A novel immobilization technique for the development of sustainable anammox gel beads for low nitrogen loadings

This study aimed to develop a sustainable anammox gel beads using sodium alginate (SA) mixed with three different support materials including sodium silicate (SS), polyvinyl alcohol (PVA), and colloidal silica (CS). A detailed characterization and comparison of anammox gel beads were conducted using four lab-scale semi-continuous stirred tank reactors (Semi-CSTRs) and SA?SS beads showed superior durability with better reactor performance. SA?SS (B2) beads showed the minimum reduction effective diameter of 24% in comparison to SA (B1) beads, SA?PVA (B3) beads, and SA?CS (B4) beads of 98%, 57%, and 96%, respectively indicating higher integrity of B2 beads. Moreover, R2 reactor containing B2 beads showed the maximum biomass retention after 30 days of operation, relative to the initial mass of 72% compared to R1, R3, and 3%, 44%, and 5%, in R1, R3, and R4, respectively. Total nitrogen removal efficiencies of 8%, 80%, 64%, and 10% were achieved by R1, R2, R3, and R4 reactors, respectively. The diffusion coefficients (De) of ammonium in anammox gel beads was maximum for B2 beads (26.2 ?m2/s) compared to B1 (18.8 ?m2/s), B3 (22.4 ?m2/s), and B4 (13.9 ?m2/s) beads indicating the enhanced internal mass transfer. Crown Copyright @& nbsp;2021 Published by Elsevier B.V. All rights reserved.

Automated summary

The study aimed to develop sustainable anammox gel beads using sodium alginate mixed with different support materials. Through detailed characterization and comparison, SA-SS beads showed superior durability and reactor performance.