Colloidal silica removal in coagulation processes for wastewater reuse in a high-tech industrial park.
Four experiments of coagulation and flocculation were conducted to investigate the characteristics of colloidal silica removal in a high-tech industrial wastewater treatment plant for reclamation and reuse of the effluent. Experimental results illustrated that poly-aluminium chloride (PACl) showed higher performances on colloidal silica removal than alum. Interestingly, the two coagulants demonstrated the same capacity on silica removal. The specific silica removal capacity was approximately 0.135 mg SiO2/mg Al2O3 when the dosage of coagulants was in the range 30-150 mg/L Al2O3. In addition, the silica was reduced significantly at the condition of pH above 8. Experimental data implied that precipitation of aluminium flocs was the major mechanism for colloid silica removal in PACl and alum coagulation, besides, charge adsorption was also important for improving removal efficiency. Moreover, the addition of polyacrylic acid (PAA) as a flocculant could slightly advance silica removal in the PACl coagulation. The combined PACl/PAA/flocs coagulation was effective for the removal of colloidal silica, soluble COD, and turbidity and also suitable as a pretreatment unit in wastewater reclamation and reuse processes.
Chuang
S H
SH
Department of Environmental Engineering and Management, Chaoyang University of Technology, Wufeng, Taichung County 413, Chinese Taiwan. shchuang@mail.cyut.edu.tw
Chang
T C
TC
Ouyang
C F
CF
Leu
J M
JM
D000534:Alum Compounds / Q000737:chemistry; D000077410:Aluminum Chloride; D017607:Aluminum Compounds / Q000737:chemistry; D011232:Chemical Precipitation; D002712:Chlorides / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007220:Industrial Waste; D012822:Silicon Dioxide / Q000302:isolation & purification*; D014865:Waste Disposal, Fluid; D014874:Water Pollutants, Chemical / Q000302:isolation & purification*; D018508:Water Purification / Q000379:methods
D000534:Alum Compounds; D017607:Aluminum Compounds; D002712:Chlorides; D007220:Industrial Waste; D014874:Water Pollutants, Chemical; C041524:aluminum sulfate; D000077410:Aluminum Chloride; D012822:Silicon Dioxide