltration system has low hydraulic loading rate, occupy large ground area, clogging problem, low nitrogen and phosphorus removal efficiency. The aim of this paper is to look for high hydraulic loading rate, prevent clogging, high nitrogen and phosphorus removal efficiency of subsurface wastewater infiltration system to solute the above problems.1. On the base of mechanism of the soil clogging problem, we adopted multi-transitional layer to increase the interface of organism matter granule and oxygen, adopted high-penetrability interlayer to increase supplying oxygen that can enhance greatly hydraulic loading rate of subsurface soil sewage treatment system. The hydraulic loading rate of this system can reach 25cm/d.2. The technology is sound and advanced with model experiment and pilot field's demonstration. And the system has no soil clogging problem. So the technology can be widely applied.3. Experiment data indicated that nitrogen and phosphorus removal efficiency is superior to traditional wastewater land treating system. TN removal efficiency got up to 70% from 30%-50%. TP removal rates were over 98%.4. A method for on-site treatment of domestic wastewater for small urban or town communities is developed, because of its lower investment costs, lower maintenance and operation costs, simple operation and maintenance. Furthermore water resource can reuse. The treating system is in subsurface, that it doesn't affect the use of soil.5. A pilot plant of subsurface wastewater treating system was built and has been operated for several months. The experiment results showed that average removal rates of SS, CODCr, BOD5, TN and TP were 95.2%, 95.0%, 96.7%, 58.2% and 95.5%.
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