The Curing Processing of River Silt and Building Mud at Keqiao

Dong-ying Xu College of Civil Engineering, University Shaoxing, Zhejiang312000, [email protected]

ABSTRACT For further proceed with the "five water work", economical utilization of land resources, and earnestly solve the problem of mud piled up, it is difficult to eliminate the mud to the surrounding environment such as river secondary pollution. The curing measures were used to deal with the river silt and mud at keqiao district by cooperative mode with hubei wuhan Luther environmental technology co., LTD, which invested thirty million Yuan to build mud curing processing center in the ability to deal with mud of 1 million square. It was ensured to supply not less than 700000 square muds into the center processing each year by Keqiao party. Using solidification disposal technology, the mud cake volume after dehydration is 70% less than the mud volume, water suspension index SS less than 20 mg/L. This method is effective to solve the problem of Keqiao silt. KEYWORDS: silt; mud; curing; mud cake

INTRODUCTION River dredging silt of Keqiao district is stacked in the low-lying land, farmland and other unused land. With the passage of time and the propulsion of urbanization, less and less land can be piled up with silt. With the development and utilization of the blocks, it is necessary to transport silt again which was piled up [1]. Mud even flows into the river again with rain water. If silt natural stacked, it did not thoroughly remove the pollution sources of silt. From the urgency of the intensive utilization of land resources and mud ultimate way, it is necessary for non-hazardous disposal of mud [2].

Current situation analysis The annual dredging volume was 2000000 parties at the towns (street) of Keqiao area. It was about 1000000 in the implementation of the dredging project, another 1000000 in the important channel dredging river and city. At present, the need for sludge disposal is the main river silt, volume location relative concentration on river dredging river and important city every year about 1000000 parties.

1879

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Objective and significance In order to solve the difficult problem of mud piled up, stop the pollution of river mud at surrounding environment, intense using land resources, the river silt and building mud was formed by solidification into high strength, convenient transportation, appropriate disposal, mud cake without pollution [3]. Mud cake after treatment was transported to the brick factory or used for landfill and greening project.

PROCESSING TECHNOLOGY AND OPERATION MODE

Processing technology Solidification disposal of mud has been adopted on land resources tense region [4]. The technology is mature, strong operability, and is approved the promotion by the relevant departments of the state. The analysis results are shown in table 1 about the advantages and disadvantages of mud solidification mode and traditional mode [5]. Table 1: Analysis of mud solidification mode and tradition mode

Processing Dredging The Sinotrans mod Project Stacking Comprehensive The manage- treatment manage- comparative investment area evaluation factor ment effect ment

The Jiangsu Mud More Big relatively The larger The general The general Oriental piling complex simple ecological The dredging Brick The larger relatively Unwanted The general Simple Better mode simple Luther The Mud environ- Smaller Routine Smaller Good relatively Better piling ment mud simple drying Brick Smaller Routine Unwanted Good Simple Good mode The traditional Small Routine Big Bad Complex Poor dredging mode Dredging mud dewatering consolidation interacted processing system is based on the characteristics of high water content, very small particle size in the city of lake [2]. The main mean is removed by mechanical extrusion free water in the mud which rapidly separated the dredging mud into water and cake, which finished complexation, passivation and sealing on the heavy metals, organic water, and micro fine pathogens. Soil strength was improved and solidified by new material [6]. According to the disposal amount, multi module device was run at the same time. The dehydrated mud cake was less than 70% at the volume of mud, less than 40% at moisture content, high strength, convenient transportation, appropriate disposal. Water suspension index ss was less than 20mg/L which reached the wastewater discharge standard of national town [7]. The mud cake after treatment was transported to the brick factory or used for landfill and greening project. The technological process was shown in Figure 1.

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Operation mode Lude Environment and Technology Inc in Hubei Wuhan，is considered as partner with Keqiao area of mud solidification processing cooperation object, using the BOO (building, own and operation) model. Keqiao is to prepare the land leveling and free use of land, the location is shown in Figure 2. The company has invested thirty million Yuan in the construction of solidified mud processing center, with the ability of annual processing 1000000 parties (solidified mud cake 330000 parties) mud solidification, equipped with 6 sets of dehydration consolidation of integration system, and equipped with equipment to increase processing capacity at any time according to the need. Keqiao should ensure that not less than 700000 square muds would be sent to the central processing every year. Processing technology and operation pattern of different company is shown in table 2.

Figure 2: Sludge solidification Figure 1: Technological process processing center position

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Table 2: Processing technology and operation pattern of different company company Processing technology treatment effect Operation Cost mode Jiangsu Sludge solidification technology: After treatment，the acceptable 80 Yuan / Juhui adding curing materials in mud, volume of underwater mud BOO water Technolog using of a series of physical, and dried mud reduce more (building, below y Co., Ltd. chemical action between curing than 50%, waste sludge own and square material and silt to reduce the sludge hazardous become useful operation) moisture content, to improve the silt resources that can be used model strength, to enclose organic matter for filling engineering, and heavy metal in silt particles, road engineering and green suitable for a large number of sludge land soil. treatment work.

