Apparatus and method for treating waste water

An apparatus for treating waste water comprising:

• a first flocculation tank configured to receive a waste water comprising fluorine is introduced and where a water-insoluble calcium salt is produced and flows out in a first outflow water;
• a second flocculation tank configured to receive the first outflow water and carbon dioxide from a first source for adjusting a pH of the first outflow water introduced and flows out in a second outflow water;
• a third flocculation tank configured to receive the second outflow water and in which floc comprising the water-insoluble calcium salt is produced and flows out in a third outflow water;
• a first sedimentation tank configured to receive the third outflow water from the third flocculation tank and which is separated into a first sludge containing the floc and first supernatant water;
• a nitrification tank configured to receive the first supernatant water in which ammoniacal nitrogen is oxidized, wherein the nitrification tank is not dosed with an alkaline material for providing alkalinity from an external source, and which flows out as a fourth outflow water, wherein the nitrification tank is provided with alkalinity by a carbonate formed from the carbon dioxide dosed to the second flocculation tank;
• and
• a second sedimentation tank configured to receive the fourth outflow water which is separated into a second sludge and second supernatant water.

A method for treating waste water, the method comprising:

• producing a first flocculated material in which fluorine in waste water is coagulated in a first flocculation tank;
• producing a second flocculated material in which residual fluorine in first outflow water introduced from the first flocculation tank is flocculated in a second flocculation tank and adjusting a pH by dosing carbon dioxide to the second flocculation tank;
• producing a third flocculated material in which the first flocculated material and the second flocculated material in second outflow water introduced from the second flocculation tank are flocculated, in a third flocculation tank;
• solid-liquid separating third outflow water introduced from the third flocculation tank into first sludge containing the third flocculated material and first supernatant water in a first sedimentation tank;
• oxidizing ammoniacal nitrogen in the first supernatant water introduced from the first sedimentation tank, in a nitrification tank, alkalinity is provided by a carbonate formed from the carbon dioxide dosed in the adjusting of pH;
• and
• solid-liquid separating fourth outflow water introduced from the nitrification tank into second sludge and second supernatant water in a second sedimentation tank.