Alginate-like polymers from full-scale aerobic granular sludge: content, recovery, characterization, and application for cadmium adsorption

Abstract

Aerobic granular sludge (AGS) is a proven resource for the recovery of biopolymers like alginate-like polymers (ALP). This is the first report on the dynamics of ALP produced by AGS (ALP-AGS) in a full-scale wastewater treatment plant (WWTP), optimization of ALP recovery from AGS, and adsorption of cadmium (Cd2+) by ALP. Recovery of ALP was highest when using 120 mL of 0.2 M Na2CO3 at 70 °C for 45 min. Seasonal (1.5 years, over 3100 cycles) and intra-cycle changes in ALP-AGS in the WWTP were monitored. The ALP content in AGS increased in the transition period between winter and spring, reaching over 150 mg/g MLSS. In the batch reactor cycle, the ALP-AGS level peaked 2 h after the start of aeration (mean peak level: 120 mg/g MLSS), then decreased about two-fold by the end of the cycle. The ALP-AGS had a small surface area and a lamellar structure with crystalline outgrowths. The optimal conditions of Cd2+ adsorption with ALP were a dosage of 7.9 g d.m./L, a pH of 4–8, and an equilibrium time of 60 min. Carboxyl and hydroxyl groups were the key functional groups involved in Cd2+ adsorption. According to the Sips model, the maximum Cd2+ adsorption capacity of ALP-AGS was 29.5 mg/g d.m., which is similar to that of commercial alginate. AGS is a richer source of ALP than activated sludge, which ensures the cost-effectiveness of ALP recovery and increases the sustainability of wastewater treatment. Information on the chemical properties and yields of ALP from full-scale WWTPs is important for downstream applications with the recovered ALP.

Microbial Ecology of Granular Biofilm Technologies for Wastewater Treatment: A Review

“…The recovery and application of interesting substances from AGS are being studied [ 31 ]. Cydzik-Kwiatkowska et al [ 73 ] have extracted ALEs from a full-scale AGS, and they have used it for cadmium adsorption. The AGS microbial community is involved in these activities.…”

Aerobic Granular Sludge: Perspectives for Excess Sludge Management and Resource Recovery

“…[5,114] ALE can be utilized for heavy metals as Cd 2+ removal from aqueous solutions. [125] P / multi-industrial applications It can be used for detergents, cosmetics, and animal feed. In addition, a large portion is being utilized in fertilized production.…”

Reinvestigating the Composition of Alginate-Like Exopolymers Extracted from Activated Sludge

“…As of 2024, there are about 70 studies associating the EPS investigation with ALE extraction and characterization (search in Web of Science with keywords, sludge and alginate-like-). These studies covered a broad range of fields, including the production and functions of ALE in sludge, − as well as their chemical/physical properties and potential applications. ,− Among them, over 40 papers directly considered the ALE as exactly the same as alginates in the chemical composition.…”