Use of ferrate pre-oxidation in enhancing the treatment of NOM-rich lake waters

Natural organic materials (NOMs) have a very strong influence on the stability of inorganic particles through interactions (e.g. adsorption, coating, and so on), and thus make the surface water with high NOM content difficult to be coagulated. In this study, standard jar tests and a pilot study were conducted to evaluate the effectiveness of ferrate pre-oxidation in enhancing the coagulation of NOM-rich lake water. A substantial reduction of residual turbidity after sedimentation and filtration was obtained by ferrate pre-oxidation at low dosage (1–5 mg L^‒1 as K₂FeO₄). It was suggested that in order to maintain an acceptable residual turbidity, ferrate pre-oxidation can substantially reduce the dosage of coagulant. The improvement of water quality, as indicated by the reduction of color, DOC, iron, manganese, total bacteria, was observed to be similar in nature to the enhancement of residual turbidity. Formation of additional coagulant (Fe (III)) after decomposition was believed to be an important role of ferrate in enhancing coagulation. Ferrate could be employed in drinking water treatment by simple addition of ferrate solution just before coagulation.