Effectiveness of priority PAH removal in a water coagulation process

Abstract

The paper presents results of research on the removal of priority hazardous polycyclic aromatic hydrocarbons (PAHs) (anthracene, benzo[a]pyrene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[g,h,i]perylene, indeno[1,2,3-cd]pyrene) from water in the coagulation and sedimentation process. Coagulants chosen for the analysis were aluminum(VI)sulfate and two pre-hydrolyzed coagulants – FLOKOR 1.2A and FLOKOR 1ASW/B. Water samples subjected to coagulation were collected from selected water treatment plants following the pre-ozonation process. Tested coagulants were dosed at optimal doses (1.2; and 1.8 mg Al3+/L). The process was carried out at optimum parameters: rapid mixing – 3 min at the rotational speed of 200 rpm; slow mixing – 10 min at 30 rpm; sedimentation – 60 min. Summary concentration of six priority hazardous PAHs in water after pre-ozonation amounted to 12.6 ng/L; after volumetric coagulation using selected coagulants it was in the range 6.8–8.3 ng/L. The highest efficiency in the removal of priority hazardous aromatic hydrocarbons was obtained after application of the preparation FLOKOR 1 ASW/B. Decrease in the summary concentration amounted to 46.4%. For the removal of individual priority PAHs, FLOKOR 1ASW/B was also more effective using lower coagulant dose than was aluminum(VI)sulfate (decrease in the range 23.6%–56.1%).