The fully automatic filter rapid infiltration system is a type of sewage land treatment system. The traditional RI system has a large land area, low hydraulic load, and a high daily hydraulic load of only 0.03m. This is because the traditional RI system mainly uses natural sand land for infiltration, and the soil layer on the site is uneven, making it impossible to increase the hydraulic load.
The filtration tank of the CRI system is filled with artificially graded natural river sand, and a certain amount of special fillers are added to ensure high hydraulic load and meet the treatment requirements of the effluent. The CRI system is an ecological treatment method that utilizes artificial media and special fillers in a rapid infiltration tank to filter, adsorb, and degrade microorganisms. It decomposes and removes organic matter in wastewater, thereby achieving the goal of water quality purification. It is suitable for river sewage resource utilization and domestic sewage treatment. The CRI system not only has the advantages of simple operation, convenient operation and management, low energy consumption, low investment, and low operation and management costs, but also has the characteristics of high hydraulic load and good effluent quality.
1. CRI system process flow CRI system process flow: The main function of the pre sedimentation tank is to reduce SS in sewage, in order to improve the filtration rate of the infiltration tank and prevent blockage. During the process of sewage passing through the infiltration tank, comprehensive physical, chemical, and biological reactions are generated to remove pollutants, mainly biochemical reactions, which remove organic pollutants through biodegradation. The function of underground water collection system is to collect purified water, which is stored in clean water tank for reuse. The main body of the rapid infiltration method is the rapid infiltration tank, which is composed of at least two filter tanks filled with a certain thickness of sand and gravel filler. It operates in a dry wet alternating mode and degrades pollutants through aerobic, anaerobic, and facultative microorganisms inside the filter tank. During the drying period, most of the infiltration tanks are in an aerobic environment, while during the flooding period, the infiltration tanks are in an anaerobic environment. Therefore, aerobic and anaerobic environments often alternate in the infiltration tanks, which is conducive to the comprehensive treatment effect of microorganisms and the removal of organic matter. As far as nitrogen removal is concerned, ammonium and Nitrification will be produced when falling dry, and denitrification will be produced during flooding period, and nitrogen will be removed through the above conversion process; Suspended solids are removed by filtration; Heavy metals are removed through adsorption and precipitation; Phosphorus is removed by adsorption and precipitation with special fillers in the infiltration tank to form hydroxycalcium phosphate; Pathogens are removed through filtration, adsorption, drying, radiation, and phagocytosis; Organic matter is removed through volatilization, biological, and chemical degradation processes.
2. The CRI system treatment effect test proves that the daily hydraulic load of the CRI system can reach more than 2m, and the effluent quality meets or exceeds the secondary treatment effluent standard. CODcr is generally below 50mg/L, with a minimum of 20mg/L, and BOD5 is generally below 20mg/L;
3. Advantages of CRI system
(1) The construction cost is low, and the operating cost is lower. The investment in the CRI system, which accounts for the construction cost, is mainly filled with river sand. Generally, the construction cost per ton of water treatment is approximately 800-1000 RMB; If sewage self flow can be achieved without the need for improvement, the operating cost will be less than 0.2 RMB/ton.
(2) The CRI system has strong impact load resistance and good system stability. The volume of 1m3 can treat more than 2 tons of river sewage, which is 6 times the treatment efficiency of the general traditional Constructed wetland system. The COD load range can be 100~900mg/L, and the system can still operate stably.
(3) Emergency treatment and advanced treatment can be organically combined, resulting in good effluent effect and no investment waste. In CRI system, by adjusting hydraulic load, different water quantities can be processed, and hydraulic load changes within a certain range, with little impact on effluent effect. The size of hydraulic load is related to the selection of filter material grading. Therefore, by selecting filter materials with different grading, different hydraulic loads can be adjusted to achieve different treatment effects. For advanced treatment, reducing hydraulic load, the effluent is superior to secondary treatment, and the phosphorus removal effect is good. It also has a certain nitrogen removal function. As long as some filter materials are replaced, advanced treatment can be achieved. Other facilities can be left unchanged, without causing investment waste, achieving an organic combination of emergency and advanced treatment.
(4) No secondary pollution is caused and no sludge is treated. The CRI system does not require the addition of chemicals and mainly treats wastewater through biochemical processes, without causing secondary pollution; Sludge is digested by bacteria in the filler and does not produce sludge. There is no need to backwash the system, mainly through special filter materials.
(5) The floor area is relatively small. The optimal depth of the CRI system filter layer is about 2m. A volume of 1m3 can treat more than 2m3 of sewage. 100000 m3 of sewage needs to cover an area of about 50000 m2, which is much smaller than the traditional Constructed wetland, and is equivalent to the requirements of the general secondary sewage treatment process.
4. The Application Prospects of CRI System: China is a country with a scarcity of water resources per capita, and the ecological environment of surface water bodies has seriously deteriorated, leading to severe water shortages in many regions and cities. The serious water pollution and shortage of water resources in China have become prominent issues that constrain economic development, endanger the ecological environment, and affect people's lives and physical health. Therefore, it is necessary to adopt a combination of decentralized and centralized sewage treatment technology according to local conditions to achieve harmless and resourceful sewage treatment. In addition, the treatment of domestic sewage at the village and town levels has also become an important aspect of environmental protection in China. The sewage treatment technology with a large rural population, poor economic comprehensive strength, low construction cost, and easy management is the main mode of sewage treatment in villages and towns. The CRI system is in line with the basic national conditions of rural sewage treatment and will definitely play an important role in this field. Therefore, CRI technology has important economic, environmental, and social benefits in the resource utilization of river sewage and urban domestic sewage treatment.
