Coagulation and Filtration Improvement Using Ozone Water Treatment

Ozone has been reported to improve coagulation and filtration efficiency. This effect has been called, among other things, micro flocculation or ozone micro flocculation.

Data from water treatment plants show that pre-ozonation (ozonation of the raw water) was more effective than pre- chlorination to reduce filter effluent turbidities.

The cause of the improved coagulation is not clear, but several possibilities have been offered including:

• Ozone forms organic compounds with functional groups such as carboxylic acid. These groups can complex with aluminum oxide to aid in the association of the aluminum with the organic material.
• Carboxylic functional groups can also complex calcium which may improve adsorption of organics to the metal oxide surfaces.
• Ozonation of NOM may create organic polymers that either enhance coagulation of are more easily coagulated.
• Ozone can breakdown complexed Fe and Mn which might be tied up with NOM. The release of the oxidized metals creates a source of coagulant.

For a large number of WTP improved particulate removal for filtration has been observed after the installation of ozone generators in terms of lower turbidity, lower particle counts in the filtered water and increased filter runs. In pre-ozonation applications, lower dosages of coagulant have also been observed. This reduction in chemical use can be in the range of 20 to 50%.

These benefits are normally not predicted by laboratory scale studies and models do not exist to predict that ozone water treatment will improve coagulation and flocculation. The effect is normally observed upon full scale operation. Nevertheless, enhanced filtration is an important economic and performance benefit observed with the use of ozone generators in the treatment of drinking water and other water treatment applications.

Kerwin L. Rakness, “Ozone in Drinking Water Treatment: Process Design, Operation and Optimization”. AWWA 2005
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Reckhow, D.A., J.K. Edzwald, and J.E. Tobiason. 1993. “Ozone as an Aid to Coagulation and Filtration.” AWWARF and AWWA, Denver, CO.
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