Dear Carlos, The increase ...

Dear Carlos,

The increase of both COD and color after biological treatment is explained by the higher fraction of recalcitrant organics including lignin compounds (brownish color) after changing the washing in the bleaching stage.

Because traditional activated sludge systems including MBR, remove mainly readily biodegradable soluble organics (“fast” food), we upgrade this to capture and biodegrade the “slow” food  and recalcitrant organics including color as well without using any chemicals. In 2009 we applied this in a large pulp & paper wastewater treatment resulting in very low COD and color (80% - 90% removal).

If interested, I would be happy to send you more information via email.

Regards, Bruno.