Crosslinking of PVA/alginate carriers by glutaraldehyde with improved mechanical strength and enhanced inhibition of deammonification sludge

This study was carried out to improve the mechanical strength of polyvinyl alcohol (PVA)/alginate carriers for long-term stability of deammonification process. The post-treatment of PVA/alginate carriers with glutaraldehyde (Gl) under mild conditions was proposed for stronger crosslinking and the utilization for deammonification operation. FTIR spectra showed enhanced crosslinking with increasing Gl concentration (0.2, 0.5, 1.0, and 2.0%), acid catalyst concentration (0, 0.1 and 0.5%), and reaction duration. Among the physical parameters affected by Gl crosslinking, the mechanical strength, as tested by the endurance to internal pressure test, was markedly improved by the enhanced crosslinking. The optimal crosslinking conditions were selected for the deammonification test based on the physical parameters under the mildest possible conditions. The selected carriers were tested for inhibition of deammonification microorganisms under toxic crosslinking conditions. Deammonification activity (DA) showed no clear inhibition in Gl compared with the control. After mild variations due to changing environmental conditions for the deammonification bacteria, the total nitrogen (TN) removal efficiency of all Gl-crosslinked carriers was superior to that of the control after 20 days of operation. Therefore, the pre-treatment of PVA/alginate by Gl can improve the durability of the carrier and the stability of the deammonification process.