Effect of freeze/thaw conditions, polyelectrolyte addition, and sludge loading on sludge electro-dewatering process

Laboratory scale pressure-driven electro-dewatering reactor was set up to study the effect of polyelectrolyte addition and freeze/thaw conditions on solid content in the final sludge cake at different sludge loading rates. An increase in freezing temperature and extended natural freezing periods resulted in a significant increase in sludge dewatering ability. However, dry solid (DS) content in the final sludge cake after electro-dewatering was similar (39.3-41.5%) regardless the experimental strategies. The reduction in sludge loading rate from 20 to 3kg DS/m² resulted in the increase in DS content of the final sludge cake (35.8-48.7%) using both, the polyelectrolyte addition and freezing condition sludge samples. During electro-dewatering using sludge amended with polymers, the DS content in the final sludge cake by the anode and the cathode was similar or a bit higher at the cathode either at high sludge loading or using high amount of polymers. It was found that polymer addition had a negative effect on the electro-osmotic flow.