研究結果顯示，原廢水pH<2.28，氟離子(F-)值為300ppm，且含硝酸、硫酸、鹽酸陰離子，屬於低濃度含氟廢水，以鈣鹽沉澱法處理結果顯示，pH=7、0.15ml PAC、1.5ml Polymer為各處理單元加藥劑量對氟離子濃度去除效率的最佳加藥參數，而氯化鈣(Ca/F=1.4)、熟石灰(Ca/F=3)及石灰石(Ca/F=2.4)分別添加於各處理單元最佳參數對氟離子濃度均有95%(約13.3ppm)的去除效率。另外在汙泥資源再利用化方面(汙泥有效氟化鈣濃度>70%)只有添加氯化鈣藥劑(84.61%)達到再利用之條件。以氯化鈣做為主要鈣鹽的化學混凝程序中，分別導入迴流汙泥(2ml)及鐵材(0.8g)可提升21.4%(10.3ppm)及15%(11.3ppm)對氟離子的去除效率，另將迴流汙泥(2ml)導入化學混凝程序，改變氯化鈣添加量(Ca/F=1.2)可提升12.5%(13.9ppm)對氟離子濃度(處理水水質)的去除效率且符合放流水管制標準及降低藥劑成本，以廢水廠每千噸廢水的運作成本換算可降低約1,920元。
;The study mainly involues the chemical coagulation and precipitation method to treat the wastewater containing low concentration of fluoride generated by a crystalline silicon solar cell plant. The experiment is conducted based on the operating factors such as different pH values, dose of chemicals added to the processing parts, different calcium salts, different volume of refluxing sludge and iron material, as well as the acid mixed in the wastewater. Moreover, it analyzes the effect of various operating factors on F- removal, and the valid CaF2 concentration of the sludge.
As shown in the results, the original wastewater has pH<2.28, with the F- value of 300ppm, which also contains HNO3, H2SO4, HCl and anion. It is the wastewater containing low concentration of fluoride. As shown in the treatment results of calcium salt precipitation method, the optimal parameters for adding chemicals into various processing units to remove F- concentration are pH=7, 0.15ml PAC, and 1.5ml Polymer. When CaCl2(Ca/F=1.4), Ca(OH)2(Ca/F=3) and CaCO3 (Ca/F=2.4) are added to various processing units, it will reach the F- removal efficiency as high as 95%(about 13.3ppm) under the optimal parameters. In addition, in terms of reusing resources in the sludge (the valid CaF2 concentration of the sludge>70%), only when the CaCl2(84.61%) is added, can it reach the reuse conditions. During the chemical coagulation process with respecl to CaCl2 as the main calcium salt, addition of refluxing sludge (2ml) and iron material (0.8g) can increase the F- removal efficiency by 21.4%(10.3ppm) and 15%(11.3ppm) respectively. Moreover, when the refluxing sludge (2ml) is added in the chemical coagulation process, change in the volume of added CaCl2 (Ca/F=1.2) can increase the F- removal efficiency(quality of treated water) by 12.5%(13.9ppm). Moreover, it confirms the Discharged Water Control Standards and reduces the chemical cost. The operation cost per kiloton wastewater in the treatment plant can be saved by about NTD1,920.
Moreover, the original water contains some other anions, and so H2SO4 is added to change the property of original water. As shown in the results, high H2SO4 content in the wastewater favours the F- removal efficiency and valid CaF2 concentration of the sludge.