River Sediment Treatment Technology Based on Zero Emission

The sediment is the main source of the river pollution, therefore, how to rapidly treat the river sediment with low cost and without secondary pollution is key point for the polluted river rehabilitation. In this study, taking the sediment treatment of the Qingxi River in Dongguan, Guangdong, China as an example, an ecological sediment treatment process was developed based on zero emission to reduce the amount of the contaminated sediment treatment. The process also employ 4R (Reduce, Recycle, Reuse and Revolution) concept and centrifugal solid-liquid separation technology. The sediment of the polluted Qingxi River is accurately divided into gravel, sand, silt and clay by the four-stage treatment process, and the treated sediment can be recycled and reused for backfill and building material. The gravel, sand and silt in the sediment mainly separated by the centrifugal solid-liquid separation equipment made in Texas, USA, which can treat 454.25m³ of slurry containing 15% solids per hour. The first stage screens out gravel with a particle diameter greater than 2 mm; the second stage screens out sand with a diameter greater than 0.075 mm; and the third stage screens out silt with a diameter greater than 0.025 mm. Clay less than 0.025mm (the fourth stage) are flocculated to sediment with a moisture content of 80% by an inclined plate settling equipment made in Dongguan, China, and then further dehydrated into clay with a moisture content of less than 60% by belt dewatering equipment. The dewatered clay is made into the mixture soil of the sponge city facilities, permeable bricks or other building materials, gravel and sand are directly used as concrete aggregate, and the silts are mainly used for backfill.

The efficiency of the newly developed river sediment treatment process is more than three times of the traditional sediment treatment process used in China, and there is no secondary pollution and cost savings. The investment of the new treatment system is about RMB 20 to 30 million Yuan. It can be widely applied to quick treatment of the deposits in the polluted rivers, reservoirs and lakes and construction wastes of subway and tunnels.