Gravity Thickening

A gravity thickener is similar to a conventional circular sedimentation basin. Dilute sludge is fed to a centre feed well and allowed to settle and compact before being withdrawn from the bottom of the basin. The sludge scraping mechanism incorporates vertical pickets, which gently agitate the sludge and contribute to its densification by releasing trapped gas and waters. The thickened sludge is pumped to digesters or dewatering equipment, while the supernatant is returned to the head works of the treatment plant, or to the primary settling tank. This method is most effective with primary sludge.