CONTROL OF BULKING IN A FULL-SCALE PLANT BY ADDITION OF TALC (PE-8418)

A very severe bulking problem (Type 021N) in the water treatment plant of Bodegraven in The Netherlands was solved by the addition of a spec ially 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. Dur ing the first 2 weeks of the experiment, scum on the final clarifier a nd the aeration tank caused some problems. It is assumed that the comp lete incorporation of PE 8418 particles into the flocs takes some time , if a large quantity of this product is added at once. Meanwhile, fre e particles may contribute to stabilization of gas bubbles. viz. flota tion of activated sludge. (C) 1998 IAWQ. Published by Elsevier Science Ltd.