System and method for advanced defluorination of wastewater

A system for advanced defluorination of wastewater, comprising:

• a first dosing tank;
• a second dosing tank;
• a calcium fluoride crystallizer;
• a fluoride-selective ion exchange column;
• a third dosing tank;
• and
• a fourth dosing tank;
• wherein the first dosing tank, the second dosing tank, the calcium fluoride crystallizer, the fluoride-selective ion exchange column, the third dosing tank and the fourth dosing tank are arranged in sequence;
• the calcium fluoride crystallizer is filled with quartz sand;
• and a bottom of the calcium fluoride crystallizer is provided with a water distribution plate;
• the water distribution plate is connected to an end of a first inlet pipe and a first end of a return pipe;
• the first inlet pipe is provided with a first inlet pump and a first inlet valve;
• the return pipe is provided with a return pump;
• an overflow port is provided at a top of the calcium fluoride crystallizer, and is connected to a first end of a second inlet pipe;
• the second inlet pipe is provided with a second inlet valve;
• a lower portion of the overflow port is connected to a second end of the return pipe;
• the fluoride-selective ion exchange column is filled with a zirconium-loaded resin;
• a top of the fluoride-selective ion exchange column is connected to a second end of the second inlet pipe and a first end of a regeneration wastewater delivery pipe;
• a bottom of the fluoride-selective ion exchange column is connected to an end of an outlet pipe;
• and the outlet pipe is provided with an outlet valve;
• the first dosing tank is connected to the return pipe through a first dosing pipe;
• the first dosing pipe is provided with a first dosing pump and a first dosing valve;
• and the first dosing tank is configured to store a sodium fluoride solution with a first preset concentration a mg/L;
• the second dosing tank is connected to the second inlet pipe through a second dosing pipe;
• the second dosing pipe is provided with a second dosing pump and a second dosing valve;
• a connection between the second dosing pipe and the second inlet pipe is located at an upstream side of the second inlet valve;
• and the second dosing tank is configured to store a hydrochloric acid solution with a second preset concentration b mg/L;
• the third dosing tank is connected to the outlet pipe through a third dosing pipe;
• the third dosing pipe is provided with a third dosing pump and a third dosing valve;
• a connection between the third dosing pipe and the outlet pipe is located at an upstream side of the outlet valve;
• and the third dosing tank is configured to store a sodium hydroxide solution with a third preset concentration c mg/L;
• a second end of the regeneration wastewater delivery pipe is connected to the fourth dosing tank;
• the fourth dosing tank is connected to the return pipe through a fourth dosing pipe;
• the fourth dosing pipe is provided with a fourth dosing pump and a fourth dosing valve;
• and an agitator is provided inside the fourth dosing tank;
• the first inlet pipe is further provided with a first fluoride ion-selective electrode and a calcium ion-selective electrode;
• and the first fluoride ion-selective electrode and the calcium ion-selective electrode are provided at an upstream side of the first inlet valve;
• the second inlet pipe is further provided with a second fluoride ion-selective electrode and a first pH meter;
• the second fluoride ion-selective electrode is provided at the upstream side of the second inlet valve;
• and the first pH meter is located between an end of the second dosing pipe and the second inlet valve;
• the outlet pipe is further provided with a third fluoride ion-selective electrode and a second pH meter;
• and the third fluoride ion-selective electrode and the second pH meter are provided at a downstream side of the outlet valve;
• and
• a side wall at a bottom of the fourth dosing tank is provided with a fourth fluoride ion-selective electrode;
• and a flow meter is provided at an outlet at a bottom of the fourth dosing tank to measure a flow rate of a regeneration wastewater.