Removal of hydrophobic organic pollutants by coagulation-precipitation process with dissolved humic matter

Abstract

The removal of hydrophobic organic pollutants (HOPs) from water with precipitating dissolved humic matter (DHM) was found to depend on the physical and chemical properties of the HOPs themselves, and could be estimated theoretically. The removal efficiency of HOPs was decreased at high pH and with increasing ionic strength; in particular, when ionic strength increased, the decrease was small. In deionised water, the removal efficiencies of pyrene, fluoranthene, anthracene and phenanthrene were about 75%, 57%, 40% and 30% respectively in the DHM range used, and increased clearly with increasing concentration of DHM. The difference of removal efficiency resulted from the physical and chemical characteristics of the HOPs such as partition coefficient to DHM (KOC), whose order is pyrene > fluoranthene > anthracene > phenanthrene. Because of the large partition coefficients of dioxins to DHM, removal efficiencies of 90 to 99.9% could be obtained with only a few mg l-1 of organic carbon (OC) in DHM and 99 to 99.99% with over ten mg-OC l-1 in DHM.