NOM - Removal by biofiltration after ozonation - Results of a pilot plant test

In the region of Eastern Germany high levels of natural organic matter in surface water cause the violation of THM standards while using chlorine for final disinfection in waterworks, using bank-filtered water as raw water source. Therefore a DOC removal during the treatment is necessary. In a pilot plant the efficiency of an ozonation with subsequent biofiltration as pretreatment step for GAC filtration was tested. A maximum BDOC formation of 25 to 30% of the DOC could be obtained by ozonation. App. 50% of the formed BDOC was eliminated in the biofilter. So the DOC concentration in the influent of the GAC filter was 15% lower than in the water without this pretreatment. The lower influent DOC concentrations were connected with lower DOC concentrations after GAC filtration. As a result of the pilot plant test it could be shown that the use of the combination of ozonation with subsequent biofiltration can be an alternative for the use of flocculation.