The Effect of Wastewater Cations on Activated Sludge Characteristics: Effects of Aluminum and Iron in Floc

Abstract

Wastewater samples collected from seven wastewater treatment plants (WWTPs) were characterized to assess the impacts of wastewater cations on the activated sludge process. The cations included in this study were sodium (Na+), potassium, ammonium, calcium, magnesium, aluminum (Al), and iron (Fe). Among the selected cations, Al and Fe were of most interest to this study because their role in bioflocculation has not been extensively studied and remains largely unknown. The data showed that WWTPs contained highly varying concentrations of Na+, Al, and Fe in the wastewater and that these cations were responsible for differences between WWTPs as to sludge dewatering rates and effluent quality. In general, a high influent Na+ concentration caused poor sludge dewatering and effluent characteristics. However, when sufficient Al and Fe were present in floc, the deleterious effects of Na+ were offset. The data associated with Al further revealed that waste activated sludge with low Al contained high concentrations of soluble and colloidal biopolymer (protein + polysaccharide), resulting in a high effluent chemical oxygen demand, high conditioning chemical requirements, and poor sludge dewatering properties. These results suggest that Al will improve activated sludge effluent quality by scavenging organic compounds from solution and binding them to floc.

Impact of sludge cation distribution pattern on its filterability in membrane bioreactor

“…Due to high charge density of Fe 3+ , the best flocculation ability (68% on average) was observed in the MBR-Fe. The previous investigations also supported this result that the trivalent cations showed considerable higher flocculating ability than bivalent or monovalent cations (Park et al, 2006;Li et al, 2012).…”

“…Furthermore, it is generally accepted that polysaccharides (PS) and proteins (PN) are the major components of EPSs (Park et al, 2006). Since the sludge flocs possess a multilayered structure consisting of supernatant, slime, LB, TB, and pellet, the distribution pattern of PS and PN directly influence the AS characteristics (Yu et al, 2008).…”

Zero Valent Iron Significantly Enhances Methane Production from Waste Activated Sludge by Improving Biochemical Methane Potential Rather Than Hydrolysis Rate

“…On the contrary, biochemical methane potential (B 0 ) was significantly improved by ZVI addition, indicating that ZVI increased the extent of sludge conversion and altered the sludge property 35 . It has been reported that VS destruction during anaerobic digestion of waste activated sludge generally increased with the increase of ferrous iron content in the sludge 36,37 . Indeed, ZVI can release from Fe 0 to Fe…”

Enhanced synergistic denitrification and chemical precipitation in a modified BAF process by using Fe2+

“…Despite the lack of a clear understanding, sludge dewatering could be affected by a number of EPS-related parameters, such as floc size, structure, and bound water content (Liu and Fang, 2003). The increasing in bound EPS resulting from the addition of multivalent cations has been reported in numerous studies (Liu and Fang, 2003;Park et al, 2006), and the bound EPS showed improving sludge dewaterability (Higgins and Novak, 1997;Murthy and Novak, 1999). Though a better settleability was observed for Fe 2+ dosed sludge than Fe 3+ dosed one in this study, the sludge dewatering performance was not found affected by which Fe species was dosed.…”