1 Overview of river siltation in Zhejiang Province Due to soil erosion, lack of revetment of dikes and human factors, the total amount of river siltation of about 60,000 km in the province has reached 2 billion m 3, with an average annual siltation of 1 100 million m 3. The siltation leads to poor flood discharge and drainage, reduced storage capacity, decreased water supply and drought resistance, shrinking shipping and water pollution. The water environment is deteriorating day by day. The average siltation of the rivers in Hangjiahu Plain is 0.7m, with a total siltation of 394 million m 3, accounting for 20% of the total siltation in the province. In the "99.6.30" flood, the highest flood level of each water level station exceeded the historical water level, and the river siltation raised the flood level and reduced the discharge capacity. It has aggravated the disaster. The backward appearance of river water environment can no longer meet the needs of the rapid social and economic development and people's production and life in the province. It is urgent to comprehensively improve the river water environment with dredging and hardening and greening of dikes, which has become the knowledge of the people of the province. During the tenth five-year plan period, the province plans to dredge rivers 1. 1 10,000 km, and the dredging project amount is nearly 500 million m 3. It is estimated that the investment is 7.63 billion yuan, with an average annual dredging of 2200km, the dredging amount is about 1 100 million m 3, and the investment is1526 million yuan. At present, the dredging capacity of rivers in the province is not up to the requirements, and the reasons for the failure to achieve rapid development of river dredging are mainly due to insufficient capital investment and difficulties in sludge treatment. River dredging is a water conservancy project with strong social welfare. While increasing financial support, governments at all levels should also study and popularize all kinds of advanced dredging machinery and sludge treatment technologies, so as to reduce project investment, improve work efficiency and speed up the pace of river dredging. It has reference and promotion value in the whole province. 2. 1 As a kind of "sunset industry", the brick and tile industry directly uses sludge to make bricks. With the adjustment of agricultural industrial structure, the scope of land consolidation is further expanded, and the available surface clay resources are less and less, and its survival crisis will become more and more obvious. Directly using sludge to make bricks is a treatment method that turns waste into treasure, which not only reduces the occupation of cultivated land due to stacking, At the same time, it alleviates the shortage of soil source in brick and tile factory and the damage of soil to farmland, and has remarkable social benefits. After many trial-productions, Shaoxing City has achieved relatively mature technology. The adopted technology: dredging river mud → stacking → feeding → processing raw soil → making bricks → drying bricks in the sun → burning bricks → making finished bricks → warehousing → selling. Corresponding equipment: dredger → transporting iron barge → lifting soil and landing crane → three pairs of rollers → two mixers → blank cutter → transporting equipment → brick kiln. Proportion of raw materials: river after landing for two months. The size deviation is completely controlled within the allowable range of national standards. Tongxiang City has also summed up the production process of river silt brick making through repeated tests. The process flow is as follows: dredging silt in the river designated by the water conservancy department by dredgers ↓ loading dredged earthwork into a transport ship with four bottom-leaking mud containers ↓ transporting the silt to the dock of the mud dump by the transport ship. Hoist the sludge to the sludge dump by crane ↓ Spread the sludge on the threshing ground by forklift for dry drying and dehydration ↓ Transport the dried sludge to the brick-making workshop by bulldozer with shovel bucket, and mix it with dry clay ↓ After secondary stirring and three bone rollers, make a brick blank for dry drying and dehydration, generally dry drying at normal temperature for 3 ~ 4 days, and dry drying at high temperature in summer1~ 2 days. Clay is mixed with 60% sludge. The appearance standard and various technical indexes of the red brick have reached the standard requirements. According to comprehensive calculation, the cost of dredging mud from the river to entering the mud pond is about 6.5 yuan /m 3, which is slightly higher than the cost of directly taking soil from the field. If calculated according to 50% of the river siltation in Tongxiang City, there are18 million m 3 of mud and1300,000 m 3 of dynamic siltation for brick making. Calculated by 50% of silt content, it can be exploited by 50 brick and tile enterprises in the city for 13 years. The promotion and application of silt brick-making technology requires the active guidance of the government. Relevant departments should first formulate river dredging plans and clay exploitation and utilization plans, and issue the planned indicators of river silt soil use by the year through quota supply for the exploitation of surface clay resources in brick and tile factories. To achieve the purpose of reducing the total exploitation of surface clay resources and dredging rivers, the use of dredged earth to make bricks is regarded as one of the "three wastes" utilization, and the tax authorities strictly implement the "three wastes" tax preferential policies, and timely apply for tax reduction and exemption. For those who take mud to make bricks within the dredging planning scope, the finance may consider giving appropriate assistance. The method of "cultivating rivers with soil" has achieved great success (table 1). The so-called "cultivating rivers with soil" refers to bidding and auctioning the "green land" soil outside the dikes on both sides of the river within1~ 3m to the surrounding brick and tile factories, and it is stipulated that the soil borrowing should be limited to 1m depth. After the soil is borrowed, the winning bidder will use an amphibious dredger to transfer it. There are no roads, houses, bamboo and wood on both sides of the river; The width and depth of the river channel can adapt