Where should polyferric sulfate be added?

Where should polyferric sulfate be added?

Polyferric sulfate (PFS) is a polymer coagulant that should be widely used in sewage treatment. More and more people use PFS to replace polyaluminum chloride. PFS has the characteristics of simple operation, low cost, stable treatment effect, high treatment efficiency, etc., and can perform various functions such as coagulation, phosphorus removal, COD removal, and decolorization in sewage treatment. So when using polyferric sulfate, where should it be added?

   Some people say that polyferric sulfate has been used in primary sedimentation tanks, biochemical outlets, aeration tanks, etc. So in order to improve the processing effect, where should the dosing be, and what are the differences between these different dosing positions.

1. Primary sedimentation tank

   Adding polymeric ferric sulfate before the primary sedimentation tank is not uncommon in high turbidity wastewater. This type of wastewater contains a large amount of SS and insoluble substances (such as COD, colored groups, etc.). At this time, it mainly plays the role of removing non-soluble suspended matter, reducing the load of subsequent processing procedures, and increasing the rate of compliance.

   2. Biochemical water outlet

   Polyferric sulfate can be added to the biochemical effluent before the residual phosphorus, COD and other substances in the biochemical effluent can be treated, so that the phosphorus and COD in the wastewater can meet the sewage discharge standards. In practical applications, the dosing position can be determined according to its use function.

      (1) When using polymeric ferric sulfate as a phosphorus removal agent, the phosphorus content is small and can be added to the primary sedimentation tank, if the phosphorus concentration is high, it is added before the water in the secondary sedimentation tank.

         (2) When used as a COD remover, it can be added to the secondary sedimentation tank or biochemical outlet.

         (3)  When coagulation is used to remove turbidity and SS, it is added to the coagulation tank or the front end of the sedimentation tank.

   3. Aeration tank

   When it is added to the aeration tank or the pipeline between the aeration tank and the secondary sedimentation tank, it is mainly used as a coagulant for coagulation, and the aeration tank is beneficial to accelerate the dissolution rate of polyferric sulfate and The reaction speed between the phosphate, insoluble organic matter, suspended particles and colored groups in the secondary sedimentation tank makes the reaction more complete, saves coagulation time and improves the coagulation effect.