USING DISSOLVED HUMIC-ACID TO REMOVE HYDROPHOBIC CONTAMINANTS FROM WATER BY COMPLEXATION-FLOCCULATION PROCESS

Dissolved humic acid (DHA) can be used as a complexing agent to remove hydrophobic contaminants from water by complexation-flocculation proc ess. The treatment process is composed of two stages: (a) DHA is added to the contaminated water and allowed to interact (bind) with the dis solved contaminants to form DHA-contaminant complexes (complexation st age). (b) A flocculant (alum or ferric chloride) is added, resulting i n precipitation and flocculation of the DHA and the associated contami nant (flocculation stage). Flocculation of DHA at concentrations of 1- 50 mg/L OCHA was highly efficient with both alum and ferric chloride. The removal of three polycyclic aromatic hydrocarbons (PAHs) was studi ed using this process. DHA-PAH complexes did not disintegrate upon add ition of AI(III) or Fe(III) salts, they were efficiently removed by fl occulation, and the experimental results corresponded to those predict ed by computations of the bound fractions. The proposed process is eff ective in removing pollutants of medium to high hydrophobicity (log K- ow > 4.5). It is simple, does not require special treatment facilities , can be coupled with common water treatment technology, and has a pot ential to be useful in cases of periodic contamination events. Additio nally, the efficient removal of DHA-contaminant complexes by flocculat ion emphasizes the importance of enhanced coagulation, not only to red uce the formation of disinfection byproducts (DBPs), but also to remov e organic micropollutants associated with dissolved organic matter.