to the operation of amphibious dredgers, and the waste soil can be sent to the shore at one time. Bricks are made by replacing soil with mud, which will bring some inconvenience to farmers' farming. It is necessary for the government to introduce corresponding land compensation policies to match it. Only by measuring the siltation volume and dredging volume of each section of the river channel in advance can the excavation volume of the field soil be determined, and the acceptance will be organized after the field soil excavation to avoid less excavation or over-excavation, resulting in uneven surface of the waste soil. Table 1 Brick-making by replacing soil with mud in Luqiao and Dinghai shows unit price of field soil for dredging technical measures Dredging benefits luqiao district Jinqing Town 5 ~ 6 yuan /m 37 ~ 8 yuan/m 3 dredger dredged, digging the river with a depth of 2m 1m, which saved the dredging cost, eased the soil used by brick factories and increased the water storage capacity of the river. Improve the flood control and drainage water supply capacity, reduce the number of farmers' labor input, increase the yield of crops such as late rice without fertilization, and promote farmers' income. 4.5 yuan, Ma 'ao Town, Dinghai District /m 3 6.25 yuan /m 3 Mechanical dredging, digging river depth 1.5m, digging soil depth 1.2m 2.3 Utilizing silt and fertile soil, improving soil quality with less impurities and less pollution. The river mud can be diluted and filtered by mud pump from the drained river course or mud barge, and then transported to the paddy field for soil improvement. The mud is evenly input after ploughing and leveling in the paddy field, and the thickness is10 ~12 cm, which is not higher than the height of the ridge. It can also be transported after ploughing in the agricultural field. In the process of transporting the mud, there should be a special person at the outlet of the mud pipe. Generally, the pipes should be moved every 20 ~ 80m, and a filter screen should be set at the outlet of the mud slurry to filter out a small amount of impurities in the mud. After the mud has settled in the field, the water should be drained, and the seedlings should be inserted after 10 days. Wenling City chose 6000m 2 experimental rice field and 870m 2 control field for the experiment. In the experimental field, only 25% green manure was applied. In contrast field, there was no obvious difference in the growth and development period of seedlings after applying 2kg green manure and 0.05kg phosphate fertilizer per m 2. In the field with mud application, the seedlings showed the characteristics of faster tillering, increased effective panicle number, enhanced plant lodging resistance and improved seed setting rate, and the early rice yield reached 6585kg/hm 2, which was 390kg/hm 2 higher than that in the control field. Nitrogen fertilizer should not be applied to green manure fields in season, and the amount of chemical fertilizer used in winter fallow fields should be properly controlled; Don't insert seedlings until the mud is fully settled; Seedling density should be reasonable and can be relaxed appropriately; Attention should be paid to field disposal and pest control. Sludge containing impurities and toxic substances can't be sent directly to the field, and it can only be used to improve the soil after separation. There is a dehydration and separation technology in Japan that is worth learning from. It separates the sludge by mechanical drying or adding dehydrating agent, and divides it into toxic sludge and non-toxic sludge. The toxic sludge is landfilled and the non-toxic sludge is sent to the field. Increase soil fertility. 2.4 Other sludge treatment measures can be used as low-lying land to fill up or raise the elevation of farmland on both sides of the river in urban construction for sludge that cannot be directly used for brick making; In the construction of dikes along the Yangtze River and the renovation of polder areas in plain river network, river silt can be used to heighten and strengthen dikes. In flood-prone and waterlogged areas, we can consider setting up a dump for flood control and emergency materials. Conclusion At present, most of the sludge treatment methods in the province are relatively simple, such as strengthening dikes and filling high and low places, but the technology of recycling sludge as a resource needs further study. After industrialization, sludge will be used as advanced technologies such as fuel, fertilizer and building materials. It has a broad application prospect in river dredging. Name of the promotion organization Hohai University Technical source (manufacturer) Hitachi Construction Machinery Co., Ltd. National Japanese product model SR-G2000 self-propelled soil improvement machine Reference price is 50 million yen. The main application fields are water conservancy, environment, Brief introduction of traffic technology (production) The solidification technology of river and lake sludge is to change the sludge into a soil material that can be used for various purposes by adding solidification materials to the sludge, which not only solves the purpose of rapid land circulation, but also generates new soil resources. It is a new technology to turn waste into treasure and promote the high utilization of land. SR-G2000 self-propelled soil improvement machine is the key equipment in sludge solidification treatment. This equipment can evenly mix a large amount of sludge with solidified materials in a short time to meet the engineering requirements of mass treatment. At the same time, it has the characteristics of convenient movement, high construction efficiency and strong construction ability. The main index length is 12500mm; Width: 2990mm；; Height: 4355mm；; Total weight: 18600kg: grounding pressure: 58.0kPa；; Walking speed: 5.3 km/h and 2.5 km/h, with two gears switched; Climbing ability: 24 degrees; Standard handling capacity: 40 ~135m3/h; Maximum particle size150 mm; Power: 99kw/ 1950min-1; The maximum torque is 466N·M；; Mixing tank:1040mm×1715mm; Supply capacity of solidified materials:13m3/h. Domestic and international situation: After the successful development in 2005, Japan dredged rivers and built dikes; There have been many application examples in soft clay excavation and reuse engineering. The maneuverability, construction efficiency and wide application scope