A FEASIBILITY STUDY OF USING HEMATITE TO REMOVE DISSOLVED ORGANIC CARBON IN WATER TREATMENT

Abstract

An experimental investigation of using hematite to remove natural organic substances from water was carried out. Hematite sols (iron oxide, α-Fe₂O₃) prepared in the laboratory were found to form flocs with natural organic substances. Jar tests revealed that when a 85 mg/L hematite concentration (as Fe) was used, natural organic substances in the form of fulvic acid (4 mg/L) were totally removed. Direct filtration experiments using hematite were effective in removing dissolved organic carbon (DOC) from water; however the large hematite-organic flocs clogged the filter and reduced the filter run.

A conventional filtration system, which included flocculation and sedimentation prior to filtration, was found to be very effective at removing total DOC from water. An 86 mg/L hematite concentration (as Fe) was found to effectively remove 4 mg/L of fulvic acid from Milli-Q water. A residual iron concentration in the final effluent from the filtration unit was well below the allowable Australian drinking water guideline. Further research is warranted to optimize hematite concentration, pH, and ionic strength for application of this process in conventional water treatment plants.

Keywords:

• Dissolved organic carbon (DOC)
• Fulvic acid
• Hematite
• Coagulation
• Sedimentation
• Filtration

ACKNOWLEDGMENTS

The authors acknowledge the support received from Internal Research Grants from the University of Technology, Sydney, and from the Key Research Strength Project in Water and Waste Management.