| Traditional sewage land treating systems have ubiquitous problems of lower hydraulic load rates and lower wastewater treating capabilities per unit area. To solve the problem, based on the summarization of all kinds of land treating systems, Constructed Rapid Infiltration sewage treating system (CRI for short) was developed. During the development course, rapid infiltration land treating system and wetland system were mainly used for references. By learning from their advantages and offsetting their weaknesses, the CRI system, a new wastewater treatment technique with its special characteristics was developed step by step. But study of CRI is just in the initial stage in China, and many of its aspects need to be further studied. In this study, a pilot experiment with new combined packing has been conducted with polluted river water. Results are the followings:(1)Under the Hydraulic Loading (HL) of 2.0 m/d and the operateing-drying schedule of 5:3, the CRI-2 in combined ceramic pellet-lava-steel slag was more suitable for removing COD, TP and SS than the other two CRI systems. The average removal rates of CRI-2 for COD, TP and SS were 57.7%, 56.5% and 75.3% respectively. But the removing rates of CRI-2 for NH3-N and TN were 66.8% and 53.6% respectively, lower than that of CRI-1 combined quartz sand-zeolite which were 80.2% and 64.5% respectively. CRI-3 combined ceramic particle-lime stone was the worst for removing COD, TP, SS, NH3-N and TN. During the trial period, CRI-3 had never been clogged, compared with 3 and more than 10 times of CRI-2 and CRI-1 respectively. CRI systems filled with light filler or bigger particles would be clogged less.(2)When the Hydraulic Loading, the operateing-drying schedule, the height of filler-I , filler-II, unsaturated zone and saturated zone were 2 m/d, 5: 3, 500mm, 600mm, 500mm, 600mm respectively, the results indicated: the removal of CRI for COD occurred mainly in the upper 0～750mm through aerobic biodegradation in unsaturated zone and anaerobic biodegradation in saturated zone. The removal for nitrogen occurred mainly in 500～1100mm through nitrification and denitrification after the adsorption of zeolite in CRI-1. The removal for nitrogen occurred through nitrification in the upper layer and denitrification in the under layer in CRI-2. The removal for TP occurred mainly in 500～1100mm through the adsorption and chemical precipitation of zeolite in CRI-1. The removal for TP occurred mainly in 0～500mm in CRI-2.(3)It can't solve its clogging problem through disturbing the upper filler. CRI needs backwashing when it has been clogged to make sure that it could failure-free operate for long. Organic matter was the main substance that clogged the CRI. The optimum water backwashing time and intensities were 5 minutes and 3.4L/(m2·s).(4)The operateing-drying schedule of 5:3 was suitable for the removal of NH3-N and TN, while the operateing-drying schedule of 1:3 was suitable for the removal of COD and TP. The optimum Hydraulic Loading was 1m/d. It could improve the removal rates of TN by adding the height of saturated zone. It could improve the removal rates of COD, NH3-N and TP by adding the height of unsaturated zone, but it would reduce the removal rates of TN because of lacking for carbon sources.(5)When CRI-2 was drying at night, the removal rates of NH3-N, through the correlation analysis, was relative with both of the air-temperature and relative humidity, the significant levels were 0.013 and 0.001 respectively, and the Pearson Correlation were -0.5711 and -0.6975 respectively. The air speed was not relative with removal rates of COD, NH3-N, TN or TP.
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