Hubei patented technology "sediment After treatment，the acceptable 80-120 Lude dredging mud integration processing volume ratio is 3:1 BOO Yuan / stem environme dehydration consolidation method" between underwater mud (building, square (40 ntal and “the core material FSA and dried mud, volume own and Yuan / Polytron coagulation agent and HEC reduction is nearly 2/3, the operation) water Technolog consolidation agent”, stirring the soil strength is high, the model below ies Inc mud, forming mud cake after soil does not soften or mud square) mechanical dehydration. with water.

Dredging Curing agent conditioning, After treatment, moisture acceptable 100-140 Engineeri mechanical dewatering content of mud is between BOO Yuan / stem ng Co. 40-50%, wet volume of (building, square (50- Ltd. in mud is below 0.5 dry own and 70 volume of mud. operation) Yuan/water Province model below square) Hubei Using the continuous treatment After treatment, wet acceptable About 115 solid process of sludge mechanical volume of mud is below BOO Yuan / stem Polytron dewatering chemical curing, making 0.5 dry volume of mud. (building, square (46 Technolog the use of independent research and Moisture content of mud is own and Yuan / ies Inc development company patented HAS less than 40%, it can be operation) water curing agent modified effects of silt, used as engineering model below the silt is from hydrophilic to backfill, garden soil, square) hydrophobic modification, and then landfill cover soil. At the through the mechanical filter same time, it realize curing function, the silt is processed into and stabilization of the soil solid with the water content heavy metals in the mud by below 40%. curing agent. Technology advantage

Factory Matching dredging equipment (a set of equipment with the ability of mud dredging 600-900m³ / d), reducing dewatering sediment, completing one-time consolidation hardening, it achieves a continuous operation of the factory within 24 hours day, using a special mechanical dewatering, mixing machinery, unaffected by the weather.

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Real-time The core material recipe combination of "FSA + HEC" can be adjusted in real time according to the sediment properties (particle size, organic matter, heavy metals and other indicators), adjusted the material combination and dosage according to the mud, soil and use.

Reduction Dewatered cake was shown in Figure 3, reduction of 60-75% comparing with the underwater natural volume, reduction of 90-95% comparing with dredging mud, moisture content less than 40%. Transport costs and covering area substantially reduced.

Harmless Bacteria contained in mud cake are killed. Heavy metal is formed of complexation, passivation or solid seal and not dissolution by HEC. Filter tail water shown in Figure 4 is clear [6]. Suspended solid index ss is less than 20mg/l which meet the national standard “urban sewage treatment plant pollutant discharge standard” (GB18918-2002).

Stabilization Dewatered cake was plastic, hard plastic state. The moisture content was below 40%, 7d unconfined compressive strength was more than 0.2MPa [4]. It does not soften under the influence of water softening, no mudding, no secondary pollutant transfer and diffusion.

Resources Dewatered cake can be used for engineering backfill, building materials and other raw materials.

Localization The main equipment can be achieved domestically; the technology is mature, convenient maintenance.

Cheaper Dredged overall disposal costs significantly reduced above 20% comparing to conventional mechanical dewatering, stirring consolidation engineering methods [8]. Integrated cost was low and freight decline comparing to the traditional technology such as "big excavation, fill a large, large transport".

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Figure 3: Dewatered cake Figure 4: Emission clear tail water

FUNDING ARRANGEMENTS

Billing model According to the comparative analysis of previous research stage, using the mode of cooperation to introduce the Hubei Wuhan Luther environmental Polytron Technologies Inc that invests thirty million to construct the Mud curing treatment center and signing cooperation with keqiao district for 5 years, keqiao district ensures that there are not less than 700000 square mud for processing each year. By way of single curing processing and curing integration dredging, mud cakes after curing are calculated in accordance with 115 Yuan / square, or after transported to the coastal mud field, the mud cake after curing are calculated in accordance with 120 Yuan / square. Considering the prices and other factors, the price increases by 5% per year. From the second year, basing on the result of dredging and curing accounting in first years, it can determine the dredging quantity of water below, the conversion ratio of the cured sludge and the integrated unit. In the previous research, there are three ways about the statistical analysis of the cost, shown in Table 3.

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Table 3: Three ways of cost statistics

Project investment River Sludge drying Dry mud Site Total dredging Sinotrans management

pattern

Jiangsu Mud Oriental 10000 1750 750 12500 Stacking ecological dredging Brick 10000 1500 500 12000 mode Luther Mud 4000 4000 750 8750 environment Stacking mud drying Brick 4000 3800 500 8350 mode The traditional dredging 4000 0 2450 750 7200 mode In conclusion, it is more favorable with adopting the program of the Hubei Lutheran environmental Polytron Technologies Inc River silt to handle the river silt and the mud buildings in Keqiao District dredging.

Billing payment Hydropower Bureau entrusts the supervision mechanism with the supervision and control of the curing processing center operation, product quality and the number of solidified mud cake, with periodically testing the quality of mud cake, and weighing the mud cake after curing, then converting it into volume and determining the monthly workload, approving amount paid monthly.

CONCLUSION The implementation of river silt, building mud solidification treatment in Keqiao area, is benefit to the solution of this problem, and conforms to the status quo of Keqiao area. The implementation of river silt, mud solidification treatment is the effective measure to strengthen the building of silt disposal, deepen the “five water co governance”.

ACKNOWLEDGMENT This research was supported by the Education Planning Projects and Curriculum Reform of Teaching Mode in 2015 Shaoxing city（SGJ15046）.

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