Integrated magnetic flocculation-horizontal tube sedimentation process for Treating Dredging Residual Water: Environmental Restoration of Wolong Lake

Abstract

The dredge residual water contains high concentrations of heavy metals and causes severe environmental pollution of lakes. This present study develops an integrated magnetic flocculation-horizontal tube sedimentation equipment. In the Wolong Lake region of China, the device's treatment impact on the residual water from dredged sludge under various inlet water flows was investigated. In a single-factor experiment, flocculants such as Poly Aluminum Chloride (PAC), Polymeric Ferric Sulfate (PFS), Ferric chloride (FeCl3), and Aluminum Sulphate (Al2(SO4)3) were used at a dose of 20–120 mg/L to treat the residual water from dredged sludge. The residual wastewater from dredging sludge treated better with PAC 60 mg/L; the removal efficiency of suspended solids (SS), chemical oxygen demand (COD), total phosphorous (TP), and ammonia nitrogen (NH3-N) were 81.37%, 44.65%, 76.48%, and 16.64%, respectively. The pollutants in the water were further removed using magnetic flocculation (single-factor test and orthogonal analysis). The response surface method was used to optimize the agents PAC, magnetic powder, and polyacrylamide (PAM) doses. The COD, SS, TP, and ammonia nitrogen removal reached 71.2%, 93.1%, 91.2%, and 21.2%, respectively. The actual operation of the device for 30 consecutive days at various water intake volumes (4, 6, and 8 m³/h) was carried out. The residual water's COD, SS, TP, and NH3-N levels effectively meet the environmental quality standards for surface water. With Space Claim as the pre-processing software and Fluent as the solver, the CFD simulation analysis of the test device was conducted. The reliability and rationality of the test device's operation were verified through simulation and analysis using the dual Euler model. Key Words: Dredged sludge residual water, Magnetic flocculation technology, Horizontal pipe sedimentation technology, Integrated wastewater treatment equipment, CFD simulation