of the equipment have been verified by the project. There is no similar product application in China. The technical system of urban river silt cleaning and treatment 1. Introduction to the dredging methods of urban river silt in China, both excavation and hydraulic methods are adopted, but both transportation and disposal are wet operation (dredging mud). Therefore, it is impossible to control the release of secondary pollution in the process of natural drying and final disposal of seriously polluted sludge, and the disposal area is wide, which may lead to a wide range of pollution diffusion, and it is also very difficult to implement the disposal site; Discharging mud directly into large water bodies will cause serious environmental problems. This system has completely overcome the shortcomings of the existing domestic technology because of the on-site dehydration of mud and the establishment of an environmentally safe disposal and utilization process. The research results are systematic technical scheme and key production equipment, which are mainly applied to the cleaning and disposal of polluted sludge in urban rivers. The key problems to be solved by the system are: 1) targeted removal of the pollutant-rich part of river sludge; 2) Meet the requirements for the integration of silt removal construction in urban built-up areas and narrow construction sites of small rivers; 3) Improve the transportation economy of dredged sludge slurry; 4) Control the secondary pollution that may occur in the process of transportation and consumption after dredging. Through the analysis of the characteristics of polluted sludge in the urban river course of the cleaning object and the study of the characteristics of external constraints (construction site, transportation conditions and environmental protection requirements for the disposal of polluted sludge) in the cleaning process, the key technical units and principles included in the technical system are: 1) hydraulic method to remove floating polluted and enriched sludge; 2) Centrifugal sedimentation can reduce and solidify the dredged mud; 3) Choose appropriate utilization or disposal methods for solidified sludge (cement cake) according to its pollutant content or pollutant leachability index and relevant environmental protection standards, such as greening (agriculture), landfill and building materials; 4) The central unit of the technical system is dehydration and solidification, which has the functions of: a. transportation and site reduction; B. Sludge can be directly treated and utilized, which avoids the secondary pollution release that is difficult to control due to natural drying. Second, the main technical index 1) Dredging: flow (solid content of mud) is greater than or equal to 15%: treatment capacity is greater than or equal to 200m3/h. 2) Dehydration: treatment capacity is greater than or equal to1. Water content of mud cake < 30%; Direct reduction strength > 〉8kPa；; Supernatant, solid content < 3%; The solid recovery rate is more than 90%; Single cost: 8.6 yuan /m 3 mud. 3) Transportation: mud cake can be transported by general trucks and barges, and there is no possibility of dripping. 4) Disposal and utilization: environmental protection, which meets GB4284-84 pollution control standard for sludge agriculture when greening and farming; The leachate from the landfill meets GB8978-88 comprehensive wastewater discharge standard; The leaching quality of sintered building materials is lower than GB5749-85 sanitary standard for drinking water. 5) Overall economy (according to different points of disposal and utilization): 43.4 yuan /m 3 underwater mud when used as urban greening soil; When sanitary landfill, 140.4/m 3 underwater mud; When making building materials, 1 15.4 yuan /m 3 underwater mud all meet the expected technical requirements. Third, the prospect of popularization and application. The engineering implementation of this technology can first bring remarkable social and environmental benefits, and urban river regulation is of great significance to improving the community life and investment environment along the line and thus improving the overall degree of civilization. However, the regulation system must include sludge cleaning. This technology can reduce the infeasible factors in the cleaning process, eliminate the adverse effects on the environment, promote the development of river regulation, reduce potential environmental hazards, and contribute to the society. The economic benefits of the technology should be direct and indirect: the indirect performance is in the aspects of reducing pollution, avoiding losses, improving the appearance of the city and increasing the wealth of the whole society; Directly, the transportation cost of sludge slurry is mainly reduced. After dehydration, the volume of sludge cake is 16% of the unit price of sludge, 8.6 yuan /m 3 sludge, and the unit price of sludge transportation (two-way calculation) is 2*0.9 yuan/m 3 km. Therefore, when the transportation distance is greater than 6km, the net benefit can be obtained by dehydration, and according to the average distance of the river sludge disposal site in the city of 40km, The net benefit of mud treatment per m 3 is 67 yuan. There are thousands of rivers in Shanghai with a total length of tens of thousands of kilometers, of which 10000km is the key remediation object, and more than 70 million m 3 of mud is added annually, of which 1/5 is counted as the system cleaning. The economic benefit of this technology promotion is more than 300 million yuan, and its promotion value is very significant. Therefore, this technology can be mainly promoted in the sludge cleaning project of polluted rivers in Shanghai and domestic cities, and it is also applicable to the dredging of sediment in other water bodies. Because the benefit index of the technology itself is "hard", the prospect of promotion is optimistic. The promotion measures that can be adopted are to establish professional engineering teams based on technology and participate in market competition. At the same time, the competent department should take favorable actions to crack down on unfair competition means (such as dumping mud into large water bodies and transporting heavily polluted mud to rural areas for stacking), so that the popularization of technology will gain a bumper harvest of economic and social benefits.