Waste water treatment and recycling in the production of food grade calcium carbonate

The food grade calcium carbonate is usually calcined with limestone and then digested, carbonized, finally filtered and desiccated. The filtered water in the production process contains calcium, magnesium, iron and other metal ions, and decomposition of carbonate ions, if the filtered water is not treated for re digestion, it will affect the carbonization reaction of late, so the water can not be used as filtration digested with water, can only reach the national emission standard at after the exclusion to industrial wastewater treatment. The following biochemical wastewater treatment process and principle: (1) the removal of impurities and large drift is pre processed by the grid (2) value to 7~9 in regulating pond to regulate pH of the water, the water temperature does not exceed 35 degrees, the water balance (3) adding coagulant PAC in the coagulation bath, the reaction suspension colloid the material and fine in the wastewater and the formation of floc (4) into PAM in flocculation flocculation, floc formation in alum coagulant effect. (5) the flocculation of sewage flowing into the primary sedimentation tank, the upper clear liquid flows into the anaerobic biochemical treatment system, a mud bucket is collected into the sludge tank bottom sludge, the content of COD decreased to 800ml/L (6) macromolecular organic matter in anaerobic pond in wastewater by hydrolysis, fermentation, acid and methane production phase drop into small molecular organic compounds, the content of COD decreased to 300mg/L (7) on the organic matter after aeration aerobic pool was a good support for CO2 on microbial and water content decreased to below 100mg/L, COD (8) on the aerobic effluent containing residual biochemical sludge and biological debris fall off slurry separation, bottom sludge to the anaerobic tank and the pond, part of playing to the sludge pond, directly discharged after the filter press. By the two stage sedimentation tank of natural sedimentation, wastewater COD supernatant is less than 100ml/L, ph6.5~8.5, SS is less than 20mg/L, fully meet the national effluent standard, so as to achieve recycling, environmental protection production.