Control of bulking in a full scale plant by addition of talc (PE 8418)

Abstract

A very severe bulking problem (Type 021N) in the water treatment plant of Bodegraven in The Netherlands was solved by the addition of a specially shaped talqueous powder, PE 8418. After addition of this mineral product, the SVI dropped almost instantaneously from 850 ml/g to 250 ml/g and over the next 2 weeks decreased further to 100 to 125 ml/g. A ratio PE 8418/biomass of 0.6:1 was sufficient to keep the SVI at this level. The settling velocity of the sludge increased from <1.0m/h to 1.5 m/h. These settling properties allowed normal plant operation. During the first 2 weeks of the experiment, scum on the final clarifier and the aeration tank caused some problems. It is assumed that the complete incorporation of PE 8418 particles into the flocs takes some time, if a large quantity of this product is added at once. Meanwhile, free particles may contribute to stabilization of gas bubbles, viz. flotation of activated sludge.