The use of ferric chloride and anionic polymer in the Chemically Assisted Primary Sedimentation Process

Chemically Enhanced Primary Treatment (CEPT) or Chemically Assisted Primary Sedimentation Process (CAPS) involves the use of chemical coagulants to enhance the coagulation or flocculation of wastewater particles. The effect of a metal salt, ferric chloride (FeCl3) and an anionic polymer on the removal of suspended solids (SS) of wastewater collected from two sewage treatment plants was studied by jar test experiments. The results showed that the optimum dosage for the removal of 60% of SS was 30 ppm of FeCl3with 0.5 ppm polymer. A larger scale test further revealed that the addition of 30 ppm of FeCl3and 0.5 ppm polymer could provide a reduction of SS, total nitrogen (N) and total phosphorous (P) higher than 80%, 70% and 40%, respectively. The experimental results confirmed that CAPS can be used as an alternative for the treatment of sewage to traditional biological processes.