Dewatering characteristics of algae-containing alum sludge

Abstract

The presence of algae in source waters not only causes problems in the water treatment process, but also complicates the treatment and disposal of sludge. This has become a major concern in Taiwan because of the increasing eutrophication of water sources. The purpose of this study was to determine the effects of algae during aging process on the characteristics of potable water treatment residuals and investigate their conditioning in order to provide water treatment plants with guidelines for treating algae-containing sludge. In this study, we measured the bound water content and CST to evaluate the influence of algae and their exudates on sludge conditioning. The change in zeta potential was monitored during sludge aging. During the aging process up to 5 days, the surface charge of sludge became more negative and the dewaterability was enhanced by algal exudates. Microphotographs of the algae-containing sludge suggest that algae and their exudates cause the bio-flocculation phenomenon.

Improved Microalgal Biomass Harvesting Using Optimized Environmental Conditions and Bacterial Bioflocculants

“…Over the course of the sludge storage, the pH and the total solids content remained unchanged (Pan et al, 1999). The TOC, zeta potential, and bound water content, however, decreased throughout storage (Pan et al, 1999).…”

“…However, enhanced bioflocculation was achieved during stationary growth phase given greater amounts of EPS were present over the uronic acids present (uronic acids with respect to EPS was low) (Badireddy et al, 2010). Therefore, In a study by Pan et al (1999), algal biomass was shown to improve the dewatering characteristics and bioflocculation capability of activated sludge. In this study, sludge with Pediastrum, Ankistrodesmus, and some diatom algal species was aged in a container free of sunlight.…”

“…In this study, sludge with Pediastrum, Ankistrodesmus, and some diatom algal species was aged in a container free of sunlight. After 5 days of sludge storage, significant flocculation was found between the sludge particles and the algae by microscopic analysis (Pan et al, 1999). On the tenth day, the flocculation began to breakdown and the algae and its exudates were degraded by the bacteria (Pan et al, 1999).…”

“…After 5 days of sludge storage, significant flocculation was found between the sludge particles and the algae by microscopic analysis (Pan et al, 1999). On the tenth day, the flocculation began to breakdown and the algae and its exudates were degraded by the bacteria (Pan et al, 1999). It was found that as the algae aged, more EPS was released and the flocs became larger due to more advanced flocculation (Pan et al, 1999).…”

“…On the tenth day, the flocculation began to breakdown and the algae and its exudates were degraded by the bacteria (Pan et al, 1999). It was found that as the algae aged, more EPS was released and the flocs became larger due to more advanced flocculation (Pan et al, 1999).…”