Wastewater treatment process

1. A wastewater treatment process for treating wastewater discharged during a process for producing an electrophotographic toner comprising a water-based dispersion containing a surfactant, a colorant, silica and other solid matter, the process comprising:

a reaction step of adding a coagulant to the wastewater and conducting a coagulation reaction;

a flock formation step of forming a flock from aggregates generated in the coagulation reaction of the reaction step; and

a separation step of separating the flock and a separated liquid;

wherein:

the wastewater is treated using a polysilicato-iron coagulant;

a quantity of the polysilicato-iron coagulant added is equivalent to a concentration within a range from about 1 mg/L to about 500 mg/L relative to the wastewater;

a temperature of the wastewater during the reaction step is from about 10° C. to about 30° C.;

the quantity of the surfactant in the wastewater is within a range from about 0.1 to about 4 weight percent of the weight of the wastewater; and

the quantity of silica in the wastewater is within a range from about 0.1 to about 4 weight percent of the weight of the wastewater.

2. The wastewater treatment process according to claim 1 , wherein a Si/Fe molar ratio within the polysilicato-iron coagulant is within a range from about 0.1 to about 4.0.

3. The wastewater treatment process according to claim 1 , wherein a pH of a reaction liquid during wastewater treatment using the polysilicato-iron coagulant is within a range from about 4 to about 9.

4. The wastewater treatment process according to claim 1 , wherein treatment of the wastewater is conducted using the polysilicato-iron coagulant and an inorganic coagulant.

5. The wastewater treatment process according to claim 4 , wherein the inorganic coagulant is at least one of aluminum polychloride and ferric chloride.

6. The wastewater treatment process according to claim 4 , wherein a quantity added of the inorganic coagulant is equivalent to a concentration within a range from about 500 mg/L to about 5,000 mg/L relative to the wastewater.

7. The wastewater treatment process according to claim 1 , wherein treatment of the wastewater is conducted using the polysilicato-iron coagulant and an organic coagulant.

8. The wastewater treatment process according to claim 7 , wherein a quantity added of the organic coagulant is equivalent to a concentration within a range from about 1 mg/L to about 500 mg/L relative to the wastewater.

9. The wastewater treatment process according to claim 1 , wherein in the separation step, at least one of a coagulation-sedimentation treatment and a pressure flotation treatment is conducted.

10. A wastewater treatment process for treating wastewater discharged during a process for producing an electrophotographic toner comprising a water-based dispersion containing a surfactant, a colorant, silica and other solid matter, the process comprising:

a reaction step of adding a coagulant to the wastewater and conducting a coagulation reaction;

a flock formation step of forming a flock from aggregates generated in the coagulation reaction of the reaction step; and

a separation step of separating the flock and a separated liquid,

wherein:

the other solid matter comprises electrostatic latent image developing toner;

the wastewater is treated using a polysilicato-iron coagulant;

a quantity of the polysilicato-iron coagulant added is equivalent to a concentration within a range from about 1 mg/L to about 500 mg/L relative to the wastewater;

a temperature of the wastewater during the reaction step is from about 10° C. to about 30° C.;

the quantity of the surfactant in the wastewater is within a range from about 0.1 to about 4 weight percent of the weight of the wastewater; and

the quantity of silica in the wastewater is within a range from about 0.1 to about 4 weight percent of the weight of the wastewater.