Presenter
Dr. Xia Chen
Co-author(s)
Miss. Qi Lu, Dr. Zeyu Fan, Dr. Xian Zhou, Mrs. Ziling Peng, Dr. Zhuo Fan Gao, Dr. Shanshan Deng, Dr. Wei Han
Organisation
Changjiang River Scientific Research Institute
Sub-theme
2. Promoting Water Efficiency, Productivity and Services
Topic
2-4. Wastewater treatment and reuse
Body
The economical utilization of water resources and zero discharge of wastewater are the inevitable requirements of green water conservancy and hydropower projects. During the construction of large-scale water conservancy and hydropower projects, aggregate washing processing accounts for the majority of water consumption. However, the aggregate washing device is simply designed and inefficient in the existing engineering construction. The water resources are seriously wasted, and the ecological risk of direct discharge of wastewater is high. This work optimizes the utilization of water resources in aggregate processing system from source and terminal, with object of saving water and realizing the wastewater self-consumption in hydropower project. Thus, a new type of efficient water-saving washing process for aggregate processing plant is designed, and the feasibility of using recycled water for concrete mixing is verified. The laboratory simulation test shows that the type of nozzle, the distribution of outlet points, the number and arrangement of outlet pipes will significantly affect the washing effect. The spiral nozzle and the non-equidistant arrangement of spray pipes can reduce water consumption and improve washing effect. Compared with the traditional way, the new designed washing process can save water by at least 50%. The new process has been applied to the aggregate processing system of a hydropower station in China, and the results are similar to those of the laboratory. Chloride ion and suspended solids (SS) concentration are important parameters affecting the quality of concrete mixing water. Then, the quality of recycled water from sand and gravel wastewater is characterized by ion chromatography. It is found that the chloride ion concentration of recycled water after 7 times of flocculation treatment with 10 mg/L PAC is 32.19 mg/L, and the chloride ion concentration of recycled water after 50 mg/L PAC treatment exceeds 100 mg/L. This meets the specification requirements of concrete mixing water. Recycled water with different SS concentrations is used to mix concrete. When the SS concentration is 1854 mg/L, the maximum reduction of compressive strength of mixed concrete at 7 days and 28 days is less than 2.7%. It is proved that recycled water with SS concentration of less than 1800 mg/L can be used to mix concrete.